2 Key Questions How do nerve cells operate and communicate? What are the functions of major parts of the nervous systems?How is the brain organized and what do its higher structure do?Why are the brain’s association areas important? What happens when they are injured?What kinds of behaviors are controlled by the subcortex?Does the glandular system affect behavior?In what ways do right-and left—handed individuals differ?How do biopsychologists study the brain?
3 Neuron and Its PartsNeuron: Individual nerve cell; 100 billion in brainDendrites: Receive messages from other neuronsSoma: Cell body; body of the neuron. Receives messages and sends messages down axonAxon: Carries information away from the cell bodyAxon Terminals: Branches that link the dendrites and somas of other neurons
4 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.
5 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.)
6 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 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.
7 The Nerve ImpulseResting Potential: Electrical charge of an inactive neuronThreshold: Trigger point for a neuron’s firingAction Potential: Nerve impulseIon Channels: Axon membrane has these tiny holes or tunnelsNegative After-Potential: When a neuron is less willing to fire
8 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.
9 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.
11 Synapses and Neurotransmitters Synapse: The microscopic space between two neurons, over with messages passNeurotransmitters: Chemicals that alter activity in neurons; brain chemicalsAcetylcholine: Activates musclesDopamine: Muscle controlSerotonin: Mood and appetite controlMessages from one neuron to another pass over a microscopic gap called a synapseReceptor Site: Areas on the surface of neurons and other cells that are sensitive to neurotransmitters
13 Neural Regulators Neuropeptides: Regulate activity of other neurons Enkephalins: Relieve pain and stress; similar to endorphinsEndorphins: Released by pituitary gland; also help to relieve painPlacebos raise endorphin levels
14 The Nervous System- Wired for Action Nerves and NeuronsNerves: Large bundles of axons and dendritesMyelin: Fatty layer that coats some axonsMultiple Sclerosis (MS) occurs when myelin layer is destroyed; numbness, weakness, and paralysis occurNeurilemma: Thin layer of cells wrapped around axons outside brain and spinal cord; forms a tunnel that damaged fibers follow as they repair themselves
15 Brain Grafts and Nerve Regeneration Transplanting brain tissue
16 The Nervous System Central Nervous System (CNS): Brain and spinal cord Peripheral Nervous System: All parts of the nervous system outside of the brain and spinal cordSomatic System: Carries messages to and from skeletal muscles and sense organs; controls voluntary behaviorAutonomic System: Serves internal organs and glands; controls automatic functions such as heart rate and blood pressure
17 Two Divisions of the Autonomic System Sympathetic: Arouses body; emergency systemParasympathetic: Quiets body; most active after an emotional event
18 Fig. 3-9 (a) Central and peripheral nervous systems Fig. 3-9 (a) Central and peripheral nervous systems. (b) Spinal nerves, cranial nerves, and the autonomic nervous system.
20 Fig. 3-11 Sympathetic and parasympathetic branches of the autonomic nervous system.
21 The Spinal Cord White matter: Areas where myelin is present Spinal Nerves: 31 of them; carry sensory and motor messages to and from the spinal cordCranial Nerves: 12 pairs that leave the brain directly; also work to communicate messages
22 How is the Spinal Cord Related to Behavior? Reflex Arc: Simplest behavioral pattern; occurs when a stimulus provokes an automatic responseSensory Neuron: Nerve cell that carries messages from the senses toward the CNSConnector Neuron: Nerve cell that links two othersMotor Neuron: Cell that carries commands from the CNS to muscles and glandsEffector Cells: Cells capable of producing a response
23 Fig. 3-12 A simple sensory-motor (reflex) arc Fig 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.
24 Courtesy of Richard Haier, University of California, Irvine 3-14 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.
27 Cerebral CortexCerebral Cortex: Outer layer of the cerebrum; contains 70% of neurons in CNSCerebrum: Two large hemispheres that cover upper part of the brainCorticalization: Increase in size and wrinkling of the cortex
28 Split BrainsCerebral Hemispheres: Right and left halves of the cerebrumCorpus Callosum: Bundle of fibers connecting cerebral hemispheresCorpus Callosum is cut; done to control severe epilepsy (seizure disorder)Result: The person now has two brains in one bodyThis operation is rare and is often used as a last resort
30 Fig. 3-16 Basic nerve pathways of vision Fig 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.
31 Right Brain/Left Brain About 95 percent of our left brain is used for languageLeft hemisphere better at math, judging time and rhythm, and coordinating order of complex movementsProcesses information sequentially and is involved with analysisRight hemisphere good at perceptual skills, and at expressing and detecting other’s emotionsProcesses information simultaneously and holistically
32 Fig 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.
34 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 centersFrontal: Movement, sense of smell, higher mental functionsContains motor cortex; controls motor movement
35 The left and right brain have different information processing styles The left and right brain have different information processing styles. The right brain gets the big pattern; the left focuses on small details.
