Chapter 2 Brain and Behavior Table of Contents Exit

Neuron and Its Parts Neuron: Individual nerve cell; 100 billion in brain Dendrites: Receive messages from other neurons Soma: Cell body; body of the neuron. Receives messages and sends messages down axon Axon: Carries information away from the cell body Axon Terminals: Branches that link the dendrites and somas of other neurons Table of Contents Exit

Fig. 2.1 An example of a neuron, or nerve cell, showing several of its important features. The right foreground shows a nerve cell fiber in cross section, and the upper left inset gives a more realistic picture of the shape of neurons. The nerve impulse usually travels from the dendrites and soma to the branching ends of the axon. The neuron shown here is a motor neuron. Motor neurons originate in the brain or spinal cord and send their axons to the muscles or glands of the body. Table of Contents Exit

Fig. 2.2 Activity in an axon can be measured by placing electrical probes inside and outside the axon. (The scale is exaggerated here. Such measurements require ultra-small electrodes, as described later in this chapter.) At rest, the inside of an axon is about –60 to –70 millivolts, compared with the outside. Electrochemical changes in a nerve cell generate an action potential. When positively charged sodium ions (Na+) rush into the cell, its interior briefly becomes positive. This is the action potential. After the action potential, an outward flow of positive potassium ions (K+) restores the negative charge inside the axon. (See Figure 2.3 for further explanation.) Table of Contents Exit

Fig. 2. 5 A highly magnified view of the synapse shown in Fig. 2. 1 Fig. 2.5 A highly magnified view of the synapse shown in Fig. 2.1. Neurotransmitters are stored in tiny sacs called synaptic vesicles. When a nerve impulse arrives at an axon terminal, the vesicles move to the surface and release neurotransmitters. These transmitter molecules cross the synaptic gap to affect the next neuron. The size of the gap is exaggerated here; it is actually only about one millionth of an inch. Transmitter molecules vary in their effects: Some excite the next neuron and some inhibit its activity. Table of Contents Exit

The Nerve Impulse Resting Potential: Electrical charge of an inactive neuron Threshold: Trigger point for a neuron’s firing Action Potential: Nerve impulse Ion Channels: Axon membrane has these tiny holes or tunnels Negative After-Potential: When a neuron is less willing to fire Table of Contents Exit

Fig. 2.3 The inside of an axon normally has a negative electrical charge. The fluid surrounding an axon is normally positive. As an action potential passes along the axon, these charges reverse, so that the interior of the axon briefly becomes positive. Table of Contents Exit

Fig. 2. 4 Cross-sectional views of an axon Fig. 2.4 Cross-sectional views of an axon. The right end of the top axon is at rest, with a negatively charged interior. An action potential begins when the ion channels open and sodium ions (Na+) enter the axon. In this drawing the action potential would travel rapidly along the axon, from left to right. In the lower axon the action potential has moved to the right. After it passes, potassium ions (K+) flow out of the axon. This quickly renews the negative charge inside the axon, so it can fire again. Sodium ions that enter the axon during an action potential are pumped back out more slowly. Their removal restores the original resting potential. Table of Contents Exit

Animation: Neuron & Neural Impulse Table of Contents Exit

Neurotransmitters Chemicals that alter activity in neurons; brain chemicals Acetylcholine: Activates muscles Dopamine: Muscle control Serotonin: Mood and appetite control Messages from one neuron to another pass over a microscopic gap called a synapse Receptor Site: Areas on the surface of neurons and other cells that are sensitive to neurotransmitters Table of Contents Exit

Animation: Synaptic Transmission Table of Contents Exit

Neural Regulators Neuropeptides: Regulate activity of other neurons Enkephalins: Relieve pain and stress; similar to endorphins Endorphins: Released by pituitary gland; also help to relieve pain Placebos raise endorphin levels Table of Contents Exit

