BIoPsycChp3Outline - Kelly Young 713 65 2341 Psyc 220, Sec....

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Kelly Young 8/29/09 713 65 2341 Psyc 220, Sec. 1, Chp. 3 3.1 I. The Concept of Synapse A. Discoveries 1. Santiago Ramon y Cajal a) Narrow gap separating one neuron from the next 2. Sherrington a) Communication between one neuron and the next differs from communication along a single axon b) Specialized gap – synapse c) neurons were automatically separated from each other B. Properties of Synapse 1. reflexes - automatic 2. reflex arc – circuit from sensory neuron to muscle response a) properties suggesting special processes at junctions btwn neurons: Reflexes are slower than conduction along an axon Several weak produce stronger reflexes than one stimulus When one set of muscles is excited, the other becomes relaxed D. Establishing the existence of synapses 1. speed of a reflex 2. Sherrington’s delayed transmission inference a) a process slowed conduction through reflex occurs where neurons communicate E. Excitatory and Inhibitory synapses 1. EPSP excitatory postsynaptic potential a) Occurs when sodium ions enter the cell b) Contrast to action potential: EPSP decays over time and space; magnitude fades rapidly 2. IPSP inhibitory postsynaptic potential a) The temporary hyperpolarization of a membrane b) occurs when a synaptic input selectively opens the gates for potassium ions to leave the cell Decreases the probability of an action potential This suppresses excitation 3. Relationship btwn EPSP and IPSP a) spontaneous firing rate – periodic production of action potentials even without synaptic input EPSPs > IPSPs (threshold of excitation) = action potential IPSPs > ESPSs = lower basal rate of firing F. Temporal Summation 1. repeated stimuli within a brief time have a cumulative effect a) postsynaptic neuron – cell that receives the message b) presynaptic neuron – neuron that delivers the synaptic transmission 2. If enough excitement occurs rapidly, they combine to exceed threshold of postsynaptic neuron.
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Kelly Young 8/29/09 713 65 2341 Psyc 220, Sec. 1, Chp. 3 3. John Eccles measured change sin the electrical potential across the membrane 4. Action potentials vs. graded potentials a) action - always depolarizations b) graded – can be depolarizations (excitatory) or hyperpolarizations (inhibitory) c) graded depolarization G. Spatial Summation (also from Sherrington’s work with arcs)
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This note was uploaded on 04/27/2010 for the course BIOLOGY/PS 101/220 taught by Professor Hogan/loeb during the Fall '10 term at UNC.

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BIoPsycChp3Outline - Kelly Young 713 65 2341 Psyc 220, Sec....

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