BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 28 Nervous Systems

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The spinal cord is the central communication conduit between the brain and the body –It consists of a bundle of nerves Can an Injured Spinal Cord Be Fixed?

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Spinal cord injury disrupts communication between the central nervous system and the rest of the body –Paraplegia is paralysis of the lower half of the body –Quadriplegia is paralysis from the neck down –Research on nerve cells is leading to new therapies

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The nervous system has three interconnected functions –Sensory input –Integration –Motor output 28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands NERVOUS SYSTEM STRUCTURE AND FUNCTION

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 28.1A Sensory receptor SENSORY INPUT INTEGRATION MOTOR OUTPUT Effector Peripheral nervous system (PNS) Central nervous system (CNS) Brain and spinal cord

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The nervous system can be divided into two main divisions –The central nervous system (CNS) consists of the brain and, in vertebrates, the spinal cord –The peripheral nervous system (PNS) is made up of nerves and ganglia that carry signals into and out of the CNS

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Three types of neurons correspond to the nervous system’s three main functions –Sensory neurons convey signals from sensory receptors into the CNS –Interneurons integrate data and relay signals –Motor neurons convey signals to effectors

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 28.1B Brain 1 Sensory receptor 2 Sensory neuron 3 4 Ganglion Motor neuron Spinal cord Interneuron CNS Nerve PNS Quadriceps muscles Flexor muscles

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neurons are cells specialized to transmit nervous impulses They consist of –a cell body –dendrites (highly branched fibers) –an axon (long fiber) 28.2 Neurons are the functional units of nervous systems

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Supporting cells protect, insulate, and reinforce neurons The myelin sheath is the insulating material in vertebrates –It is composed of a chain of Schwann cells linked by nodes of Ranvier –It speeds up signal transmission –Multiple sclerosis (MS) involves the destruction of myelin sheaths by the immune system

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 28.2 Signal direction Dendrites Cell body Nucleus Axon Schwann cell Signal pathway Myelin sheath Nodes of Ranvier Synaptic knobs Node of Ranvier Myelin sheath Schwann cell Nucleus

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The resting potential of a neuron’s plasma membrane is caused by the cell membrane’s ability to maintain –a positive charge on its outer surface –a negative charge on its inner (cytoplasmic) surface 28.3 A neuron maintains a membrane potential across its membrane NERVE SIGNALS AND THEIR TRANSMISSION Plasma membrane Microelectrode inside cell Axon Neuron Microelectrode outside cell Voltmeter –70 mV Figure 28.3A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Resting potential is generated and maintained with help from sodium-potassium pumps –These pump K + into the cell and Na + out of the cell Figure 28.3B OUTSIDE OF CELL Na + Na + channel Na + K+K+ K+K+ K+K+ Plasma membrane Protein Na + K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ Na + - K + pump Na + K + channel INSIDE OF CELL

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A stimulus alters the permeability of a portion of the plasma membrane –Ions pass through the plasma membrane, changing the membrane’s voltage –It causes a nerve signal to be generated 28.4 A nerve signal begins as a change in the membrane potential

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An action potential is a nerve signal –It is an electrical change in the plasma membrane voltage from the resting potential to a maximum level and back to the resting potential

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 28.4 Resting state: voltage gated Na + and K + channels closed; resting potential is maintained A stimulus opens some Na+ channels; if threshold is reached, action potential is triggered. Additional Na + channels open, K + channels are closed; interior of cell becomes more positive. 5 The K + channels close relatively slowly, causing a brief undershoot. Na+ channels close and inactivate. K + channels open, and K + rushes out; interior of cell more negative than outside. Neuron interior Action potential Threshold potential Resting potential Na+ 1 Return to resting state. 1 Neuron interior K+K+ K+K+

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 28.5 The action potential propagates itself along the neuron Figure Axon Action potential Axon segment Action potential Na + K+K+ K+K+ Action potential Na + K+K+ K+K+

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An action potential is an all-or-none event –Its size is not affected by the stimulus strength –However, the frequency changes with the strength of the stimulus

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The synapse is a key element of nervous systems –It is a junction or relay point between two neurons or between a neuron and an effector cell Synapses are either electrical or chemical –Action potentials pass between cells at electrical synapses –At chemical synapses, neurotransmitters cross the synaptic cleft to bind to receptors on the surface of the receiving cell 28.6 Neurons communicate at synapses

