Question

Question 17 3 pts Neurons cells are found in the nervous system and provide direct protection and physical support to the neurons. One protein made by these cells is myelin that is essential in neurological function as seen in epilepsy where the degeneration of the protein is observed and patients experience neurological symptoms. J Oection 10 Ante

Answer 1

15) Sodium- Potassium pump. It is a carrier protein that is present on the surface of neuronal cells.It is responsible for generating and maintaining the resting potential of the cell.

Stage 1 -resting potential

the cell surface membrane of a nerve cell is negative from inside and called as polarised.

the potential difference between the membranes when the cell is at rest is resting potential(-70mV) .

this membrane potential is maintained by active transport and passive diffusion of ions. usually the axoplasm has more K⁺ than Na+ ions.and the fuid outside is vice versa. The Na+/ K+ pump works along with coupled ATP to allow 3 Na+ ions to go out and 2 K+ ions to get inside.

Similarly the active movement is opposed by passive diffusion of ions under the electrochemical gradient. Since K+ ions have 20 times more membrane permeability than Na+ ions there will be rapid loss of K+ from the axoplasm creating a high net negative charge inside the axonal membrane.

Stage 2- Action potential

The potential inside the axon changes from -70mV to +40mV due to an infux of Na + ions into the axoplasm.This sudden change causes depolarisation. A stimulus causes the Na+ channels to open and K+ too will open and K+ moves out. So now the membrane potential loses its positive charge and regains its original resting potential.This is called repolarisation. As the peak of action potential approaches the Na+ channels start to close again and it is acheived quickly. But this time there will be an overshoot in negative potential due to delayed K+ channels closing. This is called hyperpolarisation.

Hence the sodium potassium pump is a unique channel that preferentially controls the movement of ions according to the stimulus received across the neurons to deliver the signal.