Functions and Divisions of Nervous System

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The 3 (overlapping) functions of the nervous system:

Sensory Input - The information gathered by all the sensory receptors, about changes inside and outside body.

Integration - The process of analysing and interpreting sensory input and deciding a response at each moment.

Motor Output - Activation of effector organs (muscles and glands) to cause a response.

The principal parts of nervous system:

Central Nervous System (CNS)

Peripheral Nevrvous System (PNS)

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Central Nervous System

Consists of brain and spinal cord, occupies dorsal body cavity

Functions:

Intergrating and control center of nervous system.

Interprets sensory input and dictates motor output based on reflex, current conditions, and past experience.

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Peripheral Nervous System

All the parts of the nervous system outside the Central Nervous System (CNS). Consists mainly of nerves (bundles of axons) which extend to and from brain and spinal cord.

Carry impulses to and from:

brain - cranial nerves

spinal cord - spinal nerves

Subdivisions of Peripheral Nervous System (PNS):

Sensory/ Afferent division

Motor/ Efferent division

Sensory/ Afferent Division (af'er-ent = carrying toward)

Functions:

Consists of nerve fibers (axons) that convey impulses to the central nervous system (CNS) from sensory receptors throughout the body.

Keeps Central Nervous System (CNS) constantly informed of events going on inside and outside body.

Two types:

Somatic (soma = body) sensory fibers - convey impulses from the skin, skeletal muscles, and joints

Visceral sensory fibers - convey impulses from visceral organs (organs within the ventral body cavity)

Motor/ Efferent Division (ef'er-ent = carrying away)

Functions:

Consists of nerve fibers (axons) that convey impulses from the central nervous system (CNS) to effector organs (muscles & glands).

Impulses activate muscles to contract and glands to secrete.

Brings about a motor response

Two parts:

Somatic Nervous System - consists of somatic motor nerve fibers that conduct impulses from CNS to skeletal muscles. Also referred to as voluntary nervous system because it allows us to consciously control our skeletal muscles

Autonomic Nervous System (ANS) (autonomic = a law unto itself) - consists of visceral motor nerve fibers which regulates smooth muscles, cardiac muscles, and glands. We cannot control activities of smooth muscles, cardiac muscles, and glands so Autonomic Nervous System (ANS) is also called the involuntary nervous system. Has two subdivisions, sympathetic division and parasympathetic division.

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