Q.Give the broad organisation of the human nervous system, naming its two main divisions and their further sub-divisions.

[!TLDR] Nervous system = CNS (brain + spinal cord) + PNS (cranial + spinal nerves); PNS further divides into the somatic system (voluntary) and the autonomic/visceral system (involuntary, itself sympathetic + parasympathetic). [!ANSWER] CNS (brain, spinal cord) and PNS (cranial nerves, spinal nerves); PNS = somatic + autonomic (sympathetic + parasympathetic).

The human nervous system has two main divisions. The central nervous system (CNS) consists of the brain and the spinal cord and acts as the main integrating centre. The peripheral nervous system (PNS) consists of the cranial nerves (arising from the brain) and the spinal nerves (arising from the spinal cord), and it links the CNS to the rest of the body. The PNS is further sub-divided functionally into the somatic nervous system, which carries voluntary motor commands to skeletal muscle and general sensory information back to the CNS, and the autonomic (visceral) nervous system, which carries involuntary commands to smooth muscle, cardiac muscle and glands; the autonomic system itself has two further sub-divisions, the sympathetic and the parasympathetic. [!ANSWER] CNS (brain + spinal cord) + PNS (cranial + spinal nerves, split into somatic and autonomic, the autonomic further split into sympathetic and parasympathetic).

Build the organisation top-down as a tree: whole nervous system → CNS/PNS → PNS's somatic/autonomic → autonomic's sympathetic/parasympathetic.

Do not place the autonomic nervous system under the CNS — it is a functional division of the PNS, even though its integrating centres (e.g. hypothalamus, medulla) lie within the CNS.