Topic 11 Flashcards
(102 cards)
1
Q
Potassium is Tightly controlled–Usually changes less
than ____ mEq/liter
A
0.3 mEq/liter
2
Q
how much potassium is intracellular and how much is extracellular? %
A
Intracellular 98%
extracellular 2%
3
Q
what does the normal intake of potassium range between?
A
50 mEq/liter to 200 mEq/liter
4
Q
how much of the potassium intake is removed by feces
A
5-10%
–rest must be removed by kidneys
5
Q
After ingesting 40 mEq of K+ into ECF–[K+] would increase by how many mEq/l
A
- 8 mEq/liter
- -Most ingested K+ quickly moves into the cellular volume
6
Q
what does Insulin move into the cells following a meal
A
potassium AND glucose
7
Q
what is aldosterone secretion stimulated by
A
increased potassium concentration
–In disease state, ability to move K+ into the cells AND K+ reabsorption are affected
8
Q
Epinephrine stimulates ______ receptors increasing movement of K+ into the cell.
A
β2- adrenergic
9
Q
what do β2-adrenergic blocking agents (treat hypertension) lead to
A
hyperkalemia
10
Q
what are 4 Factors that shifts K+ into cells (Potential hypo)
A
- Insulin
- Aldosterone (also K+ secretion)
- Β-adrenergic stimulation
- Alkalosis
11
Q
what are 7 Factors that shifts K+ out of cells (Potential hyper)
A
- Insulin deficiency (diabetes mellitus)
- Aldosterone deficiency (Addison’s disease)
- Β-adrenergic blockade
- Acidosis
- Cell lysis
- Strenuous exercise
- Increased extracellular fluid osmolarity
12
Q
what will will reduce action of Na-K ATPase with less transfer of K+ into the cells
A
Increased [H+]
13
Q
what does cell lysis do
A
dumps intracellular K+ in extracellular compartment
14
Q
With an increase in extracellular osmolarity, water moves out of the cell increasing intracellular [K+] which does what?
A
increases the rate of K+ diffusion out of the cell
15
Q
the Excretion rate of potassium is determined by what 3 things?
A
Rate of potassium filtration
Rate of potassium reabsorption
Rate of potassium secretion
16
Q
how often does the Constant fraction of filtered load reabsorbed in proximal tubule and the loop of Henle change
A
Does not change day-to-day
17
Q
how much potassium is filtered in mEq/day
A
756 mEq/day
18
Q
whats the Consistent Reabsorption % in the proximal tubule
A
65%
19
Q
whats the Consistent Reabsorption % in the loop
A
25-30% (mainly thick ascending)
20
Q
Flexible Reabsorption & Secretion occurs where
A
Principle cells of distal tubule and cortical collecting tubule
21
Q
With normal K+ intake of 100 mEq/day, how much is removed by feces and how much by the kidneys
A
Feces removes 8 mEq
Kidneys must remove 92 mEq
22
Q
Proximal tubule removes ___ mEq leaving ___ mEq
Loop removes ___ mEq leaving ___ mEq
Distal tubule & cortical collecting tubule MUST secrete ___ mEq (Approximately ___ of excreted potassium)
A
Proximal tubule removes 491 mEq leaving 265 mEq
Loop removes 204 mEq leaving 61mEq
Distal tubule & cortical collecting tubule MUST secrete 31 mEq (Approximately 1/3 of excreted potassium)
23
Q
Principal Cells Make up __% of cells in late distal and cortical collecting tubule
A
90%
24
Q
what do Intercalated Cells do
A
Reabsorb potassium especially during potassium
depletion
25
describe the H-K ATPase pump
Located tubular membrane
Pumps H+ from tubular cell into lumen (secretion)
Pumps K+ from tubular lumen into cell (reabsorption)
Major effect only during potassium depletion
26
what Three factors control rate of K+ secretion
1. Activity of Na-K ATPase
2. Electrochemical gradient for K+ movement from the blood to the tubular lumen
3. Permeability of tubular membrane to K+
27
what will increase Stimulation of Potassium Secretion
Increased extracellular [K+]
Increased [aldosterone]
Increased tubular flow rate
28
what will decrease Stimulation of Potassium Secretion
Increased [H+] will DECREASE potassium secretion
29
Increase [K+] in plasma stimulated release of what?
aldosterone
30
Increased aldosterone increases what
increases rate of sodium reabsorption by late distal tubule and collecting duct
31
increases int the rate of sodium reabsorption by late distal tubule and collecting duct then increases what 2 things
1. Increases activity of Na-K ATPase–so an increase in
sodium reabsorption will also increase potassium secretion
2. Increases tubular membrane permeability for potassium
32
Normal aldosterone level is approximately __ nag/dL
6 nag/dL
33
High aldosterone (primary aldosteronism) will result in what?
Hypokalemia
34
Low aldosterone (Addison’s disease) will result in what?
Hyperkalemia
35
Increased distal tubular flow rate will do what?
increase potassium secretion
36
Increased tubular flow rate can be caused by what?
volume expansion; high sodium intake; specific diuretics
37
Relationship between tubular flow rate and potassium secretion greatly affected by potassium intake... So a Higher the intake does what?
