Quiz, block 2- Renal system Flashcards

1
Q

How does the Loop of Henle and CD play a role in the countercurrent multiplier system?

A

Loop of Henle and CD keep a progressively hyperosmotic Na+ gradient deep into the medulla to allow for reabsorption/retention of water within the interstitial fluid space. Hence, water won’t be excreted.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what organ is most responsible for maintaining acid-base homeostasis?

A

kidney!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are two reflex receptors that control body Na+?

A
  1. arterial baroreceptors in the CV system

2. sensors in kidney that monitor the filtered load of Na+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the consequences of low total body Na+?

A
  • results in low ECF volume
  • low plasma volume
  • low arterial and venous blood pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what’s the obligatory water loss volume and define it?

A

0.46L/day (minimal amount or urine- water loss- that you need to form to carry wastes away.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how is the concentrated urine gradient (hyperosmotic fluid) formed?

A
  1. in juxtamedullary nephrons, NaCl are actively pumped out of ascending limb of loop of Henle into interstitial fluid that surrounds the loop. Water would follow Na+ into the IS fluid and get retained there/can’t exit the loop b/c it’s impermeable to it.
    - -the effect is multiplied by the countercurrent flow through the loops. this concentrates the renal medullary interstitium to a maximum of about 1400 mOsmol.
  2. UREA also get trapped in the interstitium
  3. VASA RECTA (blood supply of renal medulla) has a counter current construction that prevents the “washing out” of Na+ conc gradient (prevent blood from carrying off Na+ with it).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how is urine concentration affected by high blood ADH levels?

A

high ADH levels- water diffuses out of filtrate medullary CDs into the renal medullary interstitial space, producing a small volume of hyperosmotic/concentrated urine when one is thirsty. then water enters the capillaries of the renal medulla to be carried away in venous blood.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how is urine concentration affected by low blood ADH levels?

A

both the cortical and medullary CDs are impermeable to water, so water is not reabsorbed as the filtrate flows through the CD, and a large volume of hypoosmotic urine is formed (lots of water in urine).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the two corrective reflexes in response to low BLOOD PRESSURE?

A
  1. control of GFR.
    the reflexes are set into motion by CV baroreceptors, thus regulating the mean systemic arterial pressure (MAP), simultaneously achieves regulation of total body Na+
  2. control of Na+ reabsorption (more important regulation than of GFR) via hormonal control (aldosterone)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the direct effect of controlling GFR as one of the corrective reflexes in response to low blood pressure.

A

low plasma volume (possibly due to low total body Na+, thus water).

  • leads to LOW arterial blood pressure that results in a decreased net glomerular filtration pressure, that decreased GFR
  • > decreased Na+ and water excreted
  • > bp rises
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the INdirect effect of controlling GFR as one of the corrective reflexes in response to low blood pressure.

A

Low plasma volume (possible due to low total body Na+, thus water). leads to LOW arterial blood pressure.
-this increase activity in SYMPATHETIC nerves to kidneys (motor pathway).
-constricts AFFERENT arterioles of kidney to decrease net glomerular filtration pressure.
Also:
hormonal control of secretion of angiotensin and ADH decrease net glomerular filtration pressure as well.
–> both result in decrease GFR, which decrease Na+ and water excretion.
- bp rises!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what plasma protein get secreted by the liver?

A

angiotensinogen (At’n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does the kidney secrete, and its function?

A

renin that breaks angiotensinogen into angiotensin I.

renin, an enzyme, secreted by the juxtaglomerular cells (JG cells), part of the JG apparatus of the kidney.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what does the walls of lung capillary secrete?

A

angiotensin-converting enzyme (ACE or converting enzyme) that convert angiotensin I into angiotensin II.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what organ does angiotensin II act on?

A

AT II leaves the blood and signals the adrenal cortex to secrete aldosterone to tell kidney to increase reabsorption of Na+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what organ secretes aldosterone and what is the function of that hormone?

A

adrenal cortex secretes aldosterone and other steroids.

aldosterone- increase Na+ reabsorption rate in the CD and late distal tubule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

in absence of aldosterone,
how much of total filtered Na+ is reabsorbed in the proximal tubule, in the loop of Henle and first part of distal tubule? where does most of unregulated reabsorption occur at?

