Organisation/Overview of the Nervous System

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Organisation/Overview of the Nervous System (NS)

Two types of cells make up the nervous system (neurons and glia). For convenience, understanding and teaching (pedagogy), the nervous system is divided into a number of divisions:

Central nervous system (CNS):
• consists of the brain and spinal cord – those parts that are inside the osseous casings of the skull (cranium) and spinal cord (vertebral column); the spina; cord and brain are continuous at the foramen magnum
• functions as a control and integration centre that interprets incoming information and sending out responses

Peripheral nervous system (PNS):
• that part of the nervous that is outside the osseous casings of the skull and spinal cord
• consists of the cranial and spinal nerves
• functions as the communication system between the CNS and all parts of the body
• has two functional subdivisions – sensory (afferent) and motor (efferent)

For most body functions, the division into the CNS and PNS is artificial, as they are one continuous tissue tract.

Sensory/Afferent division:
• afferent = carrying forward
• consists of somatic and visceral nerve fibres
• functions to conduct impulses from receptors to the CNS
• somatic afferents are fibres that carrying impulses from skin, skeletal muscles and joints
• visceral afferents carry impulses from the visceral organs

Motor/Efferent division:
• efferent = carrying away
• consists of motor nerve fibres
• functions to conduct impulses from the CNS to the effector organs, muscles and glands
• divided into somatic nervous system and autonomic nervous system

Somatic (voluntary) nervous system:
• consists of voluntary/somatic motor fibres
• functions to conduct impulses from the CNS to skeletal muscles

Autonomic (involuntary) nervous system (ANS):
• consists of involuntary visceral and motor fibres  controls a variety of bodily functions
• functions to conducts impulses from the CNS to cardiac muscles, smooth muscles and glands
• divided into sympathetic and parasympathetic divisions

Sympathetic division:
• function to mobilise the body during “emergencies”

Parasympathetic division:
• function is to promote “nonemergency” function and conserve energy

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