Chapter 28 Nervous Systems.

Chapter 28 Nervous Systems

Introduction Spinal cord injuries disrupt communication between
Spinal cord injuries disrupt communication between the central nervous system (brain and spinal cord) and the rest of the body. © 2012 Pearson Education, Inc. 2

Introduction Over 250,000 Americans are living with spinal cord injuries. Spinal cord injuries happen more often to men, happen mostly to people in their teens and 20s, are caused by vehicle accidents, gunshots, and falls, and are usually permanent because the spinal cord cannot be repaired. © 2012 Pearson Education, Inc. 3

Nervous System Structure and Function
Figure 28.0_1 Chapter 28: Big Ideas Nervous System Structure and Function Nerve Signals and Their Transmission Figure 28.0_1 Chapter 28: Big Ideas An Overview of Animal Nervous Systems The Human Brain 4

Figure 28.0_2 Figure 28.0_2 The brain and spinal cord 5

NERVOUS SYSTEM STRUCTURE AND FUNCTION
NERVOUS SYSTEM STRUCTURE AND FUNCTION © 2012 Pearson Education, Inc. 6

28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands
The nervous system obtains sensory information, sensory input, processes sensory information, integration, and sends commands to effector cells (muscles) that carry out appropriate responses, motor output. Student Misconceptions and Concerns 1. As students absorb additional details, often they lose sight of the fundamental functions of the nervous system, creating the risk that they will miss the forest for the trees. Remember to regularly connect the three fundamental functions of the nervous system, (a) sensory input, (b) integration, and (c) motor output, to an image of the PNS and CNS, noting where these functions occur (as in Figure 28.1A, for example). Returning to this or another familiar figure throughout lectures on the nervous system can help to remind students of key functions while allowing them to visually organize additional information. Such figures serve as “intellectual anchors” for a discussion. 2. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion. Teaching Tips 1. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 2. Challenge your students to provide examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that detect signals indicating engine performance, interpret the signals, and then send signals to make adjustments. © 2012 Pearson Education, Inc. 7

Peripheral nervous system (PNS) Central nervous system (CNS)
Figure 28.1A Sensory input Integration Sensory receptor Motor output Figure 28.1A Organization of a nervous system Brain and spinal cord Effector cells Peripheral nervous system (PNS) Central nervous system (CNS) 8

The central nervous system (CNS) consists of the brain and spinal cord (vertebrates). The peripheral nervous system (PNS) is located outside the CNS and consists of nerves (bundles of neurons wrapped in connective tissue) and ganglia (clusters of neuron cell bodies). Student Misconceptions and Concerns 1. As students absorb additional details, often they lose sight of the fundamental functions of the nervous system, creating the risk that they will miss the forest for the trees. Remember to regularly connect the three fundamental functions of the nervous system, (a) sensory input, (b) integration, and (c) motor output, to an image of the PNS and CNS, noting where these functions occur (as in Figure 28.1A, for example). Returning to this or another familiar figure throughout lectures on the nervous system can help to remind students of key functions while allowing them to visually organize additional information. Such figures serve as “intellectual anchors” for a discussion. 2. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion. Teaching Tips 1. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 2. Challenge your students to provide examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that detect signals indicating engine performance, interpret the signals, and then send signals to make adjustments. © 2012 Pearson Education, Inc. 9

Sensory neurons convey signals from sensory receptors to the CNS. Interneurons are located entirely in the CNS, integrate information, and send it to motor neurons. Motor neurons convey signals to effector cells. Student Misconceptions and Concerns 1. As students absorb additional details, often they lose sight of the fundamental functions of the nervous system, creating the risk that they will miss the forest for the trees. Remember to regularly connect the three fundamental functions of the nervous system, (a) sensory input, (b) integration, and (c) motor output, to an image of the PNS and CNS, noting where these functions occur (as in Figure 28.1A, for example). Returning to this or another familiar figure throughout lectures on the nervous system can help to remind students of key functions while allowing them to visually organize additional information. Such figures serve as “intellectual anchors” for a discussion. 2. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion. Teaching Tips 1. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 2. Challenge your students to provide examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that detect signals indicating engine performance, interpret the signals, and then send signals to make adjustments. © 2012 Pearson Education, Inc. 10

Spinal cord Interneuron Nerve PNS CNS
Figure 28.1B Sensory receptor 2 Sensory neuron 1 Brain Ganglion Spinal cord Motor neuron 3 4 Quadriceps muscles Interneuron Figure 28.1B The knee-jerk reflex Nerve Flexor muscles PNS CNS 11

28.2 Neurons are the functional units of nervous systems
Neurons are cells specialized for carrying signals and the functional units of the nervous system. A neuron consists of a cell body and two types of extensions (fibers) that conduct signals, dendrites and axons. Student Misconceptions and Concerns Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion. Teaching Tips 1. The proportion of neurons to glial cells in the brain is often quite surprising to students who might have little appreciation for the roles or even the existence of glial cells. Like the president of the United States or the head of any major organization, neurons have a large “support staff” of cells that help them perform their function. 2. Myelination is like the insulation on an electrical cord that ensures the wires are only exposed in specific locations. Breaks in this insulation, like disruption of myelin sheaths, will reduce the effectiveness of signal conduction. 3. Myelin sheaths and the nodes of Ranvier may also be described using the following analogy: Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. If you really want to make the point, you could find a fake hot dog item and bring along three hot dog buns. © 2012 Pearson Education, Inc. 12

28.2 Neurons are the functional units of nervous systems
Myelin sheaths enclose axons, form a cellular insulation, and speed up signal transmission. Student Misconceptions and Concerns Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion. Teaching Tips 1. The proportion of neurons to glial cells in the brain is often quite surprising to students who might have little appreciation for the roles or even the existence of glial cells. Like the president of the United States or the head of any major organization, neurons have a large “support staff” of cells that help them perform their function. 2. Myelination is like the insulation on an electrical cord that ensures the wires are only exposed in specific locations. Breaks in this insulation, like disruption of myelin sheaths, will reduce the effectiveness of signal conduction. 3. Myelin sheaths and the nodes of Ranvier may also be described using the following analogy: Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. If you really want to make the point, you could find a fake hot dog item and bring along three hot dog buns. © 2012 Pearson Education, Inc. 13

