ANS BY Dr.Amruta Nitin Kumbhar

Autonomic nervous system: divisions
General organization of ANS Neurons of ANS
Physiological anatomy of sympathetic nervous system& parasympathetic nervous System
Autonomic neurotransmitters and receptors
Functions of ANS: effects of autonomic nerve impulses on effector organs
Differences between sympathetic and parasympathetic systems
APPLIED ASPECTS- Autonomic drugs, Autonomic failure, Autonomic function tests

1. Autonomic Nervous System Dr. Amruta N. Kumbhar Asst. Professor Dept. of Physiology D. Y. Patil Medical College, KOP, MH.

2. SLOs Autonomic nervous system: divisions General organization of ANS Neurons of ANS Physiological anatomy of sympathetic nervous system& parasympathetic nervous System Autonomic neurotransmitters and receptors Functions of ANS: effects of autonomic nerve impulses on effector organs Differences between sympathetic and parasympathetic systems APPLIED ASPECTS- Autonomic drugs , Autonomic failure, Autonomic function tests

3. AUTONOMIC NERVOUS SYSTEM: DIVISIONS Greek words, the autos meaning ‘self’ and the nomos meaning ‘control ANS is an involuntary system. Since it controls the vegetative functions, it is also called vegetative system.

4. DIVISIONS Sympathetic division, Thoracolumbar division , consists of thoracic and lumbar chains of sympathetic ganglia. Parasympathetic division, craniosacral division , consists of the ganglia associated with third, seventh, ninth and tenth cranial nerves.

5. General arrangement of somatic part of nervous system (on left) compared with autonomic part of nervous system

6. Somatic versus autonomic nervous system Somatic autonomic Afferent (sensory) neuron of somatic system having cell body in the dorsal root ganglion terminates in dorsal horn terminates in intermediolateral horns. Interneuron has cell body in the dorsal horn and terminates in the ventral horn cell body in the intermediolateral horn and terminates in the autonomic ganglia. Efferent (motor) neuron has cell body in the ventral horn and its axon carries impulses of skeletal muscles ( effector Organ) post- ganglionic neuron in ANS has cell body outside the CNS in the autonomic ganglion and its axon terminates in the visceral effector . single efferent neuron in the somatic system, two efferent neuron chains between CNS and the effector organ: first efferent neuron (pre- ganglionic neuron) has its cell body in CNS while the second efferent neuron (post- ganglionic neuron) has its cell body outside the CNS in the ganglion

7. Somatic autonomic Somatic motor system innervates the skeletal muscles ANS innervates the smooth muscles, cardiac muscles and secretory glandular epithelium Neurotransmitter at efferent (motor) neuron ending is acetylcholine neurotransmitter released between pre and post- ganglionic neuron is also acetylcholine, but that between post- ganglionic and effector organ depends on the component of ANS always causes muscle excitation cause both excitation and inhibition always voluntary usually involuntary

8. GENERAL ORGANIZATION OF THE AUTONOMIC NERVOUS SYSTEM Autonomic areas in the cerebral hemispheres limbic system Prefrontal cortex Hypothalamus - main ganglion of the ANS Part of thalamus

9. II. Autonomic centres in the brain stem Autonomic centres in reticular formation 1.Gigantocellular nucleus and 2. Parvocellular nuclei. General visceral nuclei of cranial nerves 1.afferent nucleus is represented by the nucleus of solitary tract present in the medulla ( vagus and glossopharyngeal nerves ) 2. efferent nuclei give origin to the pre- ganglionic fibres that constitute the cranial parasympathetic outflow 1.Edinger–Westphal nucleus (of oculomotor nerve) situated in the mid brain, 2. Salivary nucleus (superior and inferior) located in the pons 3. Dorsal nucleus of vagus , present in the medulla

10. III. Autonomic centres in the spinal cord In the intermediolateral grey column of spinal cord at two levels Neurons present in T1–L2 constitute the pre- ganglionic neurons of the sympathetic nervous system Neurons present in the second, third and fourth sacral segments of spinal cord (S2–S4) are the pre- ganglionic neurons of the sacral part of parasympathetic system,

11. IV. Peripheral part of ANS all autonomic nerves and ganglia throughout the body.

12. General arrangement of somatic part of nervous system (on left) compared with autonomic part of nervous system

13. NEURONS OF ANS Pre- ganglionic neurons Post- ganglionic neuron. cell body of the pre- ganglionic neuron is located in either the brain stem or spinal cord cell body of the post- ganglionic neuron is located in the autonomic ganglion Axon projects as a thinly myelinated pre- ganglionic fibre to an autonomic ganglion unmyelinated axon to the visceral effector cells.

