Chapter 26 Test 5

Q1. Plasma is the smallest of these 3 compartments, but it is the most heavily regulated! Why?

That's where the sensors are! Easy to monitor and correct.

1) Acidosis results in increasing levels of what ion? a) sodium b) chloride c) hydrogen d) calcium e) phosphorus

c) hydrogen

5. ADH, by itself, cannot reduce an increase in osmolality in body fluids. Why not? What other mechanism is required?

ADH cannot add water—it can only conserve what is already there. In order to reduce an increase in osmolality of body fluids, the thirst mechanism is required.

10. Define acidemia and alkalemia.

Acidemia is an arterial pH below 7.35 and alkalemia is a pH above 7.45.

• 8. Review: what effects do aldosterone and ADH have on the composition of bodily fluids, and how do they cause these effects?

Aldosterone regulates sodium ions but also can reabsorb it through collecting ducts, water then follows sodium through intracellular fluid. ADH is an anti-diuretic hormone and causes kidneys to excrete urine and conserve water. ADH can control osmolarity by regulating water without the use of sodium.

4. What change in plasma is most important for triggering thirst? Where is that change sensed?

An increase in osmolality of the plasma is most important for triggering thirst. This change is sensed by osmoreceptors in the hypothalamus.

•Q1. Explain how angiotensin-II is produced, and list its five effects.

Angiotensin-II is produced when, in response to low blood pressure, the kidney releases renin, which converts angiotensinogen (originally made by the liver) in the blood to angiotensin-I, which in turn is converted to angiotensin-II by angiotensin converting enzyme in the lungs. 5 effects: vasoconstriction; increases Na+ absorption in the PCT; increases aldosterone release; increases thirst; increases ADH release.

5. If your blood pH is 7.30, and your breathing is NOT to blame, that is called A. Metabolic acidosis B. Metabolic alkalosis C. Respiratory acidosis D. Respiratory alkalosis

Answer: A

2. Which condition within the body should stimulate the greatest thirst? A. High blood pressure, high ECF osmolarity B. High blood pressure, low ECF osmolarity C. Low blood pressure, high ECF osmolarity D. Low blood pressure, low ECF osmolarity

Answer: C

3. In the context of RAAS, how many enzymes are needed to convert angiotensinogen to its most active form? A. Zero B. One C. Two D. Three E. Dozens!

Answer: C

4. Plasma concentrations of ions like sodium, potassium, and calcium are governed via negative feedback. This means they are prevented from A. Going too high B. Going too low C. Going too high OR going to low

Answer: C

6. A patient's blood pH is 7.47. You investigate the cause of this abnormality by measuring CQ levels in the blood. If CO2 level (expressed as a partial pressure in units of mm Hg) is lower than normal, the cause is likely A. Idiopathic B. Metabolic C. Respiratory D. Supernatural

Answer: C

Q1. As we have seen, calcium plays important roles in motor neurons, skeletal muscle, and cardiac muscle. Before consulting the table below, predict the consequences of hypocalcaemia.

Answers will vary, but one might guess that hypocalcaemia could lead to excessive muscle contraction, excessive neurotransmitter release, etc.

Q2. Now look at the table. Was your prediction right? (It's OK if not!)

Answers will vary, but, perhaps in contrast to some expectations, hypercalcemia results in DECREASED activity of motor neurons and muscle cells.

Q2. What examples of sensing and regulating the plasma have we already encountered?

Arterial chemoreceptors (CO2, H+, O2), arterial baroreceptors (blood pressure).

11.Which of the following factors will enhance ADH release? (a) increase in ECF volume, (b) decrease in ECF volume, (c) decrease in ECF osmolality, (d) increase in ECF osmolality.

B, D

How do we sense blood pressure

Baroreceptors

Q4. To what extent (completely, partly, not at all) do you agree with the following statement: the body uses negative feedback to homeostatically regulate blood volume? Explain.