Signal direction Cell body Nucleus Node of Ranvier Signal pathway
Figure 28.2 Signal direction Cell body Nucleus Node of Ranvier Signal pathway Layers of myelin Nodes of Ranvier Myelin sheath Figure 28.2 Structure of a myelinated motor neuron Schwann cell Synaptic terminals Nucleus Dendrites Cell body Schwann cell Axon 14

Schwann cell Dendrites Cell body Axon
Figure 28.2_1 Signal direction Nucleus Signal pathway Nodes of Ranvier Figure 28.2_1 Structure of a myelinated motor neuron (part 1) Myelin sheath Schwann cell Synaptic terminals Dendrites Cell body Axon 15

Node of Ranvier Layers of myelin Nucleus Schwann cell Figure 28.2_2
Figure 28.2_2 Structure of a myelinated motor neuron (part 2) Schwann cell 16

Figure 28.2_3 Cell body Figure 28.2_3 Structure of a myelinated motor neuron (part 3) 17

NERVE SIGNALS AND THEIR TRANSMISSION
NERVE SIGNALS AND THEIR TRANSMISSION © 2012 Pearson Education, Inc. 18

28.3 Nerve function depends on charge differences across neuron membranes
At rest, a neuron’s plasma membrane has potential energy—the membrane potential, in which just inside the cell is slightly negative and just outside the cell is slightly positive. The resting potential is the voltage across the plasma membrane of a resting neuron. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips Students may require a review of the basic concept of potential energy. A simple demonstration in class, such as holding an object and then letting it plummet to the floor, can provide a quick, clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. © 2012 Pearson Education, Inc. 19

Animation: Resting Potential
28.3 Nerve function depends on charge differences across neuron membranes The resting potential exists because of differences in ion concentration of the fluids inside and outside the neuron. Inside the neuron K+ is high and Na+ is low. Outside the neuron K+ is low and Na+ is high. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips Students may require a review of the basic concept of potential energy. A simple demonstration in class, such as holding an object and then letting it plummet to the floor, can provide a quick, clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. Animation: Resting Potential © 2012 Pearson Education, Inc. 20

Neuron Axon Plasma membrane Figure 28.3 Outside of neuron Na Na Na
K Na K K Na Na Na Na Na Na channel Na Na Figure 28.3 How the resting potential is generated Plasma membrane K K Na-K pump ATP Na K channel K K Na K K Na K Na K K K K K K K Inside of neuron 21

Neuron Axon Plasma membrane Figure 28.3_1
Figure 28.3_1 How the resting potential is generated (part 1) Plasma membrane 22

Outside of neuron Na Na Na Na Na Na Na K Na K K Na Na Na
Figure 28.3_2 Outside of neuron Na Na Na Na Na Na Na K Na K K Na Na Na Na Na channel Na Na Na Na-K pump K K Plasma membrane ATP Na K channel Figure 28.3_2 How the resting potential is generated (part 2) K K Na K K Na K Na K K K K K K K Inside of neuron 23

28.4 A nerve signal begins as a change in the membrane potential
A stimulus is any factor that causes a nerve signal to be generated. A stimulus alters the permeability of a portion of the membrane, allows ions to pass through, and changes the membrane’s voltage. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. Students might benefit most by first learning how sodium and potassium ions move during an action potential before addressing the resulting changes in membrane potential. 2. Students may better comprehend the idea of the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person can reach a “threshold” where he or she is stimulated enough to get up and turn it off. © 2012 Pearson Education, Inc. 24

28.4 A nerve signal begins as a change in the membrane potential
A nerve signal, called an action potential, is a change in the membrane voltage, from the resting potential, to a maximum level, and back to the resting potential. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. Students might benefit most by first learning how sodium and potassium ions move during an action potential before addressing the resulting changes in membrane potential. 2. Students may better comprehend the idea of the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person can reach a “threshold” where he or she is stimulated enough to get up and turn it off. Animation: Action Potential © 2012 Pearson Education, Inc. 25

Membrane potential (mV)
Figure 28.4 Na Na Na Na K 3 Additional Na channels open, K channels are closed; interior of cell becomes more positive. K 50 Action potential 4 Na channels close and inactivate; K channels open, and K rushes out; interior of cell is more negative than outside. 3 Na Na 4 Membrane potential (mV) 2 50 Threshold 1 1 5 Resting potential K 100 5 The K channels close relatively slowly, causing a brief undershoot. Time (msec) 2 A stimulus opens some Na channels; if threshold is reached, an action potential is triggered. Figure 28.4 The action potential Sodium channel Potassium channel Na Na Outside of neuron Na Na Plasma membrane Inside of neuron K K 1 Resting state: Voltage-gated Na and K channels are closed; resting potential is maintained by ungated channels (not shown). 1 Return to resting state. 26

Figure 28.4_s1 50 Action potential Membrane potential (mV) Threshold 50 1 Resting potential 100 Time (msec) 1 Resting state: Voltage- gated Na and K channels are closed; resting potential is maintained by ungated channels (not shown). Sodium channel Potassium channel Na Na Outside of neuron Figure 28.4_s1 The action potential (step 1) Plasma membrane Inside of neuron K 27

Figure 28.4_s2 50 Action potential Membrane potential (mV) 2 Threshold 50 1 Resting potential 100 Time (msec) 2 A stimulus opens some Na channels; if threshold is reached, an action potential is triggered. Figure 28.4_s2 The action potential (step 2) Na Na K 28

Figure 28.4_s3 50 Action potential 3 Membrane potential (mV) 2 Threshold 50 1 Resting potential 100 Time (msec) 3 Additional Na channels open, K channels are closed; interior of cell becomes more positive. Na Na Figure 28.4_s3 The action potential (step 3) K 29

Figure 28.4_s4 50 Action potential 3 4 Membrane potential (mV) 2 Threshold 50 1 Resting potential 100 Time (msec) 4 Na channels close and inactivate; K channels open, and K rushes out; interior of cell is more negative than outside. Na Na Figure 28.4_s4 The action potential (step 4) K 30

