Lecture0908final

Lecture0908final - A neural circuit the basic unit of...

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A neural circuit – the basic unit of function
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1.7 A simple reflex circuit, the knee-jerk response. (Part 2)
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Information is carried long distances encoded by the rate (frequency) of all-or nothing action potentials Stretch of dendrites of sensory neuron Stretch is transduced into an increased action potential frequency within the sensory neuron A.p.’s transmitted along axon to spinal cord, to the synapse at sensory neuron’s axon terminal. Release of NT’s onto spinal motorneuron (extensor) Motorneuron a.p. frequency increases. A.p’s travel along motor neuron axon to synapse onto muscle cells Muscle cell contracts
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Information is carried long distances encoded by the rate of all-or nothing action potentials Higher sensory stimulus strength > higher a.p. frequencies in sensory, motor neuron (extensor) (frequency coding, F.M.) > (eventually) stronger contraction. Maximum rate of 1000 a.p./s. Most cells show a basal “resting” a.p. rate So “Information” can be conveyed be EITHER an increase OR a decrease in a.p. frequency
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Action potentials can be recorded by extracellular electrodes – wires placed just outside neurons, that pick up the currents that circulate around a neuron when it prodices an a.p. .
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Intracellular electrodes may also be used – measure the membrane potential
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Potential changes recorded by intracellular electrodes Depolarization /hyperpolarization = more +ve/more –ve membrane potential
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Potential changes recorded by intracellular electrodes
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This document was uploaded on 10/27/2011 for the course BSCI 453 at Maryland.

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Lecture0908final - A neural circuit the basic unit of...

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