Autonomic Nervous System PDF

The Autonomic Nervous System Dr. Hala Osman Eltony The whole nervous system can be anatomically divided into: * Central nervous system. * Peripheral nervous system. Physiological organization of the nervous system are: * Somatic nervous system mainly deals with the voluntary aspects...

The Autonomic Nervous System Dr. Hala Osman Eltony The whole nervous system can be anatomically divided into: * Central nervous system. * Peripheral nervous system. Physiological organization of the nervous system are: * Somatic nervous system mainly deals with the voluntary aspects of neurological control. * The autonomic nervous system (ANS): deals with involuntary control mechanisms. Divisions of the autonomic nervous system SYMPATHETIC: thoracolumbar outflow, (from all the 12 thoracic and upper 2 lumber segment of spinal cord) Activated in stress. * PARASYMPATHETIC: craniosacral outflow, rest and digest. Cranial nerves, i.e. III, VII, IX & X (3-7-9-10). 2nd, 3rd and 4th sacral segments Sympathatic out flow parasympathatic out flow Autonomic ganglia Definition: A ganglion is a collection of nerve cells out side the CNS. Types: Three types: Lateral: site for relay of sympathetic nerves. Collateral: It is site for relay of both sympathetic and parasympathetic nerves. Terminal: site of relay for parasympathetic nerves. Function of autonomic ganglia: Relay stations. Release of chemical transmittion Distributing function. Regeneration of post ganglionoic fibers. General functions of the sympathetic nervous system: (stress response) In emergency conditions: e.g. in cases of fight, flight, muscular exercise, emotions, pain and cold, generalized sympathetic excitement occurs (the alarm response or stress response):  1. Eye: Motor to dilator pupillae muscle → mydriasis (dilation of the pupil). 2. Skin: Sweat glands → increase secretion Blood vessels → vasoconstriction. 3. The heart: they simulate all the properties of the cardiac muscle (increase heart rate) and increase its metabolism & 02 consumption.  Coronary vessels: coronary vessels dilate due to increased metabolism of the heart. 4. lung: bronchodilation and inhibition of bronchial secretions. 5. Gastrointestinal tract (GIT) : relaxation of the wall but constriction of the sphincters and inhibition of GIT secretions. 6. The spleen: motor of smooth muscle fibers of the capsule → 50 ml of stored blood is poured 7.The liver: glycongenolysis → blood glucose level rises. 8.The kidney: decreased renal blood flow, decreased urinary output and stimulation of rennin secretion. 9.The adrenal medulla: secretion of catecholamine, adrenaline (80%) and noradrenalin (20%). 10.The urinary bladder: inhibitory to the wall (detrusor muscle) and motor to the internal urethral sphincter → retention of urine. 11- emission of semen during sexual intercourse (ejaculation). 12. Delay muscle fatigue due to vasodilatation of Blood vessels of skeletal muscles. Horner's Syndrome: damage of the superior cervical sympathetic ganglion leads to: Ptosis. drop of upper eye lid. Miosis. pupilloconstriction, due to paralysis of the dilator of pupillae muscle. Anhydrosis. No sweet. Vasodilatation. appearing more red.  The Parasympathetic Nervous System Origin and distribution of parasympat hetic nervous system General functions of parasympathetic system: Parasympathetic functions are anabolic and energy preserving Its function becomes most apparent in a person at rest after a meal and reading a newspaper. General functions of parasympathetic system: Parasympathetic functions are anabolic and energy preserving Its function becomes most apparent in a person at rest after a meal and reading a newspaper.  1. Eye: Motor to the constrictor pupillae muscle → miosis (constriction of the pupil) Motor to the ciliary muscle →, preparing the eye for near vision. 2. Salivary gland: salivary glands → copious secretion 3. The heart: decrease of heart rate (bradycardia). It inhibits contractility It coronary vessels vasoconstrictor. 4. lung: bronchoconstriction and stimulation of mucus secretion. 5. Gastrointestinal tract (GIT) : motor to the wall but inhibitory to its sphincters. Stimulation of secretion. 6. The urinary bladder: motor to the detrusor muscle of the bladder wall and inhibitory to the internal urethral sphincter → micturition. 7. external genitalia: vasodilatation → erection of penis & clitoris.  CHEMICAL TRANSMITTERS The most widely distributed transmitters are acetylcholine (ACH) and noradrenalin. acetylcholine cholinergic nerve cholinergic receptors. Subtypes of cholinergic receptor are nicotinic and muscarinic receptors. noradrenalin adrenergic nerve adrenergic receptors. adrenergic receptors : there are ά and β receptors, ά receptors are divided into ά1 and ά 2 receptors.  Acetylcholine Site of release of acetylcholine (the cholinergic nerve fibers): I- Central cholinergic fibers: a) All the preganglionic sympathetic. b) All the preganglionic parasympathetic. c) All the somatic motor fibers supplying the skeletal muscles. II- Peripheral cholinergic fibers: a) All the parasympathetic postganglionic fibers. b) Sympathetic postganglionic secretary fibers to sweat glands. c) Sympathetic postganglionic vasodilator fibers to blood vessels of skeletal muscle. Myasthenia Gravis * It is a disease of the neuromuscular junction characterized by weakness and easy fatigability of skeletal muscles due to autoimmunity. * Destruction of the cell membrane over the motor end plate decreasing the receptor area for acetyl choline. Catecholamines Is the chemical transmitter of most of the postganglionic sympathetic nerves. ADRENERGIC RECEPTORS: There are 2 main types of adrenergic receptors; ά and β. In each type there are 2 subtypes. So, there are ά1, ά2, β1 and β2 adrenergic receptors. Thank you