Figure 28.4_s5 50 Action potential 3 4 Membrane potential (mV) 2 Threshold 50 1 5 Resting potential 100 Time (msec) 5 The K channels close relatively slowly, causing a brief undershoot. Figure 28.4_s5 The action potential (step 5) 31

Figure 28.4_s6 50 Action potential 3 4 Membrane potential (mV) 2 Threshold 50 1 1 5 Resting potential 100 Time (msec) 1 Return to resting state. Figure 28.4_s6 The action potential (step 6) Na Na K 32

28.5 The action potential propagates itself along the axon
Action potentials are self-propagated in a one-way chain reaction along a neuron and all-or-none events. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. An action potential spreading along the length of an axon retains its strength. The overall process is therefore like the “wave” sometimes created by audiences at sporting events. 2. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. © 2012 Pearson Education, Inc. 33

Action potential Plasma membrane Axon segment Figure 28.5_s1 Na Na
Figure 28.5_s1 Propagation of the action potential along an axon (detail, step 1) 34

Action potential Plasma membrane Axon segment Action potential
Figure 28.5_s2 Action potential Plasma membrane Na 1 Axon segment Na Action potential Na K 2 K Na Figure 28.5_s2 Propagation of the action potential along an axon (detail, step 2) 35

Action potential Plasma membrane Axon segment Action potential
Figure 28.5_s3 Action potential Plasma membrane Na 1 Axon segment Na Action potential Na K 2 K Na Figure 28.5_s3 Propagation of the action potential along an axon (detail, step 3) Action potential Na K 3 K Na 36

Figure 28.5 Propagation of the action potential along an axon
Plasma membrane Na 1 Axon segment Na Action potential Na K 2 Figure 28.5 Propagation of the action potential along an axon K Na Action potential Na K 3 K Na 37

28.5 The action potential propagates itself along the axon
The frequency of action potentials (but not their strength) changes with the strength of the stimulus. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. An action potential spreading along the length of an axon retains its strength. The overall process is therefore like the “wave” sometimes created by audiences at sporting events. 2. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. © 2012 Pearson Education, Inc. 38

28.6 Neurons communicate at synapses
Synapses are junctions where signals are transmitted between two neurons or between neurons and effector cells. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, then driving away on a road on the other side. The movement of the traveler (or the signal) continues, but changes mechanisms along the way. © 2012 Pearson Education, Inc. 39

28.6 Neurons communicate at synapses
Electrical signals pass between cells at electrical synapses. At chemical synapses the ending (presynaptic) cell secretes a chemical signal, a neurotransmitter, the neurotransmitter crosses the synaptic cleft, and the neurotransmitter binds to a specific receptor on the surface of the receiving (postsynaptic) cell. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, then driving away on a road on the other side. The movement of the traveler (or the signal) continues, but changes mechanisms along the way. Animation: Synapse © 2012 Pearson Education, Inc. 40

Figure 28.6 Neuron communication at a typical chemical synapse
1 Sending cell Action potential arrives Axon of sending cell Synaptic vesicles Synaptic terminal of sending cell Synaptic terminal 2 Vesicle fuses with plasma membrane 3 Neurotransmitter is released into synaptic cleft Dendrite of receiving cell Synaptic cleft 4 Neurotransmitter binds to receptor Receiving cell Neurotransmitter molecules Ion channels Neurotransmitter Neurotransmitter broken down and released Figure 28.6 Neuron communication at a typical chemical synapse Receptor Ions 5 Ion channel opens 6 Ion channel closes 41

Action potential arrives Axon of sending cell Synaptic vesicles
Figure 28.6_1 1 Sending cell Action potential arrives Axon of sending cell Synaptic vesicles Synaptic terminal of sending cell Synaptic terminal 2 Vesicle fuses with plasma membrane 3 Neurotransmitter is released into synaptic cleft Dendrite of receiving cell Figure 28.6_1 Neuron communication at a typical chemical synapse (part 1) Synaptic cleft 4 Neurotransmitter binds to receptor Receiving cell Neurotransmitter molecules Ion channels 42

Neurotransmitter broken down and released Receptor
Figure 28.6_2 Neurotransmitter Neurotransmitter broken down and released Receptor Ions Figure 28.6_2 Neuron communication at a typical chemical synapse (part 2) 5 Ion channel opens 6 Ion channel closes 43

28.7 Chemical synapses enable complex information to be processed
Some neurotransmitters excite a receiving cell, and others inhibit a receiving cell’s activity by decreasing its ability to develop action potentials. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. The authors compare a neuron’s diverse contacts with other neurons (potentially, hundreds of them) to a living circuit board. 2. Another analogy to the diverse signal input to a neuron might be helpful, even amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd cheering for and against them. Game shows often demonstrate similar situations, as players’ decisions are influenced by the shouted suggestions of the audience. © 2012 Pearson Education, Inc. 44

28.7 Chemical synapses enable complex information to be processed
A receiving neuron’s membrane may receive signals that are both excitatory and inhibitory and from many different sending neurons. The summation of excitation and inhibition determines if a neuron will transmit a nerve signal. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. The authors compare a neuron’s diverse contacts with other neurons (potentially, hundreds of them) to a living circuit board. 2. Another analogy to the diverse signal input to a neuron might be helpful, even amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd cheering for and against them. Game shows often demonstrate similar situations, as players’ decisions are influenced by the shouted suggestions of the audience. © 2012 Pearson Education, Inc. 45

Synaptic terminals Inhibitory Excitatory Dendrites Myelin sheath
Figure 28.7 Synaptic terminals Inhibitory Excitatory Dendrites Myelin sheath Receiving cell body Axon Synaptic terminals Figure 28.7 A neuron’s multiple synaptic inputs 46

Synaptic terminals Figure 28.7_1
Figure 28.7_1 A neuron’s multiple synaptic inputs (micrograph) 47

