Lecture 2 Functions of ANS

Functions of ANS are carried out by Sympathetic division Parasympathetic division [=Thoraco-Lumbar outflow] [=Cranio-Sacral outflow] Dr.Gehan El-Salamony

Both divisions of ANS antagonize each other in most of the body organs. (one speeds up an organ, while the other slows down the same organ) e.g. sympathetic NS increases heart rate while parasympathetic NS decreases heart rate. At rest, the body is regulated by the parasympathetic NS. In stress conditions, the sympathetic NS dominates. Dr.Gehan El-Salamony

Sympathetic NS  Sympathetic division of the ANS prepares the body to deal with stress  It is called the fight and flight division Dr.Gehan El-Salamony

Sympathetic NS Dr.Gehan El-Salamony Origin of the Sympathetic NS = Thoraco-lumber outflow 1)LHC of all thoracic segments. 2)LHC of upper 3 or 4 lumber segments.

Parasympathetic NS  Parasympathetic NS allows the body to recover from stress  It is called the rest and sleep division of the ANS Dr.Gehan El-Salamony

Parasympathetic NS Dr.Gehan El-Salamony Origin of parasympathetic NS = Cranio-sacral outflow 1) Cranial nerves III, VII, IX & X 2) LHC of S2, 3 & 4.

Short Short preganglionic Long Long postganglionic Ganglia close to spinal cord Long Long preganglionic Short Short postganglionic Ganglia on/in target organ

Sympathetic Ganglia Sympathetic Ganglia (long post-ganglionic nerve fibers) 1. Lateral ganglia. 2. Collateral ganglia. Parasympathetic Ganglia (short post-ganglionic nerve fibers) * Terminal ganglia. Dr.Gehan El-Salamony

Functions of Sympathetic & Parasympathetic Nervous System

Sympathetic NS It is characterized by: emergency and stress fear, fight and flight reactions  It discharges during emergency and stress (fear, fight and flight reactions). one unit generalized action  It acts as one unit (generalized action). WHY ?? to prepare the body to face stress Dr.Gehan El-Salamony

Sympathetic Nervous System prepares the body through the following effects :

1-Heart: 1- Heart: increase cardiac activity (to blood supply to active tissues) 2- Blood vessels: 2- Blood vessels: Vasoconstriction [ Vasodilation of Sk.Muscle blood vessels] 3- Lungs: 3- Lungs: bronchodilation (to increase ventilation & O 2 supply ) 4-Metabolism: 4- Metabolism: increase blood glucose It has catabolicaction (It has catabolic action) 5-Sweat glands: 5- Sweat glands: profuse secretion to control body temperature (to control body temperature) Dr.Gehan El-Salamony

6-Digestive & urinary system activities 6- Digestive & urinary system activities: It delays evacuation of visceral content (causes wall relaxation + sphincter contraction) (inhibits defecation & micturation) Dr.Gehan El-Salamony

Other effects of sympathetic activation  Eye:  Eye: dilatation of the pupil + widening of the palpebral fissure + exophthalmos. (enables the subject to assess his surrounding)  Adrenal medulla:  Adrenal medulla: secretion of adrenaline & noradrenalin (augments sympathetic activity) Dr.Gehan El-Salamony

Question What will be the result of cervical symp. chain injury? Affect symp. Supply of the face Eye Skin Dr.Gehan El-Salamony

Horner’s syndrome Caused by injury of cervical sympathetic chain on one side. Symptoms: 1-Ptosis. 2-Miosis. 3-Enophthalmos. 4-Anhydrosis. 5-Redness of skin (V.D.) On the same side of injury

Parasympathetic NS It is characterized by rest and sleep  It discharges during rest and sleep localized  Its action is localized anabolic conserve body stores  It has anabolic action ( conserve body stores ). secreto-motor.  It increases gastrointestinal secretion & motility i.e. secreto-motor. Dr.Gehan El-Salamony

3 rd cranial nerve (III n. / Occulomotor nerve): Eye: 1-Pupil constriction (Miosis). 2-Accomodation to near vision 7 th (VII n. /Facial nerve) & 9 th ( IX n./ Glossopharyngeal nerve): Salivary glands: Increases secretion (watery saliva + large volume). 10 th Cranial nerve (X n./ Vagus nerve): Viscera in the thorax & abdomen Heart, lungs, GIT Sacral division (= Pelvic nerve): Urinary bladder & Rectum: Contraction of wall and Relaxation of sphincter micturation & defecation External genitalia: Vasodilatation of the blood vessels erection Dr.Gehan El-Salamony

ParasympatheticSympatheticEffector ConstrictionDilatationPupil decreases heart rateIncreases heart rateHeart ConstrictionDilatationBronchi Stimulates secretion & movement Inhibits secretion & movement GIT Contraction of walls & relaxation of sphincter Relaxation of walls & contraction of sphincter Urinary bladder & Rectum ErectionEjaculationGenital organs ---StimulationAdrenal medulla ---Sweat secretionSweat glands ---ConstrictionSystemic arterioles ---DilatationSkeletal muscle arterioles

Vagal stimulation causes: 1- Heart decreases heart rate. (It has no direct effect on ventricles) 2- Lungs bronchoconstriction. 3- GIT increases secretion & motility. Dr.Gehan El-Salamony

Question Compare between the 2 divisions of ANS regarding:  Origin  Relay in ganglia  Effect of stimulation  Chemical transmission Dr.Gehan El-Salamony