homeostasis Flashcards
describe negative feedback
(1) change in factor away from the norm/set point
(2) detected by a receptor
(3) hormone released or impulse sent
(4) (hormone/impulse) reaches the target organ/effector
(5) effector preforms corrective action
(6) factor returns to norm/set point
How bowman’s capsule is adapted?
(1) afferent arteriole has wider lumen than efferent
(2) causes high blood pressure in glomerulus
(3) pores in capillary endothelium
(4) basement membrane acts as a filter
(5) basement membrane stops blood cells, large proteins , molecules above 68000-70000; however, allows urea, glucose, amino acids, water , ions
(6) podocytes - finger like structures
(7) network of capillaries
How PCT is adapted?
(1) microvilli/ basal membrane folds to increase surface area
(2) for many transport proteins
(3) sodium ions and glucose/ amino acids are co-transported into cell from lumen
(4) sodium ions pumped out of cell into blood
(5) by active transport
(6) many mitochondria give energy /ATP
(7) tight junctions to stop filtrate from leaving without passing through the PCT cells for selective reabsorption
describe the roles of the hypothalamus and the posterior pituitary in osmoregulation
(1) hypothalamus/ osmoreceptors detect changes in the water potential of blood
(2) causes posterior pituitary gland
(3) to release ADH into blood
(4) ADH binds to receptors
(5) on the cell surface of the collecting duct cells
(6) stimulates enzyme cascade/ phosphorylase enzyme produced
(7) vesicles move towards and fuse with cell surface membrane
(8) vesicles have aquaporins
(9) collecting duct membrane more permeable to water
(10) water moves down water potential gradient by osmosis
(11) into collecting duct cells / blood/ tissue fluid
(12) water potential of blood returns to set point
describe the process of ultrafiltration in nephron
(1) diameter of lumen of afferent arteriole is wider than efferent arteriole
(2) leads to high blood/hydrostatic pressure
(3) plasma passes through gaps between endothelial cells of capillaries
(4) basement membrane acts as a filter
(5) red blood cells. large proteins, molecules over 68000 MM can not pass through
(6) podocytes allow filtrate to pass through
(7) filtrate passes into renal capsule
outline the formation of urea from excess amino acids by liver cells
(1) deamination/ amine group removed
(2) ammonia formed
(3) combined with carbon dioxide
(4) urea cycle
describe and explain how all the glucose in the glomerular filtrate is reabsorbed into the blood
(1) active transport/pumping of sodium ions out of cells into blood
(2) sodium potassium pumps in basal membrane
(3) sodium ion concentration decreases in cells/sodium ion concentration gradient set up
(4) so sodium ions enter tubule cells from lumen/filtrate
(5) by facilitated diffusion
(6) sodium ions co-transport glucose into the cell
(7) this is secondary/indirect active transport
(8) facilitated diffusion of glucose out of cells into blood
(9) through GLUT proteins
define homeostasis
homeostasis is the maintenance of constant internal conditions
