Signal transmission at a typical synapse in a neural network is a –

A synapse is the junction where one neuron communicates with the next, and this junction is classified into two general types: an electrical synapse, where ionic current passes directly between the two cells through gap-junction channels, and a chemical synapse, where a chemical messenger (a neurotransmitter) is released by one neuron, diffuses across a narrow gap, and binds receptors on the neighbouring neuron to regenerate the signal. The vast majority of synapses in the vertebrate nervous system are of the chemical type; electrical synapses are the much rarer exception.

The introductory biological-neuron model taught alongside Artificial Neural Networks — and the "typical synapse" this question refers to — is the standard, chemical-type synapse: the presynaptic terminal releases neurotransmitter molecules that diffuse across the synaptic cleft and bind postsynaptic receptors, regenerating an electrical impulse in the receiving neuron. This is why the syllabus for ANN (and this UPPSC Computer Science paper) tests the biological neuron before introducing the artificial one — the artificial neuron's weighted inputs are a simplified stand-in for how a real neuron receives many such synaptic inputs of varying strength.

• Physical Process and Chemical Process both — a given synapse is classified as electrical or chemical, not both operating together at the same junction; the typical synapse this question refers to uses only the chemical route.

• Physical Process — this names the electrical (gap-junction) mechanism found at the rarer, non-typical synapse type; the typical synapse this question refers to crosses the gap chemically, not electrically.

• None of the above — the typical synapse's crossing mechanism is well-described as chemical, one of the given categories, so ruling out every listed description misses that match.