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Chapter 3

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PSYC 101
Peter Graf

Pscy Chap. 3 Note Types of Cells  Neurons  Nerve cells specialized for communication  100 billion cell with ~160 trillion connections among them  Glial Cells  Support cells in the nervous system  Much smaller than neuron, but 10 times more numerous than neurons  Essential for myelinization of neurons, blood-brain barrier, repair, removal of debris, etc Neurons Nervous Tissue: The Basic Hardware  Neurons - individual cells in the nervous system that receive, integrate, and transmit info.  basic links  mostly communicate btw neurons, sometimes to/from muscle  Parts of Neurons  Soma (Cell body) - contains the cell nucleus and much of the chemical machinery common to most cells (make proteins, replenishes molecules vital to cell function, the engine/factory supporting the neuron)  Dendrites - the parts of a neuron that are specialized to receive info. (receive info.)  Axon - a long, thin fibre that transmits signals away from the soma to other neurons or to muscles or glands. (transmitting portion)  Myelin Sheath - insulating material, derived from glial cells, that encases some axons. (speed up the transmission)  Terminal Buttons - small knobs that secrete chemicals called Neurotransmitters. (messengers)  Synapses - junction where info. is transmitted from one neuron to another. (neurons interconnect)  The information is received at the dendrites, is passed through the soma and along the axon, and is transmitted to the dendrites of other cells at meeting points call synapses. Glial Cells  Glia - cells found throughout the nervous system that provide various types of support for neurons  supply nourishment, remove wastes, provide insulation around axons  transmission and integration of info. signals  send/receive chemical signals  contribute to Alzheimer's disease 1 Pscy Chap. 3 Note Communication in Nervous System Within the Neurons: Using Electricity  Ions - the electrically charged atoms and molecules on both inside and outside of neuron.  The Resting Potential - its stable, negative charge when the cell is inactive.  a tiny battery with a store of potential energy  The Action Potential (a neural message) - very brief shift in a neuron's electrical charge that travels along an axon.  Some time is needed before the next firing  The action potential results in the inside of the cell becomeing positively charged for a brief period  The action potential travels all the way down the axon in an all-or-none manner.  Absolute Refractory Period - the min. length of time after an action potential during which another action potential can not begin  All-or-None Law  All action potentials are equal in size  Stimulus intensity is coded as frequency of action potentials. Between the Neurons : Use Chemicals  Action potentials travel along the axon, and arrive at the terminal buttons  Chemical Messengers (NT) are stored in synatic vesicles  When then action potential reaches the terminal button, vesicles fuse with the pre-synaptic membrane  NT is released into the synaptic cleft, the microscopic gap btw the terminal button of one neuron and the cell membrane of another neuron  NT binds to receptors in a lock-and-key fashion  The activity of the NT is halted via 1) chemical breakdown or 2) reuptake into the pre-synaptic axon terminal  Sending Signals: Chemicals as Couriers  Synaptic Cleft - a microscopic gap btw the terminal button of one neuron and the cell membrane of another neuron.  Presynaptic Neuron - sends a signal across the synaptic cleft  Postsynaptic Neuron - receive a signal across the synaptic cleft  Neurotransmitters - chemicals that transmit info. from one neuron to another  Synaptic Vesicles - small sacs that stored chemicals  Receptor Sites - recognize and respond to specific neurotransmitters.  Receiving Signals: Postsynaptic Potentials  Postsynaptic Potential(PSP) - a voltage change at a receptor site on a postsynaptic cell membrane  No all-or-none law, but graded as size  An action potential begins when stimulation of sufficient intensity disrupts the resting membrane portential 2 Pscy Chap. 3 Note  Excitatory PSP - a positive voltage shift that increases the likelihood that the postsynaptic neuron will fire action potentials  Inhibitory PSP - a negative voltage shift that decreases the likelihood that the postsynaptic neuron will fire action potentials  Reuptake - a process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane.  Integrating Signals: Neural Networks  Synaptic Pruning - elimination of old or less-active synapses  Spatial Summation (summing inputs from different areas of the neuron) - Occurs when two/more postsynaptic potentials occur simultaneously at different receptor sites of the same neuron.  Temporal Summation (summing input occurring at different time) - Occurs when two/more postsynaptic potentials follow one another in rapid succession at a receptor site. Neurotransmitters and Behaviour  Glutamate - most prevalent  Consists of amino acids  Excitatory effect  Required for relaying sensory info, and for learning  Key role in long term potentiation  GABA  Consists of amino acids  Produce only inhibitory postsynaptic potentials (inhibitory effect)  Key role in regulating neuronal excitability throughout the nervous system, is directly responsible to relax muscle (opposite of ACh)  Function: 1. Valium and similar antianxiety drugs  Dopamine(DA)  For which abnormal levels have been implicated in schizophrenia  Function: 1. control of voluntary movement, pleasurable emotions 2. decreased levels associated w Parkinson's 3. Overactivity at DA synapses associated w schizophrenia 4. Cocaine and amphetamines elevate activity at DA synapses  Serotonin  Key role in depression  Function: 1. Regulation of sleep eat, aggression, etc 2. Contribute to depression and obsessive disorder  Acetylcholine(ACh)  Throughout the nervous system  Only transmitter btw motor neurons and voluntary muscles  Agonist - chemical that mimics the action of a neurotransmitter  Antagonist - chemical that opposes the action of a neurotransmitter  Function: 1. Activates motor neurons controlling skeletal muscles 2. Contributes to the regulation of attention, arousal, memory 3. Some ACh receptor stimulated by nicotine  Norepinephrine(NE)  Function: 1. Modulation of mood and arousal 2. Cocaine and amphetamines elevate activity at NE synapses  Endorphins - internally produced chemicals that resemble opiates in structure and effect.  Chemicals that resemble opiate drugs in structure and that are involved in pa
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