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PSY100 ch 3

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Bruce Schneider

Oct/6/2003 CHANAPS Notes From Reading C HAPTER3: THE B IOLOGICALB ASIS OB EHAVIOR I. Communication in the Nervous System A. Nervous Tissue: The Basic Hardware 1. 2 Major Categories for Cells in Nervous System a. Glia – cells found throughout the nervous system that provide structural support and insulations for neurons. Help maintain the chemical environment of the neurons b. Nuerons- the individual cells in the nervous sytem that receive, integrate, and transmit info. Permit communication (mostly within other neurons) – only sensory organs revieve signals from outside the nervous system. 2. Parts of a Neuron: a. Soma (cell body) – contains the nucleus and muc of the chemical machinery common to most cells. b. Rest of neuron dedicated to handling info. c. Dendrites – parts of the neuron that are speacialized to receive info. d. Axon – info travels from dendrites to axon, which are the long thin fiber that transmit signals away from the soma to other neurons or muscles and glands. e. Myelin sheath – many axons wrapped in cells with a high concentration of myelin. Insulating material, from glial cells, that encases some neurons. Speeds up transmissiono of info. i. Multiple Scleroris due to deterioration of myelin sheath. f. Terminal buttons – small knobs that secrete chemicals called neurotransmitters. At end of axons in clusters. g. Synapse – point at which neurons connect. Junction where info is transmitted from one neuron to another. B. The Neural Impulse: Using Energy to Send Information 1. The Nueron at Rest: A Tiny Battery a. Neural impulse is a complex electrochemical raction. b. The resting potential of a neuron is it’s stable, negative charge when the cell is inactive. (Potential Energy of a Nueron). 2. The Action Potential – brief shift in a nueron’s electrical charge that travels along an axon. a. Absolure Refractory Period – the minimum length of time after an action potential during which another action potential can not begin (down time) 3. The All or None Law a. Either the neuron fires or it doesn’t, and its action potentials are always the same. i.e. weaker stimuli don’t produce smaller action potentials. b. However, they can change the rate of action potentials. A stronger stimulus will make for more rapid action potentials in a shorter period of time. C. The Synapse: Where Nuerons Meet 1. Sending Messages: Chemicals as Couriers a. Synaptic Cleft – a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. 1/5 Oct/6/2003 CHANAPS Notes From Reading C HAPTER 3: THEB IOLOGICALB ASIS OFBEHAVIOR b. Presynaptic Neuron – sends the signal, postsynaptic neuron receives the signal. c. Neurotransmitters – chemicals that transmit info from one neuron to another. 2. Receiving Signals: Postsynaptic Potentials a. Postsynaptic Potential (PSP) – a voltage change at a receptor site on a postsynaptic cell membrane. i. Graded – vary in size and increase/decrease the possibility of a neural impulse in the receiving cell in proportion to the amount of voltage change. b. 2 Types of Signals: i. Excitatory PSP is a positive voltage change that increases the likelihood that postsynaptic neuron will fire action potentials. ii. Inhibitory PSP negative voltage change that decreases the likelihood that the postsynaptic neuron will fire action potentials. c. Reuptake – process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane. 3. Integrating Signals: A Balancing Act a. State of a Neuron is the weighted balance between excitatory and inhibitory PSP’s. D. Neurotransmitters and Behavior  Good Table 3.1 – Common Nuerotransmitters and Their functions 1. Acetylcholine (ACh) a. Only transmitter between motor neurons and voluntary muscles. b. Contribute to attention, arousal, memory. c. Agonist – chemical that mimics the action of a neurotransmitter – PRODUCE PSP after binding to receptor sites (i.e. Nicotine). d. Antagonist – opposes the action of a neurotransmitter. Bind to receptor sites but DO NOT PRODUCE PSP, but instead block action of normal neurotransmitter. 2. Monoamines – regulate everday behavior such as voluntary movements (Parkinson Disease). a. Includes 3 nuerotransmitters – dopamine (DA), norepinephrine, and serotonin. b. Serotonin releasing neurons appear to play a role in regulation of sleep and wakefulness. may control aggressive behavior in animals. c. Abnormal levels of monoamines has been linked to psych disorders – depression from lower levels. d. Abnormalties in activity linked to schizophrenia 3. Endorphins – family of internally produced chemicals that resemble opiates (morphine, opium) in structure and effect II. Organization of the Nervous System A. The Peripheral Nervous System  Those nerves that lie outside the brain and spinal cord. 1. Nerves are bundles of neron fibbers (axons) that are routed together in the peripheral nervous system. 2/5 Oct/6/2003 CHANAPS Notes From Reading C HAPTER3: THE B IOLOGICALBASIS OFB EHAVIOR 2. Somatic Nervous System – nerves that connecet to voluntary skeletal muscles and to sensory receptors. (skin, muscles, joints a. Afferent Nerve fibers are axons that carry info INWARD to the central nervous system from the periphery of the body.
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