Ch. 26 Study Guide

[Ch. 26 CQ #22] All of the following factors would stimulate the hypothalamic thirst center EXCEPT __________. (a) hypotonic extracellular fluid (b) decreased saliva production (c) increased angiotensin II secretion (d) a decline in blood volume

(a) hypotonic extracellular fluid

[Ch. 26 CQ #1] A major stimulus for the release of antidiuretic hormone is __________. (a) an increase in potassium levels in the ICF (b) a rise in plasma osmolality (c) stimulation of the baroreceptors (d) inhibition of the osmoreceptors (e) an increase in ECF water concentration

(b) a rise in plasma osmolality A major stimulus for the release of antidiuretic hormone is a rise in plasma osmolality. ADH results in increased water reabsorption.

[Ch. 26 RQ #11] Which of the following factors will enhance ADH release? (a) increase in ECF volume (b) decrease in ECF volume (c) decrease in ECF osmolarity (d) increase in ECF osmolality

(b) decrease in ECF volume and (d) increase in ECF osmolality

[Ch. 26 CQ #12] Which condition would cause a drop in pH? (a) hypokalemia (b) hypoventilation (c) hyperventilation (d) hypernatremia

(b) hypoventilation Hypoventilation causes a drop in pH. Breathing slowly increases PCO2.

[Ch. 26 CQ #21] All of the following would occur if there were an increase in plasma osmolality EXCEPT __________. (a) thirst (b) production of large amounts of urine (c) concentrated urine (d) release of ADH

(b) production of large amounts of urine If the plasma osmolality were to increase, the body would conserve water and scant amounts of concentrated urine would be formed. If plasma osmolality were to increase, thirst would result. If the plasma osmolality were to increase, the urine would be concentrated. If the plasma osmolality were to increase, ADH would be released.

[Ch. 26 PT #14] Someone who is suffocating would develop __________. (a) respiratory alkalosis (b) respiratory acidosis (c) metabolic acidosis (d) metabolic alkalosis

(b) respiratory acidosis The most common cause of acid-base imbalance is respiratory acidosis, a result of elevated blood levels of CO2 due to shallow breathing, suffocation, or lung diseases that impede O2 and CO2 exchange.

[Ch. 26 PT #12] Hyperventilation can lead to __________. (a) respiratory acidosis (b) respiratory alkalosis (c) metabolic alkalosis (d) metabolic acidosis

(b) respiratory alkalosis Decreased CO2 levels will increase blood pH. If one hyperventilates, the levels of CO2 drop to below normal levels and can cause respiratory alkalosis. Increased CO2 will lower blood pH. In response to high CO2 levels, the rate of and depth of breathing will increase in an effort to vent off excess CO2. If one is unable to breathe, CO2 levels increase, leading to respiratory acidosis.

[Ch. 26 CQ #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

[Ch. 26 CQ #6] The condition in which sodium levels are too low is referred to as __________. (a) hypernatremia (b) hypokalemia (c) hyponatremia (d) Cushing's syndrome (e) aldosteronism

(c) hyponatremia Hypo- means low, and natrium is Latin for sodium.

[Ch. 26 CQ #10] The only organ(s) of the body that can remove excess nonvolatile fixed acids is/are the __________. (a) liver (b) lungs (c) kidney (d) sweat glands (e) spleen

(c) kidney The only organ of the body that can remove excess nonvolatile fixed acids is the kidney. Fixed acids are also called metabolic acids.

[Ch. 26 RQ #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) rapid, deep breathing

[Ch. 26 CQ #4] Normal arterial blood pH is __________. (a) highly acidic (b) slightly acidic (c) slightly alkaline (d) neutral (e) strongly alkaline

(c) slightly alkaline Normal arterial blood pH is 7.4, which is slightly alkaline.

[Ch. 26 CQ #14] The only cation exerting significant osmotic pressure in the ECF is __________. (a) Ca2+ (b) Mg2+ (c) Fe2+ (d) Na+ (e) K+

(d) Na+ Na+ is the only cation exerting significant osmotic pressure in the ECF.

[Ch. 26 PT #2] Which of the following is NOT an electrolyte? (a) sodium (b) potassium (c) chloride (d) glucose

(d) glucose Electrolytes are inorganic substances that dissociate into ions in water. Examples of electrolytes include salts [for example, sodium chloride (NaCl) and magnesium chloride (MgCl2)] and ions [for example, potassium (K+)]. Nonelectrolytes have bonds (usually covalent bonds) that prevent them from dissociating in water. Most nonelectrolytes are organic molecules. For example, glucose, lipids, urea, creatinine, and cholesterol are nonelectrolytes.

