Foundation 1 Lecture 6 (Physiology) PDF

Lecture 6 Sympathetic and parasympathetic Effects Dr. M. Abdelmohsen Assistant Professor of Physiology MBBCh, MSc, DMSc, DHPE Faculty of Medicine 2024-2025  Objec...

Lecture 6 Sympathetic and parasympathetic Effects Dr. M. Abdelmohsen Assistant Professor of Physiology MBBCh, MSc, DMSc, DHPE Faculty of Medicine 2024-2025  Objectives ❖ At the end of this lecture, the first year student should be able to: Summarize the functions of sympathetic and parasympathetic nervous system on different parts of the body. ▪ Reference Text Book: Guyton & Hall physiology text book  Functions of autonomic nervous system The two systems occasionally act reciprocally to each other. (1) The Eye Sympathetic Parasympathetic A) Pupil: Dilate the pupil (mydriasis) → Oculomotor (III) nerve: increases light entering the eye. Constrict the pupil (myosis) → decreases light entering the eye Sympathetic Parasympathetic B) Lens: Relaxes the ciliary muscle → Oculomotor (III) nerve: Tense suspensory ligaments → Contracts the ciliary muscle → Lens become less convex → Releases tension on the ligaments → good far vision. Lens become more convex → Good near vision.  (1) The Eye Sympathetic Parasympathetic C) Eyelid: Contracts levator palpebrae superioris muscle → NA elevation of the upper eyelid. Sympathetic Parasympathetic D) Contracts Muller's muscle → NA exophthalmos. Eyeball: Sympathetic Parasympathetic E) blood Vasoconstriction. NA vessels:  Horner's syndrome Cause: Damage of sympathetic chain & superior cervical ganglion. Location: half of the face. Symptoms and signs: ✓ Ptosis (dropped upper eyelid) ✓ Miosis ✓ Anhidrosis (loss of sweating) ✓ Enophthalmos ✓ Erythematosus (vascular dilatation)  (2) Glands of the Body Sympathetic Parasympathetic A) Nasal, ✓ Little, viscous and ✓ Copious watery enzymatic concentrated secretion. (Amylase) secretion. lacrimal, ✓ High percentages of mucus. ✓ Facial (VII) nerve → salivary, and sublingual, submaxillary, many GIT lacrimal, nasal glands. ✓ Glossopharyngeal (IX) nerve → glands parotid gland. Sympathetic Parasympathetic B) Sweat ✓ Large quantities of sweat. NA ✓ Cholinergic not adrenergic glands (except palms and soles). Sympathetic Parasympathetic C) Axillary ✓ Thick, odoriferous secretion NA ✓ Lubricant to allow easy sliding apocrine glands motion.  Sympathetic Parasympathetic A) Heart and ✓ Increases heart rate. Vagus nerve (X): ✓ Increases the force of contraction ✓ Decreases heart rate. coronaries ✓ Increases the heart pumping ✓ Slight decreases atrial contraction (during heavy exercise). (only atrial). ✓ Vasodilatation of coronaries. Sympathetic Parasympathetic B) Systemic ✓ Constricts most systemic blood vessels. NA (3) CVS Blood Vessels  (4) GIT Sympathetic Parasympathetic ✓ Relax walls (Inhibits peristalsis) Vagus (X) nerve: ✓ Contrcts the sphincters ✓ Contracts walls (Promoting peristalsis) ✓ Decreased secretion ✓ Relaxing the sphincters ✓ Retention of feces (constipation). ✓ Increased secretion. ✓ Contract the gall bladder wall and relax its sphincter → gall bladder evacuation. Sacral parasympathetic part (pelvic nerve): contracts the rectum wall and relaxes the internal anal sphincter → defecation. (5) Urinary Tract  (6) Lung Sympathetic Parasympathetic ✓ Bronchodilatation Vagus (X) nerve: ✓ Vasoconstriction ✓ Bronchoconstriction ✓ Vasodilatation ✓ Increases bronchial gland secretion. (7) Spleen Sympathetic Parasympathetic Contracts spleen capsule → NA Evacuation of stored blood to circulation. (8) Sexual organs Sympathetic Parasympathetic ✓ Contracts smooth muscles of: vas Sacral parasympathetic part (pelvic nerve): deference, seminal vesicle and prostate ✓ Stimulates secretion of seminal vesicle and → semen ejaculation. prostate. ✓ Causes erection of the penis.  (9) Skin Sympathetic Parasympathetic Vasoconstriction, sweat secretion and hair erection. NA (10) Skeletal muscles Sympathetic Parasympathetic ✓ Vasodilates skeletal blood vessels NA ✓ Delay fatigue and early recovery (Orbelli phenomenon). (11) Metabolism Sympathetic Parasympathetic Generally catabolic. NA ✓ Increases glycogenolysis in both liver and muscle → May be anabolic Increasing blood glucose concentration. ✓ Increases skeletal muscle strength. ✓ Increases basal metabolic rate. ✓ Increases mental activity 2.Parasympathetic stimulation: No clear effect but may be anabolic. Figure 5: sympathetic nervous system  Figure 6: Parasympathetic nervous system ▪ Generalized sympatho-adrenal effect (Fight or flight):  Generalized sympatho-adrenal effect (Fight or flight) Alarm or stress response of the sympathetic nervous system. Time: Occurs during stress and emergency situations Involvement: generalized sympathetic discharge & large secretion of adrenal medulla. Goal: Aids the body to perform sever muscle activity. Actions: 1) ↑ arterial pressure and cardiac output. 2) ↑ blood flow to active muscles. 3) ↓ blood flow to GIT and kidneys. 4) ↑ muscle strength. 5) ↑ rate of metabolism of the body. 6) ↑ blood glucose concentration through glycolysis. 7) Splenic contraction to add more blood. 8) Bronchodilatation to help good ventilation. 9) Mydriasis to increase visual acuity. 10) ↑ blood coagulation rate. 11) ↑ mental activity and alertness. Comparison between sympathetic and parasympathetic Sympathetic Parasympathetic Origin Thoracolumbar Craniosacral Relay ganglia Lateral or Terminal collateral Fiber type & Preganglionic: Preganglionic: long length short cholinergic. cholinergic. Postganglionic: short Postganglionic: cholinergic. long adrenergic Effector organs Generalized Specific discrete mass effect effect Dominant Emergency (fight Rest and relaxed situation or flight) Preganglionic Ach Ach neurotransmitter Its receptors Cholinergic Cholinergic nicotinic  Preganglionic Ach Ach Comparison between sympathetic and parasympathetic neurotransmitter Its receptors Cholinergic Cholinergic nicotinic nicotinic Postganglionic Norepinephrine Ach neurotransmitter Its receptors Adrenergic (α & Cholinergic β) muscarinic Divergence & its Great (1/10) Little (1/3) pre/post importance pre/post More specific Generalized cholinergic actions (diffuse) adrenergic actions Regulators Neurons of Neurons of anterior posterior hypothalamus hypothalamus Comparison between sympathetic and parasympathetic  Thank You Faculty of Medicine 2024-2025