37 When the Brain Fails to Function Properly Association Cortex: Combine and process information from the five sensesAphasia: Language disturbance resulting from brain damageBroca’s Area: Related to language and speech productionIf damaged, person knows what s/he wants to say but can’t say the wordsWernicke’s Area: Related to language comprehension; in left temporal lobeIf damaged, person has problems with meanings of words, NOT pronunciation
38 When the Brain Fails to Function Properly (cont.) Agnosia: Inability to identify seen objectsFacial Agnosia: Inability to perceive familiar faces
41 Hindbrain (Subcortex) Immediately below cerebral hemispheresBrainstem : Consists mainly of medulla and cerebellumMedulla: Controls vital life functions such as heart rate, swallowing, and breathingPons (Bridge): Acts as a bridge between medulla and other structuresInfluences sleep and arousalCerebellum: Located at base of brainRegulates posture, muscle tone, and muscular coordination
43 Fig.3-22 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.)
44 Hindbrain (Subcortex): Reticular Formation (RF) Reticular Formation (RF): Inside medulla and brainstemAssociated with alertness, attention, and some reflexes (breathing, coughing, sneezing, vomiting)Reticular Activating System (RAS): Part of RF that keeps it active and alertRAS acts like the brain’s alarm clockActivates and arouses cerebral cortex
45 ForebrainStructures are part of Limbic System: System within forebrain closely linked to emotional response and motivating behaviorThalamus: Relays sensory information on the way to the cortex; switchboardHypothalamus: Regulates emotional behaviors and motives (e.g., sex, hunger, rage, hormone release)Amygdala: Associated with fear responsesHippocampus: Associated with storing permanent memories; helps us navigate through spaceElectrical stimulation of the brain (ESB): Is the direct electrical stimulation and activation of the brain tissue
46 Fig 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.
47 The Brain in Perspective- Beyond the Biocomputer Endocrine system: Made up of glands that pour chemicals directly into the bloodstream or lymph systemHormones: Chemicals in blood that are carried throughout the body that affect internal activities and behavior.
48 Endocrine SystemGlands that pour chemicals (hormones) directly into the bloodstream or lymph systemPituitary Gland: Master gland that regulates growth via growth hormoneToo little means person will be smaller than averageHypopituitary Dwarfs: As adults, perfectly proportioned but tinyTreatable by using human or synthetic growth hormone; will add a few inchesTreatment is long and expensive
49 Endocrine System (cont.) Too much growth hormone leads to giantismExcessive body growthAcromegaly: Enlargement of arms, hands, feet, and facial bonesCaused by too much growth hormone secreted late in growth periodAndre the GiantPituitary also governs functioning of other glands, especially thyroid, adrenals, and gonads
51 Endocrine System (cont.) Pineal Gland: Regulates body rhythms and sleep cycles.Releases hormone melatonin, which responds to daily variations in lightThyroid: In neck; regulates metabolismHyperthyroidism: Overactive thyroid; person tends to be thin, tense, excitable, nervousHypothyroidism: Underactive thyroid; person tends to be inactive, sleepy, slow, obese
52 The Adrenal GlandsAdrenals: Arouse body, regulate salt balance, adjust body to stress, regulate sexual functioning; located on top of kidneysReleases epinephrine and norepinephrine (also known as adrenaline and noradrenaline)Epinephrine arouses body; is associated with fearNorepinephrine arouses body; is linked with anger
53 The Adrenal Glands (cont.) Adrenal Medulla: Inner core of adrenals; source of epinephrine and norepinephrineAdrenal Cortex: Produces hormones known as corticoidsRegulate salt balanceDeficiency in some types will cause powerful salt cravingsAlso help body to adjust to stressSecondary source of sex hormonesOversecretion of adrenal sex hormones can cause virilism: exaggerated male characteristics (Bearded woman)May also cause premature puberty if oversecretion occurs early in life
54 RedundancyRedundancy: duplication of the brains functions in multiple brain structures, increases complexity of the brain, how a child can overcome brain damage and function have “normal” functioning brainDozens of brain areas do what one could manage alone
55 PlasticityPlasticity: Brain’s ability to change its structure and functions, flexibility of the brains organizationBased on increased branching of dendrites in young age if brain damage occurs (ages birth to 5 best)chances decrease after age 10
56 Homework Quiz #5, take home Grade 41-70 Diagnostic AP test Read page 66, write one paragraph summaryon “His & Her Brain”Read pages 75-78, write 2 paragraph summary on“Handedness”Define Follwing termsEBS, pg 70use pgs for all below, or online power Chapter 3 point found on Bird websiteCT Scan,MRIEEGMANSCANPET ScanMEG Scan
57 Fig 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.
58 Fig 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.”
59 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 tissueElectrical Stimulation of the Brain (ESB): When an electrode is used to activate target areas in the brainElectroencephalograph (EEG): Detects, amplifies, and records electrical activity in the brain
60 Researching the Brain (cont.) Computed Tomographic Scanning (CT): Computer-enhanced X-ray of the brain or bodyMagnetic Resonance Imaging (MRI): Uses a strong magnetic field, not an X-ray, to produce an image of the body’s interiorFunctional MRI: MRI that makes brain activity visiblePositron Emission Tomography (PET): Computer-generated color image of brain activity, based on glucose consumption in the brain
62 Washington University School of Medicine, St. Louis PET scans.
63 Washington University School of Medicine, St. Louis The bright spots you see here were created by a PET scan. 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).
64 Fig 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.