Transcript Chapter 2
Chapter 3 Biopsychology and the Foundations of Neuroscience Copyright © Allyn & Bacon 2007 The Structure of a Neuron Soma (Cell Body): Contains the nucleus, which includes the chromosomes Axon: Extended fiber that conducts information from the soma to the terminal buttons; information travels along this in the form of an electric charge called the action potential. Axon Terminal/Buttons: Tiny bubble-like structures at the end of the axon which contain neurotransmitters that carry the neuron’s message into the synapse. Synaptic Vesicles: Small containers holding neurotransmitters that connect to the presynaptic membrane, releasing the neurotransmitter into the synapse. Myelin Sheath: Insulating covering of the axon for neurons; facilitates the electrical impulse and protects the neuron. Dendrites: Branched fibers that carry information into the neuron and extend outward from the main cell body. Neurotransmitters: Chemical messengers that relay neural messages across the synapse The Neuron Specialized cell that responds to and sends signals • Sensory neurons: carry messages from sense receptors towards the CNS (afferent – approach CNS) • Motor neurons: carry messages from CNS toward muscles and glands (efferent – exit CNS) • Interneurons: carry messages between nerve cells The Neural Impulse Resting potential: Electrical charge of a neuron when it is ready to fire; it’s inactive state (-70mv) (+) potassium inside; (+) sodium outside; sodium wants in! Action potential: Nerve impulse caused by a reversal in the electrical charge across the axon (- to +) Depolarization: sodium gates open; let sodium (+) in Repolarization: sodium gates close, potassium gates open and let potassium (+) out; potassium gates close when charge is leveled (back to -) Refractory period: time period in which the neuron cannot reach its action potential; repolarizing to return to its resting potential (polarized) The Neural Impulse All-or-none principle: Action potential occurs full blown or not at all; must cross threshold (minimum level of stimulation needed) Synapse: Communication link between neurons Impulses only move in one direction!!! Happens in the synaptic gap b/w terminal buttons of one neuron and dendrites of another neuron Synaptic transmission: relaying of info across the synapse by means of neurotransmitters Plasticity and Glial Cells Plasticity: Ability of the nervous system to adapt or change as the result of experience Helps the nervous system adapt to physical damage Restructured/programmed by experience Neurons make new connections Example - sprout new dendrites Glial cells Provide structural support for neurons Help in forming new synapses Form myelin sheath Clean up dead cells Neurotransmitters Neurotransmitters: Chemical messengers that relay neural messages across the synapse Diffuse across synapse & connect like lock and key Agonist: drug/chemical that enhances or mimics the effects of NTs – facilitates messages; turns up volume Antagonist: drug/chemical that inhibits the effects of NTs – blocks receptor sites; turns down volume Reuptake: recycling of NT back into the presynaptic neuron Turns message volume down SSRI – inhibits reuptake, so turns up volume of serotonin Reuptake in the Synapse Neurotransmitters Dopamine: pleasure and reward, voluntary movement; Schizophrenia & Parkinson’s Serotonin: sleep, dreaming, mood, pain, aggression, appetite, sexual behavior; depression Norepinephrine: heart rate, sexual responses, stress Acetylcholine: learning, memory, motor movement; Alzheimer’s & muscular disorders Endorphins: pleasure, pain control; lower levels from opiate addiction Neurotransmitters GABA: inhibitory; anxiety & epilepsy Glutamate: excitatory, learning, memory; brain damage after a stroke Two forms: Excitatory – more likely for the next neuron to fire Inhibitory – less likely for the next neuron to fire The Organization of the Nervous System Nervous system Peripheral nervous system Autonomic nervous system Sympathetic nervous system Central nervous system (CNS) Somatic nervous system Parasympathetic nervous system The Endocrine System The body’s chemical messenger system The Endocrine System Pituitary gland : Master gland Produces hormones influencing the secretions of all other endocrine glands Produces hormones that influences growth Attached to hypothalamus How Does the Brain Produce Behavior and Mental Processes? The brain is composed of many specialized modules that work together to create mind and behavior. Three Layers of the Brain Hindbrain – vital functions Heart rate, breathing, digestion Brain stem (medulla, reticular formation) pons, cerebellum Midbrain Portion of the brain stem that connects the hindbrain and the forebrain Three Layers of the Brain Forebrain – very highly developed part Limbic system – regulates emotions, motives, memory (amygdala, hippocampus) Also included: Hypothalamus, thalamus Cerebrum (top of forebrain) Reasoning, planning, creating, problem solving Cerebral cortex Important Structures Thalamus Pons Cerebellum Medulla Brain stem Reticular Formation Important Structures Hypothalamus – Serves as the brain’s bloodtesting laboratory, constantly monitors blood to determine the condition of the body The Limbic System Amygdala – Involved in memory and emotion, particularly fear and aggression The Limbic System Hippocampus – Involved in establishing long-term memories Four Lobes of the Cerebral Cortex Frontal lobes (AKA pre-frontal cortex): planning, deciding, thinking, motor cortex, personality? Parietal lobes: touch sensation, spatial relationships, somatosensory cortex Occipital lobes: contain visual cortex Temporal lobes: sounds, including speech, auditory cortex; memory, speech production • Gyri and Sulci: ridges and valleys that divide the cortex into the lobes The Cooperative Brain Association cortex: Cortical regions that combine information from various other parts of the brain Deciding what to do when your phone rings in class Contralaterality: control of one side of your body by the other side of your brain Cerebral dominance: Tendency of each brain hemisphere to exert control over different functions Specialization of the Cerebral Hemispheres Left Hemisphere Right Hemisphere • Spontaneous speaking and writing • Responses to complex commands • Word rec./ speech • Memory for words and numbers • Sequences of movements • Feelings of anxiety • Positive emotion • Repetitive but not spontaneous speaking • Responses to simple commands • Facial recognition • Memory for shapes and music • Spatial interpretation • Emotional responsiveness • Negative emotion Windows on the Brain Brain waves: Patterns of electrical activity generated by the brain EEG (electroencephalograph): Records brain waves; electrodes placed on scalp Windows on the Brain Brain scans: Recordings of the brain’s electrical or biochemical activity at specific sites CAT/CT (computerized tomography) – soft tissue, structure, x-ray PET (positron emission tomography) – activity, not structure, detects glucose in active circuits fMRI (magnetic resonance imaging) – moving pic. of brain in action Aphasia The impairment of language (speech or understanding) Broca’s Area – interferes w/ speech production (frontal lobe damage) can understand language words not properly formed speech is slow and slurred some aware of deficits Wernicke’s Area – loss of ability to understand language (parietal/temporal) can speak clearly most of the time words put together make no sense; word salads not aware of deficits The Split Brain Split-brain patients: Individuals who have had the corpus callosum surgically severed; usually epileptic Duality of consciousness: Condition in which a splitbrain patient has a separate consciousness in each hemisphere