Chapter 20 review questions

When ventilation increases, what happens to arterial PCO2 ? To plasma pH? To plasma H+ concentration?

Arterial P CO 2 decreases, pH increases, and plasma H+ concentration decreases.

Compare and contrast the terms in each set: A. principal cells and intercalated cells

Both are in the distal nephron. P cells are associated with aldosterone-mediated Na+ reabsorption; I cells are involved with acid-base regulation.

Compare and contrast the terms in each set: E. respiratory alkalosis and metabolic alkalosis, including causes and compensations

Both—pH goes above 7.42. Metabolic—may be caused by excessive ingestion of bicarbonate-containing antacids or vomiting; respiratory—hyperventilation. Metabolic compensation—decrease ventilation, decreased renal H+ excretion, increased HCO3 − excretion. Respiratory compensation—decreased renal H+ excretion, increased HCO3 − excretion.

Write the equation that shows how CO2 is related to pH. What enzyme increases the rate of this reaction? Name two cell types that possess high concentrations of this enzyme.

CO2 + H2O ⇋ H2CO3 ⇋ H+ + HCO3 −. Carbonic anhydrase. High in renal tubule cells and RBCs.

How do the two limbs of the loop of Henle differ in their permeability to water? What makes this difference in permeability possible?

Descending limb: permeable to water but lacks transporters for salts. Ascending limb: impermeable to water but reabsorbs NaCl.

Which ion is a primary determinant of ECF volume? Which ion is the determinant of extracellular pH?

ECF volume—Na+; pH—H+

What is an electrolyte? Name five electrolytes whose concentrations must be regulated by the body.

Electrolytes are ions, which can conduct electric current through a solution. Examples: Na+, K+, Ca2+, H+, HPO4 2−, and HCO3 −.

Compare the routes by which water enters the body with the routes by which the body loses water.

Entry: ingested and a small amount from metabolism. Loss: exhaled air, evaporation and perspiration from skin, excreted by kidneys, and in feces.

List the receptors that regulate osmolarity, blood volume, blood pressure, ventilation, and pH. Where are they located, what stimulates them, and what compensatory mechanisms are triggered by them?

Table 20.1 and Figure 20.15

The interstitial fluid in contact with the basolateral side of collecting duct cells has an extremely high osmolarity, and yet the cells do not shrivel up. How can they maintain normal cell volume in the face of such high ECF osmolarity?

The cells concentrate organic solutes to increase their internal osmolarity.

List and briefly explain three reasons why monitoring and regulating ECF pH are important. What three mechanisms does the body use to cope with changing pH?

pH alters protein structure (enzyme activity, membrane transporters, neural function). Buffers, renal and respiratory compensation.

Appetite for which two substances is important in regulating fluid volume and osmolarity?

salt and water

Make a table that specifies the following for each substance listed: hormone or enzyme? steroid or peptide? produced by which cell or tissue? target cell or tissue? target has what response? A. ANP B. aldosterone C. renin D. ANG II E. vasopressin F. angiotensin-converting enzyme

(a) ANP—peptide from atrial myocardial cells. Causes Na+ and water excretion; inhibits ADH secretion.

Make a table that specifies the following for each substance listed: hormone or enzyme? steroid or peptide? produced by which cell or tissue? target cell or tissue? target has what response? B. aldosterone

(b) Aldosterone—steroid from adrenal cortex. Increases distal nephron Na+ reabsorption and K+ excretion.

Make a table that specifies the following for each substance listed: hormone or enzyme? steroid or peptide? produced by which cell or tissue? target cell or tissue? target has what response? C. renin

(c) Renin—enzyme from JG cells. Converts plasma angiotensinogen to ANG I.

Make a table that specifies the following for each substance listed: hormone or enzyme? steroid or peptide? produced by which cell or tissue? target cell or tissue? target has what response? D. ANG II

(d) ANG II—peptide hormone made from ANG I. Increases blood pressure by actions on arterioles, brain, and adrenal cortex.

