Division of nervous system

Nervous system is divided into central and peripheral nervous system.

Brain and spinal cord forms central nervous system (CNS). Brain and spinal cord are continuous at foramen magnum.

Peripheral nerves and ganglia form peripheral nervous system (PNS). PNS has sensory division and motor division. Sensory (afferent) division carries sensory impulses from various parts of the body to the CNS. Whereas, motor (efferent) division brings about the effect, mainly contraction of muscle and secretion of glands. Efferent part is further subdivided into somatic nervous system and autonomic nervous system (ANS). Somatic nerves supply skeletal muscle and makes them contract. ANS supplies cardiac muscle, smooth muscles and glands. It is subdivided into sympathetic and parasympathetic nervous system.

The neural pathways of the sympathetic nervous system orchestrate the flight-or-fight response to stress, while those of the parasympathetic nervous control recovery from this response.

When all powerful central nervous system takes care of every action of the body, what is the need of autonomic nervous system?

ANS is the natures in-built regulatory check for the most essential functions of the nervous system. ANS functions even without interference from the CNS. However, CNS can influence the ANS.

For example, when a person wakes up, gets up from sleeping, stands up from sitting position, ANS modulates the cardiac output to match the increased requirement, without conscious interference from the CNS.

Why division of the nervous system into central and peripheral nervous system is important?

ANS and PNS differ in their anatomy, physiology and pathology. Few diseases preferentially affect CNS or PNS.

Brain has three parts

Parts of CNS	Alternative name	Cavity
Forebrain Divided into Telencephalon Diencephalon	Procencephalon	Lateral ventricle Third ventricle
Midbrain	Mesencephalon	Aqueduct of Sylvius
Hindbrain	Rhombencephalon	Fourth ventricle
Spinal cord		Central canal