Human Neural System

The human neural system is organised into two major divisions:

1. The central neural system (CNS)
2. The peripheral neural system (PNS)

Central neural system (CNS)

The CNS consists of the brain and the spinal cord. It is the command centre of the body — the site where incoming information is processed and from which control over the body's activities is exercised.

Peripheral neural system (PNS)

The PNS is made up of all the nerves of the body that are connected to the CNS (that is, to the brain and spinal cord). The nerve fibres of the PNS are of two kinds, distinguished by the direction in which they carry impulses:

• Afferent (sensory) fibres — carry impulses from the tissues and organs towards the CNS.
• Efferent (motor) fibres — carry regulatory impulses from the CNS out to the concerned peripheral tissues and organs.

Divisions of the PNS

The peripheral neural system is further divided into two divisions according to the type of structures it supplies:

• Somatic neural system — relays impulses from the CNS to the skeletal (voluntary) muscles.
• Autonomic neural system — carries impulses from the CNS to the involuntary organs and the smooth muscles of the body.

The autonomic neural system is itself divided into two parts that usually act in opposition to each other:

• Sympathetic neural system
• Parasympathetic neural system

Visceral nervous system …