In the parasympathetic nervous system,which of the following is released?

What is responsible for the unidirectional transmission of nerve impulses in a neuron?

Electrical synapse shows following features $EXCEPT$ . . . . . . .

Assertion : Transmission of nerve impulse across a synapse is accomplished by neurotransmitters.
Reason : Transmission across a synapse usually requires neurotransmitters because there is a small space,i.e.,synaptic cleft,that separates one neuron from another.

$A$ : Transmission of the nerve impulse across a synapse is accomplished by neurotransmitters.
$R$ : Transmission across a synapse usually requires neurotransmitters because there is a small space,$i.e.$,synaptic cleft,that separates one neuron from another.

The venom of a cobra affects the $........$ system.