Blood volume is not itself a homeostatically regulated variable per se, as we have no means of sensing blood volume per se. However, blood volume can be regulated indirectly by keeping blood osmolarity and blood pressure near their respective setpoints; that is, osmolarity and pressure ARE regulated homeostatically via negative feedback.

•Q6. Explain how breathing rate affects blood pH. Refer to the carbonic anhydrase reaction in your answer.

Breathing reduces CO2 levels in the blood, which then reduces H+ levels and thus increases pH. The higher the breathing rate, the more CO2 gets dumped out, so the less remaining in the blood, and the higher the resulting pH. Getting CO2 out of the blood causes the following chemical reactions to run in this direction: HCO3-+ H+ => H2CO3 => H2O + CO2. This uses up H+, thus lowering [H+] and raising pH.

12.In an individual with metabolic acidosis, a clue that the respiratory system is compensating is provided by (a) high blood bicarbonate levels, (b) low blood bicarbonate levels, (c) rapid, deep breathing, (d) slow, shallow breathing.

C

Q2. What is the major.. b. extracellular anion (-)?

Chloride

What would happen if a patient who had lost blood was given pure water, rather than isotonic saline? Q2. Immediate effect on osmolarity?

Decreased osmolarity.

Q1. Where along the nephron do aldosterone's effects occur?

Distal convoluted tubule and collecting duct.

1) Most fluid in the body is in the extracellular fluid (ECF) compartment. True / False

False

1) The most abundant cation in extracellular fluid is potassium. True / False

False

•Q7. Which two main ions can be secreted/reabsorbed at nephrons to adjust the pH of urine and blood? Which gets secreted (or not), and which gets reabsorbed (or not)?

H+ gets secreted (sometimes in the form of NH4+). Bicarbonate (HCO3-) gets reabsorbed

5.Two main substances regulated by the influence of aldosterone on the kidney tubules. a. ammonium ions b. bicarbonate c. calcium d. chloride e. hydrogen ions f. magnesium g. phosphate h. potassium i. sodium j.water

H, I

• 3. Explain the meaning of the terms hyperkalemia, hypokalemia, hypernatremia, and hyponatremia in terms of the meanings of their roots (hyper-, hypo-, kal, natr, and -emia).

Hyper meaning overactive, or too much in quantity. Therefore, hyperkalemia means high abnormal levels of potassium and hypernatremia is high abnormal levels of sodium. Hypo is insufficient or too little in quantity. Therefore, hypokalemia means low potassium and hyponatremia means low sodium.

•Q2. Under what circumstances would the kidney NOT reabsorb much bicarbonate?

If the blood pH is basic (significantly higher than 7.4), bicarbonate reabsorption will drop.

3.PREDICT You eat salty pretzels without drinking. What happens to the volume of your extracellular fluid? Explain.

If you eat salty pretzels, your extracellular fluid volume will expand even if you don't ingest fluids. This is because water will flow by osmosis from the intracellular fluid to the extracellular fluid.

What would happen if a patient who had lost blood was given pure water, rather than isotonic saline? Q1. Immediate effect on blood pressure?

Increased BP

• 7. Review: what does osmolarity mean?

Is the measure of solute concentration per unit volume of a solvent.

• 5. What does alkalosis mean?

It means an excessive alkaline condition of the body tissues or fluids that can cause weakness or cramps.

• 4. In the context of physiology, what does RAAS stand for?

It stands for the renin-angiotensin-aldosterone system.

12. Joanne, a diabetic patient, is at the emergency department with acidosis due to the production of ketone bodies (p. 632). Would you expect her ventilation to be increased or decreased? Why?

Joanne's ventilation would be increased. The acidosis caused by the accumulated ketone bodies will stimulate the peripheral chemoreceptors, and this will cause more CO2 to be "blown off" in an attempt to restore pH to normal.

•Example B: A patient's plasma has a pH of 7.5. Explain how you could make an additional measurement to determine whether the cause of this unusual pH is metabolic or respiratory.

