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 |
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. |
1. | Cerebrum | 2. | Thalamus |
3. | Hypothalamus | 4. | Cerebellum |
I: | The cerebral cortex, referred to as the grey matter, is thrown into prominent folds. |
II: | The cerebral white mater contains motor areas, and association area. |
1. Both are correct | 2. Both are incorrect |
3. Only I is correct | 4. Only II is correct |
I: | The association areas of the cerebral cortex are neither clearly sensory nor motor in function. |
II: | The association areas are responsible for complex functions like intersensory associations, memory and communication. |
1. | Both are correct | 2. | Both are incorrect |
3. | Only I is correct | 4. | Only II is correct |