Homeostasis Flashcards
Homeostasis definition
Maintenance of internal environment and concentration gradients under restricted limits
Negative feedback definition
When any deviation from the norm is returned
Role of pancreas
Detects changes in blood glucose
Role of islets of langehann
Release insulin and glucagon
Insulin
B-cells detect rise in glucose Insulin secreted, binds to glycoprotein receptors on csm -enzymes activated in cells -glucose transport proteins change shape -more enzymes so GLYCOGENESIS
Glucagon
A-cells detect decrease in glucose
Glucagon secreted, binds to receptors found ONLY on the LIVER
-activates kinase enzymes
-hydrolysis of glycogen - GLYCOGENOLYSIS
-synthesis of amino acids and glycerol - GLUCONEOGENESIS
-glucose released into blood plasma
Adrenaline
Secreted from adrenal gland 2nd messenger model -adrenaline binds to receptor -activates adrenylate cyclase -converts ATP into cyclic AMP/ cAMP, that activates kinase enzymes for glycogenolysis
Type 1 diabetes
Can’t produce insulin
Born with it/ childhood, caused by autoimmune diseases
Insulin injections
Type 2 diabetes
Receptors on cells lose responsiveness to insulin
Obesity/ poor diet
Regulate carbs intake, increase exercise, sometimes insulin injections
Osmoregulation definition
Control of blood WP
Hypertonic
Too low WP in blood
Hypotonic
Too high WP in blood
Reasons for hypertonic
Too much sweating
Not enough water intake
Lots of salt/ions in diet
Reasons for hypotonic
Drinking too much water
Not enough salt in diet
Hypertonic corrective mechanisms
Osmoreceptors shrivel
Increased permeability of DCT and CD
More water reabsorbed by tubules of nephrons
Urine more concentrated and less water lost
Hypotonic corrective mechanisms
Osmoreceptors increase in size as H2O enters
Decreased permeability of DCT and CD
Less water is reabsorbed by osmosis from tubules of nephrons
Urine more dilute and more water lost
Nephron structure
Glomerulus PCT Loop of henle DT Collecting duct
Ultrafiltration
Occurs in Bowman’s capsule
Afferent>efferent arteriole = large hydrostatic pressure, forces small molecules out
-podocytes - specialised epithelial cells, form gaps, increased SA, shorter diffusion pathway
-gaps in epithelial cells - shorter diffusion pathway
What occurs in PCT
Co-transport/ selective reabsorption
What does loop of henle consist of
2 limbs
Counter current flow
Descending limb
Permeable to water
Water moves into interstial spaces via osmosis
Na+ diffuses in
WP decreases
Ascending limb
Impermeable to water
Na+ actively transported out into interstial space
WP increases
What occurs in DCT
AT of various salts
Removes ions
Maintains optimum pH
Microvilli and mitochondria
How is ADH produced
Low WP
Cells in hypothalamus stimulated
Production of ADH increased
