The chemicals which regulate the synaptic transmission at chemical synapses are called

Options

A. Neurohormones
B. Neurotransmitters
C. Iodothyronines
D. Second messengers

Answer

**Step-by-Step Solution:**

1. **Understanding Synaptic Transmission**: Synaptic transmission occurs at the junction between two neurons, specifically at the chemical synapse. This involves the pre-synaptic membrane (the end of the sending neuron) and the post-synaptic membrane (the beginning of the receiving neuron).

2. **Identifying the Components**: At the synapse, the pre-synaptic neuron contains synaptic knobs that house synaptic vesicles. These vesicles are crucial for the transmission process.

3. **Role of Neurotransmitters**: The synaptic vesicles contain specific chemicals that are released into the synaptic cleft (the space between the two membranes). These chemicals are responsible for transmitting signals from one neuron to another.

4. **Naming the Chemicals**: The chemicals that facilitate this transmission are known as neurotransmitters. They bind to receptors on the post-synaptic membrane, leading to the continuation of the nerve impulse.

5. **Eliminating Other Options**:
- Neurohormones are hormones released by endocrine glands and are not involved in synaptic transmission.
- Idothyronines are hormones produced by the thyroid gland and also do not play a role in synaptic transmission.
- Second messengers are molecules that relay signals received at receptors on the cell surface but are not the primary chemicals involved in synaptic transmission.

6. **Conclusion**: Therefore, the chemicals that regulate synaptic transmission at chemical synapses are called neurotransmitters.

**Final Answer**: Neurotransmitters.

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