Nerves and Neurons Nerves: Large bundles of axons and dendrites Myelin: Fatty layer that coats some axons Multiple Sclerosis (MS) occurs when myelin layer is destroyed; numbness, weakness, and paralysis occur Neurilemma: Thin layer of cells wrapped around axons outside brain and spinal cord; forms a tunnel that damaged fibers follow as they repair themselves Table of Contents Exit

Neural Networks Central Nervous System (CNS): Brain and spinal cord Peripheral Nervous System: All parts of the nervous system outside of the brain and spinal cord Somatic System: Carries messages to and from skeletal muscles and sense organs; controls voluntary behavior Autonomic System: Serves internal organs and glands; controls automatic functions such as heart rate and blood pressure Table of Contents Exit

Two Divisions of the Autonomic System Sympathetic: Arouses body; emergency system Parasympathetic: Quiets body; most active after an emotional event Table of Contents Exit

Fig. 2. 6 (a) Central and peripheral nervous systems Fig. 2.6 (a) Central and peripheral nervous systems. (b) Spinal nerves, cranial nerves, and the autonomic nervous system. Table of Contents Exit

Fig. 2.7 Subparts of the nervous system. Table of Contents Exit Fig. 2.7 Subparts of the nervous system.

Fig. 2.8 Sympathetic and parasympathetic branches of the autonomic nervous system. Table of Contents Exit

Fig. 2. 9 A simple sensory-motor (reflex) arc Fig. 2.9 A simple sensory-motor (reflex) arc. A simple reflex is set in motion by a stimulus to the skin (or other part of the body). The nerve impulse travels to the spinal cord and then back out to a muscle, which contracts. Reflexes provide an “automatic” protective device for the body. Table of Contents Exit

The Spinal Cord Spinal Nerves: 31 of them; carry sensory and motor messages to and from the spinal cord Cranial Nerves: 12 pairs that leave the brain directly; also work to communicate messages Table of Contents Exit

How is the Spinal Cord Related to Behavior? Reflex Arc: Simplest behavioral pattern; occurs when a stimulus provokes an automatic response Sensory Neuron: Nerve cell that carries messages from the senses toward the CNS Connector Neuron: Nerve cell that links two others Motor Neuron: Cell that carries commands from the CNS to muscles and glands Effector Cells: Cells capable of producing a response Table of Contents Exit

Researching the Brain Ablation: Surgical removal of parts of the brain Deep Lesioning: A thin wire electrode is lowered into a specific area inside the brain; Electrical current is then used to destroy a small amount of brain tissue Electrical Stimulation of the Brain (ESB): When an electrode is used to activate target areas in the brain Electroencephalograph (EEG): Detects, amplifies, and records electrical activity in the brain Table of Contents Exit

Fig. 2.10 The functions of brain structures are explored by selectively activating or removing them. Brain research is often based on electrical stimulation, but chemical stimulation is also used at times. Table of Contents Exit

Fig. 2.11 An EEG recording. Table of Contents Exit

Researching the Brain (cont.) Computed Tomographic Scanning (CT): Computer-enhanced X-ray of the brain or body Magnetic Resonance Imaging (MRI): Uses a strong magnetic field, not an X-ray, to produce an image of the body’s interior Functional MRI: MRI that makes brain activity visible Positron Emission Tomography (PET): Computer-generated color image of brain activity, based on glucose consumption in the brain Table of Contents Exit

Fig. 2.12 An MRI scan of the brain. © Huntington Magnetic Resonance Center, Pasadena, California Fig. 2.12 An MRI scan of the brain. Table of Contents Exit

Fig. 2.13 PET scans. Table of Contents Exit Washington University School of Medicine, St. Louis Fig. 2.13 PET scans. Table of Contents Exit

Washington University School of Medicine, St. Louis Fig. 2.14 The bright spots you see here were created by a PET scan. They are similar to the spots in Figure 2.13. However, here they have been placed over an MRI scan so that the brain’s anatomy is visible. The three bright spots are areas in the left brain related to language. The spot on the right is active during reading. The top-middle area is connected with speech. The area to the left, in the frontal lobe is linked with thinking about a word’s meaning (Montgomery, 1989). Table of Contents Exit