A

65% (not regulated) of total filtered Na+ is reabsorbed in the proximal tubule,
with another 30-32% reabsorbed in the loop of Henle and first part of distal tubule (regulated?).
**most reabsorption occurs early and not regulated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

at high plasma levels of aldosterone,
how much of filtered Na+ is reabsorbed in the proximal tubule. Complete reabsorption of the last 4% occur at the late DT and CD.

A

nearly 100% of filtered Na+ is reabsorbed, with the remaining Na+ being reabsorbed in the late DT and CD.
Complete reabsorption of the last 4%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the 3 inputs that JG cells receive to increase renin secretion?

A

Renin is secreted by JG cells. JG cells receive 3 inputs that activate it.
1. Stimulation of sympathetic nerves to the JG cells in kidneys. Sympathetic nerves- activated by the baroreceptor reflex that was discussed in low blood pressure scenario.

  1. baroreceptors within the kidney that get activated by DECREASED stretch resulting from decreased blood pressure within the kidney
    * less stretch: activate baroreceptors.
  2. paracrine factors released from macula densa. This is in response to a decreased volume and/or conc. of Na+ in tubular fluid flowing past the macula densa cells.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what effect does increased Na+ in the body leads to regulation of arterial blood pressure?

A

cause water to be reabsorbed and also due to osmotic considerations.
this reabsorbed water plus retained Na+ –> increases ECF volume (thus plasma volume). This plays an important role in long-term regulation of arterial blood pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the function of the cardiac hormone? its function?

A

atrial natriuretic peptide (ANP) decreases Na+ reabsorption by directly inhibiting aldosterone secretion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are the 3 ways that plasma ANP increase Na+ excretion under condition of high plasma volume, so less Na+ are present in plasma (thus lower plasma volume)?

A
  1. kidney tubules decrease Na+ reabsorption
  2. kidney vessels: dilate the afferent arterioles and constrict efferent arterioles. this damn up blood and increase bp or increase GFR
  3. inhibit adrenal cortex from secreting more aldosterone, which increase Na+ excretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how is water regulated?

A

unlike Na+, which stays in the ECF when added to the body, water distributes throughout all the body fluid compartments w/ 2/3 entering the intracellular comparment. Thus, pure water (w/o Na+) gains or losses only slightly influence BLOOD PRESSURE (and thus baroreceptors).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what’s involved in water excretion reflexes?

A

there are reflexes that alter water excretion without altering sodium excretion. this reflex is:
a. initiated by sensory receptors in the hypothalamus called OSMORECEPTORS that detect ECF osmolarity level.

b. mediated by posterior pituitary hormone, ADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

how are hypothalamic osmoreceptors respond to high ECF osmolarity via control of ADH secretion rate?

A

they are neurons that increase their frequency of action potentials when they shrink. they shrink when ECF osmolarity is ABOVE NORMAL, which causes water to be pulled out of the cells and into the ECF by osmosis.

-osmoreceptors synapse on neurons that have cell bodies in the hypothalamus and have axons that travel down into and release ADH from the posterior pituitary.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what are steps following ingestion of excess distilled water?

A

this decrease ECF osmolarity
–> leads to inhibition of (decrease firing) by hypothalamic osmoreceptors
–> decrease ADH secretion from posterior pituitary
–> decrease plasma ADH
–> decrease permeability of renal collecting ducts to water
–> decrease water reabsorption
INCREASE water excretion (more water end up in urine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what other inputs (aside from osmoreceptor) also influence ADH secretion rates?

A

input from arterial baroreceptors and other CV baroreceptors. Less important input compare to osmoreceptor input, can become important in scenario of hemorrhage.

28
Q

ADH also causes widespread constriction of arterioles, which influences ___ in the CV system.

A

total peripheral resistance in the cardiovascular system

29
Q

why does regulation of ECF osmolarity requires separation of water excretion from Na+ excretion?

A

can’t take away both.

kidneys need to excrete a concentrated urine when water is short and a dilute urine when water is in excess.

30
Q

how do we control the water secretion rate to produce a concentrated or dilute urine?

A
  1. excrete a concentrated urine- hyperosmotic renal interstitial fluid coupled with collecting ducts that are made permeable to water by lots of ADH presence, which allow water reabsorption without concurrent Na+ reabsorption happening at the same time.
  2. excrete a dilute urine- collecting ducts are not water permeable, coupled with a lack of ADH secretion
31
Q

what are the components of reflex arc in a cardiac attack ?

