You are watching a horror movie and you notice that your heart is beating fast and mouth is dry. This is due to:

Given below is a table comparing the effects of sympathetic and parasympathetic nervous system for four features. Which one feature is correctly described?

Explain the following:
$(a)$ Role of $Na ^{+}$ in the generation of action potential
$(b)$ Mechanism of generation of light-induced impulse in the retina.
$(c)$ Mechanism through which a sound produces a nerve impulse in the inner ear.

Read the following statements:
$(A)$ The neural system provides an organized network for point-to-point connections.
$(B)$ The endocrine system provides chemical integration through hormones.
$(C)$ The neural system is very simple in lower invertebrates.
$(D)$ Neurons can detect and receive stimuli but cannot conduct them.
How many of the above statements are incorrect?

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

Where is postganglionic sympathetic cholinergic innervation found?