Make a table that specifies the following for each substance listed: hormone or enzyme? steroid or peptide? produced by which cell or tissue? target cell or tissue? target has what response? E. vasopressin

(e) Vasopressin—hypothalamic peptide. Increases distal nephron water reabsorption.

Make a table that specifies the following for each substance listed: hormone or enzyme? steroid or peptide? produced by which cell or tissue? target cell or tissue? target has what response? F. angiotensin-converting enzyme

(f) ACE—enzyme on vascular endothelium. Converts ANG I to ANG II.

What is a buffer? List three intracellular buffers. Name the primary extracellular buffer.

A molecule that moderates changes in pH. Intracellular: proteins, HPO4 2−, and hemoglobin. Extracellular: HCO3 −.

Write out the words for the following abbreviations: ADH, ANP, ACE, ANG II, JG apparatus, P cell, I cell.

ADH = antidiuretic hormone, ANP = atrial natriuretic peptide, ACE = angiotensin-converting enzyme, ANG II = angiotensin II, JG (apparatus) = juxtaglomerular, P cell = principal cell, I cell = intercalated cell

Which is more likely to accumulate in the body, acids or bases? List some sources of each.

Acids from CO2, metabolism, and food are more likely. Sources of bases include some foods.

Compare and contrast the terms in each set: B. renin, ANG II, aldosterone, ACE

All are parts of the RAS system. Renin and ACE—enzymes; ANG II and aldosterone—hormones. See Fig. 20.10.

Diagram the mechanism by which vasopressin alters the composition of urine.

Figure 20.6

Explain how the loop of Henle and vasa recta work together to create dilute renal filtrate.

Figure 20.7

normal cell volume in the face of such high ECF osmolarity? Compare and contrast the terms in each set: C. respiratory acidosis and metabolic acidosis, including causes and compensations

In both, body pH falls below 7.38. Respiratory—results from CO2 retention (from any number of causes); metabolic—results from excessive production of metabolic acids. Respiratory compensation—renal H+ excretion and HCO3 − retention. Metabolic compensation—increased ventilation, renal H+ excretion, and HCO3 − retention. Respiratory—arterial P CO 2 is elevated; metabolic— P CO 2 usually decreased.

Name two ways the kidneys alter plasma pH. Which compounds serve as urinary buffers?

Kidneys excrete or reabsorb H+ or HCO3 −. Ammonia and phosphates.

What happens to the resting membrane potential of excitable cells when plasma K+ concentrations decrease? Which organ is most likely to be affected by changes in K+ concentration?

More K+ leaves the cell, and membrane potential becomes more negative (hyperpolarizes). The heart is most likely to be affected.

List five organs and four hormones important in maintaining fluid and electrolyte balance.

Organs: kidneys, lungs, heart, blood vessels, digestive tract. Hormones: vasopressin or antidiuretic hormone (AVP or ADH), aldosterone, atrial natriuretic peptides (ANP), RAS pathway.

Compare and contrast the terms in each set: D. water reabsorption in proximal tubule, distal tubule, and ascending limb of the loop of Henle

Proximal tubule—not regulated; distal nephron—regulated by vasopressin. Ascending limb—impermeable to water.

Make a list of all the different membrane transporters in the kidney. For each transporter, tell (a) which section(s) of the nephron contain(s) the transporter; (b) whether the transporter is on the apical membrane only, on the basolateral membrane only, or on both; (c) whether it participates in reabsorption only, in secretion only, or in both.

Use Figs. 19.8, 19.12, 20.5c, 20.7d, 20.9b, 20.17, and 20.18.

Name the four main compensatory mechanisms for restoring low blood pressure to normal. Why do you think there are so many homeostatic pathways for raising low blood pressure?

Vasoconstriction, increased cardiac output, water conservation by kidneys, and increased thirst. If blood pressure falls too low, oxygen supply to the brain will decrease, resulting in damage or death.