Courtesy of Richard Haier, University of California, Irvine Fig. 2.16 In the images you see here, red, orange, and yellow indicate high consumption of glucose; green, blue, and pink show areas of low glucose use. The PET scan of the brain on the left shows that a man who solved 11 out of 36 reasoning problems burned more glucose than the man on the right, who solved 33. Table of Contents Exit

CNN – Brain Mapping Table of Contents Exit

Cerebral Cortex Definition: Outer layer of the cerebrum; contains 70% of neurons in CNS Cerebrum: Two large hemispheres that cover upper part of the brain Corticalization: Increase in size and wrinkling of the cortex Cerebral Hemispheres: Right and left halves of the cerebrum Corpus Callosum: Bundle of fibers connecting cerebral hemispheres Table of Contents Exit

Split Brains Corpus Callosum is cut; done to control severe epilepsy (seizure disorder) Result: The person now has two brains in one body This operation is rare and is often used as a last resort Table of Contents Exit

Figure 2.17 Corpus Callosum Table of Contents Exit

Fig. 2. 19 Basic nerve pathways of vision Fig. 2.19 Basic nerve pathways of vision. Notice that the left portion of each eye connects only to the left half of the brain; likewise, the right portion of each eye connects to the right brain. When the corpus callosum is cut, a “split brain” results. Then visual information can be directed to one hemisphere or the other by flashing it in the right or left visual field as the person stares straight ahead. Table of Contents Exit

Right Brain/Left Brain About 95 percent of our left brain is used for language Left hemisphere better at math, judging time and rhythm, and coordinating order of complex movements Processes information sequentially and is involved with analysis Right hemisphere good at perceptual skills, and at expressing and detecting other’s emotions Processes information simultaneously and holistically Table of Contents Exit

Fig. 2.20 If a circle is flashed to the left brain and a split-brain patient is asked to say what she or he saw, the circle is easily named. The person can also pick out the circle by touching shapes with the right hand, out of sight under a tabletop (shown semi-transparent in the drawing). However, the left hand will be unable to identify the shape. If a triangle is flashed to the right brain, the person cannot say what was seen (speech is controlled by the left hemisphere). The person will also be unable to identify the correct shape by touch with the right hand. Now, however, the left hand will have no difficulty picking out the hidden triangle. Separate testing of each hemisphere reveals distinct specializations, as listed above. Table of Contents Exit

Central Cortex Lobes Occipital: Back of brain; vision center Parietal: Just above occipital; bodily sensations such as touch, pain, and temperature (somatosensory area) Temporal: Each side of the brain; auditory and language centers Frontal: Movement, sense of smell, higher mental functions Contains motor cortex; controls motor movement Table of Contents Exit

Fig. 2.21 The left and right brain have different information processing styles. The right brain gets the big pattern; the left focuses on small details. Table of Contents Exit

When the Brain Fails to Function Properly Association Cortex: Combine and process information from the five senses Aphasia: Language disturbance resulting from brain damage Broca’s Area: Related to language and speech production If damaged, person knows what s/he wants to say but can’t say the words Wernicke’s Area: Related to language comprehension; in left temporal lobe If damaged, person has problems with meanings of words, NOT pronunciation Table of Contents Exit

When the Brain Fails to Function Properly (cont.) Agnosia: Inability to identify seen objects Facial Agnosia: Inability to perceive familiar faces Table of Contents Exit

Subcortex Immediately below cerebral hemispheres Hindbrain (Brainstem): Consists mainly of medulla and cerebellum Medulla: Controls vital life functions such as heart rate, swallowing, and breathing Pons (Bridge): Acts as a bridge between medulla and other structures Influences sleep and arousal Cerebellum: Located at base of brain Regulates posture, muscle tone, and muscular coordination Table of Contents Exit

