BIO2A03-2011-L22 - Biology 2A03 2011 Lecture 22 Click to...

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Click to edit Master subtitle style 4/13/11 Biology 2A03 - 2011 Lecture 22 Neurophysiology IV
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4/13/11 Absolute refractory Absolute refractory No 2nd AP possible regardless of stimulus In absolute refractory period most of the Na+ channels are open then inactivated and most of the K+ channels start to open In relative refractory more and more Na+ channels are able to be activated and many of the K+ channels start to slowly close Relative refractory Stronger than normal stimulus needed for AP
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4/13/11 Refractory period: important in information coding at the initial segment, because the further above threshold is the G.P., the greater the frequency, until the absolute refractory period is reached. At sensory receptors, the greater the intensity of the stimulus, the greater the G.P., and the greater the frequency, until adaptation occurs. Information is coded as the frequency of A.P.’s Increased stimulus duration Increased stimulus strength Suprathreshold stimuli Time between AP directly related to amplitude of GP Fig. 8-
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4/13/11 Adaptation - a property of all sensory receptors For any constantly applied stimulus, the frequency of A.P.s, and therefore the perception of intensity, gradually declines with time. Very complex - explained by electrochemical (e.g. channel closing), mechanical (e.g. gradual deformation of receptor structure), and sometimes synaptic events. Tonic receptors - adapt very slowly - generally associated with life-critical sensation - e.g. pain receptors, blood gas chemoreceptors. Phasic Receptors
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This note was uploaded on 04/12/2011 for the course BIOL 2A03 taught by Professor Mccelland&dej during the Winter '11 term at McMaster University.

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BIO2A03-2011-L22 - Biology 2A03 2011 Lecture 22 Click to...

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