Question

In a synapse, a chemical signal is transmitted from.

• A. Dendritic end of one neuron to axonal end of another neuron
• B. Axon to the cell body of the same neuron
• C. Cell body to axonal end of the same neuron
• D. Axonal end of one neuron to dendritic end of another neuron

Answer 1

The correct option is D

Axonal end of one neuron to dendritic end of another neuron

The correct option is D.

Explanation of the correct option:

Option D:

1. Synapse is an electrical signal that is generated when a neurotransmitter (chemical) released by one neuron into the synaptic cleft reaches the other neuron.
2. The synapse is formed between a presynaptic and postsynaptic neuron at a neuro-muscular junction (between neuron and muscle).
3. The neurotransmitters are released by the axonal end of the presynaptic neuron.
4. The neurotransmitters enter into the synaptic (gap) cleft between the presynaptic and postsynaptic neurons.
5. There are specialized receptors for the neurotransmitters on the dendrites of the postsynaptic neuron.
6. Hence, this leads to the generation of an action potential (electric signal) which is established when a chemical signal is conducted between the axonal end of a presynaptic neuron to the dendritic end of another postsynaptic neuron.
7. This process continues and the synapse is conducted to the successive neuron via an axon terminal of a neuron to dendrites of the next neuron.
8. The signal can be electrical or chemical.

Explanation of the incorrect options:

Option A:

1. The synapse is generated upon the conduction of a chemical neurotransmitter between the axonal end of one neuron (presynaptic) to the dendritic end of the successive (postsynaptic) neuron.
2. Whilst the synapse cannot be conducted in the reverse direction from the dendritic end of one neuron to the axonal end of another neuron.
3. Hence, this is an incorrect option.

Option B:

1. A synapse cannot be conducted in the reverse direction from an axonal end to the cell body of the same neuron.
2. As the dendritic end receives the signal, it then transfers it to the cell body and from there to the axon.
3. The axon secretes neurotransmitters for the postsynaptic neuron.
4. Hence, this is an incorrect option.

Option C:

1. The cell body of a neuron helps in the reciprocation of the generated action potential across the neuron to transfer it to the axonal end of the same neuron so that a new action potential can be generated at the successive neuron.
2. Hence, it is not a synapse when the generated electrical energy is conducted through the cell body to the axon of the same neuron.
3. This is an incorrect option.

Final answer: In a synapse, a chemical signal is transmitted from the Axonal end of one neuron to the dendritic end of another neuron.