Question

Depolarisation of nerve impulse involves:
A. Entry of \[N{{a}^{+}}\]only.
B. Entry of ${{K}^{+}}$only
C. Entry of $N{{a}^{+}}$and exit of ${{K}^{+}}$
D. Entry of ${{K}^{+}}$ and exit of $N{{a}^{+}}$

Answer 1

Hint: Transmission of nerve impulses depends on the depolarisation of nerve cells. When specific positively charged ions enter the neuron membrane, it depolarises.

Complete Step by Step Answer:
Point-to-point connections are possible in the highly organised network of the brain system, allowing for fast coordination. Animals have a neurological system made up of cells with a high degree of specialisation that can sense, receive, and transmit different sorts of stimulus. They are referred to as neurons. To guarantee that the correct impulse travels along the path, each neuron must pass the impulse on to the following neuron after receiving it. An impulse is picked up by the dendrites by a sequence of chemical reactions, which are then sent through the axon to the following cell.

The nerve fibre is in a resting stage when no impulse is present to activate it. When a neuron is at rest, or not conducting any impulses, the concentration of potassium ${{K}^{+}}$ ions is greater inside the axoplasm, but the concentration of sodium $N{{a}^{+}}$ions is greater outside the axoplasm. As a result, potassium ions move from the inside to the outside more quickly than sodium ions. The membrane then has a positive charge on the outside and a negative charge within. This is referred to as polarised nerve or membrane polarisation.

The polarised membrane becomes free-permeable to $N{{a}^{+}}$ as a stimulus is applied. As a result, there is an abrupt release of $N{{a}^{+}}$ and its entry takes place whiles the exit of${{K}^{+}}$and that leads to the polarity reversal at that location. The membrane's inner surface acquires a positive charge, while the outside surface acquires a negative charge. Thus, the membrane polarity is reversed, leading to depolarisation.

Hence, the correct options is C. Entry of $N{{a}^{+}}$and exit of ${{K}^{+}}$

Note: The synapses, which connect two neurons, are the points at which a nerve impulse is passed. A synapse is made up of the membranes of a presynaptic neuron and a postsynaptic neuron.