Assertion (A): | Neurons are excitable cells. |
Reason (R): | Their membranes are in a polarised state. |
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | (A) is False but (R) is True. |
1. | is comparatively more permeable to sodium ions and nearly impermeable to potassium ions. |
2. | is freely permeable to sodium ions and potassium ions. |
3. | is impermeable to sodium ions and potassium ions. |
4. | is comparatively more permeable to potassium ions and nearly impermeable to sodium ions. |
The resting axonal membrane is impermeable to:
I: Sodium ions
II: Potassium ions
III: Negatively charges proteins present in the axoplasm
1. | I and II only | 2. | I and III only |
3. | II and III only | 4. | I, II and III |
1. | 3 sodium ions outwards and 2 potassium ions into the cell. |
2. | 3 sodium ions into the cells and 2 potassium outwards. |
3. | 2 sodium ions outwards and 3 potassium ions into the cell. |
4. | 2 sodium ions into the cells and 3 potassium ions outwards. |
1. | The outer surface possesses a positive charge while its inner surface becomes negatively charged. |
2. | The outer surface possesses a negative charge while its inner surface becomes positively charged. |
3. | Both the outer and the inner surface are positively charged. |
4. | Both the outer and the inner surface are negatively charged. |
1. Resting potential | 2. Action potential |
3. Threshold potential | 4. Reversal potential |
Identify the correct statements regarding the events A and B in the given diagram:
I: | A is depolarization and is caused by the influx of sodium ions. |
II: | B is repolarization and is caused by the efflux of potassium ions. |
I: | When a stimulus is applied at a site on the polarised axonal membrane, the membrane at that site becomes freely permeable to sodium ions. |
II: | A rapid influx of sodium at this point leads to reversal of polarity and the membrane at the site is said to be depolarised. |
III: | The electric potential difference at the site is called the action potential which is in fact termed as nerve impulse. |
The re-establishment of the resting membrane potential after depolarization is primarily due to:
1. Sodium potassium pump | 2. Influx of sodium |
3. Efflux of potassium | 4. Efflux of sodium |
The change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated, serving to transmit nerve signals is called as:
1. Action potential
2. Threshold potential
3. Reversal potential
4. Excitatory post synaptic potential