Gastric motility Flashcards
What is the frequency of peristaltic waves?
3 per minute
What is it controlled by?
1- Pacemaker cells in the longitudinal muscle which act as a functional syncytium
-The pacemaker cells depolarise spontaneosly
-The pacemaker cells cause the smooth muscle cells to depolarise
-This depolarisation is spread from the stomach to the intestine as all the cells of the longitudinal muscle are connected via tight junctions.
2- This depolarisation is known as Basic electrical rhythm=slow waves of depolarisation/repolarisation
-When there is increased stimulation e.g. from increased gastrin, increased distension of the stomach then the depolarisation can reach sub-threshold which causes an AP to be generated.
What determines the strength of contraction?
The frequency of Ads
Where is there a higher strength of contraction?
In the antrum: thick muscle
Body only has thin muscle
What happens to Chyme which has not been pushed into duodenum from antrum?
Remixed in antrum
What stimuli alter the contraction of peristaltic waves?
- gastrin secretion and distension of the stomach increase peristalsis
- fat/aminoacids/release of CCk inhibit peristaltic waves
Neutralisation of acid in the duodenum?
Release of HCO3- from Brunner glands
HCO3- reacts with H+ to form H20 and C02
How is it controlled?
Negative feedback system
-Long( vagal) and short (ENS) reflexes
-release of secretin- causes release of bicarbonate ions from the liver and pancreas
Pancreas Anatomy
- head- into duodenum
- body
- tail- into spleen
Endocrine glands- insulin/glucagon/somatostatin production
Exocrine glands: Acini cells- into intercalated discs- intercalated duct- intralobular duct- interlobular duct to pancreatic duct
Pancreatic duct goes to common bile duct- Sphincter of Oddi - to duodenum
How are zymogens in acing cells activated?
Enterokinases found on the brush border of duodenal enterocytes come into contact with the trypsinogen
Convert trypsinogen into trypsin
Trypsin activates zymogens to peptides
Different types of pancreatic enzymes
lipases elastase- break down collagen alpha-amylases: comverts starch to maltose proteases nucleases
How does the negative system of secretin release work?/
When the duodenum has been neutralised again- no more secretin is release- no more HCO3- is released.
How is an increase in stimulation of peristalsis represented
An increase in stomach movement is symbolised by increased strength frequency of contraction.
