Autonomic Nervous System

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Autonomic Nervous System

• Dr
  Dileep Verma
• Associate
  Professor
• Deptt of
  Physiology
• KGMU

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Lecture-4 Topics

• Parasympathetic division-
• Preganglionic parasympathetic fibre
• Autonomic Ganglia
• Postganglionic parasympathetic fibre

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Learning Objectives

• Details organization and distribution
  Parasympathetic nervous system

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Organization Parasympathetic NS
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Parasympathetic division

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

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Contd.

• Parasympathetic Nervous System
• Parasympathetic Preganglionic neurons
• -Cranial parasympathetic outflow
• Midbrain outflow
• Bulbar outflow
• -Sacral parasympathetic outflow
• Preganglionic fibers
• Postganglionic fibers

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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

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CONTD..

• Parasympathetic postganglionic fibres
• Innervate the target tissue
• Very small fiber
• Nonmyelinated
• Conduction velocity low

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Receptors

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

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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.

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Distribution of neurons
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Parasympathetic Responses
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Effects of stimulation of ANS
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Anatomical Differences between the Sympathetic
and Parasympathetic Divisions
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1-Parasympathetic stimulation causes--

1. Constriction of pyloric sphincter
2. Positive inotropic effect
3. Negative inotropic effect
4. Increased gastric secretion

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2-What percentage of all parasympathetic nerve
fibers are in the vagus nerve ?

• 25
• 50
• 75
• 100

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3-Which cranial nerve have parasympathetic
fibers?

1. 3rd
2. 4th
3. 5th
4. 6th

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4-The maximum parasympathetic fibers are
contained in the

1. III nerve
2. VII nerve
3. IX nerve
4. X nerve

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5-Stimulation of postganglionic parasympathetic
neurons causes--

• Dilatation of pupil
• Secretion of saliva
• Release of epinephrine from adrenal medulla
• Sweating

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