1. Gastro-intestinal Physiology General
Prof. K. Sivapalan.

2. Why Eat? Hunger. Taste and satisfaction. Passing time Energy. Growth.
Socialization.
Health.
2013
GIT Grneral

3. Functions of GIT Tranquility [oral activity] Ingestion. Digestion.
Absorption
Excretion.
Protection- immunity
2013
GIT Grneral

4. Gastro-Intestinal Tract
2013
GIT Grneral

5. General Organization of GIT
Dorsum
Mesentery
Glands:
Goblet cells Mucosal Sub mucosal Glands outside.
Mucosa
Sub mucosa
Sub mucus muscle
Sub mucus [Meissner’s] plexus
Circular muscle
Myenteric [Auerbach’s] plexus
Longitudinal muscle.
Serosa.
2013
GIT Grneral

6. Smooth muscle in GIT
Smooth muscles in intestine form a syncytium with tight junctions and gap junctions.
Membrane potential shows slow waves. More in pace makers. (Basic electrical rhythm (BER) of gastrointestinal smooth muscle)
When the waves reach threshold level, spike potentials occur.
Muscle tension increases or decreases depending on the number of spikes.
Acetylcholine increases and adrenaline reduces tension.
2013
GIT Grneral

7. Innervation
Sub mucus [Meissner’s] plexus is mainly sensory - stimulated by, irritation, distention or chemicals.
Autonomic afferents from tissues [vagal (80 %) and sympathetic] and Meissner’s plexus go centrally.
Myenteric [Auerbach’s] plexus is motor.
Parasympathetic [Vagus] end on cells of Myenteric plexus.
Sympathetic fibers end on Myenteric plexus, muscles and glands.
Sensory neurons
2013
GIT Grneral

8. Gut Reflexes
Coltroll within the gut- secretions, peristalsis, mixing, local inhibitions etc.
Coordinated in para vertibral sympathetic ganglia- enterogastric reflex, colonoilial reflex
Coordinated in brain stem- stomach to stomach: motor and secretary, pain inhibiting entire GIT function, defecation
2013
GIT Grneral

9. Peristalsis. Coordinated by myenteric plexus
Contraction of circular muscles proximal to the stimulus and relaxation distally.
Longitudinal muscles contract and pull over the contents.
The relaxed circular muscles contract.
The sequence is propagated in oral to caudal direction.
2013
GIT Grneral

10. Migrating Motor Complex
Cycles of motor activity, initiated by motilin, migrate from the stomach to the distal ileum during fasting at 90 minute intervals at 5 cm/min
Clear the stomach and small intestine of luminal contents in preparation for the next meal
Quiescent period (phase I), irregular electrical and mechanical activity (phase II), burst of regular activity (phase III)
2013
GIT Grneral

11. Voluntary and Involuntary Aspects
Searching, cooking, serving, placing in the mouth, mastication- voluntary.
Swallowing- begins as voluntary and ends as involuntary.
Gastric functions- involuntary but affected by moods.
Small intestinal functions- fully involuntary.
Storage of feces- involuntary.
Defecation- starts as involuntary and ends as voluntary.
2013
GIT Grneral

12. Regulation of the functions
Voluntary actions are generally conditioned reflex.
Intrinsic plexus coordinates local reflexes.
Sympathetics inhibit [stimulate sphincters].
Nerve endings on muscles and glands
Parasympathetic- stimulate [inhibit sphincters].
Nerve endings on Myenteric plexus [preganglionic]
Pace makers in GIT.
2013
GIT Grneral