Lecture 12 Sympathetic/Parasympathetic PDF

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102 04/12/2024 HBF - 102 1 SYMPATHETIC NERVOUS SYSTEM III & PARASYMPATHETIC NERVOUS SYSTEM I By:...

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102 04/12/2024 HBF - 102 1 SYMPATHETIC NERVOUS SYSTEM III & PARASYMPATHETIC NERVOUS SYSTEM I By: Dr. Ayman Saied Soliman Ass. Professor – Faculty of Medicine – Beni Suef University Department: Medical Physiology 04/12/2024 12/7/2024 HBF - 102 22  Objectives By the end of this lecture the student should be able to: 1.Describe the functions of the sympathetic system on limbs (Skin and skeletal muscles), 2.General functions of the sympathetic system during rest (Sympathetic tone) and in emergency conditions (alarm response). 04/12/2024 HBF - 102 33  Objectives By the end of this lecture the student should be able to: 3. Define the origin of the parasympathetic nervous system (Craniosacral outflow). 4. List the parts of the body, which are supplied or not supplied by the parasympathetic system. 5. Describe the functions of the parasympathetic cranial nerves (III. Oculomotor nerve). 04/12/2024 HBF - 102 44  Introduction ☼The autonomic nervous system (ANS) is the part of the nervous system that is responsible for homeostasis. ☼The autonomic nervous system is composed of: Sympathetic nervous system. Parasympathetic nervous system. 04/12/2024 HBF - 102 55  Sympathetic nervous system. Sympathetic system is catabolic and energy consuming system It functions at stress, fight, fear and flight. 04/12/2024 HBF - 102 6 Sympathetic Nervous System Fear  Sympathetic nervous system. Somatic division This division of the sympathetic nervous system accompanies the somatic nerves (which arise from the anterior horn cells). It supplies the skin & the skeletal muscles blood vessels. 04/12/2024 HBF - 102 8  Sympathetic nervous system. Somatic division Origin Those which supply the upper limbs arise from the 4th. – 8th. thoracic segments and reach them via the brachial plexuses. While those which supply the lower lamps arise from the 10th.- 12th. thoracic segments and reach them via the lumbosacral plexuses. 04/12/2024 HBF - 102 9 Sympathetic Nervous System Thoraco- lumbar  Sympathetic nervous system. Somatic division Relay: Lateral ganglia at the same level 04/12/2024 HBF - 102 11  Sympathetic nervous system. Somatic division Effects: 1- Skin Sweat secretion Hair erection VC of blood vessels 04/12/2024 HBF - 102 12 Functions of Sympathetic Nervous System Contraction of piloerector muscle (erection of hairs) Skin Secretory to sweat glands Vasoconstriction to cutaneous blood vessels  Sympathetic nervous system. Somatic division Effects: 2- Skeletal muscle blood vessels: The skeletal muscles receive both nor adrenergic sympathetic nerve fibers (that cause VC) as well as cholinergic sympathetic nerve fibers (that cause VD). 04/12/2024 HBF - 102 14  Sympathetic nervous system. Somatic division Effects: 2- Skeletal muscle blood vessels: Accordingly, sympathetic stimulation may cause VC or VD in the skeletal muscles the depending on the underlying condition. 04/12/2024 HBF - 102 15  Sympathetic nervous system. Somatic division Effects: 2- skeletal muscle blood vessels: In case of hemorrhage : VC occurs, which helps elevation of the arterial blood pressure. 04/12/2024 HBF - 102 16  Sympathetic nervous system. Somatic division Effects: 2- skeletal muscle blood vessels: Whereas, during muscular exercise: VD occurs which increases the blood supply to the active muscles 04/12/2024 HBF - 102 17  Sympathetic nervous system. Somatic division Sympathetic stimulation also accelerates the chemical reactions in the active muscles and this together with vasodilation led to a better contraction delayed fatigue and the early recovery after exercise. 04/12/2024 HBF - 102 18  General sympathetic actions (sympathetic tone) There are continuous sympathetic impulses even during rest to: ❑ Adrenal medulla: leading to basal secretion of small amounts of catecholamines. ❑ Smooth muscles of arterioles: leading to partial continuous degree of VC. 04/12/2024 HBF - 102 19 HBF - 102 General sympathetic actions (sympathetic tone) 04/12/2024 20  General sympathetic actions (sympathetic tone) These actions are called sympathetic tone and they help in maintenance of blood pressure and blood glucose 04/12/2024 HBF - 102 21 HBF - 102 General sympathetic actions (sympathetic tone) 04/12/2024 22  Alarm (Stress) Response Of Sympathetic Nervous System The sympathetic nervous system discharges as one unit in emergency situations to prepare the individual to cope with the emergency i.e. preparation for flight, fear or fight. For example: 04/12/2024 HBF - 102 23  Alarm (Stress) Response Of Sympathetic Nervous System Dilates the pupils —> letting more light into the eyes, Accelerates the heart beats and raises the blood pressure —> provide better perfusion of vital organs and muscles. 04/12/2024 HBF - 102 24  Alarm (Stress) Response Of Sympathetic Nervous System Constricts the blood vessels of the skin —> which limits bleeding from wounds. Lowers threshold in the reticular formation in the brain i.e. reinforcing the alert and aroused state. Stimulates Lipolysis and glycogenolysis —> supplying more energy (glucose and free fatty acids). 