I\'m so tired no matter how much I read I still cant figure it out help!!! Actio

Question

I'm so tired no matter how much I read I still cant figure it out help!!!

Action potentials 70 mV IMP Stimuli singe, quck thoks HRESHOLDSTMuim level of depolarization, "threshold" before an AP is generated depolarization - A stimulus must reach a minimum cannot generate an AP A stimulus less than threshold "subthreshold" - Any stimulus greater than threshold will generate an AP to the all-or-none principle of APs, the frequency with which a neuron can cannot sum because the absolute refractory periods prevent any overlap REFRACTORY PERIOD contribute AP and the 1-way (unidirectional) propagation of APs along the axon generate an Unlike graded potentials APs hoctorA Membrane cannot produce another AP because Na+ channels are nactivated occurs when voltage-gated K+ channels are open, making it harder to depolarize to threshold Refractory periods are also important in the coding of information that arrives in the form of an AP Information regarding the stimulus intensity is encoded by changes in the frequency of APs Absolute Relative refractory refractory period period due to inactivated (due to continued outward dillusion 30Na channels) k -55 70 Time imilliseconds) CODING OF STIMULUS INTENSITY Increased stimulus intensity causes more APs to be fired-

Explanation / Answer

The refractory period in simple words prevents any backwards travel of the action potential.Refractory period is of two types.Absolute and Relative refractory period. In the absolute refractory period,the membrane fails to generate another action potential irrespective of the fact that how large the stimulus is. This is mainly due to the reason that voltage-gated sodium ion channels become inactivated during this period.On the other hand,in the the relative refractory period if the stimulus is very large than the niormal stimulus,then the membrane can produce another action potential.This is mainly due to the fact that some of the the voltage-gated sodium ion channels become recovered and the voltage-gated potassium ion channels are remain open.The relative refractory period depicts the hyperpolarization period that occurs after an action potential.

So,

Absolute refractory period:Membrane cannot produce another AP because Na channels are inactivated.

Hyperpolarisation:occurs when voltage gated K + channels are open,making it harder to depolarise to threshold.

Coding of stimulus intensity:Stimulus intensity is always coded depending on the number of impulses per second ,also known as frequency of APs and not the amplitude increase of the individual AP.

So,

Increased stimulus intensity causes more APs to be fired = Frequency coding /spike firing increases.

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