ch 27 Water, Electrolyte, Acid Base Balance

Question 1

1. Fluids make up about ….. % in males and …….. % in females in body weight.
2. What are the 2 major fluid compartments of the body?
3. What are the subcompartments of the extracellular fluid and their percentages?
4. T or F, the ECF subcompartments have significant water and ion exchange. What occurs when excess fluid leaves the plasma?
5. What factors contribute to edema?

Answer 1

1. 60%, 50%
2. The intracellular fluid compartment (2/3 of body’s fluids) and the extracellular fluid compartment (about 1/3 of body’s fluids).
3. interstitial fluid 80%, plasma 20%, lymph, cerebrospinal fluid, and synovial fluid
4. T. Edema
5. increases in capillary permeability (due to inflammation), and increased hydrostatic pressure in capillaries (from blockages).

Question 2

1. How is the total volume of water in the body kept constant?
2. What happens when water volume in the body changes?
3. How much of water gain is by ingestion? How much water is gained as a by-product of cellular respiration?
4. How much water is lost in urine? Feces? Evaporation?

Answer 2

1. The body keeps water gain and water loss equal.
2. It alters solute concentrations of body fluids, blood volume and pressure, and interstitial fluid pressure.
3. 90%, 10%
4. 61%, 4%, 35%

Question 3

1. How is water intake regulated?
2. Neurons in the supraoptic nucleus of the hypothalamus cause thirst when?
3. What happens when baroreceptors detect low blood pressure?
4. What happens when renin is released from the juxtaglomerular apparatus in response to low BP?
5. What does drinking fluids do temporarily? Permanently?

Answer 3

1. By thirst regulation.
2. extracellular fluid solute concentration increases.
3. They trigger thirst
4. It triggers the RAAS axis. The angiotensin II triggers thirst.
5. Temporarily reduces thirst, and permanently reduces thirst if solute concentration and BP have returned to normal.

Question 4

1. What is it called when water is lost through the skin and respiratory system? What is it affected by?
2. What is it called when we sweat? What is sweat affected by? Can this be substantial water loss?
3. How do the kidneys regulate the concentration and volume of body fluids?
4. Can conscious learned behavior help reduce water loss?

Answer 4

1. Insensible perspiration. Humidity and temperature.
2. Sensible perspiration. Activity and temperature. Yes.
3. By regulating the concentration and volume of urine produced.
4. Yes.

Question 5

1. T or F, altering water content of a solution will change its osmolarity?
2. What 3 things happen with an increase of ECF osmolarity?
3. What happens with a decrease of the osmolarity of the ECF?

Answer 5

1. T
2. Water will enter the ECF, thirst increases, ADH is triggered to reduce water loss.
3. Thirst and ADH are inhibited. Water is lost from ECF in urine.

Question 6

1. If ECF volume increases, it will ………… BP.

2. What are the 4 mechanisms that regulate ECF volume and normally work together?

Answer 6

1. increase

2. Neural mechanism (baroreceptors), RAAS, ANP, ADH

Question 7

How does the baroreceptor mechanism work to regulate ECF volume?

Answer 7

Baroreceptors detect increases in BP and reduce sympathetic stimulation of afferent arteriole. This opens the afferent arteriole and increases GFR and urine volume. Opposite happens in low BP situation.

Question 8

how does the RAAS hormonal mechanism regulate ECF volume?

Answer 8

in low BP, renin is released from juxtaglomerular app. This triggers angiotensin II and aldosterone which cause vasoconstriction, increased Na+ and water reabsorption in nephron and reduced urine volume.

Question 9

How does ANP regulate ECF volume?

Answer 9

The atrium releases ANP when cells are stretched. ANP reduces Na+ and water reabsorption and increased urine volume (exact opposite of RAAS).

Question 10

How does ADH regulate ECF volume?

Answer 10

Low BP triggers release of ADH from posterior pituitary. It causes increased water recovery in nephron and reduced urine volume.

Question 11

1. Why is the composition of intracellular fluid (ICF) different than the composition of ECF (3 reasons)?
2. What does the cell’s membrane have that regulates its ICF composition?
3. How does water move across the cell’s membrane?
4. Can the ICF compensate for changes in the ECF’s changes in volume?
5. What will changes in ECF composition do to the water in ICF?

