Question

1. Which of the following is true? a.During the polarized state, the inside of the cell...

1. Which of the following is true?

a.During the polarized state, the inside of the cell is positively charged.

b.Depolarization occurs when there is a rapid influx of positively charged ions from outside to inside the cell.

c.Repolarization begins with the removal of sodium from the interior of the cell.

d.During depolarization, sodium enters the cells through the slow channels.

2. How soon can the cell respond to its next electrical stimulus?

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Answer #1

Question 1

Answer - option b

The cell is said to be polarised when there is a negative membrane potential inside the cell.For nerve fibre, it is -90 mV.This is also called the resting membrane potential or the resting state of nerve fibre.During depolarisation,there is sudden influx of sodium ions to the interior.This happens by the activation of voltage gated sodium ion channels.There is a sudden confirmational change in the voltage gated sodium ion channels when the membrane potential become less negative than the resting state.This causes the sudden influx of sodium ions producing depolarization.Repolarisation occurs with the removal of potassium from the interior through the voltage gated potassium ion channels.

Question 2

The period during which a second action potential cannot be initiated even with a strong stimulus is called absolute refractory period.This is 1/2500 of a second for a large myelinated nerve fibre.This is because shortly after the action potential is initiated,there is inactivation of sodium channel gates.Only when the membrane potential reach the resting membrane potential level,these inactivation gates open.Only then another stimulus can initiate an action potential.

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