The Autonomic Nervous System

Nervous System

Central Peripheral

SomaticControl out

AutonomicControl inside

Def: Involuntary control of the visceral organ activities eg (circulation, digestion, sweating, papillary size)

Division: Sympathetic

Parasympathetic

Functional Anatomy

The autonomic nerves consist of two neutrons.

1. Preganglionic: Its cell body is located in the CNS.

2. Postganglionic: Its cell body in a ganglion outside the CNS. It innervates the effector organ.

Single preganglionic neuron synapses with several postganalionic neuronsspreading the effect over a larger area.

Functional anatomy..cont

Originate in the lateral horn cells in the spinal cord.

Sympathetic: originate in the thoracic and lumbar regions of the spinal cord. (Thoracolumbar)

Parasympathetic: originate from cranial nerves (3rd, 7th, 9th, 10th),

and sacral spinal nerves. (craniosacral)

C3,7,9,10

P

P

SYMP

S2-4

T1-12L2-3

Site of Ganglia Both systems are 2 neuron system. Sympathetic:Preganglionic fibers are very

short, synapsing with cell bodies of postganglionic neurons within ganglia lie in sympathetic ganglion chain (sympathetic trunk).

Postganglionic fibers originate in the ganglion chain terminate on the effector organs.

Some preganglionic fibers pass through the ganglion chain without synapsing and terminate later in sympathetic collateral ganglia located halfway between the CNS and innervated organs.

C °

T1 оT2 оT3 о effector organ

PrePost

Site of ganglia

Parasympathetic: Ganglia are near or within the

effector organs. Postganglionic fibers are

shorter than Preganglionic

Functions of the ANS The ANS controls involuntary visceral

organ activities. Such as: circulation, digestion, sweating,

and papillary size. The sympathetic and parasympathetic

systems exert opposite effects. The sympathetic is activated during

stress & emergencies. Prepare for “fight or flight”.

The parasympathetic is concerned with vegetative functions (general housekeeping), eg: feeding, resting and sexual stimulation.

EyeIrisCiliary ms

Lacrimal glands

heart

Peripheral bl vessels

GIT

Dilatation of pupilRelaxation (far vision)

non

VasoconstrictionVasodilatation of sk ms

Increase H.RIncrease force of contDilatation of coronary bl vessl

Relax of walls &Const of sphincters(filling promoted)

bronchodilationlungs

Costriction of pupilContraction (nearvision)lacrimation

non

Decrease H.R

Increase motility &secretionRelaxation of sphincters(emptying promoted)

constriction

Sympathetic Parasympathetic

Urinary bladder

Sex organs

Relax of walls &Cont of internal sphincter(filling promoted)

ejaculation

Cont of walls &Relax of internal sphincter(emptying promoted)

Erection of penisOr clitoris

Sympathetic Parasympathetic

Chemical or neural transmitter All preganglionic fibers release acetylcholin

(Ach). All parasympathetic postganglionic release

Ach. All sympathetic postganglionic release

noradrenalin except sweat glands & bl vessels to skeletal muscles. Ach

AchPara

Noradrenalin (except sweat

glands & bl vessels to sk ms) Symp

Ach

Chemical Division of ANS Cholinergic

(Ach)

1. All preganglionic (para+symp)

2. All Para Post ganglionic.

3. Symp postganglionic at sweat glands and blood vessels in skletal ms.

Adrenergic (adrenalin&nor)

most symp post ganglionicnoradrenalin.

Adrenalin Adrenal medulla is a

modified symp ganglion that does not give rise to postganglionic fibers. It secretes mainly adrenalin upon stimulation by preganglionic.

AdrenalinAch