Endocrine regulation of energy Flashcards
Glucose levels are regulated by hormones that affect __ and __
Glucose levels are regulated by hormones that affect appetite and cell metabolism
What are the major hormones involved in glucose control?
Insulin
Glucagon
Other important Hormones of glucose control
Epinephrine Cortisol Growth hormone Thyroid hormone Secretin Cholecystokinin
Which hormone is the only hormone that lowers blood glucose?
Insulin
What is the class of insulin receptor
RTK
What is the class of glucagon receptor
GPCR
What is the class of epinephrin receptor
GPCR
Which class of enzymes carries out phosphorylation? Dephosphorylation?
phosphorylation (→ kinases) dephosphorylation (→ phosphatases)
Which class of biological molecules do Gastrointestinal Hormones belong to?
peptides
What do Gastrointestinal Hormones do? apart from regulating glucose levels
Regulate activity of the stomach, the intestine and the pancreas (in addition to the regulation by blood glucose)
Where are many of Gastrointestinal Hormones also found? What role do they play there? Where do they get produced?
Many of these hormones are also found in the central or peripheral nervous system (somatostatin, gastrin, cholecystokinine, vasointestinal peptide, insulin, calcitonin)
- Function unknown
- Produced in the cell body of neurons
- May modulate signal transmission
What is the most common endocrine disorder?
Diabetes mellitus.
How was the function of the islets of Langerhans discovered?
Minkowski (1889) observes diabetes in dogs after pancreatectomy
v Discovery of abnormalities of the islets of Langerhans
Apart from insulin, what are some other hormones secreted by pancreas?
glucagon, somatostatin, pancreatic peptide
What are the exocrine and endocrine sections of pancreas?
Endocrine: islets of langerhans
Exocrine: duct cells, acinar cells
Do islets of langerhans take up a large or a small section of pancreas?
very small (2% of pancreatic mass)
role of acinar cells
Secretion of digestive enzymes (proteases, amylase, lipase)
role of duct cells
Secretion of NaHCO3 (bicarbonate)
reduces the acidity of food in duodenum
Role of islets of langerhans
– α-cells: Glucagon
– β-cells: Insulin
– D-cells: Somatostatin
– E-cell: Ghrelin (mainly produced by the stomach; some by pancreas)
– F-cells (also known as PP cells): PancreaticPolypeptide
Where do the products of exocrine section of pancreas empty?
Empties into the duodenum
Which hormones that are produced by pancreas are also produced by gastrointestinal mucosa?
Glucagon, somatostatin and pancreatic polypeptide are also produced by cells of the gastrointesinal mucosa
What is the localization of various endocrine pancreatic cells?
Alpha and beta cells are the most numerous cell
alpha cells on the periphery; beta in the center
D, PP and E cells are closer to the periphery
Describe the blood flow of the pancreas
- islets highly vascularized (5 to 10 x blood flow of exocrine pancreas)
- blood first supplies centrally located B cells i.e. detects glucose levels
- then blood travels to more peripheral A and D cells i.e. exposed to insulin secreted by B cells
How are PP, Somatostatin, Insulin and glucagon inter-connected?
Glucagon stimulates insulin and somatostatin; insulin and somatostatin inhibit glucagon
Somatostatin inhibits insulin and PP production
glucagon also produced as __; processed to __ to __
glucagon also produced as preproglucagon processed to proglucagon to glucagon
Describe insulin synthesis
1) Preproinsulin
removal of its signal peptide ->
2) proinsulin
Proinsulin consists of three domains: A, B and C chains. Within the endoplasmic reticulum, proinsulin is exposed to several specific endopeptidases which excise the C peptide->
3) Active insulin that has a and b chains that are connected by disulphide bond
Insulin and free C peptide are packaged in the Golgi into secretory granules which accumulate in the cytoplasm
Describe glucagon synthesis
glucagon is made as (1) proglucagon
- in pancreas, most of the other fragments are removed
in alpha cells 33-61 aa of the gene are retained-> glucagon
- in gut cells and brain different aa of the same gene are retained-> glicentin, GLP-1 and GLP-2 are formed
- active glucagon is a short single amino acid chain
Effect of high glucose on alpha and beta cells
Overall effect?
- Inhibition of alpha cells-> decreased glucagon
- Stimulation of beta cells-> increased insulin
Overall effect: reduction of blood glucose to normal level
Effect of low glucose on alpha and beta cells
Overall effect?
- Stimulation of alpha cells-> increased glucagon
- Inhibition of beta cells-> decreased insulin
Overall effect: increase of blood glucose to normal level
