Q. No.| Assertion (A): | Neurons are excitable cells. |
| Reason (R): | Their membranes are in a polarised state. |
In the light of the above statements choose the correct answer from the options given below:
| 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. |
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| 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. |
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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 |
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| 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. |
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| 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. |
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| 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.
| 1. Only I | 2. Only II |
| 3. Both I and II | 4. Neither I nor II |
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. Only I and II are correct | 2. Only I and III are correct |
| 3. Only II and III are correct | 4. I, II and III are correct |
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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 |
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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 |
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