Choose the correct statement

Options

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

Answer

To solve the question "Choose the correct statement," we will analyze each of the provided options step by step to identify which statement is correct.

### Step-by-Step Solution:

1. **Evaluate the First Option:**
- **Statement:** Nociceptors respond to changes in pressure.
- **Analysis:** Nociceptors are sensory receptors that specifically respond to pain stimuli, not pressure. Therefore, this statement is incorrect.

2. **Evaluate the Second Option:**
- **Statement:** Meissner corpuscles are thermoreceptors.
- **Analysis:** Meissner corpuscles are actually mechanoreceptors that are sensitive to light touch and are not thermoreceptors. Thus, this statement is also incorrect.

3. **Evaluate the Third Option:**
- **Statement:** Photoreceptors in the human eye are depolarized during darkness and become hyperpolarized in response to the light stimulus.
- **Analysis:** This statement is correct. In the absence of light (darkness), photoreceptors (rods and cones) are depolarized. When light hits them, they hyperpolarize, reducing the release of neurotransmitters. This is a fundamental aspect of how vision works.

4. **Evaluate the Fourth Option:**
- **Statement:** Receptors do not produce graded potential.
- **Analysis:** This statement is incorrect. Receptors do produce graded potentials, which are changes in membrane potential that vary in magnitude. These graded potentials can lead to action potentials if they reach a certain threshold.

### Conclusion:
After evaluating all the options, the correct statement is the third one: **Photoreceptors in the human eye are depolarized during darkness and become hyperpolarized in response to the light stimulus.**