A

a. failing heart due to reduced cardiac output
b. decreased arterial blood pressure. baroreceptors increase sympathetic signal to ventricles to increase cardiac output and increase peripheral resistance.
c. lead to more renin is secreted into the plasma. renin converts At’n to ATI. Converting enzyme convert ATI to angiotensin II in plasma
d. AT II signals adrenal cortex to secrete aldosterone in plasma
e. increased aldosterone retain Na+ and less Na+ is excreted.
f. water follows Na+ and more is water is retained.
g. water backs in interstitial space result in edema

32
Q

how is K+ regulated?

a. reabsorbed
b. filtered
c. excreted
d. all of the above

A

d.
K+ get filtered, reabsorbed, and excreted.
almost none of the filtered K+ is excreted in urine b/c all but a tiny amount of filtered K+ gets reabsorbed.

33
Q

what portion of CD can secrete K+ into the filtrate at a rate that is regulated according to physiological need?

A

the cortical CD

34
Q

how does K+ get secreted into the tubular lumen fluid?

A

Na+/K+ pump moves K+ from renal interstitial fluid across the basolateral membrane of tubular cells into the cells.
K+ then moves by diffusion through K+ channels across the luminal membrane into tubular fluid.

35
Q

what role does aldosterone play in sensing the conc of K+?

A

the aldosterone-secreting cells of the adrenal cortex can sense the conc. of K+ in the surrounding ECF.
when the K+ conc is higher than normal, the cells secrete more aldosterone.
aldosterone (beside increase Na+ reabsorption into the cell), also acts on CD cells to secrete K+ into the tubular fluid to drive K+ level in ECF down.

36
Q

ADH induce insert of what protein in the luminal membrane?

A

ADH induce more aquaporins.

increase gene expression of Na+/K+ pump

37
Q

what are the conditions necessary to secrete K+ into the urine?

A

Na+/K+ pump in basolateral membrane of CD cells are stimulated by high K+ in interstitial fluid. this pump K+ inside the cell to build a high K+ conc. With this gradient of high K+ inside the cells and low in the tubular lumen, K+ can diffuse across and be excreted.

38
Q

functions of calcium

A
  1. cell division
  2. function of many enzymes as secondary messenger
  3. heart electrical activity
  4. neurotransmitter secretion
  5. hormone secretion
  6. oocyte activation
  7. removal of inhibition of muscle contraction
  8. blood clotting
39
Q

what are the 3 organs involved in calcium regulation?

A

kidney, small intestines and bones

40
Q

what is hypercalcemia? how does it affect activity?

A

higher than normal Ca+2 in the ECF. it depresses nervous system and muscle activity

41
Q

what is hypocalcemia? how does it affect activity?

A

it is lower than normal Ca+2 in the ECF. it causes nervous system excitement and tetany

42
Q

where are the 3 storage spaces of calcium?

A
  1. about 0.1% is in the ECF
  2. about 1% is within CELLS and their organelles (SR and cytoplasm)
  3. rest is in BONES. store excess calcium and release it when ECF conc is low.
    * bones give up calcium to maintain the ECF conc., regulated based on the need of ECF.
43
Q

what 3 forms do calcium found in?

A
  1. 50% of it is ionized- in calcium ions
  2. 9% combined with anions ie. citrate or phosphate
  3. 41% is bound to plasma proteins (not filterable)

Only 59% is filterable, diffusible through the capillary membrane.

about 35% of dietary calcium is absorbed across the intestinal wall (a process promoted by vitamin D)
-remainder is excreted in the feces

44
Q

what are the ways that calcium is maintained?

A
  1. calcium intake through diet. Ca+2 get absorbed by small intestine and get excreted in feces. Also, Ca+ is also exchanged between small intestines and ECF. Ca+ in the small intestine is absorbed by the ECF, and the ECF secretes Ca+ into the small intestine
  2. cells also exchange Ca+ with the ECF
  3. ca+ is deposited into bones and take back by ECF when its conc is low
  4. ca+ is filtered in urine by kidney and reabsorbed, and excess is excreted in urine.
45
Q

what is “organic matrix” of bone made up of?

A

collagen fibers plus ground substance (a homogeneous gelatinous substance)

46
Q

what is in the crystalline salt?

A

calcium and phosphate salts are deposited in a crystalline form in this organic matrix.
the main crystalline salt is called hydroxyapatite. lots of calcium and fair amount of phosphates there.