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Action potential arrives 2 Vesicle fuses with plasma membrane 3 Neurotransmitter is released into synaptic cleft Axon of sending neuron Vesicles SENDING NEURON Synaptic knob SYNAPSE SYNAPTIC CLEFT RECEIVING NEURON Ion channels Neurotransmitter molecules 4 Neuro- transmitter binds to receptor Receiving neuron 5 Ion channel opens Receptor Ions Neurotransmitter 6 Ion channel closes Neurotransmitter broken down and released

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Excitatory neurotransmitters trigger action potentials in the receiving cell Inhibitory neurotransmitters decrease the cell’s ability to develop action potentials The summation of excitation and inhibition determines whether or not the cell will transmit a nerve signal 28.7 Chemical synapses make complex information processing possible

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A neuron may receive input from hundreds of other neurons via thousands of synaptic knobs Figure 28.7 DendritesSynaptic knobs Myelin sheath Receiving cell body Axon Synaptic knobs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most neurotransmitters are small, nitrogen- containing organic molecules –Acetylcholine –Biogenic amines (epinephrine, norepinephrine, serotonin, dopamine) –Amino acids (aspartate, glutamate, glycine, GABA) –Peptides (substance P and endorphins) –Dissolved gases (nitric oxide) 28.8 A variety of small molecules function as neurotransmitters

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Drugs act at synapses and may increase or decrease the normal effect of neurotransmitters –Caffeine –Nicotine –Alcohol –Prescription and illegal drugs 28.9 Connection: Many drugs act at chemical synapses Figure 28.9

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Radially symmetrical animals have a nervous system arranged in a nerve net –Example: Hydras Nervous system organization usually correlates with body symmetry NERVOUS SYSTEMS Figure 28.10A A. Hydra (cnidarian) Nerve net Neuron

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most bilaterally symmetrical animals exhibit –cephalization, the concentration of the nervous system in the head end –centralization, the presence of a central nervous system Figure 28.10B-E B. Planarian (flatworm) Eye Brain Nerve cord Transverse nerve C. Leech (annelid) Brain Ventral nerve cord Segmental ganglion D. Insect (arthropod) Brain Ventral nerve cord Ganglia Brain Giant axon E. Squid (mollusk)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Vertebrate nervous systems are highly centralized and cephalized Figure 28.11A CENTRAL NERVOUS SYSTEM (CNS) PERIPHERAL NERVOUS SYSTEM (PNS) Brain Spinal cord Cranial nerve Ganglia outside CNS Spinal nerves

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The brain and spinal cord contain fluid-filled spaces Figure 28.11B BRAIN Meninges Ventricles Central canal of spinal cord Spinal cord White matter Gray matter Dorsal root ganglion (part of PNS) Central canalSpinal nerve (part of PNS) SPINAL CORD (cross section)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The peripheral nervous system of vertebrates is a functional hierarchy Figure 28.12A Peripheral nervous system Sensory division Motor division Sensing external environment Sensing internal environment Autonomic nervous system (involuntary) Somatic nervous system (voluntary) Sympathetic division Parasympathetic division

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Referred pain is when we feel pain from an internal organ on the body surface –This happens because neurons carrying information from the skin and those carrying information from the internal organs synapse with the same neurons in the CNS Figure 28.12B Liver Gallbladder Liver Small intestine Appendix Colon Urinary bladder Heart Lungs and diaphragm Lungs and diaphragm Heart Stomach Pancreas Ovaries Kidney Ureters

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The motor division of the PNS –The autonomic nervous system exerts involuntary control over the internal organs –The somatic nervous system exerts voluntary control over skeletal muscles

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The autonomic nervous system consists of two sets of neurons that function antagonistically on most body organs –The parasympathetic division primes the body for activities that gain and conserve energy –The sympathetic division prepares the body for intense, energy-consuming activities Opposing actions of sympathetic and parasympathetic neurons regulate the internal environment

