Y2: Homeostasis Flashcards
Define homeostasis?
long 4
- The maintenance of a stable internal environment
- it is controlled by nervous and hormonal system
- keep conditions within a certain range (optimum)
- keep the organism in a state of balanced equilibrium
Define homeostasis?
short, 1
Maintenance of the internal body conditions/environment
What is the hormonal system?
Input–>change detected–>info integrated–>brings about change–>return system to optimum
What are the two types of hormonal feedback systems?
- Positive
- Negative
Define negative feedback
Response results in inhibition of corrective measures
Define positive feedback
Response stimulates corrective measures to remain on
What is end-point inhibition?
The product in a series of enzyme controlled reactions inhibits the first enzyme
What happens if the blood glucose levels get too high?
5
- Beta-cells in the islets of langerhans detect increase in blood glucose levels
- Release insulin into the blood
- Insulin binds to glycoproteins in the phospholipid bilayer membranes
- Results in measures to remove glucose from the blood and into cells
- Decreases the concentration of glucose in the blood
What measures remove glucose from the blood into the cells?
4
- More glycogenesis
- Increased no. of glucose transporters (previously in vesicles that fuse w/ membrane)
- Glucose transporters are activated (change in tertiary structure)
- Activation of enzyme that converts glucose into fat
What happens if the blood glucose levels get too low?
4
- Alpha-cells in the islets of langerhans detect decrease in blood glucose levels
- Release glucagon into the blood
- Binds to receptors on liver cells
- Results in measures to increase the concentration of blood glucose
What measures increase the concentration of glucose in the blood?
2
where does it take place?
1
- Activates enzymes that cause glycogenolysis
- Activates enzymes that cause gluconeogenesis
-The liver
What is the second messenger model
4
- Adrenaline binds to the adrenergic receptor in the phospholipid bilayer membrane
- This activates adrenylate cyclase which catalyses the production of cAMP from ATP
- cAMP is converted into pyruvate kinase
- pyruvate kinase catalyses glycogenolysis
What is the difference between type 1 and type 2 diabetes?
Treatment
- Type 1 requires injections of insulin
- Type 2 can be reversed sometimes by a low carb diet
What is the difference between type 1 and type 2 diabetes?
Science?
In type 1 the immune system attacks beta cells in the islets of langerhans so they no longer produce insulin
whereas in type 2 the cells no longer respond to insulin as the receptors are desensitised
What is the difference between type 1 and type 2 diabetes?
Cause?
- Type 1: random
- Type 2: diet and genetic components
Why is gluconeogenesis needed?
The brain can only use glucose for respiration so cant use pyruvate made form amino acids or lipids
Why are kidneys vunerable?
Because all the blood in the body goes through it
What are the two ways to change the water potential of the blood?
Change solute
Change water
Kidney: What is the pathway of the nephron?
- bowmans capsule
- proximal convoluted tubule
- loop of henle
- distal convoluted tubule
- collecting duct
Kidney: Proximal convoluted tubule?
4
- the Na+-K+ pump actively transports Na+ out of the epithelial cell into the lumen of the capillary, generating and maintaining a conc gradient of Na+ from the lumen of the PCT to the ep cell
- Na+ binds to co-transporter and is transported down conc gradient taking one molecule of glucose or AA with it into ep cell
- glucose or AA going against its conc gradient
- glucose in ep cell travels down its gonc gradient to lumen of capillary via fac diffusion
Kidney: loop of henle?
6
- Na+ is actively transported out of the ascending loop of henle into the interstitial space
- Cl- ions follow down electrical gradient via fac diff
- this lowers the water potential of the interstitial space
- t4 water moves out of descending loop of henle down water potential gradient via osmosis as ascending loop is impermeable to water
- makes the liquid at the bottom of the loop more conc , becoming more dilute w/ loss of ions going up ascending loop
- overall volume decreases
Kidney: bowmans capsule, glomerular filtration?
4
- Blood into the glomerulus from wide afferent renal artery, and leaves through a narrower efferent renal artery. So blood is under high pressure
- causes the contents of the blood to be forced through the capillary wall, like a sieve, then through the basement membrane (a second ‘sieve’ made of collagen fibres and protein) into the nephron.
- The cells in the wall of the bowman’s capsule contain podocytes, with extensions called pedicels wrapped around the capillaries meaning any cells, large proteins or platelets which leave the capillary walls don’t enter the tubule.
- Filtrates include water, amino acids, glucose, ions and importantly: urea and other nitrogenous waste products.
Kidney: collecting duct?
4
- The urine enters the collecting duct which transports it down through the medulla to the pelvis.
- The urine becomes more concentrated as it passes through the medulla, as the salty conditions created by the loop of henle mean water osmoses out down a potential gradient.
- ADH also controls the permeability of the collecting duct,
- more adh = more aquaporins in the membrane (from vesicles) which allow additional water to escape through.
What are nephrons?
Millions of little filtering units that make up the kidneys