47
Q

In low calcium ECF,

bone matrix increase activity of ______ to break down bone matrix to release calcium and added to the ECF.

A

osteoclasts

48
Q

what hormone stimulates osteoclast activity?

what is the function of osteoclast?

A

parathyroid hormone (PTH) stimulate osteoclast activity.

osteoclast then secrete proteolytic enzymes to digest organic elements of bone matrix and secrete acids that dissolve the bone salts.

49
Q

what locates behind the thyroid gland and wrapped around the larynx?

A

4 parathyroid glands

50
Q

what are 2 complications resulted from ca+ regulation with increased PTH and in absence of active vitamin D?

A
  1. PTH’s effect of increasing the resorption of bone also causes phosphate ions to leave bone matrix and enter the ECF.
  2. in the absence of active vitamin D, the effect of PTH in causing bone resorption is reduced.
51
Q

what bone cells get stimulated in the present of excess calcium?

PTH binds to receptors on _____ bone cells, causing them to release a substance that binds to preosteoClast cells. This binding triggers preosteoClasts to differentiate into mature osteoclasts.

A

osteoblasts to build up bone matrix.

binds to receptors on ostetoblasts

52
Q

how do the kidneys and blood make use of calcium?

A
  1. about 59% of calcium in plasma is available for glomerular filtration
  2. rest is bound to blood proteins
53
Q

About 99% of filtered calcium is reabsorbed.
Over 80% of ca+ reabsorption occurs in the proximal tubule, loop of Henle and early distal tubule, that is mostly not under hormonal control.
Reabsorption in late DT and early CD is ____?

A

reabsorption in late DT and early collecting duct is REGULATED.

54
Q

what impact does a slight increase in blood Ca+2 above normal has?

A

decrease PTH secretion and increase calcium excretion in urine markedly

55
Q

T/F. A sensor of Ca+2 exist in the parathyroid gland.

A

True

56
Q

what is PTH function?

A

PTH activates an ENZYME (1alpha-hydroxylase) that catalyzes the conversion of inactive vitamin D into active vitamin D (1,25 dihydroxyvitamin or calcitreul)

*we eat calcium in an INACTIVE form

57
Q

what is required to transform a cholesterol derivative in skin into inactive vitamin D3?

A

sunlight!
Vitamin D2 and some inactive D3 is dietary require sunlight for activation.
to become active, both undergo a reaction in the liver and then final activation in the kidney.

58
Q

what is the role of 1,25 dihyoxyvitamin D?

A

it’s considered to be a hormone, that is carried by the blood to the intestine. there, it increases the absorption of dietary calcium and phosphate ion into the body.

59
Q

what are the regulation mechanisms of PTH on kidney under high plasma Ca+ con.?

A

in high ca+ plasma conc, PTH activates the kidneys’s enzymes to convert the precursors, from 25-hydroxy… into 1,25-dihydroxy. it inhibits small intestine. activate the negative feedback to lower the calcium level. ??

second scenario:
in case of high precursor 25-hydroxy, it inhibits the liver to turn off production of vitamin D3.

60
Q

what effect does the thyroid hormone, calcitonin, has on calcium conc?

A

calcitonin acts mainly on bone to decrease ECF calcium conc. Little importance in calcium regulations in human.

61
Q

what are 2 forms of inorganic phosphate found in the plasma?

A

Hpo-2 and H2p04 (both ionized)

62
Q
About half of plasma phosphate is filterable. Most that is filtered is \_\_\_\_ in the proximal tubule? 
a. secreted
b. reabsorbed
c. excreted
d both b and c
A

b.

63
Q

how does low blood calcium affect phosphate ion excretion in urine?

A

when blood calcium is low,
resulting in increased secretion of PTH levels and increased calcium reabsorption. Phosphate ion excretion in urine is increased.

64
Q

what are the functions of phosphate?

a. phosphate is part of bone matrix (forming the bone)
b. involved in controlling acid-base balance
c. part of ATP, ADP, cAMP, GTP, cGMP, DNA, RNA and some proteins
d. all of above

A

d.

65
Q

Kidneys regulate ECF by regulating its volume and osmolarity. this based on how it handles Na+ and water.

a. Na+ is related to volume
b. water is related to osmolarity
c. want reabsorption of both water and Na+, not only or the other.
d. Na+ and water both affect only osmolarity
e. a,b,c are correct

A

e.