Measure the CO2 level in the plasma. If the high plasma pH is due to a respiratory problem, the CO2 concentration will be low. If the high pH is NOT due to a respiratory problem, the CO2 will not be low, and may be high if the person is undergoing respiratory compensation for a metabolic alkalosis.

Q1. Which receptor proteins sense changes in cell size/shape? Chemoreceptors Mechanoreceptors Nociceptors Photoreceptors Thermoreceptors

Mechanoreceptors

•Q8. Be able to classify an acid-base disorder as metabolic or respiratory acidosis or alkalosis that is or is not fully compensated ("fully compensated"=pH is normal). Or summarize any of these in terms of their plasma pH (high, normal, or low?) and CO2level (high or low?). •Example A: Plasma pH is 7.32, CO2levels in blood are low. What is this?

Metabolic acidosis.

20.Mr. Jessup, a 55-year-old man, is operated on for a cerebral tumor. About a month later, he appears at his physician's office complaining of excessive thirst. He claims to have been drinking about 20 liters of water daily for the past week and says he has been voiding nearly continuously. A urine sample is collected and its specific gravity is reported as 1.001. What is your diagnosis of Mr. Jessup's problem? What connection might exist between his previous surgery and his present problem?

Mr. Jessup has diabetes insipidus caused by insufficient production of ADH by the hypothalamus. The operation for the removal of the cerebral tumor has damaged the hypothalamus or the hypothalamo-hypophyseal tract leading to the posterior pituitary. Because of the lack of ADH, the collecting tubules and possibly the convoluted part of the distal convoluted tubule are not absorbing water from the glomerular filtrate. The large volume of very dilute urine voided by this man and the intense thirst that he experiences are the result. (pp. 1017-1018)

9. Nathan has Addison's disease (insufficient aldosterone release). How does this affect his plasma

Na+ and K+ levels? How does this affect his blood pressure? Explain. Answer: Insufficient aldosterone would cause Nathan's plasma Na+ to be decreased and his plasma K+ to be elevated. The decrease in plasma Na+ would cause a decrease in blood pressure, because plasma Na+ is directly related to blood volume, which is a major determinant of blood pressure.

Q1. How closely do the plasma and interstitial fluid resemble each other? (Identical? Similar? Quite different?)

Not identical, but similar (protein anions being the biggest difference).

What would happen if a patient who had lost blood was given pure water, rather than isotonic saline? Q3. Response to altered osmolarity?

Osmoreceptors sense lower osmolarity. Person NOT thirsty, ADH not secreted, release of copious dilute urine. The extra H2O essentially gets peed out.

• 6. Is perspiration (sweat) typically hypotonic, isotonic, or hypertonic, relative to the blood and other body fluids?

Perspiration is isotonic.

Q2. What is the major.. d. intracellular anion (-)?

Phosphate (HPO4).

Q2. What is the major.. C. intracellular cation (+)?

Potassium

• 2. Which chemical element is known in Latin as kalium, and which is known as natrium? (Hint: consider the one- and two-letter chemical symbols in the periodic table.)

Potassium is known as kalium in Latin. Sodium is known in Latin as natrium.

•Q5. In terms of ECF osmolarity and volume, how is the body's response to sweating similar and different from its response to bleeding?

SIMILAR: both involve a reduction in blood volume, which leads to a reduction in blood pressure and triggering of RAAS to restore blood pressure via vasoconstriction, thirst, and increased sodium reabsorption in the distal tubule/collecting duct (because of aldosterone) and the proximal tubule. DIFFERENT: sweating also perturbs fluid osmolarity. Specifically, sweating hypotonic fluid makes the fluid remaining in the body hypertonic. The osmoreceptors in the hypothalamus and stimulate thirst and ADH release to a greater extent than would occur in the bleeding situation.

18. How do the kidneys compensate for respiratory acidosis?

The kidneys compensate for respiratory acidosis by excreting more H+ and generating new HCO3− to buffer the acidosis.

