Kaplan Prep - Fluid and Electrolyte Balance - Problem Set 2 Flashcards Preview

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Flashcards in Kaplan Prep - Fluid and Electrolyte Balance - Problem Set 2 Deck (26)
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1
Q

What are the salts which are of greatest physiological importance?

A

The salts which are of greatest physiological importance are Na+, K+, Ca+2 and Mg+2.

2
Q

How are these salts gained by the body?

A

These salts are obtained from:

ingested foods and fluids.

3
Q

How are these salts lost?

A

These salts are lost by way of:

defecation, sweating and urination.

4
Q

What is the predominant positively-charged ion in extracellular fluid?

A

Na+ is the predominant positive ion of the plasma and interstitial fluid (extracellular) compartments

5
Q

What does the statement:

“water follows salt” mean?

A

When salt is absorbed, water must also be absorbed to maintain osmotic pressure from which comes the familiar statement “water follows salt”.

6
Q

What are the 3 main ways in which sodium balance (and water) is maintained?

A

There are 3 main ways in which sodium balance (and water) is maintained: (1) the effect of the hormone aldosterone, (2) the cardiovascular baroceptors and (3) the antidiuretic hormone (ADH).

7
Q

Explain, in detail, how the cardiovascular baroceptors work to maintain blood pressure.

A

The cardiovascular baroceptors monitor and regulate blood volume (which is influenced directly by Na+ ion concentration) to maintain blood pressure. If blood volume (and consequently blood pressure) rises, the baroceptors signal the kidney causing a dramatic increase in the filtration rate, increasing the output of water and Na+ which reduces blood volume to quickly normalize the pressure.

8
Q

Explain, in detail, how Antidiuretic hormone (ADH) maintains Na+ concentration (and water volume) in the extracellular fluid compartment.

A

Antidiuretic hormone (ADH) is released by the posterior pituitary in response to triggers by the hypothalamus osmoreceptors which have sensed higher Na+ concentration (likely due to a lower water volume) in the extracellular fluid compartment. ADH binds to receptors cells of the collecting ducts of the kidney and promotes reabsorption of water into the blood system. In the absence of ADH (likely due to higher water volume in the extracellular compartment, low Na+ concentration), the collecting ducts allow all water to be freely excreted as very dilute urine.

9
Q

What is hypernatremia?

A

Sodium ion excess is called hypernatremia

10
Q

What is the one cause of hypernatremia?

A

Hypernatremia is usually caused by dehydration. (Too much salt, not enough water)

11
Q

What is hyponatremia?

A

Sodium ion deficiency is called hyponatremia (too low sodium)

12
Q

What are the six causes of hyponatremia?

A

Hyponatremia can be caused by solute loss and/or water retention due to:
skin burns
excessive sweating
vomiting
diarrhea
renal disease
Addison’s disease (aldosterone deficiency).

13
Q

What are the 2 main ways in which potassium balance is maintained?

A

The 2 main ways in which potassium balance is maintained are:

  1. the collecting ducts
    and
  2. the hormone aldosterone.
14
Q

Explain, in detail, how the renal cortical collecting ducts act to maintain potassium balance.

A

When K+ is high in blood plasma because of high K+ in the diet, the renal cortical collecting ducts reabsorb 90% of the ion, allowing the remainder to be excreted in the urine. When K+ is low in blood plasma because of low K+ in the diet, the intercalated cells of the renal cortical collecting ducts reabsorb greater than 90% of the ion, allowing a smaller amount to be excreted in the urine.

15
Q

Explain in detail, how aldosterone acts to maintain potassium balance.

A

The adrenal cortex cells which secrete aldosterone are triggered by higher K+ levels to increase the excretion of K+ to maintain potassium balance.

16
Q

What is hyperkalemia?

A

Hyperkalemia is potassium ion excess

17
Q

Hyperkalemia is potassium ion excess

A

Hyperkalemia can be due to renal or adrenal gland disease or potassium leaking out of cells into the blood circulation due to severe tissue damage.

18
Q

What is hypokalemia?

A

Hypokalmia is potassium ion deficiency

19
Q

What are the causes of hypokalemia?

A

Hypokalemia can be due to diarrhea, vomiting or hyperaldosteronism (over-secretion of aldosterone).

20
Q

What are the 2 main ways in which calcium balance is maintained?

A

Calcium balance is maintained by the action of calcitonin and parathyroid hormones which cause the reabsorption of 98% of calcium by the kidney, small intestines and bones.

21
Q

Explain, in detail, how calcitonin and parathyroid hormones act to maintain calcium balance.

A

If plasma calcium levels decrease, the parathyroid glands secrete parathyroid hormone (PTH) which causes a subsequent increase in calcium levels by: (1) activating bone-digesting osteoclasts which release Ca+2 from the bones into the blood, (2) stimulating the small intestine to absorb Ca+2 and (3) increasing the reabsorption of Ca+2 by the renal tubules. In response to increasing plasma calcium levels, calcitonin is released by the thyroid, inhibiting the bone reabsorption action of osteoclasts.

22
Q

What do you call calcium ion excess?

A

hypercalcemia

23
Q

What do you call calcium ion deficiency?

A

hypocalcemia

24
Q

What is the cause of hypercalcemia?

A

Hypercalcemia (Calcium ion excess) can be due to hyperparathyroidism or renal disease.

25
Q

What is the cause of hypocalcemia?

A

Hypocalcemia (Calcium ion deficiency) can be due to diarrhea, burns, Vitamin D deficiency and alkalosis.

26
Q

Where is a majority of Mg+2 found in the body?

A

About 60% of all body Mg+2 is found in the skeleton (in the bones)

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