Renal Test Two

Question 1

What is the final step in reabsorption of water and sodium?

Answer 1

Water sodium and everything else dissolved in interstitial fluid move by bulk flow into peritubular capilllaries as final step

Question 2

What organ is most responsible for homeostasis?

Answer 2

Kidneys

Question 3

Fill in equation: Na excreted = ______

Answer 3

Na filtered - Na reabsorbed

Question 4

What are the receptors for reflexes that control body sodium?

Answer 4

Baroreceptors in the cardiovascular system and sensors in the kidney that monitor filtered load of sodium

Question 5

What is the most abundant cation in the ECF?

Answer 5

sodium

Question 6

How does sodium link to low blood pressure?

Answer 6

low body sodium leads to low ECF volume and plasma which leads to low artery and venous pressure

Question 7

What are the corrective reflexes to fix low BP?

Answer 7

Control the amount of sodium filtered by controlling GFR. This happens by activating cardiovascular baroreceptors to regulate the MAP

Question 8

What is the “more important” pathway for correcting low plasma volume?

Answer 8

Increase activity in the sympathetic nerves to the kidneys in response to low BP from low plasma volume. Which will cause constriction of renal arterioles and decrease the net GFR to decrease sodium and water excretion.

Question 9

Renin aldosterone system?

Answer 9

Angiotensinogen is produced by the liver and in response to low BP renin is released from the kidneys. Renin cleaves angiotensiongen to angiotensin I. AcE comes from the lungs to cleave angiotensin I into angiotensin II which is active and can then act on the adrenal glands to secrete aldosterone to cause an increase of Na reabsorption.

Question 10

What sends the signal to produce Renin?

Answer 10

Macula densa sends a signal to the juxtaglomerurlar cells in the kidney to produce renin

Question 11

In the absence of aldosterone where is most of the filtered sodium reabsorbed?

Answer 11

In the proximal tubule (65%)

and 30-32% in loop of henle and distal tubule

Question 12

What is the rate limiting step of producing aldosterone?

Answer 12

Renin secretion

Question 13

What are three inputs to the juxtaglomerular cells that increase the secretion of renin?

Answer 13

Sympathetic nerves activated by the baroreceptor reflex to JG cells

Baroreceptors within the kidney due to a decreased stretch from decreased BP

Paracrine factors released from macula densa

Question 14

What plays a role in the long term regulation of arteriole BP?

Answer 14

an increase in body sodium causes water to be re absorbed so this re absorbed water along with the retained sodium increases the ECF and plasma volume.

Question 15

When is the later tubule permeable to water?

Answer 15

In the presence of ADH

Question 16

How can the heart impact high blood pressure?

Answer 16

With high plasma volume there is distension in the atria. This increases secretion of ANP into the plasma and causes decreased Na re absorption and dilation of afferent arterioles and constriction of efferent to raise GFR which increases the excretion of NA

Question 17

What hormone directly inhibits aldosterone to increase sodium excretion?

Answer 17

ANP

Question 18

Describe how water is regulated without altering Na.

Answer 18

Sodium will stay in the ECF when added to the body, but water distributes throughout all compartments so pure water gains/losses only slightly change BP

Question 19

What reflexes alter water excretion without sodium excretion?

Answer 19

Osmoreceptors in the hypothalamus detect ECF and are mediated by ADH

Question 20

What happens to the hypothalmic osmoreceptors when they shrink?

Answer 20

they increase their frequency of action potentials.
Osmoreceptors synapse on neurons that have c ell bodies in hypothalamus and axons that travel down into posterior pituitary

Question 21

When excess water is ingested what is the pathway that leads to water excetion?

Answer 21

ECF osmolarity goes down and inhibition of hypothalmic osmoreceptors occurs.
ADH secretion and therefore plasma concentration of it is decreased due to lack of osmoreceptor firing.
Permeability of renal collecting ducts is decreased due to lack of ADH, so decreased water reabsorption and increased excretion occurs

Question 22

How does ADH influence TRP?

Answer 22

it causes widespread constriction of arterioles

Question 23

In order to excrete a concentrated urine to allow water reabsorption without concurrent sodium reabsorption what needs to happen?

Answer 23

The hyperosmotic renal interstitial fluid is coupled with collecting ducts that are permeable to water due to ADH. Water will be reabsorbed .

Question 24

How is dilute urine excreted?