[Ch. 26 CQ #7] The largest percentage of body water is located in what compartment? (a) extracellular fluid (b) blood plasma (c) interstitial fluid (d) intracellular fluid

(d) intracellular fluid

[Ch. 26 PT #5] Antidiuretic hormone (ADH) acts on the __________ to __________ water excretion. (a) kidneys; increase (b) intestines; increase (c) intestines; decrease (d) kidneys; decrease

(d) kidneys; decrease Antidiuretic hormone (ADH) acts on the kidneys to decrease water excretion. When ADH levels are high, most or all of the filtered water is reabsorbed and a small amount of concentrated urine is excreted. When ADH levels are low, less water is reabsorbed and dilute urine is excreted.

[Ch. 26 CQ #3] What is the most abundant cation in intracellular fluid? (a) calcium (b) bicarbonate (c) magnesium (d) potassium (e) sodium

(d) potassium Potassium is the most abundant cation in the intracellular fluid and is required for essential metabolic activities, influencing the resting membrane potential and normal neuromuscular functioning.

[Ch. 26 CQ #2] Acidosis results in increasing levels of what ion? (a) chloride (b) sodium (c) phosphorus (d) calcium (e) hydrogen

(e) hydrogen Acidosis refers to high H+ concentration.

[Ch. 26 RQ #5] Two main substances regulated by the influence of aldosterone on the kidney tubules.

(h) potassium and (i) sodium

[Ch. 26 Clicker Question #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

A. metabolic acidosis

[Ch. 26 CYU #5] ADH, by itself, cannot reduce an increase in osmolality in body fluids. Why not?

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.

[Ch. 26 CYU #10] Define acidemia and alkalemia.

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

[Ch. 26 CYU #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.

[Ch. 26 Specific Question #1] 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.

[Ch. 26 Specific Question #4] To what extent (completely, partly, not at all) do you agree with the following statement: the body uses negative feedback to homeostaticallyregulate 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.

[Ch. 26 Specific Question #6] 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.

[Ch. 26 Clicker Question #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 too low

C. going too high OR going too low

[Ch. 26 Clicker Question #2] Which should cause 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

C. low blood pressure, high ECF osmolarity

[Ch. 26 Clicker Question #6] A patient's blood pH is 7.47. You investigate the cause of this abnormality by measuring CO2 levels in the blood. If CO2 level (expressed as apartial pressure in units of mm Hg) is LOW, the cause is likely A. idiopathic B. metabolic C. respiratory D. supernatural

C. respiratory

[Ch. 26 Clicker Question #3] How many enzymes are needed for full activation of the Renin-Angiotensin-Aldosterone System (RAAS)? A. zero B. one C. two D. three E. dozens!

C. two

[Ch. 26 Specific Question #8] Be able to classify an acid-base disorder as metabolic acidosis, metabolic acidosis, respiratory acidosis, or respiratory alkalosis. Or summarize any of these in terms of their plasma pH (high or low?) and CO2 level (high or low?). •Example A: Plasma pH is 7.32, CO2levels in blood are low. What is this? •Example B: A patient's blood 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.

Example A: metabolic acidosis. Example B: 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.

[Ch. 26 PT #3] The most abundant cation in extracellular fluid is potassium. True or False?

False The most abundant cation (or positively charged ion) in the extracellular fluid (ECF) is sodium (Na+). The most abundant anion (or negatively charged ion) in the ECF is chloride (Cl-). The most abundant cation in the intracellular fluid (ICF) is potassium (K+). The most abundant anion in the ICF is hydrogen phosphate (HPO4-).

[Ch. 26 PT #1] Most fluid in the body is in the extracellular fluid (ECF) compartment. True or False?

False Water in the body occupies two main fluid compartments. Most fluid (about two-thirds) is in the intracellular fluid (ICF) compartment. ICF is fluid found inside of cells. The rest of our body water (about one-third) is in the extracellular fluid (ECF) compartment. The ECF consists of plasma and interstitial fluid (IF), the fluid in the spaces between tissue cells.

[Ch. 26 Specific Question #7] 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.

[Ch. 26 Specific Question #2] 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.

[Ch. 26 CYU #3] 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.

[Ch. 26 CYU #9] Nathan has Addison's disease (insufficient aldosterone release). How does this affect his plasma Na+ and K+ levels?

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.

[Ch. 26 CYU #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.

[Ch. 26 RQ #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)

[Ch. 26 Specific Question #5] 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.

[Ch. 26 CYU #18] How do the kidneys compensate for respiratory acidosis?

The kidney's compensate for respiratory acidosis by excreting more H+ and generating new HCO3- to buffer the acidosis.

[Ch. 26 Specific Question #3] 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.

[Ch. 26 CYU #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.