Answer 11

1. large organic molecules inside cell, ion transport across cell membrane, and electrical charge difference from inside cell to outside cell.
2. channels and pumps
3. osmosis
4. Yes, to an extent
5. It will cause the water to move either into or out of the cell by osmosis.

Question 12

1. What is the most prevalent cation in the ECF and what percentage does it make up? What percentage of osmotic pressure does it make up?
2. What is the main hormone that causes Na+ reabsorption? What happens when this hormone is absent?
3. What happens when Na+ levels increase?
4. What happens when BP increases?
5. What happens when BP decreases?

Answer 12

1. Na+. 90-95% of all cations in ECF. Makes up 1/2 of the osmotic pressure in ECF.
2. Aldosterone. Na+ is excreted in urine.
3. ADH is secreted to reduce water loss so the water will go into ECF and reduce the osmolarity.
4. ANP is released so Na+ and water are excreted in urine.
5. RAAS is activated to recover Na+ and water

Question 13

1. What is the dominant anion in the ECF?

2. T or F, the same mechanisms that regulate Na+ in ECF also regulate Cl-?

Answer 13

1. Cl-

2. T

Question 14

1. What is the major cation in ICF?
2. What type of cells is this cation especially important for? Why?
3. What are abnormal levels of K+ called? Does this refer to extracellular or intracellular levels? Are these serious conditions?
4. K+ is ……………. in the PCT and ……………. as needed in the ………….. and ……………. ……….. .
5. What hormone do both high levels of K+ and angiotensin II trigger? What will this do to the K+?

Answer 14

1. K+
2. Electrically excitable cells like neurons and muscle cells. Because it causes depolarization when extra-cellular levels are increased.
3. Hyperkalemia and hypokalemia. Extracellular. Yes.
4. reabsorbed. secreted. DCT and collecting ducts
5. Aldosterone. It will cause K+ to be excreted in urine

Question 15

1. Regulation of Ca+2 is critical for ………… and …………..
2. What hormone is released in hypocalcemia?
3. What 4 things are stimulated by PTH?
4. What does an increase in the activation of vitamin D do?

Answer 15

1. neurons and muscles.
2. Parathyroid hormone PTH
3. Osteoclast activity, Increased renal absorption of Ca+2, secretion of phosphate, and vitamin D activation.
4. increases Ca+2 absorption in small intestine

Question 16

1. What happens in hypercalcemia? What is inhibited?
2. What is main function of PHT?
3. What is main function of Calcitonin?
4. What is main function of Vitamin D?

Answer 16

1. PTH seretion declines and Calcitonin is secreted by thyroid. Osteoclast activity.
2. Increase extracellular Ca+2 levels
3. Decrease Ca+2 levels by inhibiting osteoclast activity.
4. Transports Ca+2 across digestive tract

Question 17

1. Where are most of the body’s Mg+2 ions stored?
2. Mg+2 is an important ……………. for some enzymes. What’s an example?
3. What happens to the excess Mg+2 in Hypermagnesemia? What happens in Hypomagnesemia?

Answer 17

1. In bones and Intracellular fluid ICF.
2. Cofactor. Sodium-potassium pump
3. Will be excreted into urine. Not reabsorbed in renal tubules. All of it gets reabsorbed.

Question 18

1. Where is 85% of the body’s phosphate stored?
2. How does increased PTH affect tubular phosphate reabsorption?
3. What is the most common phosphate ion?
4. What is excess phosphate called? Insufficient?

Answer 18

1. In bones and teeth as hydroxyapetite.
2. As PTH releases Ca+2 and phosphate into blood, less phosphate is reabsorbed in tubules
3. HPO42-
4. Hyperphosphatemia and hypophosphatemia

Question 19

1. Is a normal acid base balance critical for normal cell function?
2. Does normal cellular function generate H+ formation? What must happen in response?
3. What do strong acids and bases do? Give an example.
4. What do weak acids and bases do? Give an example
5. Weak acids can ………… H+ and weak bases can ………….. H+

Answer 19

1. yes
2. Yes, it needs to be eliminated
3. Completely dissociate. HCl becomes H+ + Cl-
4. Partially dissociate. H2CO3 becomes H+ + HCO3
5. Release, bind.