Fig. 2.25 This simplified drawing shows the main structures of the human brain and describes some of their most important features. (You can use the color code in the foreground to identify which areas are part of the forebrain, midbrain, and hindbrain.) Table of Contents Exit

Subcortex: Reticular Formation (RF) Reticular Formation: Inside medulla and brainstem Associated with alertness, attention, and some reflexes (breathing, coughing, sneezing, vomiting) Reticular Activating System (RAS): Part of RF that keeps it active and alert RAS acts like the brain’s alarm clock Activates and arouses cerebral cortex Table of Contents Exit

Forebrain Structures are part of Limbic System: System within forebrain closely linked to emotional response and motivating behavior Thalamus: Relays sensory information on the way to the cortex; switchboard Hypothalamus: Regulates emotional behaviors and motives (e.g., sex, hunger, rage, hormone release) Amygdala: Associated with fear responses Hippocampus: Associated with storing permanent memories; helps us navigate through space Table of Contents Exit

Endocrine System Glands that pour chemicals (hormones) directly into the bloodstream or lymph system Pituitary Gland: Regulates growth via growth hormone Too little means person will be smaller than average Hypopituitary Dwarfs: As adults, perfectly proportioned but tiny Treatable by using human or synthetic growth hormone; will add a few inches Treatment is long and expensive Table of Contents Exit

CNN – Thought Control Table of Contents Exit

Fig. 2.26 Parts of the limbic system are shown in this highly simplified drawing. Although only one side is shown, the hippocampus and the amygdala extend out into the temporal lobes at each side of the brain. The limbic system is a sort of “primitive core” of the brain strongly associated with emotion. Table of Contents Exit

Endocrine System (cont.) Too much growth hormone leads to giantism Excessive body growth Acromegaly: Enlargement of arms, hands, feet, and facial bones Caused by too much growth hormone secreted late in growth period Andre the Giant Pituitary also governs functioning of other glands, especially thyroid, adrenals, and gonads Table of Contents Exit

Endocrine System (cont.) Pineal Gland: Regulates body rhythms and sleep cycles. Releases hormone melatonin, which responds to daily variations in light Thyroid: In neck; regulates metabolism Hyperthyroidism: Overactive thyroid; person tends to be thin, tense, excitable, nervous Hypothyroidism: Underactive thyroid; person tends to be inactive, sleepy, slow, obese Table of Contents Exit

The Adrenal Glands Adrenals: Arouse body, regulate salt balance, adjust body to stress, regulate sexual functioning; located on top of kidneys Releases epinephrine and norepinephrine (also known as adrenaline and noradrenaline) Epinephrine arouses body; is associated with fear Norepinephrine arouses body; is linked with anger Table of Contents Exit

The Adrenal Glands (cont.) Adrenal Medulla: Inner core of adrenals; source of epinephrine and norepinephrine Adrenal Cortex: Produces hormones known as corticoids Regulate salt balance Deficiency in some types will cause powerful salt cravings Also help body to adjust to stress Secondary source of sex hormones Oversecretion of adrenal sex hormones can cause virilism: exaggerated male characteristics (Bearded woman) May also cause premature puberty if oversecretion occurs early in life Table of Contents Exit

Neurogenesis and Plasticity Neurogenesis: Production of new brain cells Plasticity: Brain’s ability to change its structure and functions Table of Contents Exit

Fig. 2.31 Neuroscientists are searching for ways to repair damage caused by strokes and other brain injuries. One promising technique involves growing neurons in the laboratory and injecting them into the brain. These immature cells are placed near damaged areas, where they can link up with healthy neurons. The technique has proved successful in animals and is now under study in humans. Table of Contents Exit

Fig. 2.27 A direct brain-computer link may provide a way of communicating for people who are paralyzed and unable to speak. Activity in the patient’s motor cortex is detected by an implanted electrode. The signal is then amplified and transmitted to a nearby computer. By thinking in certain ways, patients can move an on-screen cursor. This allows them to spell out words or select from a list of messages, such as “I am thirsty.” Table of Contents Exit