salivary glands are:
1. parotid
2. submandibular
3. sublingual.

they are made of:
- serous cells
- mucous cells
- duct cells
- myoepitheial cells

- Na
- K
- Cl
- HCO3
- water
- enzymes: amylase, lipase
- IgA for enamel protection.

-the salivary acini secrete the mucous or serous secretion cotaining water, ions and enzymes.

- the duct cells modify them along the way by absorbing Na & HCO3, and secrete K & Cl.

-water is not permeable.

1. unconditioned: when object or substance put in oral cavity.

2. conditioned: when senses detect food related sight, smell or thought.

parasympathetic:

food in oral cavity > eferent to (IX)or (VII) > salivary nucleus in medulla > chorda tympani (IX) > glands > secretion. (ach as mediator)

sypathetic:

food in OC >aferent > superior cervical ganglion > norepinephrine release > glands > secretion.

conditioned reflex: senses > brain > salivary reflex centre > seterusnya..

1. VIP released
2. blood vessel dilate
3. myoepithelial contract
4. increase modification of secretion fluid in duct cells.

Auerbach's plexus (myenteric) supply OL and IC muscle for motility.

Meissner's plexus (submucosal): supply intestinal epithelium, endocrine cells to regulate secretion.

single unit
- gap junction
- stimulated by stretch
- regulation by hormones, nerve, local factors.

multi unit
- behave as many
- numerous autonomic nerve branchings.
- not stimulated by stretch
- regulation: hormonal n neuronal.

- slow waves: slow undulating changes of RMP in GIT cells. due to slow pumping activity of K/Na pump.

- spike potential: occurs automatically when RMP becomes more positive than usual -50mV. usually arise when RMP reach -40mV. regulated by slow waves.

- above treshold -40mV
- rate 1-10 per second.
- last longer in GIT sm than nerve fibers.
- last for 10-20 miliscnds.
- generated by fast influx of Ca but slow influx of Na.

- electrical rhythm by interstitial cells of Cajal.
- stelate mesenchymal pacemaker cells.
- sm-like features multiply branches into intestinal sm.

to regulate peristaltic and other motor activity.

-hormones

- neurotransmitters of ANS (ach-increase, para-decrease)

- stretch

- polypeptides (locally induced)

- stomach: 4/min

- duodenum: 12/min

- ileum distal: 8/min

- caecum: 9/min

- sigmoid colon: 16/min

ca+calmodulin > bind to n activate myosin kinase > phosphorylate myosin taken from ATP compound > ATP becomes ADP > produced myosin-phosphate. > phophorylated myosin interact with actin > contraction > myosin dephosphorylated by myosin phosphatase > Phosphate taken by ADP becomes ATP again and re-used.

-ingest food
-digest food
-absorb digested food
-excete toxic waste
-secrete digestive enzyme.

what is the mechanism for HCl secretion?

1. by parietal cells.
2. on the luminal surface H/K ATPase.
3. the OH left in the cell neutralized by CO2, forming bicarb.
4. bicarb released into blood, rising the pH. H is stopped from secreted.
5. the bicarb secretion is exchanged with chloride by Cl/HCO3 antiport.
6. cyclic AMP chloride channel will at the luminal surface will then secrete Cl.
7. H and Cl secreted, water is secreted, forming HCl acid.

1. activate pepsinogen > pepsin
2. provide optimal pH for pepsin's act.
3.defense mech for killing bact in food.
4. breakdown of CT or fibers of meat ingeste.
5. HCl + Fe and Ca, become soluble salts that will help in absorption

-ach
-gastrin
-histamine > stimulated by gastrin and ach as well.

-chief cell: secrete 7 types of pepsinogens according to site of secretion.
-HCl activate into pepsin.
-it hydrolyse peptide at aromatic bond of a.a. at pH 1.5-3.5.

- intrinsic factor.
- glycoprotein secreted by parietal cell.
- bind to B12
- transport B12 to ileum terminal n absorbed.

a) idiopathic gastric atropathy
b) gastrectomy

-treatment: parenteral injection of cyanocobalamin.

a) distension of stomach. - initiate:
1. short myenteric reflex
2. long vagovagal reflex

b) chemical contents of the food. - increase the secretion.

- increased secretion of somatostatin by D cells (in gastric gland as well)

- only contribute to 5% of total secretion.
- happens when partially digested food enters duodenum.
-intestinal G cells secrete gastrin n lead to HCl secretion.
- short-lived, bcoz acid chyme entering duodenum initiate enterogastric reflex
-entgstrc reflex: release hormones like secretin, cck, gip - all inhibit gastric secretion.

a) the tight junction within the mucosal cells do not allow entry of gastric secretion into underlying tissue of stomach.

b) the mucosal barrier of 200microns thick mucous layer provide protection of surface epithelial cells from being digested. -contain bicarb and prostaglandin neutralise acid.

1. disruption of mucosal barrier. - drugs or helicobacter pylori.

2. excessive amount of HCl (zollinger-ellison syndrome) secreted. - tumor

-stomach cn accomodate 50ml to 1.0 L of food without changes in IG pressure.

-when stretched, stimulates the vagal reflex.

-inhibit contraction of stomach muscle.

-allow increase in curvature's radius.

-follow laplace's law = IG maintain.

the BER produced by the gastric pacemaker located at the greater curvature.

slow waves of depolarize and repolarize in the rate of 20second.

-triphasic in nature.
-10 times longer than cardiac AP
-depolarize due toinflux of Ca.
-plateau bcoz of influx of Na and Ca.
-repolarization due to slow eflux of K.