homeostasis

Question 1

homeostasis

Answer 1

-it is the maintenance of a constant internal environment in organisms

Question 2

negative feedback

Answer 2

-it is a change that triggers a response that reduces an effect of a change

Question 3

positive feedback

Answer 3

-the actions that occur to continue the deviation from normal when a change is detected

Question 4

pancreas

Answer 4

-the pancreas is a gland
-it contains islets of langerhans
-these are made of alpha cells (which secrete glucagon) and beta cells (which secrete insulin)

Question 5

insulin

Answer 5

-it lowers blood glucose
-it targets the liver and muscles
-it is made in the beta cells in the pancreas
-it is transported in the blood
-it increases the permeability of glucose, meaning that more glucose is taken up in diffusion
-it also increases the respiration rate in the muscles
-it increases the conversion of glucose to fat

Question 6

glucagon

Answer 6

-it raises blood glucose
-it targets the liver and muscles
-it is made in the alpha cells
-it is transported in the blood
-it activates enzymes in the liver to turn glycogen into glucose (glycogenesis)
-it promotes the making of glucose from fatty acids and amino acids (gluconeogenesis)
-it decreases the respiration rate in the muscles

Question 7

adrenaline

Answer 7

-it causes the fight or flight response
-it’s made in the adrenal gland (which is near the kidneys)
-it targets low blood sugar
-it increases metabolism
-it activates glycogenolysis
-it inhibits glycogenesis
-it is hydrophobic but not lipid soluble, meaning it can’t get into cells
-so it has to use the second messenger model

Question 8

second messenger model

Answer 8

-adrenaline binds to the specific receptors on target cells in the liver
-the enzyme adenylate cyclase changes shape and is activated
-adenylate cyclase catalyses the conversion of ATP to cAMP
-cAMP activates the protein kinase
-cAMP and kinase stimulate glycogenolysis

Question 9

type 1 diabetes

Answer 9

-beta cells don’t produce insulin or an autoimmune response
-it is diagnosed in childhood
-the blood glucose is too high after eating (hyperglycaemia)
-the excess glucose is excreted in urine
-it is treated with insulin injections

Question 10

type 2 diabetes

Answer 10

-beta cells don’t produce enough insulin/ cells don’t respond to the insulin (the glycoproteins on the body cells are damaged or lost)
-it is usually diagnosed in over 40s
-the blood glucose is higher than normal
-it is treated with dietary control and glucose lowering medicine

Question 11

osmoregulation

Answer 11

-the control of water and ions in the blood

Question 12

ultrafiltration

Answer 12

-there is high hydrostatic pressure in the glomerulus as the diameter of the afferent arteriole is larger than the efferent arteriole
-blood enters the glomerulus and is filtered through gaps in the capillary endothelium
-podocyte cells lining the renal capsule have large gaps, allowing substances to pass through
-small substances like glucose, water, amino acids, ions and urea pass through the basement membrane into the renal capsule forming the glomerular filtrate
-larger substances like red and white blood cells and proteins do not pass through

Question 13

selective reabsorption

Answer 13

-Na+ is actively pumped out of the cell and into the blood by the Na+/ K+ pump
-this lowers the concentration of Na+ in the proximal convoluted tubule
-Na+ moves into the cell from the lumen by facilitated diffusion and glucose/ amino acids/ salts are then co-transported with it
-glucose/ amino acids/ salts are then transported into the blood by facilitated diffusion
-absorption of the solutes increased the water potential of the lumen
-water is absorbed from the PCT to the blood by osmosis

Question 14

glucose in type 1 diabetics urine

Answer 14

-due to the lack of insulin, there is more glucose in the proximal convoluted tubule
-this increase of glucose means that the co-transport carrier proteins become saturated
-since the proteins are saturated, no more glucose can be transported and absorbed, meaning that it ends up in the collecting duct and then the urine

Question 15

role of ADH in collecting duct and distal convoluted tubule

Answer 15

-water potential in the blood decreases
-osmoreceptors in the hypothalamus shrink, this stimulates the hypothalamus
-increases ADH released by the posterior pituitary gland
-ADH carried in the blood to the distal convoluted tubule (DCT) and the collecting duct
-ADH binds to complimentary receptors on specific target cells in the collecting duct and the DCT
-this activates the enzyme phosphorylase
-leading to aquaphorins fusing with the membrane of epithelial cells in the collecting duct
-membrane permeability to water increases
-water moves from a higher water potential in the collecting duct to a lower water potential in the blood via osmosis

Question 16

loop of henle

Answer 16

-water can’t move out of the ascending limb. Na+ and Cl- are actively transported out of the ascending limb of the loop of henle
-water moves out of the descending limb via osmosis due to high conc. of Na+/Cl- (lowering water potential) in the tissue fluid. Na+ moves into the descending limb
-this loss of water means Na+/Cl- conc. has increased
-as fluid moves down descending limb and starts to ascend, Na+/Cl- diffuse out of the loop
-this causes more water to be lost from the lowest part of the descending limb via osmosis
-the longer the loop, the greater the water potential, so more can be absorbed