Question

During refractory period
A) Nerve transmits impulse very slowly
B) Nerve cannot transmit impulse
C) Nerve transmits impulse very rapidly
D) None of the above

Answer 1

The term refractory period is defined as the time during which a particular cell or organ cannot repeat a particular function that it is known to perform such as action potential in case of nervous system.

Complete answer:
Refractory period can be of two types- absolute refractory period and relative refractory period. The absolute refractory period is mostly similar in time to the entire action potential in case of neurons. It is caused by the inactivation of the Na+ channels that normally open during the polarization of the nerve membrane. These channels continue to be inactivated unless hyperpolarization takes place following which they close and can then respond to another stimulus. The relative refractory period is the one that follows the absolute one. The K+ channels open to depolarize the membrane during this period the potassium ions also move out of the membrane due to increased permeability leading to hyperpolarization. This is followed by returning of the membrane to its normal resting potential that also marks the end of the relative refractory period.

So the correct answer is option (B) Nerve cannot transmit impulse.

Note: Thus the refractory period produces a time lag between two action potentials. Unless the membrane comes back to its original resting state it cannot be excited with another stimulus. Thus it helps in limiting the rate at which action potentials are generated and also plays a role in the unidirectional propagation of action potential through a particular axon.