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Autonomic Nervous System
Dr Dileep Verma
Associate Professor
Deptt of Physiology
KGMU
Lecture-4 :Topics
Parasympathetic division


Preganglionic
parasympathetic fibre
Autonomic Ganglia
Postganglionic
parasympathetic fibre
Learning Objectives
 Details
organization and
distribution Parasympathetic
nervous system
Organization: Parasympathetic NS
Parasympathetic division
Preganglionic neurons in the
brainstem and sacral segments of
spinal cord
 Ganglionic neurons in peripheral
ganglia located within or near target
organs

Contd….
Parasympathetic Nervous System
 Parasympathetic Preganglionic
neurons
-Cranial parasympathetic outflow
Midbrain outflow
Bulbar outflow
-Sacral parasympathetic outflow
Preganglionic fibers
Postganglionic fibers
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
CONTD..
Parasympathetic postganglionic fibres
–
Innervate the target tissue
 Very small fiber
 Nonmyelinated
 Conduction velocity low

Receptors

The parasympathetic nervous system uses only
acetylcholine (ACh) as its neurotransmitter.

Receptor-Cholinergic

The ACh acts on two types of receptors –
Muscarinic
Nicotinic
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.
Distribution of neurons
Parasympathetic Responses
Effects of stimulation of ANS
Anatomical Differences between
the Sympathetic and
Parasympathetic Divisions
1-Parasympathetic stimulation causes-Constriction of pyloric sphincter
B. Positive inotropic effect
C. Negative inotropic effect
D. Increased gastric secretion
A.
2-What percentage of all parasympathetic
nerve fibers are in the vagus nerve ?
A.
B.
C.
D.
25
50
75
100
3-Which cranial nerve have
parasympathetic fibers?
3rd
B. 4th
C. 5th
D. 6th
A.
4-The maximum parasympathetic fibers are
contained in the:
III nerve
B. VII nerve
C. IX nerve
D. X nerve
A.
5-Stimulation of postganglionic
parasympathetic neurons causes-A. Dilatation of pupil
B. Secretion of saliva
C. Release of epinephrine from adrenal
medulla
D. Sweating
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