The release of chemical messenger from synaptic vesucles is under the influence of which of these ion (s) ?

Options

A. `Cl^(-)`
B. `Fe^(++) and S^(++)`
C. `Ca^(++)`
D. `Mg^(++) and Sr^(++)`

Answer

To solve the question regarding which ion is responsible for the release of chemical messengers from synaptic vesicles, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Synaptic Vesicles**:
- Synaptic vesicles are small sacs within the presynaptic neuron that contain neurotransmitters, which are chemical messengers.

2. **Role of Calcium Ions**:
- When an electrical impulse (action potential) reaches the presynaptic terminal (or knob), it causes depolarization of the membrane.

3. **Calcium Ion Permeability**:
- The depolarization of the presynaptic membrane increases its permeability to calcium ions (Ca²⁺).

4. **Calcium Influx**:
- Calcium ions flow into the presynaptic neuron through voltage-gated calcium channels due to the concentration gradient.

5. **Triggering Neurotransmitter Release**:
- The influx of calcium ions causes synaptic vesicles to move toward the presynaptic membrane and fuse with it, leading to the release of neurotransmitters into the synaptic cleft.

6. **Conclusion**:
- Therefore, the release of chemical messengers from synaptic vesicles is primarily influenced by calcium ions (Ca²⁺).

### Final Answer:
The correct ion responsible for the release of chemical messengers from synaptic vesicles is **Calcium ions (Ca²⁺)**.

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