04/12/2024 HBF - 102 25 Alarm (Stress) Response Of Sympathetic Nervous System N.B.: ▪ The sympathetic system is catabolic (= energy consuming), ▪ While The parasympathetic system is anabolic (= energy preserving) as it favors digestion and absorption of food substances. 04/12/2024 HBF - 102 26  Alarm (Stress) Response of Sympathetic Nervous System 04/12/2024 HBF - 102 27 Alarm (Stress) Response Of Sympathetic Nervous System 04/12/2024 HBF - 102 28  The Parasympathetic Nervous System (Cranio-sacral) I. The cranial outflow: 1)Oculomotor (III). 2)Facial (VII). 3)Glossopharyngeal nerves (IX). 4)Vagus nerves (X): 04/12/2024 HBF - 102 29  The Parasympathetic Nervous System (Cranio-sacral) I. The cranial outflow: Supplies the visceral structures in the head and neck through: 1)Oculomotor (III). 2)Facial (VII). 3)Glossopharyngeal nerves (IX). 04/12/2024 HBF - 102 30  The Parasympathetic Nervous System (Cranio-sacral) Vagus nerves (X): it is responsible for: a)About 75% of all parasympathetic nerve fibers. b)To the entire thoracic and abdominal viscera. 04/12/2024 HBF - 102 31  The Parasympathetic Nervous System (Cranio-sacral) II. The sacral outflow: Supplies the pelvic viscera via the pelvic branches of the 2, 3, 4 sacral spinal nerves (pelvic nerve). 04/12/2024 HBF - 102 32  The Parasympathetic Nervous System (Cranio-sacral) N.B: The preganglionic parasympathetic fibers end on short postganglionic neurons located on or near the visceral structures, i.e., terminal autonomic ganglia. 04/12/2024 HBF - 102 33 Parasympathetic Nervous System Cranio - Sacral  Sympathetic and parasympathetic supply Most visceral organs are innervated by both sympathetic and the parasympathetic fibers and this is called the dual innervations 04/12/2024 HBF - 102 35  Organs without dual innervation: Although most organs are innervated by both sympathetic and parasympathetic nerves some organs receive only sympathetic innervation including: 1) Adrenal medulla 2) Erector pili muscles 3) Sweat glands 4) Most blood vessels 04/12/2024 HBF - 102 36  Organs without dual innervation: In this cases regulation is achieved by increases or decreases in the tone (firing rate) of the sympathetic fibers. 04/12/2024 HBF - 102 37  Organs without dual innervation: For Example: The sympathetic fibers to blood vessels have a baseline sympathetic tone that keeps the vessels in partial constriction called vasomotor tone. 04/12/2024 HBF - 102 38  Organs without dual innervation: For Example: An increase in firing constricts the vessel, while a decrease dilates it, therefore, letting the sympathetic division exert different effects on the vessels. The vasomotor tone acts to shift blood flow from one organ to the next based on the body's need.. 04/12/2024 HBF - 102 39  Organs without dual innervation: For Example: The vasomotor tone acts to shift blood flow from one organ to the next based on the body's need.. 04/12/2024 HBF - 102 40 HBF - 102 Organs without dual innervation: 04/12/2024 41  Functions of the Parasympathetic Nervous System: Parasympathetic system is anabolic and energy preserving at rest, digest, reading 1.Inhibits cardiac properties. 2.Increases activity of GIT. 04/12/2024 HBF - 102 42  The Occulomotor nerve (=Cranial nerve No III): Origin: Edinger- Westphal nucleus in the midbrain, Relay: ▪ in the ciliary ganglion. ▪ The postganglionic fibers enter the eye as short ciliary nerves 04/12/2024 HBF - 102 43 Functions of Parasympathetic Nervous System Head and Neck The Occulomotor nerve III  The Occulomotor nerve (=Cranial nerve No III): Functions: a)Contraction of the constrictor pupillae muscle leading to constriction of the pupil (=miosis). 04/12/2024 HBF - 102 45 Functions of Parasympathetic Nervous System Head and Neck The Occulomotor nerve III Contraction of the constrictor pupillae muscle (Miosis)  The Occulomotor nerve (=Cranial nerve No III): Functions: b) Contraction of the ciliary muscle leading to increase in the power of the lens preparing the eye for near vision. 04/12/2024 HBF - 102 47 Functions of Parasympathetic Nervous System Head and Neck The Occulomotor nerve III Contraction of the ciliary muscle increase in the power of the lens preparing the eye for near vision  Question: Adrenal medulla: A.Receive preganglionic parasympathetic fibers. B.Secrete adrenaline and noradrenaline in response to sympathetic stimulation. C.Secretes 80% noradrenaline. D.Secretes 20 % adrenaline. E.Has short post ganglionic fibers. 04/12/2024 HBF - 102 49  Summary ▪ The sympathetic system is catabolic (= energy consuming), ▪ While The parasympathetic system is anabolic (= energy preserving) as it favors digestion and absorption of food substances. ▪ sympathetic tone and they help in maintenance of blood pressure and blood glucose 04/12/2024 HBF - 102 50  References 1) GUYTON AND HALL: TEEXT BOOK OF MEDICAL PHYSIOLOGY: 14th. Edition; Philadelphia: Elsevier, Inc.,2020. 2) Staff Members of Physiology Department: Medical physiology books; Faculty of Medicine – Cairo University, 2016. 3) Barerett KE et al.: Ganong's Review of Medical Physiology: 26th. Edition; New York: The McGraw- Hill companies, 2019. 4) Linda S. Costanzo, : BRS Physiology Seventh Edition. 04/12/2024 HBF - 102 51 51