Answer 24

Though a lack of ADH which will result in collecting ducts that are not water permable

Question 25

In congestive heart failure are renin angiotensin II and aldosterone high or low?

Answer 25

High, which leads to retention of water and sodium leading to the edema

Question 26

How does severe sweating impact sodium excretion?

Answer 26

It decreases plasma volume and therefore pressure, which leads to an increase in aldosterone to decrease sodium excretion

Question 27

How does severe sweating impact water excretion?

Answer 27

It increases plasma osmolarity which increases ADH to decrease water excretion

Question 28

In general how much potassium is reabsorbed/excreted?

Answer 28

Most filtered potassium is NOT excreted in urine because almost all filtered potassium is reabsorbed

Question 29

Is K secreted regulated or not?

Answer 29

Regulated by the cortical collecting duct according to body's need

Question 30

Describe what happens when there is an increase in K intake?

Answer 30

Secreted K can be added to the filtered and not reabsorbed potassium and the amount that is excreted in the urine (small) goes up a small degree.

Question 31

Potassium depletion, what happens?

Answer 31

There is no secretion so the only potassium that is excreted is what was filtered

Question 32

How does potassium move from renal interstitial fluid to the tubular fluid?

Answer 32

The Na/K pump moves from renal interstitial fluid across the basolateral membrane of tubule cells into the cells. Then potassium moves by diffusion through K channels into tubular fluid after crossing the luminal membrane

Question 33

How does aldosterone impact potassium?

Answer 33

it acts on CD cells to increase the rate of K secretion (which leads to increase Na reabsorption)

Question 34

What are a few things calcium is important for?

Answer 34

Cell division, enzyme function, heart electrical activity, neurotransmitter secretion and Hm. oocyte activation, blood clotting, muscle contraction, bone/teeth formation

Question 35

What metabolic shift can cause a depressed nervous system and increased muscle activity?

Answer 35

Hypercalcemia

Question 36

What can cause nervous system excitement and tetany?

Answer 36

Hypocalcemia

Question 37

Where is calcium concentration greater, ECF or Intracellular compartment?

Answer 37

ECF

Question 38

How is calcium stored in plasma?

Answer 38

50% ionized Ca in plasma, 9% combined with citrate and PO4, 41% bound to plasma proteins

Question 39

What promotes absorption of dietary calcium across intestinal walls?

Answer 39

Vitamin D

Question 40

What is the organic matrix of bone?

Answer 40

Collagen fibers and ground substance

Question 41

If ECF Ca is low what happens to raise it?

Answer 41

Osteoclasts are activated indirectly by PTH, which increases resorption of bone and causes phosphate ions to leave bone matrix and enter ECF

Question 42

How are vitamin D and PTH related?

Answer 42

In the absence of active vitamin D the effect of PTH is reduced. So there is decreased bone resorption

Question 43

What happens if there is excess calcium in the ECF?

Answer 43

Osteoblasts incorporate it into bones

Question 44

How much calcium is re absorbed?

Answer 44

~99% of filtered calcium is re absorbed and 59% of calcium in plasma is available for glomerular filtration

Question 45

Where does most Ca reabsorption occur?

Answer 45

In proximal tubule loop of henle and early distal tubule and is mostly not under hormonal control

Question 46

Where is calcium reabsorption regulated?

Answer 46

IN the late DT and early collecting duct. Low Ca concentration increases PTH which increases calcium reabsorption in the DT/CD

Question 47

A small change in blood calcium levels above normal causes what?

Answer 47

decreased PTH and increase calcium excretion in the urine

Question 48

What hormone activates an enzyme that catalyzes conversion of inactive vitamin D into the active form?

Answer 48

PTH

Question 49

In order for vitamin D to become actiove it undergoes a reaction in ___ and ___.

Answer 49

Liver and final activation in the kdineys

Question 50

Describe calcitonin?

Answer 50

acts on bone to decrease ECF calcium concentration and is of little importance in normal calcium regulation

Question 51

Inorganic phosphate in the plasma is filterable or not?

Answer 51

about half of plasma phosphate is filterable and most that is filtered is reabsorbed in the proximal tubule

Question 52

What decreases renal reabsorption of phosphate ions?

Answer 52

PTH so when calcium is low and PTH secretion and ca reabsorption are increased phosphate ion excretion in urine is increased