The Autonomic Nervous System
Nervous System Central Peripheral Somatic Control out Autonomic Control 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 neurons spreading 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 (3 rd, 7 th, 9 th, 10 th ), and sacral spinal nerves. (craniosacral) C3,7,9,10 P P SYMP S2-4 T1-12 L2-3
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 о T2 о T3 о effector organ Pre Post
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.
ُُ Eye Iris Ciliary ms Lacrimal glands heart Peripheral bl vessels GIT Dilatation of pupil Relaxation (far vision) non Vasoconstriction Vasodilatation of sk ms Increase H.R Increase force of cont Dilatation of coronary bl vessl Relax of walls & Const of sphincters (filling promoted) bronchodilationlungs Costriction of pupil Contraction (nearvision) lacrimation non Decrease H.R Increase motility &secretion Relaxation of sphincters (emptying promoted) constriction SympatheticParasympathetic
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 penis Or clitoris SympatheticParasympathetic
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 Para 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 ganglionic noradrenalin. Adrenalin Adrenal medulla is a modified symp ganglion that does not give rise to postganglionic fibers. It secretes mainly adrenalin upon stimulation by preganglionic. Adrenalin Ach