252. The pancreas Flashcards
How is feeding and hunger controlled?
Two centres in the hypothalmus: Feeding centre and satiety centre.
Glucostatic theory- these centres respond to blood glucose levels.
Lipostatic theory- these centres respond to fat stores
What hormone is released by fat stores to decrease feeding activity?
Leptin
What are the three ways we consume energy?
Cellular work
Mechanical work
Heat loss
If most cells can use fats, carbs or protein as an energy source why do we need a constant blood glucose level?
The brain is an obligitory glucose user. I.e. it can only use glucose for energy.
What are the normal ranges of blood glucose?
When does hypoglyceamia occur?
4.2-6.3mM (5 is useful)
Hypoglyceamia<3mM
What are the four cells found in the islets of langherhan?
Alpha cells produce glucagon
Beta cells produce insulin
Delta cells produce somatostatin
F cells produce pancreatic polypeptide (function not known)
How is insulin released into the bloodstream?
Beta cells uptake glucose causing potassium channels to close. The intracellular rise in potassium leads too ca channels opening, releasing insulin.
How does insulin work?
Only hormone that can lower blood sugar. Causes glut-4 transporters in muscle and adipose tissue to be expressed in response to insulin
This causes glucose to be taken into the cell.
What other actions does insulin have?
Increases glycogen synthesis in muscle and liver. Stimulates glycogen synthase and inhibits glycogen phosphorylase
Increases amino acid uptake into muscle
Increases protein synthesis and inhibits proteolysis
increases triacylglycerol synthesis in adipocytes and liver
inhibits the enzymes of gluconeogenesis in the liver
Promotes potassium ion entry into cells
What stimuli cause insulin to be released?
increased BG
Increased amino acids in plasma
Glucagon
other incretin hormones e.g. Gastrin, secretin, CCK, GLP-1, GIP
What stimuli cause insulin to be inhibited?
Low BG
Somatostatin
Sympathetic effects
Stress e.g. hypoxia
Why does oral glucose have more of an affect that IV?
The vagus nerve controls insulin release and so it will cause an added affect when glucose is delivered via the GI tract
Glucagon is released in response to decreasing plasma glucose. How does it work to increase plasma glucose
Increased glycogenolysis
Increased gluconeogenesis
Formation of ketones from fatty acids
How do amino acids affect insulin and glucagon?
Cause release of both. This allows insulin to utilise amino acids for protein synthesis yet glucagon stops hypoglyceamia from occurring due to this
What stimulus promote glucagon release?
Low BG High amino acid concentration Sympathetic innervation Cortisol Stress e.g. exercise/infection