Question 20

1. What are the 3 mechanisms that regulate acid base?

Answer 20

1. Buffers, respiratory system, and kidneys

Question 21

1. What do buffers do?

2. What are the 3 buffer systems?

Answer 21

1. Prevent extreme changes to pH by either binding to H+ or releasing H+, but have a finite capacity.
2. Carbonic acid/Bicarbonate buffer system, Protein Buffer system, Phosphate Buffer System.

Question 22

Describe the Carbonic acid/Bicarbonate buffer system:

Answer 22

CO2 +H2O becomes H2CO3 becomes H+ + HCO3-. Important buffer in ECF. Works only if respiratory system is functioning normally. Can’t prevent pH changes caused by excess/shortage of CO2.

Question 23

Describe the Protein Buffer System:

Answer 23

important in ICF and plasma. Carboxyl groups are a weak acid -COOH, and amino groups are a weak base -NH2.

Question 24

Describe the Phosphate Buffer System:

Answer 24

important buffer in ICF and urine because phosphate groups can bind and release H+. For example: H2PO4 becomes H+ + HPO4-2

Question 25

1. Which buffer system does the respiratory mechanism of acid-base balance utilize?
2. What happens to pH when CO2 concentration increases?
3. When the pH of blood drops, what happens to the breath? What happens to the CO2?
4. Why is breathing rate controlled?
5. Removing a CO2 from the ECF will do what to a H+ molecule?
6. Respiratory regulation begins quickly or slowly? Is its capacity limited or not?
7. How does respiratory regulation differ from buffer systems (as far as what happens to H+)?

Answer 25

1. The carbonic acid- bicarbonate buffer system.
2. it decreases
3. Rate and depth increase. CO2 decreases.
4. To regulate ECF pH.
5. It will connect it with a water molecule
6. Starts quickly, but capacity is limited.
7. Respiratory regulation removes H+ from body whereas buffers neutralize it.

Question 26

1. In renal regulation of acid-base balance, tubule cells increase pH of ECF by secreting ……… and into urine and reabsorbing ……… into the blood.
2. What are the 4 steps that happen in the tubule cells to buffer filtrate?
3. Renal mechanisms can move significant amounts of H+ but it takes …….. ……… to become maximally effective.

Answer 26

1. H+, HCO3-
2. carbonic acid formation from carbonic anhydrase CO2 and H20.

The H+ ion is exchanged for a Na+ in the tubular fluid.

Bicarbonate HCO3 moves into interstitial fluid from filtrate

Filtrate gets buffered by HPO42-, HCO3-, NH3 (ammonia). This enables more H+ to be pumped into filtrate

3. 1-2 days.

Question 27

1. Acidosis and alkalosis occur when?
2. Why are both acidosis and alkalosis dangerous (the main reason)?
3. What are the 2 types of acidosis and alkalosis?
4. Buffers ………… pH changes, but only the ……………. and …………… can ………….. H+ ions from the body.

Answer 27

1. pH drops below 7.35 or goes above 7.45
2. They affect the CNS
3. respiratory acidosis/alkalosis and metabolic acidosis/alkalosis.
4. neutralize, respiratory and kidney, remove

Question 28

1. Respiratory acidosis happens when the respiratory system is deficient and allows …….. to ………… in the blood.
2. This condition is ………….. and serious.
3. can the kidneys compensate this condition?
4. How does respiratory alkalosis happen? Is it common? Is it serious?

Answer 28

1. CO2, increase
2. common
3. Yes, but they need 1-2 days. So in an extreme asthma attack no, but in empysema, yes.
4. happens from hyperventilation. Uncommon. Not serious b/c pH will return to normal when person stops hyperventilating.

Question 29

1. What causes metabolic acidosis?
2. Is is serious? Common?
3. Can is be compensated for by the respiratory system?
4. What causes metabolic alkalosis? Is it common?
5. Can respiratory system compensate it?

Answer 29

1. Variety of causes: production of excess acids, impaired ability to excrete H+ in urine, big loss of HCO3- in ECF from diarrhea, inadequate O2 and anerobic respiration.
2. yes
3. Yes, if not severe. Hyperventilation.
4. intake of alkaline substance and big loss of acid (like excesssive vomiting). NOt common.
5. Yes, if not severe. Hypoventilation.