A synapse is formed by

Options

A. Pre-synaptic membrane
B. Post -synaptic membrane
C. Synaptic cleft
D. All of these

Answer

### Step-by-Step Solution:

1. **Definition of Synapse**: A synapse is a junction between two neurons where communication occurs. It is the site where one neuron transmits a signal to another neuron.

2. **Components of a Synapse**:
- **Pre-synaptic Neuron**: This is the neuron that sends the signal. It contains synaptic vesicles filled with neurotransmitters.
- **Post-synaptic Neuron**: This is the neuron that receives the signal. It has receptors on its membrane to detect the neurotransmitters released by the pre-synaptic neuron.
- **Synaptic Cleft**: This is the small gap between the pre-synaptic and post-synaptic neurons. It is where neurotransmitters are released and diffuse to bind to receptors on the post-synaptic neuron.

3. **Formation of a Synapse**:
- The pre-synaptic neuron releases neurotransmitters into the synaptic cleft when an action potential reaches its terminal.
- These neurotransmitters then cross the synaptic cleft and bind to specific receptors on the post-synaptic neuron.
- This binding can lead to the generation of a new action potential in the post-synaptic neuron, thus continuing the transmission of the signal.

4. **Summary of Requirements**:
- A pre-synaptic neuron that contains neurotransmitters.
- A post-synaptic neuron with receptors for those neurotransmitters.
- A synaptic cleft that separates the two neurons.