Higher the intake, the greater the effect created by tubular flow
38
As potassium diffuses into tubular lumen, what will happen?
the increase in luminal concentration will decrease the gradient thus decreasing the movement of potassium
39
Increased tubular flow carries potassium away thus
| helping to preserve the gradient. So the higher flows will do what?
The higher the flow the better the gradient is preserved, the more potassium is secreted
40
Assuming high Na+ intake, Aldosterone secretion
decreases which will produce a decrease K+ secretion...BUT since sodium reabsorption is decreased,
what will happen to the overall distal tubular flow
overall distal tubular flow is increased which results in an
increase in K+ secretion
THE TWO OFF SET EACH OTHER
41
how does Acidosis (H+) reduces potassium secretion
Reduces the activity of Na-K ATPase–decreases driving force for moving potassium from cell interior to tubular
lumen
42
what does Prolonged acidosis produce
increased potassium excretion–Result of decreased reabsorption of sodium chloride and water in proximal tubule and increased distal tubular flow
43
acidosis does what to potassium secretion
reduces potassium secretion
44
Alkalosis does what to potassium secretion
increases potassium secretion
45
Total calcium in plasma: ___ mEq/liter
5 mEq/liter
46
Total % calcium in ionized form
50%
47
Total % calcium bound to plasma protein
40%
48
Total % calcium bound in non-ionized form to other ions (phosphate, citrate)
10%
49
Amount of Ca++ bound to protein ____ with an increase in [H+].
decreases
50
Patients with alkalosis more susceptible to what
hypocalcemic tetany
51
Normal ion concentration of Ca++: __ mEq/liter (__ mmol/liter)
2.4 mEq/liter (1.2 mmol/liter)
52
Hypocalcemia does what to neuromuscular excitability
increases muscle and nerve excitability (hypocalcemic tetany)
53
Hypercalcemia does what to neuromuscular excitability
depressed neuromuscular excitability which can lead to cardiac arrhythmias
54
what % of calcium stored in bone
99%
55
what will the body do if calcium levels increase or decrease too much
- -if plasma concentration drops, body will move calcium from the bone
- -if plasma concentration rises, body will move calcium back into the bone
56
what % of calcium is present in intracellular space and cell organelles
1%
57
what % of calcium is present in extracellular fluid
0.01%
58
what is the most important control agent for calcium
Parathyroid Hormone (PTH)
59
```
Parathyroid Hormone (PTH):
__% excreted via gastrointestinal tract (feces) (≈900 mg/day)
__% excreted via kidneys (urine) (≈100 mg/day)
```
90% excreted via gastrointestinal tract (feces) (≈900 mg/day)
10% excreted via kidneys (urine) (≈100 mg/day)
60
PTH regulation accomplished through what 3 actions
1. Stimulation of bone resporption of calcium
2. Stimulation of vitamin D which stimulates calcium
reabsorption by intestines
3. Direct stimulation of renal tubule reabsorption of calcium
61
```
fill in the path:
decrease of Ca++=
______ PTH=
______ Ca++ released from bones
______ Renal Ca++ reabsorption
______ Vit D3 activation=
______ Intestinal Ca++ reabsorption
```
```
decrease of Ca++=
INCREASE PTH=
INCREASE Ca++ released from bones
INCREASE Renal Ca++ reabsorption
INCREASE Vit D3 activation=
INCREASE Intestinal Ca++ reabsorption
```
62
```
Fill in the path:
Increased Na+ intake=
_____ aldosterone
_____ GFR
_____ Prox. Tubule Reabsorption
_____ Dist. Tubule flow rate
_____ K+ secretion cortical collecting ducts/Unchanged K+ Excretion
```
Increased Na+ intake=
- -Decreased aldosterone
- -Increased GFR
- -Decreased Prox. Tubule Reabsorption
- -Increased Dist. Tubule flow rate
- -decreased with decreased alosterone OR increased with increased dist. tubule flow K+ secretion cortical collecting ducts/Unchanged K+ Excretion
63
As extracellular calcium concentration falls: Parathyroid gland directly stimulated to do what
increase secretion of PTH
64
Increased PTH concentration stimulates bone to do what
increase release of bone salts (resporption) which includes the release of large amounts of calcium
65
As extracellular calcium concentration increases: Parathyroid gland does what
decreases PTH secretion
66
Decreased PTH concentration does what
ecreases salt resporption to point where calcium will be added to the bone
67
calcium is Freely filtered, reabsorbed BUT NOT secreted... so what is the excretion formula for CALCIUM
Excretion rate = Filtration–Reabsorption
68
CALCIUM
Proximal tubule: __% filtered load reabsorbed
Loop of Henle: __ to __% filtered load reabsorbed
Distal tubule / Collecting tubule: __% filtered load
reabsorbed
Proximal tubule: 65%
Loop of Henle: 25 to 30%
Distal tubule / Collecting tubule: 4 to 9%
69
what % of calcium in the filtered load is excreted
1%
70
Proximal Tubule Reabsorption of Ca++
