3.6.4 Homeostasis Flashcards
Explain how the formation of glycogen in liver cells leads to a lowering of blood glucose concentration.
Glucose concentration in cell falls below that in blood creating diffusion gradient.
Glucose enters cell by facilitated diffusion
Describe how ultrafiltration produces glomerular filtrate
High hydrostatic pressure
Due to contraction of left ventricle wall
Small molecules
Pass through basement membrane
Proteins too large to go through
Pores in capillaries
Podocytes encourage transfer of molecules
Explain how a lack of insulin affects reabsorption of glucose in the kidneys of a person who does not secrete insulin.
High conc glucose in blood
High conc in tubule
Reabsorbed by facilitated diffusion
Requiring proteins
Working at max rate
Not all glucose reabsorbed
Some desert mammals have long loops of Henle and secrete large amounts of antidiuretic hormone (ADH). Explain how these two features are adaptations to living in desert conditions.
More water reabsorbed
By osmosis
From collecting duct
Due to longer loop of Henle
Sodium/chloride ions absorbed from filtrate in ascending limb
Gradient established in medulla
ADH acts on collecting duct
Makes cells more permeable
Which hormones are proteins
Insulin + glucagon + adrenaline
Not- ADH
Describe the process of selective reabsorption
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
Absorption of water in Loop of Henle
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
How is water balance maintained when water potential decreases
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
What structures do molecules move between during ultra filtration
Glomerular
Basement membrane
What structures to glucose and amino acid molecules move into during selective reabsorption
Proximal convoluted tubule
Blood
A drug inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons
Explain how furosemide causes an increase in the volume of urine produced
Water potential of filtrate decreased
Less water reabsorbed by osmosis
At collecting duct
