Refrectory period because Na+ Chanel is not active this time.And depolarize stimuli and not new lead action potential during this time and refectory period is 1-2 ms.

Refractory period is a short period during which a nerve is unable to conduct a nerve impulse. It is an important phenomenon that ensures the proper functioning of the nervous system. During this period, the nerve is temporarily unresponsive to additional stimuli, allowing it to recover and prepare for the next impulse.

During the refractory period, the nerve cell membrane undergoes changes in its electrical properties. These changes are caused by the movement of ions across the membrane. The refractory period can be divided into two phases: the absolute refractory period and the relative refractory period.

1. Absolute refractory period:
- This is the initial phase of the refractory period, where the nerve cell membrane is completely unresponsive to any stimulus.
- It occurs due to the inactivation of voltage-gated sodium channels, which are responsible for the depolarization phase of the action potential.
- During this phase, the channels are closed and cannot be reopened, preventing the initiation of another action potential.
- This ensures that nerve impulses travel in one direction and that the nerve cell has time to recover before being stimulated again.

2. Relative refractory period:
- This is the later phase of the refractory period, where the nerve cell membrane is gradually returning to its resting state and can respond to a stronger-than-normal stimulus.
- It occurs as the voltage-gated sodium channels begin to recover from their inactivated state and regain their ability to open.
- However, the membrane potential during this phase is still more negative than the resting potential, making it harder to reach the threshold for generating an action potential.
- If a stimulus is strong enough to overcome this membrane potential, an action potential can be generated.

The refractory period is crucial for regulating the timing and intensity of nerve impulses. It prevents the nerve cell from becoming overexcited and ensures that signals are transmitted in a controlled manner. This is vital for proper functioning of the nervous system and for maintaining the balance of electrical signals throughout the body.