Which of the following functions is affected when the $abducens$ nerve is injured in humans?

Stimulation of the sympathetic nervous system causes ....

Explain the following processes:
$(a)$ Polarisation of the membrane of a nerve fibre
$(b)$ Depolarisation of the membrane of a nerve fibre
$(c)$ Conduction of a nerve impulse along a nerve fibre
$(d)$ Transmission of a nerve impulse across a chemical synapse

$A$: Postganglionic nerve fibers of the parasympathetic nervous system have acetylcholine,while the sympathetic nervous system has adrenaline (epinephrine) as the neurotransmitter.
$R$: The sympathetic nervous system inhibits intestinal peristalsis,while the parasympathetic nervous system stimulates peristalsis.

Choose the correct option:
$(1)$ The saccule and utricle contain a projecting ridge called the $ \text{crista} / \text{macula} $.
$(2)$ The space between the cornea and the lens is called the $ \text{aqueous chamber} / \text{vitreous chamber} $.

Melanin and Lewy bodies occur in the neurons in case of