Correct Option
The correct option is Both A and R are true and R is the correct explanation of A
Explanation
A synapse is a junction between two neurons that facilitates the transmission of nerve impulses. Synapses are classified into two types: electrical synapses and chemical synapses. The mechanism of transmission differs significantly between the two based on the physical arrangement of the neurons.
Statement-wise Analysis
- Assertion (A): Correct. In an electrical synapse, the transmission of an impulse is essentially the flow of electric current from one neuron to another. This process does not involve a delay caused by the release and binding of neurotransmitters (as seen in chemical synapses). Consequently, the mechanism of impulse transmission across an electrical synapse is physically and functionally very similar to the conduction of an electrical impulse along a single axon.
- Reason (R): Correct. The defining characteristic of electrical synapses is that the membranes of the pre-synaptic and post-synaptic neurons are in extremely close proximity (separated by gap junctions). These gap junctions form protein channels (connexons) that physically connect the cytoplasm of adjacent neurons, allowing ions and electrical current to flow directly from one cell to the next.
- Causal Link: The reason the transmission is similar to conduction along a single axon (Assertion) is precisely because the membranes are in such close proximity and connected by gap junctions, allowing direct current flow (Reason). Therefore, R is the correct explanation for A.
Key Takeaway
Electrical synapses allow for faster, often bidirectional transmission of impulses compared to chemical synapses because they utilize gap junctions to permit direct ionic current flow between neurons.