1. Autonomic Nervous System INTI University Tay Ju Lee MD

2.   Autonomic Nervous System Basic Layout   Transmitters of the ANS   Function of the ANS   Overview of Neurochemical Transmission Plan for Today

3. Autonomic Nervous System Basic Layout

4.   Autonomic Nervous System   Symphathetic   Parasymphathetic   Enteric   Intrinsic nerve plexus of GIT closely interconnected with SNS & PNS   Integrated system that functions independent of CNS   Somatic Efferent Nerves   Somatic and Visceral Afferent Nerves PERIPHERAL NERVOUS SYSTEM

5. Conveys all neural output(efferents) from CNS to rest of body ENSPNS SNS AUTONOMIC NERVOUS SYSTEM Motor innervation skeletal muscle Motor innervation skeletal muscle CNS

7.   Autonomic Nervous System   Conveys output from hypothalamus to rest of body   Largely outside of voluntary control   2 neurons in a series instead of 1   Preganglionic   Postganglionic   Synapse lie in autonomic ganglion KEY FEATURES of ANS

8. SYMPHATHETIC   Sympathetic preganglionic neuron cell bodies lie in the lateral horn of grey matter   Preganglionic fibres synapse in paravertebral ganglion chains on either side of spinal column.   Ganglia contain cell body of postganglionic neuron   Except adrenal medulla - Secretes NA & A

9. Ganglia lie scattered in close relation to target organs – very short postganglionic neuron   Cranial Outflow - Cranial Nerves   CN III Oculomotor – Eye   CN VII Facial &   CN IX Glossopharyngeal   Salivary glands and Nasopharynx   CN X VAGUS – Thoracic & Abdominal Viscera   Sacral Outflow   Supply bladder, rectum & genitalia   Pelvic ganglia carry both SNS & PNS neurons PARASYMPHATHETIC

10.   Location of neurons   Myenteric plexus   Submucosal plexus   More cells than in the spinal cord   Incoming nerves from both PNS & SNS terminate on enteric neurons as well as run to smooth muscles, glands and blood vessels.   Pharmacologically more complex   ACh, Serotonin, 5HTP, NO, ATP, GABA, Substance P, VIP ENTERIC NERVOUS SYSTEM

11. Transmitters in ANS

12. Acetylcholine & Noradrenaline as transmitters in Peripheral NS

13. 3 RULES OF THUMB Two main neurotransmitters are ACh & NA   All motor nerve fibres leaving the CNS release acetylcholine, which acts on nicotinic receptors   All postganglionic parasympathetic fibres release acetylcholine acting on Muscarinic receptors   All postganglionic symphathetic fibres release noradrenaline, which acts on α or β adrenoceptors   Except sweat gland – Ach on M receptors

14. Function of ANS

15. FUNCTIONS OF ANS   Opposing effects   Visceral Smooth Muscle of Gut, Bladder & Heart   One Division operating   Sweat glands & Kidneys – SNS   Tears – PNS   One Division operating with local mediator   Small resistance arteries – SNS innervation   Vasodilation mediated by background Nitric Oxide   Skeletal muscle arteries – PNS causes dilatation   Both systems similar function   Salivary glands

16.   Generally   PNS – Rest and Digest   SNS – Fight or Flight   ANS are not simply physiological opponents.   Each serves it’s own physiological function and can be more or less active in particular organ or tissue according to the need at the moment. FUNCTION OF ANS

17.   Eyes   Pupils dilate   Pupils contract   Heart   Increased rate & contractility   Decreased rate & contractility   GI   Decrease in motility and tone   Increase in motility and tone   Genitalia in males   Ejaculation   Erection   Ureters & Bladder   Relaxes detrusor, contract sphincter   Contracts detrusor, relaxes sphincter   Trachea & Bronchioles   Dilates   Constricts ACTION of SNS & PNS on ORGANS

18. AUTONOMIC REFLEX ARC Baroreceptor in carotid sinus detects drop in BP 70/40 HR 60 SNS vasoconstrict and increase the heart rate now! HR increases to 100 & BP increases 120/80 Vagus take a break

19. Overview of Neurochemical Transmission

20. 1. 1. Uptake of precursors; 2. 2. Synthesis of transmitter 3. 3. Uptake/transport of transmitter into vesicles 4. 4. Degradation of surplus transmitter 5. 5. Depolarisation by propagated action potential 6. 6. Influx of Ca2+ in response to depolarisation 7. 7. Release of transmitter by exocytosis 8. 8. Diffusion to postsynaptic membrane 9. 9. Interaction with postsynaptic receptors 10. 10. Inactivation of transmitter 11. 11. Reuptake of transmitter or degradation products by nerve terminals 12. 12. Reuptake of transmitter by non- neuronal cells 13. 13. Interaction with presynaptic receptors. Drugs can affect any one of these steps of neurotransmission

21.   Autonomic Nervous System Basic Layout   PNS & SNS & ENS   Output & locations of Ganglions   Transmitters of the ANS   Cholinergic & Adrenergic   3 Rules of Thumb   Function of the ANS   Reflex arc, what the organ needs   Overview of Neurochemical Transmission   13 ways drugs can affect neuron transmission Summary

22.   Rang et al (2007) Rang & Dale’s Pharmacology 6 th Ed. References