Endocrine Glands- Pancreas Flashcards
The islets of Langerhans secrete which types of hormones?
- alpha cells: produces glucagon
- beta cells: produces insulin
- D cells: Somatostatin
- F cells: pancreatic polypeptides.
What is the structure of mature insulin?
- Chain A and Chain C connected by 2 disulfide bonds
How does hyperglycemia stimulate the synthesis and release of insulin in beta cells?
- Insulin independent channel -> most cells rely on insulin to uptake glucose by cell.
- Glucose is also needed for Krebs cycle, when glucose is decreased, decreased ATP. When glucose increases there will be increased ATP production.
- When ATP is increased , ADP ratio closes K+/ATP channel causing cell depolarization.
- This will open voltage gate of calcium and cause increased insulin gene expression via CREB.
- Calcium will also release C peptide and insulin into the blood via exocytosis.
How does insulin reduce blood glucose?
- Fxn of insulin is to bring sugar into cells and turn into storage to remove from ECF
- This means their will be decreased glucose, FA and AA in the blood and they will be turned into storage forms
What are the main differences between type 1 and type 2 diabetes?
Type 1 Diabetes: 10% , most common in dogs, caused by destruction of Beta cells by immune cells, leading to insulin insufficiency.
• Insulin Responsive - Lifelong supplementation
• Genetic component: HLA-DR4
Type 2 Diabetes: 90 %, most common in cats, inability of cells to respond to insulin. Preventable.
- Insulin resistance
- Cause unknown : can be • B cell hypertrophy + hyperplasia
• Risk factors: overweight/ obese. Hypertension, physically inactive. Family history, genetic factor
In short:
• Type 1: insulin dependent (often lean but ~ 50% overweight/ obese. onset usually acute)
• Type 2: Non insulin dependent ( usually obese, subtle/ slow onset)
• Type 1 will have autoantibodies against insulin
How does diabetes cause major clinical symptoms, such as glycosuria, polyuria, dehydration, polydipsia,
weight loss, and polyphagia?
Increased glucose causes lipolysis (fat breakdown) and protein breakdown. This is because though there is an excess of glucose, the lack of insulin prevents the opening of the GLUT- 4 insulin dependent channels. Therefore the body looks for an alternative source of energy. This causes weight loss and hunger. Polyphagia -> increased/ insatiable hunger. The glucose leaves in the urine, causing glucosuria. This will increase urine osmolality, increase urination (polyuria). This causes dehydration and increased thirst (polydipsia)
More water is needed to excrete glucose in urine which pulls it from ECF -> this increases Osmolality in order to counterbalance the increased particle content.
What are the mechanisms underlying diabetic ketoacidosis (DKA)?
- Body will break down adipose tissue for fuel and the adipose tissue will be broken down to ketone bodies.
• Ketones will cause increase acidity of blood -> ketoacidosis ◦ Fruity breath due to ketone bodies being converted to acetone.
How does glucagon activate intracellular signaling pathways?
Glucagon binds to cell surface receptor and activates intracellular second messenger to produce biological effects.
What are the main functions of glucagon in the liver and adipose tissues?
• Glucagon, binds to receptor, produces cAMP, which will activate PKaA and will cause gluconeogenesis, and glycogenolysis, as well as bind to pKA in fat cell, and will cause HSL to convert glycerol and FA which will be brought to liver > this will increase glucose.
How does somatostatin suppress the beta-cell secretion of insulin and the alpha-cell secretion of glucagon?
Somatostatin blocks adenylate cyclase activity, suppressing Beta cell secretion of insulin and alpha cell secretion of glucagon in pancreas. Somatostatin binds to GPCR which decreases cAMP
How does somatostatin regulate stomach pH?
If pH is too low, D cells will produce somatostatin. This will inhibit production of HCl from parietal cells, which will then increase the pH. Somatostatin can also block histamine from going to the parietal cell and causing HCl secretion.
What is the function of the somatostatin produced by the hypothalamus?
Somatostatin that is produced by the hypothalamus will inhibit anterior pituitary secretion of growth hormones.
