The chemical causing the transmission of nerve impulse across synapses is

The parasympathetic nervous system functions through the secretion of which substance?

Parkinson's disease (characterized by tremors and progressive rigidity of limbs) is caused by degeneration of brain neurons that are involved in movement and control. Identify the neurotransmitter responsible for this.

$A$ synapse is formed by

The pre-synaptic part is:

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.