28.8 A variety of small molecules function as neurotransmitters
Many small, nitrogen-containing molecules are neurotransmitters. Acetylcholine is a neurotransmitter in the brain and at synapses between motor neurons and muscle cells. Biogenic amines are important neurotransmitters in the CNS and include serotonin and dopamine, which affect sleep, mood, and attention. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. Students may have heard about chemical imbalances in the brain without specifically knowing what this means. Abnormal concentrations of neurotransmitters in the central nervous system resulting from disease or chemical exposure can change our ability to perceive and respond to our world. Many drugs, both legal and illegal, can create imbalances with potentially disastrous consequences. 2. The treatment of psychological disorders is complicated by the diversity of neurotransmitters and their interactions. Therefore, predicting how a specific prescription drug will function in a particular patient is often difficult. Students may begin with the assumption that scientists currently understand much more about these complex reactions than we actually do. Emphasizing the need for additional research in these fields may encourage students to ponder career directions they have not previously considered. 3. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why. The likely response will be that one might not trust a criminal pharmacist to carefully provide medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? © 2012 Pearson Education, Inc. 48

28.8 A variety of small molecules function as neurotransmitters
Many neuropeptides consist of relatively short chains of amino acids important in the CNS and include endorphins, decreasing our perception of pain. Nitric oxide is a dissolved gas and triggers erections during sexual arousal in men. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. Students may have heard about chemical imbalances in the brain without specifically knowing what this means. Abnormal concentrations of neurotransmitters in the central nervous system resulting from disease or chemical exposure can change our ability to perceive and respond to our world. Many drugs, both legal and illegal, can create imbalances with potentially disastrous consequences. 2. The treatment of psychological disorders is complicated by the diversity of neurotransmitters and their interactions. Therefore, predicting how a specific prescription drug will function in a particular patient is often difficult. Students may begin with the assumption that scientists currently understand much more about these complex reactions than we actually do. Emphasizing the need for additional research in these fields may encourage students to ponder career directions they have not previously considered. 3. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why. The likely response will be that one might not trust a criminal pharmacist to carefully provide medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? © 2012 Pearson Education, Inc. 49

28.9 CONNECTION: Many drugs act at chemical synapses
Many psychoactive drugs act at synapses and affect neurotransmitter action. Caffeine counters the effect of inhibitory neurotransmitters. Nicotine acts as a stimulant by binding to acetylcholine receptors. Alcohol is a depressant. Student Misconceptions and Concerns 1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details. 2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects. Teaching Tips 1. Students may have heard about chemical imbalances in the brain without specifically knowing what this means. Abnormal concentrations of neurotransmitters in the central nervous system resulting from disease or chemical exposure can change our ability to perceive and respond to our world. Many drugs, both legal and illegal, can create imbalances with potentially disastrous consequences. 2. The treatment of psychological disorders is complicated by the diversity of neurotransmitters and their interactions. Therefore, predicting how a specific prescription drug will function in a particular patient is often difficult. Students may begin with the assumption that scientists currently understand much more about these complex reactions than we actually do. Emphasizing the need for additional research in these fields may encourage students to ponder career directions they have not previously considered. 3. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why. The likely response will be that one might not trust a criminal pharmacist to carefully provide medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? © 2012 Pearson Education, Inc. 50

Figure 28.9 Figure 28.9 Alcohol, nicotine, and caffeine—drugs that alter the effects of neurotransmitters 51

AN OVERVIEW OF ANIMAL NERVOUS SYSTEMS
AN OVERVIEW OF ANIMAL NERVOUS SYSTEMS © 2012 Pearson Education, Inc. 52

28.10 EVOLUTION CONNECTION: The evolution of animal nervous systems reflects changes in body symmetry Radially symmetrical animals have a nervous system arranged in a weblike system of neurons called a nerve net. Student Misconceptions and Concerns Students may think of the human brain as completely unique. Yet, the anatomical components of the human brain mirror the basic components found in many other vertebrates. These similarities are so extensive that sheep brains are often studied in biology laboratories to better understand human anatomy. Teaching Tips Before addressing Modules 28.10–28.13, consider challenging your students to explain what we mean by a “head” in an animal. Why are heads concentrated on one end of the body? Why is the mouth usually, but not always, associated with the head? (The opening to the digestive tract of a planarian is in the middle of the body.) An analogy might be made to an airplane, whose pilot sits inside the cockpit in front gathering and processing information about where the plane is headed. Why are all six of our major senses (taste, smell, sight, touch, sound, and balance) all centered in our heads? © 2012 Pearson Education, Inc. 53

Nerve net Neuron Hydra (cnidarian) Figure 28.10A
Figure 28.10A Invertebrate nervous systems: hydra (cnidarian) Hydra (cnidarian) 54

28.10 EVOLUTION CONNECTION: The evolution of animal nervous systems reflects changes in body symmetry Most bilaterally symmetrical animals evolved cephalization, the concentration of the nervous system at the head end, and centralization, the presence of a central nervous system distinct from a peripheral nervous system. Student Misconceptions and Concerns Students may think of the human brain as completely unique. Yet, the anatomical components of the human brain mirror the basic components found in many other vertebrates. These similarities are so extensive that sheep brains are often studied in biology laboratories to better understand human anatomy. Teaching Tips Before addressing Modules 28.10–28.13, consider challenging your students to explain what we mean by a “head” in an animal. Why are heads concentrated on one end of the body? Why is the mouth usually, but not always, associated with the head? (The opening to the digestive tract of a planarian is in the middle of the body.) An analogy might be made to an airplane, whose pilot sits inside the cockpit in front gathering and processing information about where the plane is headed. Why are all six of our major senses (taste, smell, sight, touch, sound, and balance) all centered in our heads? © 2012 Pearson Education, Inc. 55

Eyespot Brain Nerve cord Transverse nerve Flatworm (planarian)
Figure 28.10B Eyespot Brain Nerve cord Transverse nerve Figure 28.10B Invertebrate nervous systems: flatworm (planarian) Flatworm (planarian) 56

Brain Ventral nerve cord Segmental ganglion Leech (annelid)
Figure 28.10C Brain Ventral nerve cord Segmental ganglion Figure 28.10C Invertebrate nervous systems: leech (annelid) Leech (annelid) 57

Brain Ventral nerve cord Ganglia Insect (arthropod) Figure 28.10D
Figure 28.10D Invertebrate nervous systems: insect (arthropod) Insect (arthropod) 58

