Gastrointestinal hormones
-
Upload
fathima-mahmood -
Category
Science
-
view
542 -
download
1
Transcript of Gastrointestinal hormones
GASTROINTESTINAL HORMONES
•OVERVIEW•GENERAL FEATURES•CHOLECYSTOKININ•FEATURES AND FUNCTIONS•MECHANISM OF ACTION•REGULATION
WHAT IS THEIR IMPORTANCE?
Robust control systems are required to coordinate
digestive processes in man and animals, and are provided
by both the nervous and endocrine systems. Endocrine
control over digestive functions is provided by
the so-called enteric endocrine system.
FEATURES OF GI Modulate activity of digestive system They are peptides Not released by endocrine glands but
secreted throughout large areas of the GI Mucosa.
These cells called enteroendocrine cells.
They enter the circulatory system and not the lumen of the GI tract
LOCATION OF ENTEROENDROCRINE CELLS
CHOLECYSTOKININ (CCK)
ABOUT CHOLECYSTOKININ It is a linear peptide synthesized by I
cells ( a type of entero-entocrine cell) of duodenum and Jejunum
Made up of 8 to 59 amino acids Also synthesized in small amounts by
the Brain Have two receptors, CCK A(present
mainly in the pancreatic acinar cells) and CCK B
Diagram showing location of I cells and secretion of CCK into the bloodstream
FUNCTIONSRelease of digestive enzymes from the pancreas into the duodenum. Older literature refers to cholecystokinin as pancreozymin, a term coined to describe this effect.
Contraction of the gallbladder to deliver bile into the duodenum. The name cholecystokinin (to "move the gallbladder") was given to describe this effect.
Inhibits gastric emptyingIncreases the action of EnterokinaseMy increases motility of intestines and colonTogether with Gastrin enhance glucagon secretionAugments contraction of pyloric sphincterPlays an important role in satiety by suppressing hunger
WHAT CAUSES CCK TO ACT?
The most potent stimuli for secretion of cholecystokinin are the presence of partially-digested fats and proteins in the lumen of the duodenum
HOW?LET’S TAKE A LOOK
MECHANISM OF ACTION
REGULATIONPOSITIVE FEEDBACK MECHANISM:CCK increases bile and pancreatic juice secretion causing more digestion of protein and fat and which further increases CCK secretion
This positive feedback mechanism stops when absorption is completed or when the products of food moves on to the lower portion of the GI tract.
Increased blood levels of cholecystokinin can be found 15 minutes after a meal has begun and levels remain raised for three hours afterwards.
What happens if I have too much cholecystokinin?
There are no known cases of too much cholecystokinin. However, weight loss drugs are currently under development that copy the appetite-reducing actions of cholecystokinin.
What happens if I have too little cholecystokinin?
There appears to be evidence of less than average cholecystokinin in very obese people, unlike the levels in obese and slim people. This low level of cholecystokinin may contribute to reduced feelings of fullness and difficulty in losing weight in very obese people. However, more research is needed to confirm this finding.
Happy Eating
It’s all under control