__% of amount reabsorbed carried by water via paracellular pathway
__% of amount reabsorbed via a transcellular pathway
80% paracellular pathway
| 20% transcellular pathway
71
what 2 ways are calcium Pumped out of cell across basolateral membrane
Ca ATPase pump
| Na-Ca counter-transport mechanism
72
Thick Ascending Loop–Ca++ Reabsorption
Paracellular pathway accounts for __% of reabsorption
Transcellular pathway accounts for __% of reabsorption
Paracellular pathway accounts for 50%
| Transcellular pathway accounts for 50%
73
in the thick ascending loop, describe how Ca++ is reabsorbed in the paracellular pathway
Passive diffusion down electrical gradient–lumen has slight positive charge compared to interstitial fluid
74
in the thick ascending loop, describe how Ca++ is reabsorbed in the transcellular pathway
```
Active process stimulated by PTH, Vitamin D (Calcitrol),
and calcitonin (PTH concentration most important)
```
75
Distal Tubule–Ca++ Reabsorption
| Almost all transport via what pathway
Transcellular pathway
| --Active transport across basolateral membrane–diffusion into cell
76
in the distal tubule what will increase reabsorption of Ca++
Increased [PTH], Vitamin D and calcitonin
77
increased [PTH] stimulates increased reabsorption in what area
Loop and Distal Tubule
78
PTH has no effect in what area
Proximal Tubule (Following sodium and water reabsorption)
79
Δ in EC fluid volume and blood pressure cause inverse changes in sodium & water reabsorption which causes what
parallel changes in calcium reabsorption
80
[Phosphate] affects [PTH]–As [Phosphate] increases, [PTH] does what
increases
81
[H+] major affect is on the transport mechanisms in what area
Distal Tubule
82
name 6 things that will increase Ca++ Reabsorption
```
increase [PTH]
increase Plasma Phosphate
decrease EC Fluid Volume
decrease Blood Pressure
Metabolic Acidosis
Vitamin D3
```
83
name 5 things that will decrease Ca++ Reabsorption
```
decrease [PTH]
decrease Plasma Phosphate
increase EC Fluid Volume
increase Blood Pressure
Metabolic Alkalosis
```
84
Phosphate: Normal tubular maximum of ___ mMol/minute
0.1 mMol/minute
85
Phosphate: If filtered load under Tmax, all phosphate is
reabsorber
86
Phosphate: If filtered load over Tmax, phosphate is
excreted
87
Phosphate: Plasma threshold level approximately ___ mMol/liter
0.8 mMol/liter
88
Phosphate: Normal plasma concentration around __ mMol/liter
1 mMol/liter
| –Large intake of phosphate each day (milk & meat)
89
PHOSPHATE
Proximal Tubule: ___% of filtered phosphate reabsorbed
Loop of Henle: _______
Distal Tubule: __% of filtered phosphate reabsorbed
Collecting Tubule: ____________
Proximal Tubule: 75-80% of filtered phosphate reabsorbed
Loop of Henle: Very small amounts
Distal Tubule: 10% of filtered phosphate reabsorbed
Collecting Tubule: Very small amounts
90
how does phosphate enter and leave the cell
- -Enters cells from lumen via Na-Phosphate co-transport mechanism
- -Leaves cell via counter-transport mechanism across basolateral membrane
91
what % of filtered phosphate is excreted
10%
92
phosphate Tmax can change based on intake. with a Low intake, what will happen to the Tmax
Tmax will increase over time
93
As PTH increases bone resorption of calcium, what happens to phosphate
phosphate is also resorbed
94
increasing [PTH] does what to the Tmax for phosphate
decreases the Tmax for phosphate so less phosphate is reabsorbed and more is excreted
95
how much magnesium is stored in bone, extracellular and intracellular volume
>50% stored in bone
Most of what is left is located in the intracellular volume
<1% located in extracellular volume
96
TOTAL plasma magnesium = __ mEq/liter BUT__% is bound to plasma proteins so free ionized is __ mEq/liter
TOTAL plasma magnesium = 1.8 mEq/liter
>50% is bound to plasma proteins
free ionized is 0.8 mEq/liter
97
what is the daily intake of magnesium, and how much is absorbed by the GI tract
Daily intake ≈ 250 to 300 mg/day BUT only 50% is actually absorbed by the gastrointestinal tract (125 to 150 mg/day)
--The amount absorbed is the amount the kidneys must
excrete each day
98
what % of magnesium is excreted from the filtered load
Renal excretion of magnesium is ≈ 10 to 15% of filtered load
99
MAGNESIUM
Proximal Tubule: __% of filtered load
Loop of Henle: Primary site of reabsorption–__% of filtered load
Distal Tubule / Collecting Tubule: <_% of filtered load
Proximal Tubule: 25%
Loop of Henle: 65%
Distal Tubule / Collecting Tubule: <5%
100
increased [magnesium] has what effects on reabsorption and excretion
decreased reabsorption
| increased excretion
101
increased EC fluid has what effects on reabsorption and excretion
decreased reabsorption
| increased excretion
102
increased [Ca++] has what effects on reabsorption and excretion
decreased reabsorption
| increased excretion
