THE SYMPATHETIC AND PARASYMPATHETIC BRANCHES OF THE AUTONOMIC NERVOUS SYSTEM

THE  SYMPATHETIC  AND  PARASYMPATHETIC  BRANCHES

OF  THE  AUTONOMIC NERVOUS SYSTEM

SYMPATHETIC SYSTEM

Ø  Dilation of pupil

Ø  Inhibition of tear glands

Ø  Inhibition of salivary

Ø  Acceleration of heart action

Ø  Opens respiratory passages

Ø  Inhibits stomach contractions and digestive secretion

Ø  Inhibits intestinal peristalsis

Ø  Relaxes bladder

Ø  Inhibits erection

v  The sympathetic system readies the organism for an emergency: it accelerates heart and lung actions, liberates nutrient, fuels for muscular effort, and inhibits digestive and sexual functions.

v  The fibers of the sympathetic system are interconnected through sa chain of ganglionic fibers outside of the spinal cord. As a result, sympathetic activation has a somewhat diffused character; any sympathetic exetation tends to affect all of the viscera rather than just some. This is in contrast to the parasympathetic system whose action is more specific.

PARASYMPATHETIC SYSTEM

Ø  Constriction of pupil

Ø  Secretion of tear glands

Ø  Salivation

Ø  Inhibition of heart action

Ø  Constriction of respiratory passages

Ø  Stomact contraction: secretion of digestive fluids

Ø  Intestinal peristalsis

Ø  Contraction of bladder

Ø  Erection

v  The parasympathetic system facilitates the vegetative functions of the organisms: it slows the heart and lungs, stimulates digestive functions, permits sexual activities,and so on.

CENTRAL CONTROLS

                The autonomic nervous system, in both its sympathetic and parasympathetic branches, is by no means as autonomous as its name implies; rather, it is largely guided by other neural centers. Some of these centers are among the oldest and most primitive portions of the cerebral cortex. These premitive cortical structures comprise the limbic system.

LIMBIC SYSTEM

                A group of structures in the brain intimately involved in the control of the emotional reactions to situations that call for flight, defense, or attack.

Ø  Electrical stimulation of certain portions of the limbic system transforms a purring cat into a spitting, hissing, halloween figure. Stimulation of the same region in humans often produces feelings of great anxiety or of range, as in a patient who said that she suddenly wanted to tear things to pieces and to slap the experimenter’s face.