Receptor sites for neurotransmitters are present on

Options

A. Membranes of synaptic vesicles
B. Pre-synaptic membrane
C. Tips of axons
D. Post-synaptic membrane

Answer

To answer the question "Receptor sites for neurotransmitters are present on?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Neurotransmitters**:
- Neurotransmitters are chemical substances that transmit signals from one neuron to another. They play a crucial role in communication within the nervous system.

2. **Identify the Role of Neurons**:
- Neurons consist of a presynaptic neuron (the sending neuron) and a postsynaptic neuron (the receiving neuron). The presynaptic neuron releases neurotransmitters into the synaptic cleft.

3. **Recognize the Synaptic Structure**:
- The synaptic cleft is the small gap between the presynaptic and postsynaptic neurons where neurotransmitters are released and received.

4. **Determine Where Receptor Sites Are Located**:
- Receptor sites for neurotransmitters are located on the postsynaptic membrane of the receiving neuron. This is where neurotransmitters bind to initiate a response in the postsynaptic neuron.

5. **Evaluate the Options**:
- Option 1: Presynaptic membrane - This is where neurotransmitters are released, not where they bind.
- Option 2: Synaptic cleft - This is the space between neurons, not where receptors are located.
- Option 3: Postsynaptic membrane - This is where receptor sites for neurotransmitters are found.
- Option 4: I channel - This is not a relevant term in this context.

6. **Select the Correct Answer**:
- Based on the analysis, the correct answer is **Option 3: Postsynaptic membrane**.

### Final Answer:
Receptor sites for neurotransmitters are present on the **postsynaptic membrane**.

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