Homeostasis Flashcards
adrenaline and how it affects blood glucose concentration (5)
Hormone that increases blood glucose concentration
1. Secreted from adrenal glands when blood glucose concentration is low (exercising / stressed)
2. Binds to receptors in the cell membrane of liver cells, activates glycogenolysis (via a second messenger), inhibits glycogenesis
3. Activates glucagon secretion, inhibits insulin secretion to increase glucose concentration
4. Gets body ready for action by making more glucose available for muscles to respire
how does antidiuretic hormone (ADH) increase blood water potential
- Water content of blood drops so water potential drops
- Detected by osmoreceptors in the hypothalamus, so the posterior pituitary gland is stimulated to release more ADH
- More ADH means the distal convoluted tubule + collecting duct become more permeable, so more water is reabsorbed into the blood
- A small amount of highly concentrated urine is produced and less water is lost
how does antidiuretic hormone (ADH) decrease blood water potential
- Water content of blood rises so water potential rises
- Detected by osmoreceptors in the hypothalamus, so the posterior pituitary gland is stimulated to release less ADH
- Less ADH means the distal convoluted tubule + collecting duct become less permeable, so less water is reabsorbed into the blood
- A large amount of dilute urine is produced and more water is lost
Type I diabetes
immune system attacks beta cells in the islets of Langerhans so they cannot produce insulin - genetic + develops during childhood
after eating: blood glucose levels remain high (hyperglycaemia) + can result in death if untreated
kidneys cannot reabsorb all glucose so some is in urine
treated with insulin therapy - injections/pump - needs to be controlled to avoid hypoglycaemia
control simple carbohydrate intake
Type II diabetes
beta cells do not produce enough insulin or cells do not respond to insulin because receptors do not work properly - acquired later in life, obesity, lack of exercise, poor diet, age, family history
treated with healthy diet, regular exercise, losing weight
Where is insulin secreted from?
Islets of Langerhans in pancreas by beta cells
How does insulin lower blood glucose concentration when it’s too high?
- Insulin bonds to specific receptors on the cell membranes of liver + muscle cells
- This increases permeability to glucose by triggering movement of GLUT4 (channel protein) to membrane so more glucose can enter by facilitated diffusion
- Activates enzymes in liver + muscle cells which control glycogenesis (converts glucose into glycogen)
- Increases rate of respiration
Where is glucagon secreted from?
Islets of Langerhans in pancreas by alpha cells
How does glucagon raise blood glucose concentration when it’s too low?
- Glucagon binds to specific receptors on the cell membranes bog liver cells
- Activates enzymes which control glycogenolysis (breaks down glycogen into glucose)
- Activates enzymes which control gluconeogenesis (formation of glucose from glycerol + amino acids)
- Decreases rate of respiration
How does adrenaline increase blood glucose concentration?
- Secreted from adrenal glands when blood glucose concentration is low, when stressed or when exercising
- Binds to receptors in cell membrane of liver cells
- Activates glycogenolysis (glycogen -> glucose) + inhibits glycogenesis
- Activates glucagon secretion + inhibits insulin secretion
Gets body ready for action by making more glucose available for muscles to respire
How do adrenaline and glucagon act via a second messenger?
- Receptors for adrenaline + glucagon have specific tertiary structures that make them complementary in shape to their hormones -> bind to receptors + activate adenylate cyclase
- Activated adenylate cyclase converts ATP into a cyclic AMP (cAMP) - a second messenger
- cAMP activates protein kinase A which activates a cascade that breaks down glycogen into glucose (glycogenolysis)
