First patient — efferent fibres damaged. Sensation is intact, so the afferent nerve fibres are still transmitting impulses from the tissue to the CNS. But movement is lost, which means the regulatory impulses from the CNS are not reaching the peripheral tissue. Since the movement of the toes is voluntary skeletal-muscle movement, the damage is in the efferent fibres of the somatic neural system.

Second patient — afferent fibres damaged. Movement is intact, so the CNS is successfully sending efferent impulses to the skeletal muscles. But the pinprick is not felt, so impulses are not reaching the CNS from the tissue — the afferent fibres have failed.

The two cases together show why the PNS needs fibres of both types: one direction alone would leave the CNS either blind or powerless.

Advantage of centralisation: in a system with a brain and ganglia, impulses arriving from many different receptors can be brought to a common point, compared, integrated and then acted upon selectively. This allows a single coordinated response to a complex situation, and it allows one part of the body to be moved in relation to another. The vertebrates carry this to the greatest extent, with a well-developed CNS as the site of information processing and control.

Why a nerve net suffices for Hydra: Hydra is radially symmetrical, sessile and has a simple body plan with a small number of response options — essentially contracting, extending and moving tentacles. A stimulus at any point can usefully spread in all directions through the net, because there is no "front" or preferred direction of action to compute. The neural organisation matches the behavioural demand; a brain would confer no advantage the animal could use.

Neural system alone would be insufficient. It provides an organised network of point-to-point connections, so it can only address tissues it is physically wired to, and its effects are brief — lasting as long as the impulses continue. Sustained, body-wide states such as growth, the long-term regulation of metabolism or reproductive cycles cannot be maintained by trains of impulses.

Endocrine system alone would be insufficient. It provides chemical integration through hormones travelling in the blood, which is comparatively slow and diffuse. Withdrawing a hand from a hot object, or adjusting the heart rate the moment exercise begins, demands a response in milliseconds and at a precise address — which hormones cannot deliver.

Conclusion: the two are complementary in speed, duration and precision of address. That is exactly why NCERT states that the neural system and the endocrine system jointly coordinate and integrate all the activities of the organs, so that they function in a synchronised fashion.

Still possible: all voluntary movement. The somatic neural system relays impulses from the CNS to skeletal muscles, so walking, writing, speaking and changing posture would be unaffected. Sensation would also be intact, since afferent fibres are not the target.

Lost or impaired: the transmission of impulses from the CNS to the involuntary organs and smooth muscles of the body. So the regulation of heart rate, the smooth muscle of the gut and blood vessels, glandular secretion and similar functions would no longer be adjustable by the nervous system. Both the sympathetic and the parasympathetic divisions would be affected, since both are subdivisions of the autonomic neural system.

The person would therefore look outwardly normal and be able to move at will, but would lose the automatic internal adjustments — for instance, the heart rate and blood flow could not be raised at the onset of exercise, so exertion would be very poorly tolerated.

The claim is not accurate, though the two are closely related.

The autonomic neural system is defined by the direction and destination of its traffic: it transmits impulses from the CNS to the involuntary organs and smooth muscles, and is classified into sympathetic and parasympathetic divisions.

The visceral nervous system is described as the part of the peripheral nervous system comprising the whole complex of nerves, fibres, ganglia and plexuses by which impulses travel from the CNS to the viscera and from the viscera to the CNS. It therefore explicitly includes the inward-bound (afferent) visceral traffic as well as the outward-bound.

So the visceral nervous system is the broader description — the complete two-way apparatus serving the viscera — whereas the autonomic neural system names the outgoing regulatory division. Treating them as identical would leave the sensory information from the viscera unaccounted for.