Which of the following is secreted at the ends of nerve fibres?

Nerve fibres conduct impulses in

In $P$,the membranes of pre-synaptic and post-synaptic neurons are in very close proximity,whereas in $Q$,there is a space between the membranes of pre-synaptic and post-synaptic neurons.
$\quad\quad\quad P\quad\quad\quad Q$

Which of the following substances leads to the inhibition of the central nervous system?

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

What is an electrical synapse?