Intro To GIT (New
Intro To GIT (New
Intro To GIT (New
- Parotid glands
- Submandibular glands
- Sublingual glands
- Buccal glands
Secretion of the saliva:
• 800 – 1500 ml/day
COMPOSITION OF THE SALIVA
• 99.5 % -water;
• 0.5 % substances
– Organic – 0.3 %
-- Inorganic – 0.5 %
Organicsubstances:
• Mucin, digestive enzymes
Inorganic substances:
• Na+, K+, Cl-, HCO3
FUNCTIONS OF SALIVA
- Facilitates swallowing
Spikes Potentials
SLOW WAVES
They are slow undulating changes in resting membrane
potential
Intensity usually varies between 5-15mV
i. 3/min in stomach
ii. 12/min in duodenum
iii. 8-9/min in terminal ileum
Frequency of slow waves determines rhythm of
contractions of different parts of GIT
They are NOT true action potentials but they control true
action potentials (spike potential)
SPIKE POTENTIAL
They are true action potential that occur when RMP rises
above -40mV
It is caused by opening of slow Na-Ca channels
Stretch
2. Reflexes from the gut to the prevertebral sympathetic ganglia & then back to
the gastrointestinal tract –
i. gastrocolic reflex- signals from the stomach to cause evacuation
of the colon
ii. enterogastric reflexes- signals from the colon & small intestine to
inhibit stomach motility & stomach secretion
iii. defecation reflexes that travel from the colon & rectum to the
spinal cord & back again to produce the powerful colonic, rectal,
& abdominal contractions required for defecation