Brain Giant axon Squid (mollusc) Figure 28.10E
Figure 28.10E Invertebrate nervous systems: squid (mollusc) Squid (mollusc) 59

28.11 Vertebrate nervous systems are highly centralized
In the vertebrates, the central nervous system (CNS) consists of the brain and spinal cord and includes spaces filled with cerebrospinal fluid forming ventricles of the brain, forming the central canal of the spinal cord, and surrounding the brain. The vertebrate peripheral nervous system (PNS) consists of cranial nerves, spinal nerves, and ganglia. Student Misconceptions and Concerns Students may think of the human brain as completely unique. Yet, the anatomical components of the human brain mirror the basic components found in many other vertebrates. These similarities are so extensive that sheep brains are often studied in biology laboratories to better understand human anatomy. Teaching Tips Students often are surprised to learn that their brain is hollow, although some students may know that the central nervous system is surrounded by cerebrospinal fluid. The basic development of the brain and spinal cord from an embryonic tube is addressed in Module © 2012 Pearson Education, Inc. 60

Central nervous system (CNS) Brain Cranial nerves Spinal cord
Figure 28.11A Central nervous system (CNS) Brain Cranial nerves Spinal cord Peripheral nervous system (PNS) Ganglia outside CNS Spinal nerves Figure 28.11A A vertebrate nervous system (back view) 61

Spinal cord (cross section)
Figure 28.11B Gray matter Cerebrospinal fluid Brain Dorsal root ganglion (part of PNS) Meninges White matter Spinal nerve (part of PNS) Central canal Ventricles Figure 28.11B Fluid-filled spaces of the vertebrate CNS Central canal of spinal cord Spinal cord (cross section) Spinal cord 62

28.12 The peripheral nervous system of vertebrates is a functional hierarchy
The PNS can be divided into two functional components: the motor system, mostly voluntary, and the autonomic nervous system, mostly involuntary. Student Misconceptions and Concerns Students often think of the motor nervous system as “voluntary” and directed by conscious thoughts. You might point out to your students that they are not likely concentrating on contracting the various muscles needed to maintain their posture as they sit in class. As noted in Module 28.12, many skeletal muscles are actually controlled by reflexes. Teaching Tips 1. Students often remember the functions of the autonomic nervous system better by thinking of them as “automatic.” 2. Students may remember the functions of the sympathetic division as “sympathetic” to our problems. For example, the sympathetic nervous system may react to stressful situations by preparing us to fight or to run (although we often choose to do neither). 3. The automatic functions of the enteric division may not be appreciated by your students. You might note that given our busy days, with so many activities and obligations, we are fortunate that our digestive system can secrete, mix, propel, and absorb our meals without our focused mental attention! Can you imagine adding all that to our to-do list? 4. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses cannot be quickly reversed. You might want to encourage students to think of how long it usually takes for them or others to calm down after having become extremely nervous or upset. Time and separation from the source of stress are usually required. For example, those who take a long walk in order to calm down often find, in the mild exercise and the retreat from the situation, an emotional comfort that also makes biological sense. © 2012 Pearson Education, Inc. 63

The motor nervous system carries signals to and from skeletal muscles and mainly responds to external stimuli. The autonomic nervous system regulates the internal environment and controls smooth and cardiac muscle and organs and glands of the digestive, cardiovascular, excretory, and endocrine systems. Student Misconceptions and Concerns Students often think of the motor nervous system as “voluntary” and directed by conscious thoughts. You might point out to your students that they are not likely concentrating on contracting the various muscles needed to maintain their posture as they sit in class. As noted in Module 28.12, many skeletal muscles are actually controlled by reflexes. Teaching Tips 1. Students often remember the functions of the autonomic nervous system better by thinking of them as “automatic.” 2. Students may remember the functions of the sympathetic division as “sympathetic” to our problems. For example, the sympathetic nervous system may react to stressful situations by preparing us to fight or to run (although we often choose to do neither). 3. The automatic functions of the enteric division may not be appreciated by your students. You might note that given our busy days, with so many activities and obligations, we are fortunate that our digestive system can secrete, mix, propel, and absorb our meals without our focused mental attention! Can you imagine adding all that to our to-do list? 4. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses cannot be quickly reversed. You might want to encourage students to think of how long it usually takes for them or others to calm down after having become extremely nervous or upset. Time and separation from the source of stress are usually required. For example, those who take a long walk in order to calm down often find, in the mild exercise and the retreat from the situation, an emotional comfort that also makes biological sense. © 2012 Pearson Education, Inc. 64

Peripheral nervous system (to and from the central nervous system)
Figure 28.12A Peripheral nervous system (to and from the central nervous system) Motor system (voluntary and involuntary; to and from skeletal muscles) Autonomic nervous system (involuntary; smooth and cardiac muscles, various glands) Parasympathetic division (“Rest and digest”) Sympathetic division (“Flight and fight”) Enteric division (muscles and glands of the digestive system) Figure 28.12A Functional divisions of the vertebrate PNS 65

The autonomic nervous system is composed of three divisions. The parasympathetic division primes the body for activities that gain and conserve energy for the body. The sympathetic division prepares the body for intense, energy-consuming activities. The enteric division consists of networks of neurons in the digestive tract, pancreas, and gallbladder that control secretion and peristalsis. Student Misconceptions and Concerns Students often think of the motor nervous system as “voluntary” and directed by conscious thoughts. You might point out to your students that they are not likely concentrating on contracting the various muscles needed to maintain their posture as they sit in class. As noted in Module 28.12, many skeletal muscles are actually controlled by reflexes. Teaching Tips 1. Students often remember the functions of the autonomic nervous system better by thinking of them as “automatic.” 2. Students may remember the functions of the sympathetic division as “sympathetic” to our problems. For example, the sympathetic nervous system may react to stressful situations by preparing us to fight or to run (although we often choose to do neither). 3. The automatic functions of the enteric division may not be appreciated by your students. You might note that given our busy days, with so many activities and obligations, we are fortunate that our digestive system can secrete, mix, propel, and absorb our meals without our focused mental attention! Can you imagine adding all that to our to-do list? 4. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses cannot be quickly reversed. You might want to encourage students to think of how long it usually takes for them or others to calm down after having become extremely nervous or upset. Time and separation from the source of stress are usually required. For example, those who take a long walk in order to calm down often find, in the mild exercise and the retreat from the situation, an emotional comfort that also makes biological sense. © 2012 Pearson Education, Inc. 66

