The action potential of a nerve cell is approximately:

The rate of rise of action potential and its amplitude are determined by the concentration of

For the maintenance of ionic gradients across the resting membrane,the sodium-potassium pump transports:

Give scientific reasons:
$(1)$ In an excited nerve fibre region,a positive charge is created inside the plasma membrane.
$(2)$ In some animals,the conduction of nerve impulses is saltatory.

During the transmission of a nerve impulse through a nerve fibre,the potential on the inner side of the plasma membrane has which type of electric change?

Give scientific reasons:
$(1)$ There is no physical connection between sequential neurons,yet nerve impulses are conducted through them.
$(2)$ The neuroplasm of a neuron contains a high $K^+$ concentration during the maintenance of the resting potential.