Question 1

Use the diagram of an action potential to answer the following questions.
 
-The action potential shown corresponds to which portion of an electrocardiogram (ECG)?

Accepted Answer

[Chapter 3, III A 4; Figure 3.3]. The action potential shown represents both depolarization and repolarization of a ventricular muscle cell. Therefore, on an electrocardiogram (ECG), it corresponds to the period of depolarization (beginning with the $\mathrm{Q}$ wave) through repolarization (completion of the $\mathrm{T}$ wave). That period is defined as the QT interval.

Question 2

Which of the following is the first step in the biosynthetic pathway for thyroid hormones that is inhibited by propylthiouracil?

Accepted Answer

[Chapter 7, IV A 2]. The oxidation of $\mathrm{I}^{-}$to $\mathrm{I}_{2}$ is catalyzed by peroxidase and inhibited by propylthiouracil, which can be used in the treatment of hyperthyroidism. Later steps in the pathway that are catalyzed by peroxidase and inhibited by propylthiouracil are iodination of tyrosine, coupling of diiodotyrosine (DIT) and DIT, and coupling of DIT and monoiodotyrosine (MIT).

Question 3

Arterial $\mathrm{pH}$ of 7.29 , arterial $\left[\mathrm{HCO}_{3}^{-}\right]$ of $14 \mathrm{mEq} / \mathrm{L}$, increased urinary excretion of $\mathrm{NH}_{4}^{+}$, and hyperventilation would be observed in a

Accepted Answer

[Chapter 5, IX D 1; Table 5.9]. The blood values are consistent with metabolic acidosis, as would occur in diabetic ketoacidosis. Hyperventilation is the respiratory compensation for metabolic acidosis. Increased urinary excretion of $\mathrm{NH}_{4}{ }^{+}$ reflects the adaptive increase in $\mathrm{NH}_{3}$ synthesis that occurs in chronic acidosis. Patients with metabolic acidosis secondary to chronic renal failure would have reduced $\mathrm{NH}_{4}^{+}$ excretion (because of diseased renal tissue).

Question 4

Activation of which of the following receptors increases total peripheral resistance (TPR)?

Accepted Answer

[Chapter 2, I C 1 a]. When adrenergic $\alpha_{1}$ receptors on the vascular smooth muscle are activated, they cause vasoconstriction and increased total peripheral resistance (TPR).

Question 5

The receptor for this hormone has tyrosine kinase activity.

Accepted Answer

[Chapter 7; Table 7.2]. Hormone receptors with tyrosine kinase activity include those for insulin and for insulin-like growth factors (IGF). The $\beta$ subunits of the insulin receptor have tyrosine kinase activity and, when activated by insulin, the receptors autophosphorylate. The phosphorylated receptors then phosphorylase intracellular proteins; this process ultimately results in the physiologic actions of insulin.

Question 6

If an artery is partially occluded by an embolism such that its radius becomes one-half the preocclusion value, which of the following parameters will decrease by a factor of 16 ?

Accepted Answer

[Chapter 3, II C, D]. Blood flow through the artery is proportional to the pressure difference and inversely proportional to the resistance $(\mathrm{Q}=\Delta \mathrm{P} / \mathrm{R})$. Because resistance increased 16 -fold when the radius decreased twofold, blood flow must decrease 16 -fold.

Question 7

Which phase of the cardiac cycle is absent if there is no $\mathrm{P}$ wave on the electrocardiogram (ECG)?

Accepted Answer

[Chapter 3, V; Figure 3.15]. The $\mathrm{P}$ wave represents electrical activation (depolarization) of the atria. Atrial contraction is always preceded by electrical activation.

Question 8

A receptor potential in the pacinian corpuscle

Accepted Answer

[Chapter 2, II A 4; Figure 2.2]. Receptor potentials in sensory receptors (such as the pacinian corpuscle) are not action potentials and therefore do not have the stereotypical size and shape or the all-or-none feature of the action potential. Instead, they are graded potentials that vary in size depending on the stimulus intensity. A hyperpolarizing receptor potential would take the membrane potential away from threshold and decrease the likelihood of action potential occurrence. A depolarizing receptor potential would bring the membrane potential toward threshold and increase the likelihood of action potential occurrence.

