Correct Option
The correct option is 1 and 3 only.
Explanation
A synapse is a functional junction between two neurons that allows the transmission of nerve impulses. Synapses are broadly classified into two types based on the mechanism of transmission: electrical synapses and chemical synapses.
Statement-wise Analysis
- Statement 1 is Correct: Electrical synapses allow the direct flow of electric current from one neuron to another through gap junctions. This mode of transmission is significantly faster than chemical synapses, which require the release, diffusion, and binding of neurotransmitters across a gap.
- Statement 2 is Incorrect: In a chemical synapse, the membranes of the pre-synaptic and post-synaptic neurons are separated by a fluid-filled space called the synaptic cleft. It is in electrical synapses that the membranes of the pre- and post-synaptic neurons are in very close proximity (closely apposed).
- Statement 3 is Correct: While electrical synapses are found in the human body (e.g., in cardiac muscle fibers and certain parts of the brain), they are rare compared to chemical synapses. Chemical synapses are the predominant mode of signal transmission in the human nervous system as they allow for complex regulation and unidirectional flow.
Key Takeaway
Electrical synapses are faster and involve direct physical connection via gap junctions, whereas chemical synapses involve a synaptic cleft and rely on neurotransmitters for signal transmission.