Sympathetic Nervous System - 2024-2025 PDF

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102  SYMPATHETIC NERVOUS SYSTEM- II By: Dr. Maessa M. Elnhas Prof. of physiology- Tanta University Dr. Mohamed abo El Hassan Prof. of physio...

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102  SYMPATHETIC NERVOUS SYSTEM- II By: Dr. Maessa M. Elnhas Prof. of physiology- Tanta University Dr. Mohamed abo El Hassan Prof. of physiology- Al-Azhar University Department: Department of Clinical physiology 12/10/2024 2  Objectives oDescribe the functions of the sympathetic nerves on the thoracic part (Heart and lungs). o Describe the organs supplied by greater splanchnic nerve and functions of it. oList the structures supplied by lesser splanchnic nerve and discuss functions of it. 3 Sympathetic Division Preganglionic neurons: located in the lateral gray horn of T1-L2 segments of spinal cord (Thoracolumbar outflow) The sympmhetic N.S. can be divided into 4 divisions: cervical, cardio-pulmonary, splanchnic and somatic. 5 Structures supplied by Sympathetic Divisions 6 2- CARDIO-PULMONARY DIVISION (Thoracic Division): Origin and relay: Preganglionic fibres arise from the L.H.Cs. of upper 4 thoracic segments and relay in the cervical and upper 4 thoracic lateral ganglia. Postganglionic fibres form the cardiac and pulmonary plexuses that supply the thoracic viscera. 7 Functions: 1) Heart:- Stimulates all properties of the cardiac muscle (increase rhythmicity, contractility, conductivity and excitability). - positive inotropic effects = ↑ contractility - positive chronotropic effect = ↑ Heart rate. = ↑ Conductivity = ↑ Excitability V.D. of coronary blood vessels (indirect effect) due to increase cardiac metabolism. The direct effect is coronary V. C. Increases o2 consumption of the heart. 8 2) Lungs:- -relaxation of smooth muscles of the bronchi and bronchioles → bronchodilatation. -↓ bronchial secretion. -V.C. to the pulmonary vessels, this prevents lung congestion. 9 3- SPLANCHIC DIVISION:To Abdomen and pelvis A- Greater splanchnic nerve (Abdominal Division): Origin and relay: Preganglionic fibres arise from the L.H.Cs. of lower 6 thoracic segments and form the greater splanchnic nerve and relay in coeliac and superior mesentric collateral ganglia but the preganglionic fibres to adrenal medulla relay in the adrenal medulla itself. Postganglionic fibres reach abdominal viscera along their B.Vs. 10 11 Functions: 1) Gastrointestinal Tract ( stomach, small intestine and proximal part of large intestine): - Inhibition (relaxation) of their wall and motor (contraction) to their sphincters (delay GIT emptying or ++ retention of food). - ↓ gastric and intestinal secretions and motility. 2) vasoconstrictor to the arterioles of the stomach, small intestine, proximal colon, kidney, pancreas and liver. Functions: 3) Gall Bladder: relaxation to the plain muscles of the wall but contraction to the sphincter of Oddi. 4) Liver: stimulates glycogenolysis → ↑ blood glucose level. 5) Spleen: contraction to the smooth muscles of the splenic capsule especially during haemorrhage → squeeze the stored blood into the circulation. 14 6) Pancreas: decrease insulin hormone and pancreatic juice secretion. 7) Kidney: - Vasoconstrictor to the renal vessels → ↓ renal blood flow and urine output. - Stimulates renin secretion. 8) Adipose tissues → lipolysis. 9) ADRENAL MEDULLA: - stimulates the secretion of adrenaline (80%) and noradrenaline (20%) hormones. - Supplied by pre-ganglionic sympathetic fibers (greater splanchnic nerve). 9) ADRENAL MEDULLA: -The circulating catecholamin have same effects of direct sympathetic stimulation, but more prolonged , So body organs can be stimulated by 2 ways, Nervous (direct) & Hormonal (indirect). N.B Adrenal meddulla is modified by sympethetic ganglion because : 1- No post-ganglionic fibers 2- Causes release of 80% epinephrin. 20% nor epinephrin. N.B Selective secretion of adrenal medulla: a) More epinephrine in unexpected stresses as haemorrhaege b) More nor-epinephrine in familiar stresses as hypoxia N.B Stimulation of greater splanchic nerve causes two peaks rise in blood pressure : a) First rise due to V.C of visceral blood vessel b) Second peak due to release of catecholamin into blood. B- Lesser splanchnic nerve ( Pelvic Division): Origin and relay: Preganglionic fibres arise from the L.H.Cs of upper 3 Lumbar segments and form the lesser splanchnic nerve and relay in the inferior mesentric (hypogastric) ganglia. Postganglionic fibres pass along Bl.Vs. to supply the pelvic viscera. 19 20 Functions: 1) Urinary Bladder: relaxation to the wall and contraction to the internal urethral sphincter → Retention of urine. 2) Distal colon and Rectum: inhibitory to the wall and motor to the internal anal sphincter → Retention of faeces. Functions: 3) Motor to the smooth muscles of epididymis, vas deferens, seminal vesicles and prostate → Ejaculation of semen. 4) V.C. to the Bl.Vs.of the pelvic viscera and V.C. to the Bl.Vs.of external genital organs → Shrinkage of penis in male and clitoris in female. 5) uterus: variable effects. 23 External genitalia: In males: -Inhibition of erection (v.c of erectile tissue) -Ejaculation of semen (contraction of vas deferens, prostate and ejaculatory duct( In females: Contraction or relaxation of female genital organ according to the stage of menstrual cycle and level of hormones in blood.  SUMMARY vasoconstriction of blood vessels to GIT. increases heart rate increases blood pressure inhibits gastrointestinal secretion and movements increases metabolism ejaculation of semen  long-term control NE is inactivated slowly adrenal medulla releases EP and NE which act longer vasomotor tone 27  INTERACTIVE QUESIONS Q1: Stimulation of the sympathetic nervous system causes: a) bronchoconstriction. b) constriction of the pupil. c) increases the heart rate & the force of ventricle contraction. d) increases the heart rate but has no effect on the force of contraction. Q2: Stimulation of the sympathetic nervous system causes: a) increases the motility of the intestine. b) increases the blood glucose level. c) decreases sweating. d) increases salivary secretion. 28 Q3: Sympathetic stimulation: a) result in increase cutaneous blood flow. b) indirectly increase the coronary blood flow (as a result of increase heart rate and force of contraction). c) results in decrease muscle blood flow. d) causes vasodilatation in all vascular beds. Q4: List the effect of lesser splanchanic nerve on external genitlia? 29  References Linda S. Costanzo HBF - 102 30 30 31