Choose the correct statement.

Options

A. Photoreceptors in the human eye are depolarised during darkness and become hyperpolarised in response to the light stimulus.
B. Receptors do not produce graded potentials
C. Nociceptors respond to changes in pressure.
D. Meissner's corpuscles are thermoreceptors.

Answer

To solve the question "Choose the correct statement," we will analyze each of the given statements one by one.

### Step-by-Step Solution:

1. **Evaluate Statement 1:**
- The statement claims that photoreceptors in the human eye are depolarized during darkness and become hyperpolarized in response to light stimulus.
- **Analysis:** This is true. In the dark, photoreceptors (rods and cones) are depolarized, allowing for the release of neurotransmitters. When exposed to light, they hyperpolarize, which reduces neurotransmitter release. This is a fundamental aspect of how vision works in different lighting conditions.
- **Conclusion:** Statement 1 is correct.

2. **Evaluate Statement 2:**
- The statement claims that receptors do not produce graded potential.
- **Analysis:** This is false. Receptors do produce graded potentials in response to stimuli. Graded potentials are changes in membrane potential that vary in size and are crucial for sensory transduction.
- **Conclusion:** Statement 2 is incorrect.

3. **Evaluate Statement 3:**
- The statement claims that nociceptors respond to changes in pressure.
- **Analysis:** This is incorrect. Nociceptors are specialized sensory receptors that respond to pain stimuli, such as extreme temperatures, chemical changes, or tissue damage, not specifically to pressure changes.
- **Conclusion:** Statement 3 is incorrect.

4. **Evaluate Statement 4:**
- The statement claims that Meissner's corpuscles are thermoreceptors.
- **Analysis:** This is false. Meissner's corpuscles are mechanoreceptors that respond to light touch and pressure, not temperature changes.
- **Conclusion:** Statement 4 is incorrect.

### Final Conclusion:
After evaluating all four statements, the only correct statement is Statement 1. Therefore, the answer to the question is:

**Answer: A. Photoreceptors in the human eye are depolarized during darkness and become hyperpolarized in response to light stimulus.**