Other controls of nephron

Question 1

how body responds to dehydration/fluid loss

Answer 1

post. pit gland releases anti-diuretic hormone (ADH) to inhibit urine output

Question 2

how ADH works

Answer 2

increases numbers of channels in the collecting ducts, which allows water to easily/quickly leave filtrate + be reabsorbed into blood stream

Question 3

how much water can ADH cause to be reabsorbed

Answer 3

99% –> very little urine secreted

Question 4

possible high osmolarity of urine when ADH has been released

Answer 4

up to 1200 mOsm/L (very concentrated)

Question 5

possible low osmolarity of urine when no ADH released

Answer 5

as low as 65 mOsm/L (very dilute)

Question 6

aldosterone control system overview

Answer 6

• works to increase blood volume (and therefore increase BP) when needed
• similar affect as RAA system but can be released directly in response to high K+ levels or low Na+ levels
• slow acting

Question 7

how aldosterone increases blood volume

Answer 7

places ion channels inside collecting duct cells (sodium-hydrogen ion channels + sodium potassium pumps)

Question 8

sodium-hydrogen ion channel

Answer 8

pumps Na + out of filtrate (for reabsorption)
pumps H+ ions into filtrate (for excretion)

water follows the salt, so water is reabsorbed along with Na+

Question 9

sodium potassium pump

Answer 9

Na+ pumped out of filtrate, K+ pumped into filtrate

water follows the salt, so water is reabsorbed along with Na+
this pump also increases potassium excretion

Question 10

aldosterone secreted by

Answer 10

adrenal cortex of adrenal glands (under control of RAA system)

Question 11

diuretics

Answer 11

substances that cause nephron to increase urinary output

ex: caffeine, alcohol, diuretic drugs

Question 12

how caffeine affects nephrons

Answer 12

causes renal tubules to dilate

• -> increases the rate of flow of filtrate moving through the tubules
• -> less time for filtrate reabsorption
• -> more filtrate excreted

Question 13

how alcohol affects nephrons

Answer 13

inhibits release of ADH –> ADH can’t do its job of inhibiting urine output

Question 14

how diuretic drugs usually affect nephrons

Answer 14

decrease Na+ reabsorption –> less water reabsorbed (with that Na+) –> more filtrate excreted

Question 15

cardiovascular baroreceptors overview

Answer 15

• located in aortic arch + carotid sinus arteries, controlled by vagus + glossopharyngeal (cranial) nerves
• mechanoreceptors that detect stretch inside vessels and send that info to medulla

Question 16

how cardiovascular baroreceptors work

Answer 16

increased blood volume

• -> increased BP
• -> baroreceptors notice change and inhibit sympathetic NS signals to kidneys
• -> afferent arterioles dilate
• -> dramatic increase in filtration rt
• -> increased excretion of water + Na+
• -> decreased blood volume
• -> decreased BP
• -> baroreceptors allows sympathetic NS signals to reach kidneys