Physiology 3.2 Flashcards
What is the primary role of insulin?
to increase glucose uptake by tissues - to lower blood glucose levels
What are other roles of insulin?
Fat synthesis Protein synthesis Glycogen synthesis Glucose oxidation Fat, protein and glycogen breakdowns are inhibited. Moves potassium into cells
Which pancreatic cell secretes insulin?
Beta cell from islets of Langerhans.
What is made alongside insulin, used in tests?
C-peptide.
How much more does C-peptide resist degradation in comparison to insulin?
5x less likely to be degraded.
What is the main stimulus causing insulin secretion?
Blood glucose concentration.
What are other stimuli causing insulin secretion?
Amino acid concentration
Glucagon
Incretin hormones
Vagal nerve activity
What are incretin hormones?
These control GI function.
Secretin, gastrin, cholecystokinin etc.
What stimuli inhibit insulin release?
Low blood glucose levels.
Somatostatin (Growth hormone inhibiting hormone).
Sympathetic alpha 2 effects.
Stress ^ causing sympathetic reaction.
How is excess glucose stored in the liver, muscles and adipose tissue?
Glycogen via Glycogenesis. - In muscles.
TAGs. - in adipose tissue.
How is excess amino acids stored in adipose tissue and the liver?
Triacylglycerol
How can glucose be stored?
As either TAGs or glycogen.
Which tissues are insulin dependant?
Only adipose and skeletal muscle tissue. But this makes up 65% of the body.
Which glucose transporter is not insulin dependant?
GLUT 1 (brain, kidney, red blood cells), GLUT 2(pancreas and liver), GLUT 3 (widespread)
Which glucose transporter is insulin dependant?
GLUT 4 (these reside in cytoplasm not the cell surface) (adipose tissue and muscle)
What is an insulin receptor?
Tyrosine kinase.
Kinase = phosphorylation = increase or decrease protein activity.
when can muscle tissue take up glucose without insulin?
During exercise in an independent process.
How does the liver take up glucose?
Via GLUT 2 transporters, these are not insulin dependant.
BUT insulin does enhance uptake.
How does insulin aid in liver uptake of glucose?
Insulin acts on tyrosine kinase, which acts on hexokinase. Hexokinase breaks glucose into G6P - maintaining a low glucose concentration to allow more glucose to move down the concentration gradient into the liver cell through GLUT2.
What does insulin have a permissive effect on?
On growth hormone
What ion pump does insulin stimulate?
Sodium-potassium ATPase. It promotes K ion entry into the cell.
How long is the half life of insulin?
5 minutes.
Do you get more insulin by consuming glucose orally or IV?
Orally - you also get vagal stimulation and release of incretin hormones. If done IV in the blood you only get an increase in BGL.
How does an increase in glucagon stimulate the release of insulin?
Because the insulin will be required to take up the new glucose created by glucagon so that BGL don’t rise too much.
