[A] : The synaptic knob contains mitochondria and synaptic vesicles rich in chemical transmitters.
[R]: Chemical transmitters are neurohormones. Their release is related to `Ca^(++)` influx.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion:**
- The assertion states that the synaptic knob contains mitochondria and synaptic vesicles rich in chemical transmitters.
- **Explanation:** The synaptic knob is the terminal part of the axon where neurotransmitters are released. It contains synaptic vesicles that store these neurotransmitters, as well as mitochondria that provide the necessary energy for the release process.

2. **Understanding the Reason:**
- The reason states that chemical transmitters are neurohormones and their release is related to calcium ion influx.
- **Explanation:** Neurotransmitters (sometimes referred to as neurohormones) are released from the synaptic vesicles when calcium ions enter the synaptic knob. This influx of calcium is triggered by the arrival of an action potential (nerve impulse) at the synaptic knob.

3. **Evaluating the Truth of the Statements:**
- Both the assertion and the reason are true.
- **Assertion:** True, as synaptic knobs do contain mitochondria and synaptic vesicles filled with neurotransmitters.
- **Reason:** True, as the release of neurotransmitters is indeed dependent on calcium ion influx.

4. **Determining the Relationship:**
- The reason provided is a correct explanation of the assertion.
- **Explanation:** The reason explains how the chemical transmitters are released from the synaptic knob, thereby supporting the assertion about the presence of these transmitters in the synaptic vesicles.

5. **Conclusion:**
- Since both the assertion and reason are true, and the reason correctly explains the assertion, the final answer is that both statements are true and the reason is the correct explanation of the assertion.

**Final Answer:**
Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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