Figure 28.12B Parasympathetic division Sympathetic division Brain Eye Constricts pupil Dilates pupil Salivary glands Stimulates saliva secretion Inhibits saliva secretion Lung Constricts bronchi Relaxes bronchi Accelerates heart Slows heart Heart Adrenal gland Spinal cord Stimulates epinephrine and norepi- nephrine release Liver Stomach Stimulates stomach, pancreas, and intestines Figure 28.12B The parasympathetic and sympathetic divisions of the autonomic nervous system Pancreas Stimulates glucose release Inhibits stomach, pancreas, and intestines Intestines Bladder Stimulates urination Inhibits urination Promotes erection of genitalia Promotes ejacu- lation and vaginal contractions Genitalia 67

Parasympathetic division Sympathetic division
Figure 28.12B_1 Parasympathetic division Sympathetic division Eye Constricts pupil Dilates pupil Salivary glands Stimulates saliva secretion Inhibits saliva secretion Lung Constricts bronchi Relaxes bronchi Figure 28.12B_1 The parasympathetic and sympathetic divisions of the autonomic nervous system (part 1) Accelerates heart Slows heart Heart 68

Parasympathetic division Sympathetic division
Figure 28.12B_2 Parasympathetic division Sympathetic division Adrenal gland Stimulates epinephrine and norepi- nephrine release Liver Stomach Stimulates stomach, pancreas, and intestines Pancreas Stimulates glucose release Inhibits stomach, pancreas, and intestines Intestines Bladder Figure 28.12B_2 The parasympathetic and sympathetic divisions of the autonomic nervous system (part 2) Stimulates urination Inhibits urination Promotes erection of genitalia Promotes ejacu- lation and vaginal contractions Genitalia 69

28.13 The vertebrate brain develops from three anterior bulges of the neural tube
The vertebrate brain evolved by the enlargement and subdivision of the forebrain, midbrain, and hindbrain. In the course of vertebrate evolution, the forebrain and hindbrain gradually became subdivided structurally and functionally. Teaching Tips The basic organization of the embryonic brain of humans is very similar to the early developmental stages in fish, amphibians, reptiles, and other mammals. The formation of a neural tube and subdivision into three and then five brain regions reflects the common ancestry of vertebrates. For biology teachers, such connections are commonplace. However, pointing out such evidence of evolution can help students understand why evolution has been widely accepted by the scientific community as a fundamental process of life. © 2012 Pearson Education, Inc. 70

Embryonic Brain Regions Brain Structures Present in Adult
Figure 28.13 Embryonic Brain Regions Brain Structures Present in Adult Cerebrum (cerebral hemispheres; includes cerebral cortex, white matter, basal ganglia) Forebrain Diencephalon (thalamus, hypothalamus, posterior pituitary, pineal gland) Midbrain Midbrain (part of brainstem) Pons (part of brainstem), cerebellum Hindbrain Medulla oblongata (part of brainstem) Diencephalon Cerebrum Midbrain Midbrain Figure Embryonic development of the human brain Hindbrain Pons Cerebellum Medulla oblongata Spinal cord Forebrain Embryo (1 month old) Fetus (3 months old) 71

Embryonic Brain Regions Brain Structures Present in Adult
Figure 28.13_1 Embryonic Brain Regions Brain Structures Present in Adult Cerebrum (cerebral hemispheres; includes cerebral cortex, white matter, basal ganglia) Forebrain Diencephalon (thalamus, hypothalamus, posterior pituitary, pineal gland) Midbrain Midbrain (part of brainstem) Figure 28.13_1 Embryonic development of the human brain (part 1) Pons (part of brainstem), cerebellum Hindbrain Medulla oblongata (part of brainstem) 72

Diencephalon Cerebrum Midbrain Midbrain Hindbrain Forebrain
Figure 28.13_2 Diencephalon Cerebrum Midbrain Midbrain Hindbrain Pons Cerebellum Medulla oblongata Spinal cord Forebrain Figure 28.13_2 Embryonic development of the human brain (part 2) Embryo (1 month old) Fetus (3 months old) 73

28.13 The vertebrate brain develops from three anterior bulges of the neural tube
In birds and mammals the cerebrum is much larger and correlates with their sophisticated behavior. Teaching Tips The basic organization of the embryonic brain of humans is very similar to the early developmental stages in fish, amphibians, reptiles, and other mammals. The formation of a neural tube and subdivision into three and then five brain regions reflects the common ancestry of vertebrates. For biology teachers, such connections are commonplace. However, pointing out such evidence of evolution can help students understand why evolution has been widely accepted by the scientific community as a fundamental process of life. © 2012 Pearson Education, Inc. 74

28.14 The structure of a living supercomputer: The human brain
The human brain is more powerful than the most sophisticated computer and composed of three main parts: forebrain, midbrain, and hindbrain. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips Tables such as Table 28.14, which provide summaries of structures and functions, can relieve lectures from the repetition of tedious detail. Instead, more class time can be spent on more interesting and meaningful aspects of the topic. Such tables also facilitate the creation of matching questions on exams! © 2012 Pearson Education, Inc. 76

Cerebral cortex (outer region of cerebrum)
Figure 28.14A Cerebral cortex (outer region of cerebrum) Cerebrum Forebrain Thalamus Hypothalamus Pituitary gland Figure 28.14A The main parts of the human brain Midbrain Pons Spinal cord Medulla oblongata Hindbrain Cerebellum 77

The midbrain, subdivisions of the hindbrain, the thalamus, and the hypothalamus conduct information to and from higher brain centers, regulate homeostatic functions, keep track of body position, and sort sensory information. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips Tables such as Table 28.14, which provide summaries of structures and functions, can relieve lectures from the repetition of tedious detail. Instead, more class time can be spent on more interesting and meaningful aspects of the topic. Such tables also facilitate the creation of matching questions on exams! © 2012 Pearson Education, Inc. 78

