ANS-1-1: Autonomic Nervous System PDF

INTRODUCTION  Regulating Systems  The endocrine system:  ductless glands that secrete chemical messengers called hormones, (carried by the blood & distant organs & acts slowly & has a prolonged action).  The nervous system:  It is responsible for rap...

INTRODUCTION  Regulating Systems  The endocrine system:  ductless glands that secrete chemical messengers called hormones, (carried by the blood & distant organs & acts slowly & has a prolonged action).  The nervous system:  It is responsible for rapid and short regulation of the functions of the various systems of the body. Two types of the nerve fibers are found: The functional unit of the nervous system is the reflex arc  The Peripheral Nervous System: 1- Afferent or sensory fibers 2- Efferent or motor fibers  Those carry nerve impulses from the periphery  They carry nerve impulses from the to the central nervous system. central nervous system to muscles, glands and other organs.  They bring information about the external world from receptors (such as light, sound, temperature or pressure) & internal state of  According to the site of origin they are the body (for example tension in muscles or divided into: distension in viscera). Cranial Nerves. Spinal Nerves  Functional classification of the nervous system Somatic nervous system Autonomic nervous system It functions on the basis of reflex it is organized on the basis of the arc to affect the activities of reflex arc but controls the skeletal muscles, (voluntary involuntary plain muscles, the heart muscles). and the secreting glands. The Autonomic Ganglia: - The Sympathetic Nervous System (thoraco- lumbar) ORIGIN: The sympathetic nerves originate from the lateral horn cells of all thoracic and upper 3 lumbar segments of the spinal cord. Head and Neck  EYE: 1) Mydriasis (pupilodilatation): motor to dilator pupillae muscle 2) decrease power of lens: see Far objects 3) widening of palpebral fissure (increase field): to muscle of upper lid (elevation) 4) Decrease tears Skin: 1) Secretory to sweat glands. 2) Vasoconstriction 3) erection of hairs.  Salivary Glands: trophic: concentrated, small in amount and viscid.  -Cerebral circulation: blood flow increased Thoracic Viscera  1. Heart 1) Increase all cardiac properties: Rate, force, excitability and rate of conduction. 2) Vasodilatation of coronaries.  2. Lungs:  - Dilatation of bronchi. –  Vasoconstriction to pulmonary vessels Abdominal Viscera  GIT: - Inhibition (relaxation) of wall plain muscles of: stomach, - small intestine and proximal large intestine. - - Motor (Contraction) to sphincters e.g. pyloric sphincter.  2. Liver: glycogenolysis: increasing level of blood glucose  3. Spleen: Contract capsule: pouring stored blood in circulation  4. Adrenal Medulla: - secretes adrenaline and noradrenaline directly into blood  5. Vasoconstriction. Pelvic Viscera  GIT: - Inhibition of wall plain muscles of: - distal large intestine and wall of rectum - Contract internal anal sphincter - (feces retention).  2. Urinary Bladder: - Inhibition of plain muscles of wall – - Contract internal urethral sphincter - (urine retention). The Parasympathetic Nervous System (cranio-sacral) Head and Neck  1) EYE: 1) Miosis(pupil constriction): Contraction of constrictor pupillae. 2) increase power of lens: for near vision  salivary glands secretomotor and vasodilator Chemical Transmission at Autonomic junctions Autonomic receptors  Alarm or "Stress" response flight, fear or fight. o Dilates the pupils —> letting more light into the eyes, o Accelerates the heart beats and raises the blood pressure —> provide better perfusion of vital organs and muscles. o Constricts the blood vessels of the skin —> which limits bleeding from wounds. o Lowers threshold in the reticular formation in the brain i.e. reinforcing the alert and aroused state. o Stimulates Lipolysis and glycogenolysis —> supplying more energy (glucose and free fatty acids). THANK YOU