Autonomic Nervous System PDF

Lecture 3: Autonomic nervous system Prepared by: Dr. Marianne Basta Lecturer of Physiology, faculty of Medicine, Alexandria university ILOS: To understand the anatomical division of human nervous system. To understand the physiological division of human nervous s...

Lecture 3: Autonomic nervous system Prepared by: Dr. Marianne Basta Lecturer of Physiology, faculty of Medicine, Alexandria university ILOS: To understand the anatomical division of human nervous system. To understand the physiological division of human nervous system. To understand the divisions and outflows of autonomic nervous system. To identify the unit structure and function of nervous system. To identify the components of the reflex arc. To discuss the autonomic ganglia. Anatomical division of human nervous system Central nervous system: a) Brain: Cerebral cortex Subcortical: thalamus, hypothalamus Brain stem: mid brain, pons and medulla cerebellum Central nervous system: b) Spinal cord consists of 31 segments: 8 cervical 12 cervical 5 lumbar 5 sacral and coccygeal Peripheral nervous system Cranial nerves: 12 pairs arising from the brain stem. Peripheral nervous system Spinal nerves: 31 pairs arising from spinal segments Physiological division of human nervous system Autonomic Nervous system ( ANS): That controls the involuntary body activities i.e., controls heart rate, respiratory rate, vessel wall diameter, eye pupil diameter, etc. Somatic Nervous System: That controls the voluntary body activities i.e., body movement. Sympathetic NS Parasympathetic NS Sympathetic division of Parasympathetic NS is the ANS is called the called the rest and sleep fight and flight division of the ANS. division. It allows the body to It prepare the body to recover from stress deal with stress. 10  Divisions of Autonomic Nervous System Anatomically Functionally Cranial Thoracolumber Sacral outflow outflow outflow Sympathetic N.S. Parasympathetic N.S. Thoraco –lumber Cranio – sacral T1 to L3 III –VII- IX- X S2 to S5 Cranial Outflow (Parasympathetic) Autonomic preganglionic fibers from cranial nerve nuclei III (oculomotor) –VII (facial)- IX (glosso- pharyngeal)- X (vagus) in midbrain and medulla oblongata Sacral Outflow (Parasympathetic) Autonomic preganglionic fibers from lateral horn cells of spinal segments S2 ,S3 & S4. Thoraco-lumber Outflow (sympathetic) Autonomic preganglionic fibers from lateral horn cells of spinal segments T1 to L3 Unit structure of Nervous System= Neuron Unit Function of Nervous System= Reflex action Reflex action: Definition: it is unavoidable, inborn, beneficial response to a stimulus Types: Somatic reflex action Autonomic reflex action Components of reflex action: Reflex Arc: Receptor Afferent neuron center efferent neuron effector organ  Reflex action Somatic Autonomic Receptor Skin Internal organ Afferent Same Same (Sensory neuron) Center AHC LHC Efferent One neuron 2 neurons (Motor neuron) Autonomic ganglion Preganglionic Postganglionic Effector Skeletal muscle Smooth, cardiac muscle gland  Synapse Definition: It is the site of contact between 2 neurons i.e., the site of contact between the axon terminals of one neuron and cell body or dendrites of another neuron. ( there is no cytoplasmic continuity between neurons). A neurotransmitter is released from the presynaptic cell to carry the message to post synaptic cell e.g., acetylcholine in autonomic ganglia  Autonomic Ganglia In autonomic innervation there are preganglionic fibers that arise from CNS and postganglionic fibers that arise from autonomic ganglia Each preganglionic fiber relays only once through it may passes through several ganglia. Autonomic Ganglia Definition Types Functions Definition: it is a collection of cell bodies outside the CNS Types: Lateral Sympathetic chain Collateral (prevertebral) Celiac, superior mesenteric, inferior mesenteric Terminal  Autonomic Ganglia They are three types Lateral ( paravertebral ) ganglia They form 2 sympathetic chains ,one on each side of the vertebral column. Each chain contain 22-24 ganglia.they receive pregang. Sympath. Fibers to head, neck and thorax b. Collateral ganglia Receive preganglionic sympathetic fibers to abdomen and pelvis c. Terminal ganglia Receive all preganglionic parasympathetic fibers Types of autonomic Ganglia Lateral collateral terminal Functions of autonomic ganglia 1- Distributing centers The preganglionic sympathetic excites several post ganglionic fibers so, sympathetic stimulation produces generalized response 2- Site of relay (synapse) 3- Chemical transmitter (Acetyl choline, Ach)  Lecture 4: Autonomic nervous system Prepared by: Dr. Marianne Basta Lecturer of Physiology, faculty of Medicine, Alexandria university ILOS: To understand functions and effects of sympathetic nervous system. To understand functions and effects of parasympathetic nervous system. To identify organs supplied by sympathetic innervation only. To identify organs supplied by parasympathetic innervation only. To discuss the Interaction between both sympathetic and parasympathetic NS. To identify the chemical transmission in ANS. To identify the control of autonomic functions.  