Left cerebral hemisphere Right cerebral hemisphere
Figure 28.14B Left cerebral hemisphere Right cerebral hemisphere Cerebrum Thalamus Cerebellum Figure 28.14B A rear view of the brain Basal nuclei Corpus callosum Medulla oblongata 79

Table 28.14 Table Major Structures of the Human Brain 80

Table 28.14_1 Table 28.14_1 Major Structures of the Human Brain (Part 1) 81

Table 28.14_2 Table 28.14_2 Major Structures of the Human Brain (Part 2) 82

The cerebrum is part of the forebrain and the largest and most complex part of the brain. Most of the cerebrum’s integrative power resides in the cerebral cortex of the two cerebral hemispheres. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips Tables such as Table 28.14, which provide summaries of structures and functions, can relieve lectures from the repetition of tedious detail. Instead, more class time can be spent on more interesting and meaningful aspects of the topic. Such tables also facilitate the creation of matching questions on exams! © 2012 Pearson Education, Inc. 83

28.15 The cerebral cortex is a mosaic of specialized, interactive regions
The cerebral cortex is less than 5 mm thick and accounts for 80% of the total human brain mass. Specialized integrative regions of the cerebral cortex include the somatosensory cortex and centers for vision, hearing, taste, and smell. Student Misconceptions and Concerns 1. Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. Popular media often suggests that lateralization is a fixed human trait; i.e., certain people are “left-brained” while others are “right-brained.” Students might therefore believe that they are one or the other. As biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree, and studies of surgical procedures, disease, and injury have revealed that the brain’s hemispheres have considerable plasticity. Teaching Tips As students learn about the structure and function of the cerebral cortex, they are actually using these sets of cells to think about these cells. As student understanding grows, these sets of cells become increasingly aware of their own properties, in a process that is like looking in a mirror! © 2012 Pearson Education, Inc. 84

28.15 The cerebral cortex is a mosaic of specialized, interactive regions
The motor cortex directs responses. Association areas make up most of the cerebrum and are concerned with higher mental activities such as reasoning and language. In a phenomenon known as lateralization, right and left cerebral hemispheres tend to specialize in different mental tasks. Student Misconceptions and Concerns 1. Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. Popular media often suggests that lateralization is a fixed human trait; i.e., certain people are “left-brained” while others are “right-brained.” Students might therefore believe that they are one or the other. As biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree, and studies of surgical procedures, disease, and injury have revealed that the brain’s hemispheres have considerable plasticity. Teaching Tips As students learn about the structure and function of the cerebral cortex, they are actually using these sets of cells to think about these cells. As student understanding grows, these sets of cells become increasingly aware of their own properties, in a process that is like looking in a mirror! © 2012 Pearson Education, Inc. 85

Somatosensory association area Frontal association area
Figure 28.15 Frontal lobe Parietal lobe Somatosensory association area Frontal association area Speech Motor cortex Somatosensory cortex Reading Speech Hearing Visual association area Smell Figure Functional areas of the left cerebral hemisphere Auditory association area Vision Temporal lobe Occipital lobe 86

28.16 CONNECTION: Injuries and brain operations provide insight into brain function
Brain injuries and surgeries reveal brain functions. After a 13-pound steel rod pierced his skull, Phineas Gage appeared to have an intact intellect but his associates noted negative changes to his personality. Stimulation of the cerebral cortex during surgeries caused patients to recall sensations and memories. Cutting the corpus callosum revealed information about brain lateralization. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips 1. Module notes that the cerebrum lacks cells that can detect pain. Consider challenging your students to explain how the source of the pain during a headache. (Some headaches can result from pain outside the brain. For example, sinus pressure, muscle tension, or a toothache can be considered a type of headache. Vascular headaches can result from pain receptors in overstretched or overconstricted blood vessels of the brain.) 2. Much of what we know about brain function comes from damage caused by accidents or disease. Challenge your students to consider the limits of these “natural” experiments. (For instance, disease or damage may have multiple physiological effects, making it difficult to trace them to the malfunction of a particular brain region.) Corroborating data from other technologies, such as fMRI scans, helps verify earlier results. Reviewing the different approaches to understanding the brain reveals how multiple, independent lines of evidence increase confidence in results. © 2012 Pearson Education, Inc. 87

Figure 28.16A Figure 28.16A Computer model of Phineas Gage’s injury 88

Figure 28.16B Figure 28.16B X-ray of hemispherectomy patient after surgery 89

28.17 CONNECTION: fMRI scans provide insight into brain structure and function
Functional magnetic resonance imaging (fMRI) is a scanning and imaging technology used to study brain functions, used on conscious patients, monitors changes in blood oxygen usage in the brain, and correlates to regions of intense brain function. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips Much of what we know about brain function comes from damage caused by accidents or disease. Challenge your students to consider the limits of these “natural” experiments. (For instance, disease or damage may have multiple physiological effects, making it difficult to trace them to the malfunction of a particular brain region.) Corroborating data from other technologies, such as fMRI scans, helps verify earlier results. Reviewing the different approaches to understanding the brain reveals how multiple, independent lines of evidence increase confidence in results. © 2012 Pearson Education, Inc. 90

Figure 28.17 Figure Comparative human fMRI images showing regions of brain activity in healthy veterans (left) and veterans with Gulf War syndrome (right) when performing the same task. 91

28.18 Several parts of the brain regulate sleep and arousal
Sleep and arousal involve activity by the hypothalamus, medulla oblongata, pons, and neurons of the reticular formation. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips As noted in Module 28.18, sleep seems to be involved in learning and memory. Study strategies that involve cramming large amounts of information into the memory in a short period of time may not permit enough sleep and review for deeper understanding. Students who engage in such practices may easily be confused on an exam. The strategy of processing smaller amounts of information over a longer period of time, allowing for both rest and frequent review, is likely to result in the retention of a better-integrated body of information. © 2012 Pearson Education, Inc. 92

