Question

Which one of the following statement explain the depolarisation state of neuron?

• A. Na gets outside through channel
• B. Na gets inside through channel
• C. Channel remain open
• D. All of the above

Answer 1

Answer: (B)

Na gets inside through channel

The nerve membrane when not stimulated is at its resting potential (-90 mv for muscle ). When a stimulus is given of threshold current, an action potential will be formed at the site of stimulus. There will be slow depolarization due to the gradual opening of volt gated Na channel and the slow influx of Na, the potential will go from -90 mv to -65 mv. As soon as -65 mv is reached, it is known as firing level. All voltage-gated Na channels open and Na rushes which takes the potential from -65 to +35 mv, this is known as rapid depolarization. This Na channel remains open for only 0.01 millisecond . Now all K+ gated channels will open and K will rush out, this is called as rapid repolarization. This will take the potential to -65 mv again. Now large of amount of Na has entered in and the large amount of K has gone out, this will operate K -Na pump and again bring the potential to -90 mv.

Hence the answer should be option B.