Autonomic Nervous System PDF

Autonomic nervous system DR. SHEREEN SAMIR PROFESSOR OF PHYSIOLOGY Lecture Objectives At the end of this lecture you will be able to: 1) Identify regulatory systems of body functions 2) Recognize the structural and functional units of the nervous system...

Autonomic nervous system DR. SHEREEN SAMIR PROFESSOR OF PHYSIOLOGY Lecture Objectives At the end of this lecture you will be able to: 1) Identify regulatory systems of body functions 2) Recognize the structural and functional units of the nervous system 3) Describe the components of divisions of nervous system 4) List the cranial nerves 5) Compare the functional divisions of PNS (Somatic and autonomic NS) 6) Identify the origin of the different parts of autonomic NS 7) Define the autonomic ganglia and list its types 8) Identify the origin of sympathetic supply to different regions of the body  Regulatory Mechanisms Body functions are regulated by 2 systems; Nervous system Endocrine system Rapid onset Slow onset Short duration Long duration  Nervous System NS is the major control system in the body which regulates many body functions necessary for life e.g. heart, kidney functions 4  Nerve Cell Neuron It is the structural unit of nervous system. Cell Body No. : 1011 neurons in NS Structure: It is formed of: a.Cell body (soma): controls the activity of the whole neuron. Cell Processes b.Cell processes: 2 types axis and dendrites 5  Types of Neurons 1. Afferent (sensory) neuron→ carries impulses from receptors to CNS. 2. Efferent (motor) neuron→ carries impulses from CNS to effector organs. 3. Interneuron (associative) →located entirely within CNS 6  Reflex Action Def.: It is an automatic (involuntary) reaction of the body to sensory stimulus  Types of Reflex Action According to its effector organ; Skeletal Ms Smooth Ms Somatic Reflexes Autonomic Reflexes  Somatic Reflex Action Flexion withdrawal reflex  Autonomic Reflex Action Sensory neuron Motor neurons Increase ++ Pressure --- Micturition Reflex Divisions of Nervous System  Brain Cerebrum Cerebellum Brain stem Spinal Cord 8 12 5 5 1  Peripheral Nervous System (PNS) It is the part of NS which communicate between the CNS and peripheral tissues. A) Anatomical division: →12 pairs of cranial nerves → 31 pairs of spinal nerves ❑Functional Division i) Afferent (sensory) nerve fibers→ convey impulses from receptors to CNS ii) Efferent (motor) nerve fibers → conduct impulses from CNS to various organs of the body (effectors). ❑Physiological Division: i) Somatic N S →controls voluntary actions. ii) Autonomic N S →controls involuntary actions  Autonomic NS Def. Part of the PNS which supplies and regulates the functions of internal organs i.e. viscera of the body. Divisions of ANS ANS is subdivided into 2 systems: A. Sympathetic (thoracolumbar) NS B. Parasympathetic (craniosacral) NS 17  Origin of Autonomic NS Sympathetic N.S.(thoracolumbar) : LHCs of 1. All thoracic segments 2. Upper 3 lumbar segments of the spinal cord 18  Origin of Autonomic NS Parasympathetic (craniosacral ) : A) Cranial part: 1.Oculomotor N. in midbrain. 2.Facial N. in pons. 3.Glossopharyngeal N. in MO. 4.Vagus nerve in MO. B) Sacral part: S2,S3,S4 and forms pelvic nerve 19  Autonomic of Ganglia Def., Are collection of cell bodies of neurons outside the central nervous system (CNS) Functions: 1. relay station for all autonomic preganglionic nerves 2. distributing center: sympathetic ---- pre: postganglionic= 1:32 parasympathetic ----- pre: postganglionic= 1:2 Types: a) Lateral (Paravertebral) ganglia: Autonomic of Ganglia Located on either side of the spinal cord (2 rows of sympathetic chain) About 22-24 ganglia on each side Act as a relay station for preganglionic sympathetic fibers only b) Collateral (Prevertebral) ganglia: Present mainly in the abdomen, midway between spinal cord and viscera Act as a relay station for sympathetic preganglionic fibers c) Terminal ganglia: Present close to or at the wall the effector organs especially pelvic organs Act as a relay station of: a) All parasympathetic preganglionic fibers  Questions 1-Which of the followings is a 2-Autonomic nervous system is part of PNS: characterized by; a) Cerebrum a) Control of voluntary functions b) Pons b) Supply bones and skeletal muscles c) Cerebellum c) Paralysis of its innervated organ after d)Spinal nerves cutting of its nerve supply e) Medulla Oblongata d) Consists of 2 neurons e) Has no synapses outside CNS Sympathetic Supply to Head and Neck LHCs of T1 and T2 Origin Ganglia Organs 23  Sympathetic Supply to Head and Neck Functions: Mydriasis 1) Eye: a) Dilatation of pupil (Mydriasis) due to contraction of dilator pupilae muscle Palpebral fissure b) Widening of palpebral fissure c) Exophthalmos. d) Helps the eye to see far objects Exophthalmos 24  Sympathetic Supply to Head and Neck Functions: 2) Salivary Glands: a) Vasoconstriction (V.C.) of blood vessels b) Trophic secretions: little, viscous, concentrated secretion; poor in water and rich in enzymes 3) Skin: a) V.C of skin blood vessels. b) Hair erection c) Sweat secretion. 25  Horner's syndrome 1) Def: - It is a group of signs which result from interruption sympathetic to head and neck. 2) Causes: a. Lesion in T1 and T2 segments. b. Lesion in superior cervical ganglia or sympathetic chain. 3) Signs: on the same side of lesion a. Ptosis → drooping of upper eye lids due to paralysis of superior tarsal ms. b. Miosis → constriction of pupil due to paralysis of dilator pupillae ms. c. Enophthalmos → sinking of eye ball into orbit due to paralysis Muller's ms. d. Anhydrosis → absence of sweat secretion leading to dryness affected side of the face. e. Vasodilatation of skin blood vessels, due to loss of sympathetic vasoconstrictor tone, so the skin becomes red and warm. Sympathetic Supply to Thorax 27  Sympathetic Supply to Thorax 1) Heart: 2) Lungs: a) ↑ the heart rate and force of contraction a) Bronchodilatation. b) Vasodilatation of coronary vessels b) Decreases mucus secretion of air passages 28 Sympathetic Supply to Abdomen 29  Sympathetic Supply to Abdomen Functions: 1) GIT : relaxation of their walls and contraction of their sphincters 2) Gall bladder: relaxation of its wall and contraction of sphincter of Oddi → retention of bile 3) Pancreas: inhibits both endocrine and exocrine pancreatic secretion. 4) Kidneys: a)It decreases renal blood flow. b)It decreases urine output. 30  Sympathetic Supply to Abdomen Functions: 5) Spleen: Contraction of smooth muscles in splenic capsule and trabeculae → pouring of about 250 ml of stored blood into the general circulation. 6) Suprarenal medulla It releases large quantities of adrenaline (80%) and noradrenalin (20%) into the circulating blood. In stress conditions, SRM acts together with sympathetic nervous system (sympatho- adrenal system). 31 Sympathetic Supply to Pelvis 32  Sympathetic Supply to Pelvis Functions: 1- Urinary bladder: It causes relaxation of its wall and contraction of internal urethral sphincter → retention of urine. 2- Rectum: It causes relaxation of its wall and contraction of internal anal sphincter → retention of faeces. 33  Questions 1. Sympathetic stimulation of heart causes a) Increase in heart rate b) Coronary vasoconstriction c) Decrease in force of contraction of the heart d) Bronchodilatation 2.The autonomic ganglia; a) Are 5 types. b) Are present in both somatic and autonomic nervous systems c) Function as relay station for preganglionic nerve fibers. d) Are located inside the CNS. THANK YOU