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure PARASYMPATHETIC DIVISIONSYMPATHETIC DIVISION Brain Constricts pupil Stimulates saliva production Constricts bronchi Slows heart Stimulates stomach, pancreas, and intestines Stimulates urination Promotes erection of genitals Spinal cord Eye Salivary glands Lung Heart Liver Stomach Adrenal gland Pancreas Intestines Bladder Genitals Dilates pupil Inhibits saliva production Relaxes bronchi Accelerates heart Stimulates epinephrine and norepi- nephrine release Stimulates glucose release Inhibits stomach, pancreas, and intestines Inhibits urination Promotes ejacu- lation and vaginal contractions

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The vertebrate brain evolved by the enlargement and subdivision of three anterior bulges of the neural tube –Forebrain –Midbrain –Hindbrain Cerebrum size and complexity in birds and mammals correlates with sophisticated behavior The vertebrate brain develops from three anterior bulges of the neural tube THE HUMAN BRAIN

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Embryonic Brain Regions Brain Structures Present in Adult Forebrain Cerebrum (cerebral hemispheres; includes cerebral cortex, white matter, basal ganglia) Diencephalon (thalamus, hypothalamus, posterior pituitary, pineal gland) Midbrain (part of brainstem)Midbrain Hindbrain Pons (part of brainstem), cerebellum Medulla oblongata (part of brainstem) Midbrain Hindbrain Forebrain Cerebral hemisphere Diencephalon Midbrain Pons Cerebellum Medulla oblongata Spinal cord Embryo one month oldFetus three months old

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The structure of a living supercomputer: The human brain Table 28.15

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 28.15A Forebrain Cerebrum Thalamus Hypothalamus Pituitary gland Midbrain Hindbrain Pons Medulla oblongata Cerebellum Spinal cord Cerebral cortex

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most of the cerebrum’s integrative power resides in the cerebral cortex of the two cerebral hemispheres Figure 28.15B Left cerebral hemisphere Right cerebral hemisphere Corpus callosum Basal ganglia

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The motor cortex sends commands to skeletal muscles The somatosensory cortex receives information about pain, pressure, and temperature Several regions receive and process sensory information (vision, hearing, taste, smell) The cerebral cortex is a mosaic of specialized, interactive regions

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The association areas are the sites of higher mental activities (thinking) –Frontal association area (judgment, planning) –Auditory association area –Somatosensory association area (reading, speech) –Visual association area

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure PARIETAL LOBE OCCIPITAL LOBE TEMPORAL LOBE Frontal association area Speech Motor cortex Somatosensory cortex Speech Taste Smell Hearing Auditory association area Somatosensory association area Reading Visual association area Vision FRONTAL LOBE

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In lateralization, areas in the two hemispheres become specialized for different functions –“Right-brained” vs. “left-brained”

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Much knowledge about the brain has come from individuals whose brains were altered through injury, illness, or surgery –The rod that pierced Phineas Gage’s skull left his intellect intact but altered his personality and behavior Connection: Injuries and brain operations have provided insight into brain function Figure 28.17A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A radical surgery called hemispherectomy removes almost half of the brain –It demonstrates the brain’s remarkable plasticity Figure 28.17B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sleep and arousal are controlled by –the hypothalamus –the medulla oblongata –the pons –neurons of reticular formation Several parts of the brain regulate sleep and arousal Figure 28.18A Eye Reticular formation Input from touch, pain, and temperature receptors Input from ears Motor output to spinal cord

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An electroencephalogram (EEG) measures brain waves during sleep and arousal Two types of deep sleep alternate –Slow-wave (delta waves) and REM sleep Figure 28.18B, C Awake but quiet (alpha waves) Awake during intense mental activity (beta waves) Asleep Delta wavesREM sleepDelta waves

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The limbic system is a functional group of integrating centers in the cerebral cortex, thalamus, and hypothalamus It is involved in emotions, memory (short-term and long-term), and learning –The amygdala is central to the formation of emotional memories –The hippocampus is involved in the formation of memories and their recall The limbic system is involved in emotions, memory, and learning

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Thalamus Hypothalamus Prefrontal cortex Smell Olfactory bulb Amygdala Hippocampus CEREBRUM

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Memory and learning involve structural and chemical changes at synapses –Long-term depression (LTD) –Long-term potentiation (LTP) The cellular changes underlying memory and learning probably occur at synapses

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Repeated action potentials Synaptic cleft Ca 2+ Cascade of chemical changes Sending neuron 3 Ca 2+ LTP Receiving neuron 2