PREVIOUS YEAR QUESTIONS
BATCH – B ( 63-69)
PIYUSH
V.PRIYADARSHINI
PREETHI
PRASHANT
PRATIBHA
PREYOSHI
PINKI
Q1. What are the movements of Small intestine? Give
characteristic features of each movements?
Ans – Segmental or pendular, Peristalsis and Tonic contractions
A. Rhythmic segmental ( or pendular) movements
(i) Appear at regular intervals Involving a localises segment of 1-2 cm
(ii) Concerned with :
(a) mixing function ( food is mixed thoroughly with digestive juices
again and again)
(b) Churning action,i.e., food is divided or segmented and is propelled
towards large intestine.
(iii) Frequency of contractions during digestion is highest in the
duodenum(12/ min) and lowest in the ileum (9/min).
(iv) Controlled by pacemaker cells in the 2 nd part of duodenum
(a) frequency of contractions is directly realted to the frequency of
BER of slow waves.
(b) strength of contraction is proportional to the frequency of
spike generated by the slow waves.
B. Peristalsis (or wormicular movements)
(i) A coordinated reaction in which a wave of contraction
preceded (come before) by a wave of relaxation which passes
down a hollow viscus.
(ii) Proceeds from proximal to the distal end of the GIT, called
polarity of the intestine or law of the gut. This is due to:
(a) frequency of BER decreases progressively from the duodenum
to the ileum; (b) receptive relaxation which appears only distally.
(iii) Function: propel the intestinal contents towards ileocaecal
valve (few cms/wave).
(iv) Usual stimulus for peristalsis is: distension wave pass 2 to 25
cm/sec. Mechanism: Local stretch →→ release 5HT activate
myenteric plexus (Myenteric reflex).
Notes:
1. A-ch and substance P → circular contraction above the point of stimulus; and
2. Nitric oxide, VIP and ATP → relaxation below the point of stimulus.
(v) Role of extrinsic innervation: (a) Strong emotion→ activate vagus nerve→ ↑ muscular
contraction and Ts the tone of small intestine; and (b) Anger, fear and pain activate
sympathetic components muscular contraction and ↓s tone of the small intestine.
Q2. Explain the Enteric nervous system
of GIT?
Ans – INTRINSIC NERVE SUPPLY- ENTERIC NERVOUS SYSTEM
Intrinsic nerves to GI tract form the enteric nervous system that controls all the
secretions and movements of GI tract. Enteric nervous system is present within the
wall of GI tract from esophagus to anus. Nerve fibers of this system are
interconnected and form two major networks called:
1. Auerbach’s plexus.
2. Meissner’s plexus.
These nerve plexus contain nerve cell bodies, pro- cesses of nerve cells and the
receptors. The receptors in the GI tract are stretch receptors and chemorecep- tors.
Enteric nervous system is controlled by extrinsic nerves.
1. Auerbach’s Plexus
Auerbach’s plexus is also known as myenteric nerve plexus. It is present in between
the inner circular muscle layer and outer longitudinal muscle layer.
Functions of Auerbach’s plexus
Major function of this plexus is to regulate the move- ments of GI tract. Some nerve
fibers of this plexus accelerate the movements by secreting the excitatory
neurotransmitter substances like acetylcholine, sero- tonin and substance P. Other fibers
of this plexus inhib- it the GI motility by secreting the inhibitory neurotrans- mitters such
as vasoactive intestinal polypeptide (VIP), neurotensin and enkephalin.
2. Meissner’s Nerve Plexus
Meissner’s plexus is otherwise called submucus nerve plexus. It is situated in between
the muscular layer and submucosal layer of GI tract.
Functions of Meissner’s plexus
Function of Meissner’s plexus is the regulation of sec- retory functions of GI tract. These
nerve fibers cause constriction of blood vessels of GI tract.
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