Homeostasis

Question 1

Glucagon

Answer 1

Glucagon is made in ∞ cells of islet of Langerhans
Released into blood
Glucagon binds to specific receptor.
On target cell - muscles and liver
Activation of adenylate cyclase
ATP converted to cyclic AMP
cAMP activates protein kinase
Protein kinase hydrolysis glycogen to form glucose (glycogenolysis)
Facilitated diffusion of glucose out of target cells
Increases blood glucose levels

Question 2

Insulin

Answer 2

Insulin made in β cells of islet of Langerhans
Released into blood
Insulin binds to specific receptors
On target vells – muscle and liver
Vesicles containing glucose channel proteins fuse with cell membrane
Increased facilitated diffusion of glucose into target cell
Decrease blood glucose level

Question 3

Ultra filtration

Answer 3

High blood pressure created in glomerulus
Due to contraction of left ventricle wall
Small molecules pass through basement membrane
Proteins/large molecules too large to go through membrane
Podocytes encourage transfer of molecules

Question 4

Selective reabsorption

Answer 4

Glucose/amino acids co-transported
Carrier protein transports sodium ion along with glucose/amino acid
Into cytoplasm of proximal convoluted tubule cell down concentration gradient of sodium ions
Low concentration of sodium ions maintained by active transport of sodium ions out of cell by sodium potassium pump
Facilitated diffusion of glucose/amino acids into blood though a channel protein

Question 5

Absorption of water in Loop of Henle

Answer 5

Sodium ions actively transported out of ascending limb
Chloride ions diffuse out to create sodium chloride
Creates low water potential in medulla/tissue fluid
Creates water potential gradient
Water moves by osmosis out of descending limb and is absorbed into capillaries
Volume of water in nephron is reduced

Question 6

Water balance

Answer 6

Decreased water potential of blood (lack of water, increased sweating, solutes in diet)
Detected by osmoreceptors in hypothalamus
Increased impulses to pituitary gland
Pituitary releases more ADH
ADH binds to specific receptors on target cell – distil convoluted tubule
Vesicles containing aquaporins fuse with cell membrane
Increases permeability of cell membrane to water
More water reabsorbed into the blood
By osmosis down water potential gradient
Water potential of blood increases