Glucose + Kidney + Water Potential

Cards (22)

  • NEGATIVE FEEDBACK - a change produced by the control system leads to a change in the stimulus detected by the receptor and turns the system off and prevents overshoot of conditions as there are positive actions in both directions
  • POSITIVE FEEDBACK - when a deviation from the optimum causes changes that result in an even greater deviation from the normal
  • α cells are larger and produce glucagon, β cells are smaller and produce insulin
  • Receptors detect increased blood concentration and then secrete insulin (globular protein) into blood plasma. This leads to a change in tertiary structure of glucose transport carrier proteins causing them to open, increasing uptake of glucose into cells, an increase in number of glucose transport carrier proteins (vesicles with membranes made of protein to make these carriers fuse with cell-surface membrane), the activation of enzymes that convert glucose to glycogen and fat and increase rate of respiration to increase uptake from blood.
    1. adrenaline binds to transmembrane protein receptor on liver cell-surface membrane
    2. protein changes shape on inside of membrane
    3. leads to activation of adenyl cyclase enzyme
    4. enzyme converts ATP to cyclic AMP (cAMP)
    5. cAMP acts as second messenger that binds to protein kinase enzyme
    6. changes shape of enzyme to activate it
    7. active protein kinase enzyme catalyses conversion of glycogen to glucose
    8. glucose moves out of liver cell by facilitated diffusion into blood through channel proteins. (SECOND MESSENGER MODEL)
  • GLYCOGENESIS - conversion of glucose into glycogen, occurs when blood glucose is higher than normal
  • GLYCOGENOLYSIS - breakdown of glycogen to glucose, occurs when blood glucose is lower than normal
  • GLUCONEOGENESIS - production of glucose from sources other than carbohydrate (glycerol, amino acids), occurs when supply of glycogen is exhausted
  • decrease in blood glucose - secrete glucagon into blood plasma, attaches to specific protein receptors on liver cell-surface membranes. This activates enzymes that convert glycogen to glucose and activates enzymes for gluconeogenesis.
  • TYPE I - body is unable to produce insulin, may be result of immune response to β cells, develops quickly, signs + symptoms normally obvious, controlled by injections of insulin (would be digested if taken orally), dose must be matched to glucose intake, biosensors monitor blood glucose
  • Proximal Convoluted Tubule:
    1. active transport of Na+ ions into blood
    2. Concentration of Na+ in the cell decreases
    3. Na+ move down the concentration gradient into a cell via co-transporters (glucose, amino acids or Cl-)
    4. Higher concentration inside the cell
    5. Co-transporters move into blood via facilitated diffusion
  • Podecytes are specially adapted cells to ultrafiltration. The gaps created speed up the filtrates moving across the renal wall to form the glomerulus filtrates.
  • Loop Of Henle:
    1. active transport of ions out of the lumen
    2. interstitial region
    3. due to interstitial region, water moves out by osmosis in blood
    4. tubular filtrate becomes more concentrated
    5. Na+ and Cl- leave by diffusion
  • Blood water potential can be too low because of not consuming enough water, too much sweating and a large amount of ions taken in.
  • Blood water potential can be too high because of consuming large volumes of water and not consuming enough salt.
  • FORMATION OF GLOMERULAR FILTRATE BY ULTRAFILTRATION
    1. blood enters kidney through renal artery and into network of arterioles into Bowman’s capsule via the afferent arteriole
    2. blood flows into glomerular capillaries
    3. efferent arteriole has lower diameter causing increased hydrostatic pressure within glomerulus
    4. water, glucose, urea and mineral ions squeezed out of capillaries via pores – forms glomerular filtrat
  • The basement membrane is the membrane between the bowman's capsule and the capillary. It allows through small substances like water, glucose, urea and mineral ions via pores which all then form the glomerular filtrate. If someone has a high concentration of substances like proteins in their urine, it is due to more carrier proteins for the substance on the membrane.
  • A higher concentration of urine is caused by more water being reabsorbed from the loop of henle. This occurs when the water potential gradient is maintained for longer which is due to an increase in Na+. A longer loop of henle means more Na+ is moved out maintaining the water potential gradient.
  • Glucose in found in the urine of people with untreated diabetes:
    • High concentration of glucose in the blood
    • Not all glucose reabsorbed at the proximal tubule
    • Not enough carrier/co-transport proteins to absorb all the glucose (all saturated)
  • Increasing a cell's sensitivity to insulin will lower blood glucose because the more insulin can bind to the receptors which activates more enzymes. This leads to more glucose channel proteins on the membrane so a higher uptake of glucose into cells and more enzymes that convert glucose to glycogen (glucogenosis).
  • In the collecting duct, protein molecules are able to act as channels because they have a tertiary structure complementary to the inside of the pore. This allows water to enter when there is a more negative water potential inside tubule so water moves in by osmosis.
  • BLOOD WATER POTENTIAL TOO LOW
    1. osmoreceptors in hypothlamus detect it and increase the frequency of nerve impulses to pituitary gland to release ADH
    2. more ADH produced and it binds to the receptor which activates phosphorylase
    3. Vesicles with aquaporins fuse with membrane leading to increased permeability of collecting duct
    4. smaller volume of urine - more concentrated urine