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Autonomic Nervous System

Dive into the organization and distribution of the parasympathetic nervous system, from preganglionic fibers to postganglionic fibers, receptor types, and functional effects. Learn about the differences between sympathetic and parasympathetic divisions.

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Autonomic Nervous System

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  1. Autonomic Nervous System Dr DileepVerma Associate Professor Deptt of Physiology KGMU

  2. Lecture-4 :Topics Parasympathetic division- Preganglionic parasympathetic fibre Autonomic Ganglia Postganglionic parasympathetic fibre

  3. Learning Objectives • Details organization and distribution Parasympathetic nervous system

  4. Organization: Parasympathetic NS

  5. Parasympathetic division • Preganglionic neurons in the brainstem and sacral segments of spinal cord • Ganglionic neurons in peripheral ganglia located within or near target organs

  6. Contd…. Parasympathetic Nervous System • Parasympathetic Preganglionic neurons -Cranial parasympathetic outflow Midbrain outflow Bulbar outflow -Sacral parasympathetic outflow Preganglionic fibers Postganglionic fibers

  7. CONTD.. • Preganglionic fibers leave the brain as cranial nerves III, VII, IX, X • Sacral neurons form the pelvic nerves • Almost 75% of all parasympathetic outflow travels along the vagus nerve (cranial nerve X) • Pre ganglionic fiber are- Large & Myelinated

  8. CONTD.. Parasympathetic postganglionic fibres – • Innervate the target tissue • Very small fiber • Nonmyelinated • Conduction velocity low

  9. Receptors • The parasympathetic nervous system uses only acetylcholine (ACh) as its neurotransmitter. • Receptor-Cholinergic • The ACh acts on two types of receptors – Muscarinic Nicotinic

  10. Contd… • Most transmissions occur in two stages: When stimulated, the preganglionic nerve releases ACh at the ganglion, which acts on nicotinic receptors of the postganglionic nerve. • The postganglionic nerve then releases ACh to stimulate the muscarinic receptors of the target organ.

  11. Distribution of neurons

  12. Parasympathetic Responses

  13. Effects of stimulation of ANS

  14. Anatomical Differences between the Sympathetic and Parasympathetic Divisions

  15. 1-Parasympathetic stimulation causes-- Constriction of pyloric sphincter Positive inotropic effect Negative inotropic effect Increased gastric secretion

  16. 2-What percentage of all parasympathetic nerve fibers are in the vagus nerve ? 25 50 75 100

  17. 3-Which cranial nerve have parasympathetic fibers? 3rd 4th 5th 6th

  18. 4-The maximum parasympathetic fibers are contained in the: III nerve VII nerve IX nerve X nerve

  19. 5-Stimulation of postganglionic parasympathetic neurons causes-- Dilatation of pupil Secretion of saliva Release of epinephrine from adrenal medulla Sweating

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