28.18 Several parts of the brain regulate sleep and arousal
Sleep is essential for survival, is an active state, and may be involved in consolidating learning and memory. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips As noted in Module 28.18, sleep seems to be involved in learning and memory. Study strategies that involve cramming large amounts of information into the memory in a short period of time may not permit enough sleep and review for deeper understanding. Students who engage in such practices may easily be confused on an exam. The strategy of processing smaller amounts of information over a longer period of time, allowing for both rest and frequent review, is likely to result in the retention of a better-integrated body of information. © 2012 Pearson Education, Inc. 93

28.19 The limbic system is involved in emotions, memory, and learning
The limbic system is a functional group of integrating centers in the cerebral cortex, thalamus, hypothalamus, and involved in emotions, such as nurturing infants and bonding emotionally to other people, memory, and learning. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips 1. Moving information from short-term memory to long-term memory requires frequent rehearsal. Using note cards to create questions and answers based upon the information for an exam is one form of rehearsal that can be very effective when studying basic information. This chapter helps students understand the underlying physiological basis of many successful study techniques. 2. The strong emotional reactions to scents and music that many humans have experienced are properties of our limbic system. © 2012 Pearson Education, Inc. 94

Thalamus Cerebrum Hypothalamus Prefrontal cortex Smell Olfactory bulb
Figure 28.19 Thalamus Cerebrum Hypothalamus Prefrontal cortex Figure The limbic system (shown in shades of gold) Smell Olfactory bulb Amygdala Hippocampus 95

28.20 CONNECTION: Changes in brain physiology can produce neurological disorders
Many neurological disorders can be linked to changes in brain physiology, including schizophrenia, major depression, Alzheimer’s disease, and Parkinson’s disease. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website 2. The frequent occurrence of the neurological disorders discussed in Module makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class. 3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure. © 2012 Pearson Education, Inc. 96

Schizophrenia is a severe mental disturbance and characterized by psychotic episodes in which patients lose the ability to distinguish reality. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website 2. The frequent occurrence of the neurological disorders discussed in Module makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class. 3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure. © 2012 Pearson Education, Inc. 97

Depression Two broad forms of depressive illness have been identified: major depression and bipolar disorder, manic-depressive disorder. Treatments may include selective serotonin reuptake inhibitors (SSRIs), which increase the amount of time serotonin is available to stimulate certain neurons in the brain. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website 2. The frequent occurrence of the neurological disorders discussed in Module makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class. 3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure. © 2012 Pearson Education, Inc. 98

Figure 28.20A Figure 28.20A PET scans showing brain activity in a depressed person (top) and healthy person (bottom) 99

Prescriptions (millions)
Figure 28.20B 140 120 100 80 Prescriptions (millions) 60 40 Figure 28.20B SSRI prescriptions in the United States 20 01 05 06 Year 100

Alzheimer’s disease is characterized by confusion, memory loss, and personality changes and difficult to diagnose. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website 2. The frequent occurrence of the neurological disorders discussed in Module makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class. 3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure. © 2012 Pearson Education, Inc. 101

Parkinson’s disease is a motor disorder and characterized by difficulty in initiating movements, slowness of movement, and rigidity. Student Misconceptions and Concerns Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website 2. The frequent occurrence of the neurological disorders discussed in Module makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class. 3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure. © 2012 Pearson Education, Inc. 102

Figure 28.20C Figure 28.20C Actor Michael J. Fox (right) and boxer Muhammad Ali, both of whom suffer from Parkinson’s disease, testifying before the United States Senate about funding for the disorder 103

You should now be able to
Describe the structural and functional subdivisions of the nervous system. Describe the three parts of a reflex, distinguishing the three types of neurons that may be involved in the reaction. Describe the structures and functions of neurons and myelin sheaths. Define a resting potential and explain how it is created. © 2012 Pearson Education, Inc. 104

Explain how an action potential is produced and the resting membrane potential restored. Explain how an action potential propagates itself along a neuron. Compare the structures, functions, and locations of electrical and chemical synapses. Compare excitatory and inhibitory neurotransmitters. Describe the types and functions of neurotransmitters known in humans. © 2012 Pearson Education, Inc. 105

Explain how drugs can alter chemical synapses. Describe the diversity of animal nervous systems and provide examples. Describe the general structure of the brain, spinal cord, and associated nerves of vertebrates. Compare the functions of the motor nervous system and autonomic nervous system. © 2012 Pearson Education, Inc. 106

Compare the structures, functions, and interrelationships of the parasympathetic, sympathetic, and enteric divisions of the peripheral nervous system. Explain how the vertebrate brain develops from an embryonic tube. Describe the main parts and functions of the human brain. Explain how injuries, illness, and surgery provide insight into the functions of the brain. © 2012 Pearson Education, Inc. 107

Explain how fMRI scans help us understand brain functions. Explain how the brain regulates sleep and arousal. Describe the structure and functions of the limbic system. Describe the causes, symptoms, and treatments of schizophrenia, depression, Alzheimer’s disease, and Parkinson’s disease. © 2012 Pearson Education, Inc. 108

Peripheral nervous system Central nervous system
Figure 28.UN01 Sensory receptor Sensory input Integration Effector cells Motor output Figure 28.UN01 Reviewing the Concepts, 28.1 Peripheral nervous system Central nervous system 109

Myelin sheath (speeds signal transmission)
Figure 28.UN02 po te nti al Action signal Figure 28.UN02 Reviewing the Concepts, 28.2 Dendrites Axon Synaptic terminals Cell body Myelin sheath (speeds signal transmission) 110

Central Nervous System (CNS) Peripheral Nervous System (PNS)
Figure 28.UN03 Central Nervous System (CNS) Peripheral Nervous System (PNS) Brain Spinal cord: nerve bundle that communicates with body Motor system: voluntary control over muscles Autonomic nervous system: involuntary control over organs • Parasympathetic division: rest and digest • Sympathetic division: fight or flight Figure 28.UN03 Reviewing the Concepts, 28.12 111

(c) (b) (a) (d) (e)  brain (f) (g) (h) (i) Figure 28.UN04
Figure 28.UN04 Connecting the Concepts, question 1  brain (f) (g) (h) (i) 112

Figure 28.UN05 Figure 28.UN05 Applying the Concepts, question 6 113

Chapter 28 Nervous Systems.

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Chapter 28 Nervous Systems.

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