•Q3. Do the kidneys have baroreceptors, osmoreceptors, both, or neither?

They have baroreceptors. The entire RAAS process is kicked off by cells near the glomerulus (juxtaglomerular cells) sensing that blood pressure is low.

1. Which do you have more of, extracellular or intracellular fluid? Plasma or interstitial fluid?

You have more intracellular than extracellular fluid and more interstitial fluid than plasma.

6) The largest percentage of body water is located in what compartment? a) intracellular fluid b) interstitial fluid c) extracellular fluid d) blood plasma

a) intracellular fluid

5) Antidiuretic hormone (ADH) acts on the __________ to __________ water excretion. a) kidneys; decrease b) kidneys; increase c) intestines; increase d) intestines; decrease

a) kidneys; decrease

14) The only cation exerting significant osmotic pressure in the ECF is __________. a) Mg2+ b) Na+ c) Fe2+ d) K+ e) Ca2+

b) Na+

14) Someone who is suffocating would develop __________. a) metabolic alkalosis b) respiratory acidosis c) metabolic acidosis d) respiratory alkalosis

b) respiratory acidosis

1) Normal arterial blood pH is __________. a) strongly alkaline b) slightly alkaline c) highly acidic d) neutral e) slightly acidic

b) slightly alkaline

1) Which of the following is NOT an electrolyte? a) sodium b) potassium c) glucose d) chloride

c) glucose

30) Any arterial pH between __________ is considered physiological acidosis. a) 6.5 and 7.0 b) 6.5 and 7.35 c) 7.0 and 7.35 d) 7.35 and 7.45

c) 7.0 and 7.35

1) What is the most abundant cation in intracellular fluid? a) sodium b) calcium c) potassium d) bicarbonate e) magnesium

c) potassium

21) All of the following would occur if there were an increase in plasma osmolality EXCEPT __________. a) release of ADH b) thirst c) production of large amounts of urine d) concentrated urine

c) production of large amounts of urine

12) Hyperventilation can lead to __________. a) respiratory acidosis b) metabolic alkalosis c) respiratory alkalosis d) metabolic acidosis

c) respiratory alkalosis

1) A major stimulus for the release of antidiuretic hormone is __________. a) inhibition of the osmoreceptors b) an increase in potassium levels in the ICF c) stimulation of the baroreceptors d) a rise in plasma osmolality e) an increase in ECF water concentration

d) a rise in plasma osmolality

21) All of the following factors would stimulate the hypothalamic thirst center EXCEPT __________. a) decreased saliva production b) increased angiotensin II secretion c) a decline in blood volume d) hypotonic extracellular fluid

d) hypotonic extracellular fluid

12) Which condition would cause a drop in pH? a) hypokalemia b) hypernatremia c) hyperventilation d) hypoventilation

d) hypoventilation

Q2. What effect does aldosterone have on the plasma levels of . . . (b) K+?

decreased plasma levels of K+ (due to increased secretion).

6) The condition in which sodium levels are too low is referred to as __________. a) hypokalemia b) aldosteronism c) hypernatremia d) Cushing's syndrome e) hyponatremia

e) hyponatremia

10) The only organ(s) of the body that can remove excess nonvolatile fixed acids is/are the __________. a) sweat glands b) spleen c) liver d) lungs e) kidney

e) kidney

Q2. What are the hypothalamus' 2 responses to high extracellular osmolarity?

extra thirst, more ADH release.

Q2. What effect does aldosterone have on the plasma levels of . . . (a) Na+?

increased plasma levels (due to increased reabsorption)

Q2. How do we sense blood osmolarity?

osmoreceptors.

Q3. How can the body get fluids to move from one compartment to another? 2 types of gradients...

osmotic pressure gradients and hydrostatic pressure gradients - both are adjustable!

Q2. What is the major.. a. extracellular cation (+)?

sodium.