Divisions of ANS Sympathetic Parasympathetic Origin Thoraco-lumbar Craniosacral Type of ganglia Paravertebral (lateral, Peripheral sympathetic chain) (terminal) Prevertebral (collateral) Preganglionic Short Long fibers (Ach) (Ach) Postganglionic Long Short fibers (nor-Adrenaline 90%, (Ach) Adrenaline 10%) Fight or flight Rest, digest Catabolic Anabolic Distribution of Sympathetic nervous system Organ Head and neck Function Eye Pupillary dilation (mydriasis) lid retraction Eyeball protrusion Lacrimal gland VC- atrophic Salivary Glands VC- Viscid secretion Skin Piloerector muscle Motor- erection Sweat glands secretion Cutaneous blood vessels VC Horner syndrome: damage of sympathetic supply to head and neck Ptosis (lid dropping) Miosis (pupillary constriction) Anhydrosis (no sweating) Enophthalmosis Flushing of the face Sympathetic Supply Thorax Function Heart Excitation Vasodilator to coronaries Lungs Bronchodilation Slight VC Inhibition of bronchial glands secretion Sympathetic Sympathetic Supply Supply abdomen Function Blood vessels VC Smooth muscles of GIT Inhibit peristaltic movement Sphincters Motor Liver Glycogenolytic Gall bladder Retention of bile Spleen Motor to splenic capsule Adrenal medulla secretory Sympathetic Supply Organ Function Colon Retention of faeces Urinary bladder Retention of urine Blood vessels VC Male sex organs Motor ejaculation of semen uterus variable Orbelli Phenomenon Better contraction, delayed fatigue and early recovery of skeletal muscle after fatigue. Due to: 1- glycogenolysis 2- sensitivity of Motor end plate to Ach 3- O2 consumption and heat production 4- vasodilatation Functions of sympathetic nervous system Sympathetic tone Alarm or stress response (mass discharge) under the basal condition, the In emergency the sympathetic sympathetic system is system continuously active & discharge a) prepares the body for impulses to the innervated activity. organs. b) its capacity and indurance The basal rate of activity of for performing severe sympathetic system is known as muscular efforts. Sympathetic tone. c) there is mass discharge Example: tonic discharge to i.e. large portion discharge arterioles. at the same time.  Functions of sympathetic nervous system during stress (mass discharge) 1- Relaxes accomodation and dilates the pupil. 2- Increases all properties of the heart. 3- Dilates the bronchioles. 4- Constriction of skin blood vessels. 5- Shift of blood flow from skin & splanchnic areas to heart, CNS and skeletal muscles. 6- Increases glycogenolysis in the liver. 7- Elevates blood glucose & free fatty acid level. 8- Contraction of splenic capsule. 9- Increases the secretion of adrenaline & noradrenaline from the adrenal medulla. 10- Orbelli phenomema. 11- Increases mental activity. 12- Increases sweat secretion. 13- Reinforcing the alert, aroused state by stimulation of reticular formation by catecholamine. Parasympathetic Nervous System The parasympathetic nervous system has a craniosacral outflow  Important Functions : 1- Pupillary constriction & accommodation (oculomotor nerve). 2- Secretion of tears (facial nerve) 3- Secretion of watery saliva (facial and glossopharyngeal) 4- Decrease heart properties (vagus) 5- Constriction of bronchioles (vagus) 6- Stimulation of GIT secretion & peristalsis (vagus and sacral nerves) 7- Stimulation of emptying mechanism of the rectum and urinary bladder micturition & defecation (sacral nerves). 8- Nerve of erection (sacral nerves). Dual innervation Almost all visceral organs are supplied by both sympathetic and parasympathetic divisions of the autonomic NS. Which division predominate at any given time is determined by the body demands at that time. The parasympathetic discharge to the heart is more powerful at rest (vagal tone or parasympathetic tone) While the sympathetic discharge to the blood vessels is more potent at rest (sympathetic tone) Structures supplied only by sympathetic nervous system: Skin sweat glands (sympathetic cholinergic) Piloerector muscle. Blood vessels all over the body except the penis. Dilator pupillae muscle. Blood vessels of the skeletal muscles Adrenal medulla. Capsule of the spleen. Structures supplied only by Parasympathetic nervous system: Constrictor pupillae muscle. Ciliary muscle Lacrimal gland Penile erectile tissue Interaction between both sympath. and parasympath. NS 1. Antagonistic : As the case in the heart 2. Synergistic ( complementary ) As the case in salivary secretion And during the sexual act Chemical transmission in ANS Parasympathetic Sympathetic Ach receptors Nicotinic Muscarinic Stimulus Ach, small dose of nicotine Ach, muscarine Sites 1. All autonomic ganglia 1. All postganglionic para- 2.Adrenal medulla sympathetic fibers 3. NMJ 2. Post-ganglionic sympathetic fibers innervating sweat glands and skeletal Ms blood vessels. Blockage 1.Large dose of nicotine Atropine 2. Hexamethonium 3. Curare Adrenergic α-receptors ß-receptors receptors Stimulus Noradrenaline Adrenaline Sites α1-receptors: ß1-receptors: All effectors Heart Excitatory except Excitatory GIT ß2-receptors: α2-receptors: GIT, lungs, UB Presynaptic Inhibitory Inhibit NA release Blockage Phentolamine Propranolol Control of Autonomic functioning Anterior hypothalamus regulates parasympathetic functions. Posterior hypothalamus regulates sympathetic functions. Limbic system and hippocampus share in regulation. Cerebral cortex also share. Thank you