14. PHYSIOLOGICAL ANATOMY OF SYMPATHETIC NERVOUS SYSTEM Sympathetic pre- ganglionic neurons Sympathetic ganglia Paravertebral ganglia- Cervical ganglia. These are three in number: superior, middle and inferior. Thoracic ganglia. These are 11–12 in number. Lumbar ganglia are four in number. 2 . Prevertebral or collateral ganglia – ( coeliac ganglion, inferior mesenteric ganglion and superior mesenteric ganglion) 3 . Peripheral or terminal ganglia- Heart, bronchi, pancreas and urinary bladder

15. Post- ganglionic sympathetic neurons

16. PHYSIOLOGICAL ANATOMY PARASYMPATHETIC NERVOUS SYSTEM Parasympathetic pre- ganglionic neurons- Cranial parasympathetic outflow- 1. Mid brain or tectal outflow- Edinger–Westphal nucleus 2.Bulbar outflow - general visceral efferent nuclei associated with bulbar outflow are- Superior salivary nucleus, Lacrimal nucleus, Inferior salivary nucleus and Dorsal vagal nucleus.

17. II. Sacral parasympathetic outflow Pre- ganglionic fibres Post- ganglionic fibres Parasympathetic afferent fibres

18. AUTONOMIC NEUROTRANSMITTERS AND RECEPTORS

19. All pre- ganglionic fibres (sympathetic as well as parasympathetic) release acetylcholine. All post- ganglionic parasympathetic fibres release acetylcholine. Most post- ganglionic sympathetic (adrenergic) fibres release norepinephrine . A few post- ganglionic sympathetic (cholinergic) fibres release acetylcholine

20. Autonomic receptors 1. Cholinergic receptors On the basis of their pharmacological properties, these are of two types: Nicotinic receptors Muscarinic receptors 2. Adrenergic receptors Alpha (a) adrenergic receptors ( α1 and α2 ) Beta (b) adrenergic receptors ( β1, β2 and β3 )

21. Nicotinic receptors Muscarinic receptors located in Autonomic ganglia of sympathetic and parasympathetic nervous system, Neuromuscular junction Adrenal medulla. Heart, Smooth muscles (except vascular smooth muscle) and Glands. activated by: Acetylcholine (Ach) and Nicotine. activated by: Acetylcholine (Ach) and Muscarine . Effect excitation Effect-Inhibitory in the heart Excitatory in smooth muscle and glands (e.g. increased gastrointestinal motility and increased secretion). Blockage. hexamethonium , trimethaphan Blockage atropine

22. α1 receptors α2 receptors Location - Vascular smooth muscles of skin and splanchnic regions. Gastrointestinal and bladder sphincters Radial muscles of the iris Location- Pre-synaptic nerve terminals, Platelets, Fat cells Walls of the gastrointestinal tract. Effect- excitation, e.g. contraction or constriction. Effect- inhibition e.g. relaxation or dilatation Mechanism of action. These receptors act by formation of IP3 and increase in intracellular Ca2 Mechanism of action. α2 receptor causes inhibition of adenylyl cyclase and decrease in cyclic adenosin monophosphate ( cAMP ).

23. β1 receptors β2 receptors Location- Sinoatrial node, Atrioventricular (AV) node Ventricular muscles of the heart. Location- Vascular smooth muscle of skeletal muscle, Bronchial smooth muscle, Walls of the gastrointestinal tract Bladder. Effect- produce excitation e.g. increased heart rate, increased conduction velocity and increased contractility Effect- produce relaxation e.g. dilation of vascular smooth muscle, dilation of bronchioles and relaxation of bladder wall β3 receptors. These receptors are located on the adipose tissue and causes lipolysis

24. FUNCTIONS OF AUTONOMIC NERVOUS SYSTEM important role in maintaining the constant internal environment (homeostasis ) Most of the visceral organs have dual innervation , i.e.are supplied by both sympathetic and parasympathetic divisions The two divisions produce antagonistic effects on each organ and provide a very fine degree of control over the effector organ Some of the visceral organs are innervated by one division of ANS only; e.g. – Uterus, adrenal medulla and most of the arterioles are innervated by sympathetic division only. – Glands of stomach and pancreas are innervated by parasympathetic division only In the case of sphincter’s muscles, both adrenergic and cholinergic innervations are excitatory, but one supplies the constrictor component of the sphincter and other the dilator.

25. APPLIED ASPECTS AUTONOMIC DRUGS- Sympathomimetic drugs- phenylephrine , isoproterenol and albuterol . Sympatholytic drugs or sympathetic blockers- phentolamine Parasympathomimetic drugs- pilocarpine , methacholine , neostigmine and physostigmine Parasympatholytic drugs or parasympathetic blockers- atropine, homatropine ,

26. Horner’s syndrome Ipsilateral oculosympathetic paresis common causes- Pancoast’s tumour of the lung, malignancy of cervical lymph nodes pressing on the cervical sympathetic chain Clinical features of Horner’s syndrome are: Ptosis ( drooping down of upper eyelid) due to paralysis of Muller’s muscle of upper eyelid. Miosis (small pupil) due to paralysis of dilator pupillae muscle. Facial anhidrosis , i.e. reduced sweating on the ipsilateral face and neck.

27. AUTONOMIC FUNCTION TESTS Valsalva’s manoeuvre Heart rate variation during deep breathing Heart rate response to standing Blood pressure response to standing Blood pressure response to sustained hand grip Test of sudomotor function Tests of bladder function

28. References Textbook of Physiology -Guyton & Hall (12 th edition ) - Textbook of Physiology - A.K.Jain 6 th edition Text book of Medical Physiology - Indukurana Principles of Anatomy & Physiology - Tortora - Internet Source for Pictures & etc.