To start the conduction of an impulse,the value of the action potential must not be

Which of these processes occur during repolarisation of nerve fibre?
$(I)$. Open $Na^+$ channel
$(II)$. Closed $Na^+$ channel
$(III)$. Closed $K^+$ channel
$(IV)$. Open $K^+$ channel

Which of the following statements is/are correct?
$(a)$ The electrical potential difference across the resting plasma membrane is called the resting potential.
$(b)$ $Na^+$ ions are responsible for the generation of an action potential.
$(c)$ $A$ nerve impulse is an action potential.

The jumping of action potential from node to node (of $Ranvier$) in a nerve fibre is called:

During the conduction of a nerve impulse, electrical energy is generated. What is the source of this energy?

When a neuron is in a resting state,i.e.,not conducting any impulse,the axonal membrane is: