Transmission of nerve impulse can be recorded with the help of

Parkinson's disease (characterized by tremors and rigidity in limbs) is caused by the degeneration of neurons in the brain that are associated with the secretion and use of which neurotransmitter?

What happens if $GABA$ is released at the synapse?

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

The enzyme required for the conduction of nerve impulses across the synapse is:

True about electrical synapses:
$(I)$. Pre and postsynaptic neurons are in very close proximity.
$(II)$. Pre and postsynaptic neurons are separated by a synaptic cleft.
$(III)$. Impulse transmission is very fast.
$(IV)$. Electrical synapses are common in our system.
Select the correct option.