Identify the labelled parts $A, B$ and $C$ from the given diagram.

Suppose the terminal ends of an axon are in contact with the dendrites of four adjacent neurons,the nerve impulse of the axon will

Synaptic vesicles are found in

Arrange the following events in proper sequence during impulse transmission across a chemical synapse:
$(a)$ Fusion of synaptic vesicles with the cell membrane of the presynaptic neuron.
$(b)$ $Ca^{++}$ channels open and $Ca^{++}$ diffuses into the synaptic knob from the extracellular fluid.
$(c)$ Neurotransmitter binds with receptors of the postsynaptic cell.
$(d)$ Release of neurotransmitter by exocytosis.

The synaptic knob possesses:

What is the primary function of acetylcholine?