Parasympathetic Nervous System 2024 PDF

GALALA 2024 PARASYMPATHETIC NERVOUS SYSTEM Mod. By Prof. Dr. Magdi A. El-Damarawi Professor of Medical physiology Faculty of Medicine  Objectives (ILOs) ◼ By the end of this lecture, you should be able to: 1. Recognize the origin of the parasymp...

GALALA 2024 PARASYMPATHETIC NERVOUS SYSTEM Mod. By Prof. Dr. Magdi A. El-Damarawi Professor of Medical physiology Faculty of Medicine  Objectives (ILOs) ◼ By the end of this lecture, you should be able to: 1. Recognize the origin of the parasympathetic nervous system. 2. List the names of the cranial nerves. 3. Understand the function of the parasympathetic nervous system to the different parts of the body. 4. Illustrate the relationship between the functions of the sympathetic and parasympathetic nervous systems 5. Define the sympathetic and parasympathetic tone.  PARASYMPATHETIC NERVOUS SYSTEM 1-CRANIAL OUTFLOW: 3,7,9,and 10 III- Oculo-motor nerve VII- Facial nerve IX- Glossopharyngeal nerve X- Vagus nerve 2- SACRAL OUTFLOW : - Arises from the LHCs of 2, 3 & 4 sacral segments. - The preganglionic fibers unite to form the pelvic nerve.  Parasympathetic supply to the head & neck III- Oculomotor nerve Relay: in the ciliary ganglion Functions: - Narrowing of the pupil (miosis) by contraction of constrictor pupillae muscle. - Contraction of the ciliary muscle leading to increased convexity of the lens of the eye (increased power) to focus on near objects (Accommodation for near vision).  VII- Facial nerve Relay: in the spheno-palatine ganglion. “Superficial petrosal nerve”. Functions: - To lacrimal glands leads to secretion of tears. - To mucous glands of nose, mouth, pharynx & palate lead to mucous secretion. - Vasodilatation (VD) of the blood vessels of the face. - Chorda tympani N. (branch of facial nerve) - Relay: in the submandibular ganglion. - Postganglionic fibers pass to: 1. Submandibular & sublingual salivary glands causing true salivary secretion (large in volume, watery & poor in organic substances). 2. Blood vessels of salivary glands, anterior 2/3 of the tongue to cause vasodilatation (VD). Chorda tympani N. (branch of facial nerve) VD of tongue blood vessels ◼ Anterior 2/3 Posterior Of tongue 1/3 of VII tongue IX  IX- Glossopharyngeal nerve Relay: in the otic ganglion. Functions: 1. To the parotid salivary gland causing true secretion. 2. To the blood vessels of the salivary gland & posterior 1/3 of the tongue causing vasodilatation (VD).  Activity 2 What are the differences between true and trophic salivary secretions?  Parasympathetic to thorax & abdomen X. Vagus nerve Relay: - In terminal ganglia present in the thoracic & abdominal viscera. Functions: - It represents 75 % of all the parasympathetic supply.  1- In the thorax (A) In the heart: - Inhibition of all cardiac properties (decrease conductivity, contractility, excitability & rhythmicity). - Vasoconstriction (VC) of coronary blood vessels (decrease blood flow to the cardiac muscle). (B) In the lungs: - Contraction of smooth muscles of the bronchi & bronchioles (broncho-constriction). - Increase mucous secretion. - Vasodilatation (VD) of pulmonary blood vessels.  2- In the abdomen Gastro-intestinal tract (G.I.T.): 1. Smooth muscles: - Contraction of the wall of esophagus, stomach, small intestine & proximal part of the large intestine and relaxation of their sphincters. 2. Secretory to the gastric glands: - Increases HCL & mucous secretion. 3. Blood vessels: Vasodilatation (VD).  The liver: 1. Stimulate bile secretion. 2. Contraction of gall bladder wall & relaxation of sphincter of Oddi leads to its evacuation. The pancreas: 1. Secretion of pancreatic juice rich in enzymes. 2. Stimulates insulin secretion by B-cells.  Parasympathetic to the pelvis - Origin: LHCs of S 2,3 & 4 (Pelvic nerve). - Relay: terminal ganglia. - Functions: 1. Urinary bladder: Contraction of the wall & relaxation of the internal urethral sphincter. So, it helps micturition. 2. Rectum & anal canal: Contraction of the wall & relaxation of the internal anal sphincter. So, it helps defecation. 3. Sex organs: VD of blood vessels and shares in the execution of sexual act. Autonomic Nervous system  Relation between Sympathetic & parasympathetic - Usually there is antagonistic relation: as in heart , lungs & pelvis. - Sometimes, the relation is synergistic (each system help the other) as in salivary secretion: Sympathetic produces trophic secretion while parasympathetic produces true secretion. -There is complementary action during sexual intercourse. The parasympathetic causes erection and the sympathetic causes ejaculation in males & orgasm in females. Structures supplied by sympathetic only: 1- The dilator pupillae muscle. 2- The ventricles of the heart. 3- Most of the blood vessels. 4- The spleen. 5- The adrenal medulla. 6- The skin. - Structures supplied by the parasympathetic only: 1- The constrictor pupillae muscles. 2- The glands of the stomach & pancreas.  SYMPATHETIC & PARASYMPATHETIC TONE - The tone is the basal rate of activity of both systems. ◼ Importance:- - The sympathetic tone: It is responsible for keeping the blood vessels constricted. - It is due to continuous discharge through sympathetic fibers & by the basal level of adrenaline & noradrenaline secreted by the adrenal medulla. The parasympathetic tone is very important in: 1-The heart (vagal tone) to decrease high inherited rhythm of the S.A.N. 2- The gastrointestinal tract to maintain its normal function.  CONTROL OF AUTONOMIC FUNCTIONS ◼ Most of the autonomic functions are mediated through the autonomic reflexes as in the gastrointestinal , cardiovascular, respiratory & genitourinary functions. ◼ The autonomic reflexes are controlled by centers present in: 1. Spinal cord: for primitive autonomic reflexes as micturition, and defecation (without higher control). 2. Brain stem: ◼ Medulla oblongata: contains the cardiovascular, respiratory, adrenaline secretion , gastrointestinal motility & secretion and the vomiting centers. ◼ Pons: contains centers that control respiration & salivary secretion. ◼ Mid brain: contains centers that controls micturition & pupillary response to light & near vision.  3.The Hypothalamus - It can control the activity of almost all the brain stem autonomic centers. - In general, the anterior nuclei of hypothalamus control parasympathetic function & the posterior nuclei control sympathetic function 4. Cerebral cortex 1- Psychogenic control of cardiovascular & gastrointestinal functions. 2- Higher control of micturition & defecation.  Assignment 2 - From your previous knowledge, mention and explain the effects of both divisions of the ANS on the coronary blood vessels and flow.