Autonomic nervous system

Autonomic nervous system was discovered by Langley.
 Autonomic nervous system (ANS) automatically regulates the activities of smooth muscles, cardiac muscles and glands.
 This co-ordination is involuntary. Autonomic nervous system usually operates without conscious control. 
Autonomic nervous system is entirely motor. All autonomic axons are efferent fibres.
 Autonomic nervous system is regulated by centres in brain like cerebral cortex, hypothalamus and medulla oblongata.
 Autonomic fibres release chemical transmitters at synapse. On the basis of the transmitter produced, these fibres may be classified as cholinergic or adrenergic.
Cholinergic fibres release acetylcholine. Adrenergic fibres produce norepinephrine (noradrenaline), also called sympathetin.
Nature of autonomic control : The autonomic nervous system regulates and co-ordinates such vital involuntary activities like heart beat, breathing, maintenance of the composition of body fluids (= homeostasis) and body temperature, gut peristalsis, secretion of glands, etc. Autonomic nervous system consists of two divisions —
(1) Sympathetic ANS (Thoracolumbar out flow)
(i)    Thoraco Lumber out flow (all thorocic + 3 lumber)
(ii)   Preganglionic nerve small.
(iii)  Post ganglionic nerve long.
(iv)  Preganglionic nerve secrete acetyl chorine.
(v)   Postganglionic nerve secrete sympathatin. (nor-epinephrine)
(vi)  It shows sympathy (generally increase the function).
(vii) Expenditure of energy takes place.
(viii) It increase defence system of body against adverse condition.
         (ix)   It is active in stress condition, pain, fear and anger.
(2) Parasympathatic ANS (Cranio-sacral outflow)
(i)    ANS Cranio sacral outflow (cranial-III, VII, IX, X Nerves)-(sacral-II, Ill, IV Nerves)
(ii)   Preganglionic nerve long.
(iii)  Postganglionic nerve small.
(iv)  Secrete acetyl choline only.
(v)  It provide relaxation, comfort, pleasure, at the time of rest.
(vi)  Restoration and conservation of energy takes place.
(vii) Collateral ganglia present in sympathetic nervous system.
(viii) Horner's syndrome results from the damage of sympathetic trunk of one side.
(ix) A patient of Hornet's syndrome exhibits lack of sweating (on affected side),
       sunken eyes and constricted pupil.




Cutting of sympathetic or parasympathetic nerve to hear will not stop functioning of heart. Heart will beat but without any nervous control
Autonomic nervous system functiuons rapidly to alter visceral functions (3-5 seconds)
It is activated mainly by centers located in spinal cord, brain stem and hypothalamus. Limbic cortex also influences its function often this system functionvia visceral reflexes i.e sensory signal        enter autonomic ganglia         spinal cord        brain stem        or
Hypothalamus can elicit reflex responses back to visceral organs to control their activities.