Question

Once a neuron is stimulated and the membrane potential is depolarized, the depolarized axonal membrane is helped to return to its resting potential by opening voltage-gated K+ channels, allowing K+ to flow out of the cell down its concentration gradient.
(a) True
(b) False

Answer 1

Answer:

False.

Explanation:

Neuron or nerve cell may be defined as the structural and functional unit of the nervous system. The neurons conduct the nerve impulse and helps in the transmission of signals.

The depolarization of the cell occurs due to the influx of sodium ions into the cell. For the cell membrane to be in resting potential, the potassium ions moves inside the cell from outside the environment and not out of the cell of the organism.

Thus, the correct answer is option (b).

Answer 2

Answer:

Explanation:

The cell membrane separates the cell from the outer environment. The extracellular fluid contains the sodium ions (Na+), chloride ions (Cl-), while intracellular fluid contains potassium (K +) and negative anions.

The potential difference arises when the membrane is selectively permeable to some ions. The resting potential is -70mV.  

When the neurons get excited, the sodium ions start to enter by sodium channels.  

Now there are more positive ions inside the cell membrane. It disturbs the resting potential i.e. -70mV. This stage is known as depolarization.

When the inside environment of the cell is more positively charged, the potassium ions start to move out of the cell. It goes out by the voltage-gated channels. Thus resting stage is maintained and it is known as repolarization.

But the initial stability of the cell membrane has to be maintained. To restore the resting stage, the sodium ions start to move out of the membrane and potassium ions enter into the cells again. This is an active transport and has done by the Na+ - K+ pump. Here 3 sodium ions move out and 2  potassium ions pumped into the cell through the plasma membrane.  

Thus the resting potential regains. The potassium ions come back into the cells against the concentration gradient and ATP provides the energy for this phenomena.