Question 9

Compared with the base of the lung, in a person who is standing, the apex of the lung has

Accepted Answer

[Chapter 4, VII C; Table 4.5]. In a person who is standing, both ventilation and perfusion are greater at the base of the lung than at the apex. However, because the regional differences for perfusion are greater than those for ventilation, the ventilation/ perfusion (V/Q) ratio is higher at the apex than at the base. The pulmonary capillary $\mathrm{PO}_{2}$ therefore is higher at the apex than at the base because the higher V/Q ratio makes gas exchange more efficient.

Question 10

A 54-year-old man with a lung tumor has high circulating levels of antidiuretic hormone (ADH), a serum osmolarity of $260 \mathrm{mOsm} / \mathrm{L}$, and a negative free-water clearance $\left(\mathrm{C}_{\mathrm{H}_{2} \mathrm{O}}\right)$. Which diagnosis is correct?

Accepted Answer

[Chapter 5, VII D 4]. A negative value for free-water clearance $\left(\mathrm{C}_{\mathrm{H}_{2} \mathrm{O}}\right)$ means that "free water" (generated in the diluting segments of the thick ascending limb and early distal tubule) is reabsorbed by the collecting ducts. A negative $\mathrm{C}_{\mathrm{H}_{2} \mathrm{O}}$ is consistent with high circulating levels of antidiuretic hormone (ADH). Because ADH levels are high at a time when the serum is very dilute, $\mathrm{ADH}$ has been secreted "inappropriately" by the lung tumor.

Question 11

End-organ resistance to which of the following hormones results in polyuria and elevated serum osmolarity?

Accepted Answer

[Chapter 5, VII C; Table 5.6]. End-organ resistance to antidiuretic hormone $(\mathrm{ADH})$ is called nephrogenic diabetes insipidus. It may be caused by lithium intoxication (which inhibits the $\mathrm{G}_{\mathrm{s}}$ protein in collecting duct cells) or by hypercalcemia (which inhibits adenylate cyclase). The result is inability to concentrate the urine, polyuria, and increased serum osmolarity (resulting from the loss of free water in the urine).

Question 12

Which diuretic causes increased urinary excretion of $\mathrm{Na}^{+}$and $\mathrm{K}^{+}$and decreased urinary excretion of $\mathrm{Ca}^{2+}$ ?

Accepted Answer

[Chapter 5, IV C 3 a; VI C 2; Table 5.11]. Thiazide diuretics act on the early distal tubule (cortical diluting segment) to inhibit $\mathrm{Na}^{+}$reabsorption. At the same site, they enhance $\mathrm{Ca}^{2+}$ reabsorption so that urinary excretion of $\mathrm{Na}^{+}$is increased while urinary excretion of $\mathrm{Ca}^{2+}$ is decreased. $\mathrm{K}^{+}$excretion is increased because the flow rate is increased at the site of distal tubular $\mathrm{K}^{+}$secretion.

Question 13

Arterial $\mathrm{PCO}_{2}$ of $72 \mathrm{~mm} \mathrm{Hg}$, arterial $\left[\mathrm{HCO}_{3}^{-}\right]$of $38 \mathrm{mEq} / \mathrm{L}$, and increased $\mathrm{H}^{+}$ excretion would be observed in a

Accepted Answer

[Chapter 5, IX D 3; Table 5.9]. The blood values are consistent with respiratory acidosis with renal compensation. The renal compensation involves increased reabsorption of $\mathrm{HCO}_{3}^{-}$(associated with increased $\mathrm{H}^{+}$secretion), which raises the serum $\left[\mathrm{HCO}_{3}^{-}\right]$.

Question 14

In a skeletal muscle capillary, the capillary hydrostatic pressure $\left(\mathrm{P}_{\mathrm{c}}\right)$ is $32 \mathrm{~mm} \mathrm{Hg}$, the capillary oncotic pressure $\left(\pi_{\mathrm{c}}\right)$ is $27 \mathrm{~mm} \mathrm{Hg}$, and the interstitial hydrostatic pressure $\left(\mathrm{P}_{\mathrm{i}}\right)$ is $2 \mathrm{~mm} \mathrm{Hg}$. Interstitial oncotic pressure $\left(\pi_{\mathrm{i}}\right)$ is negligible. What is the driving force across the capillary wall, and will it favor filtration or absorption?

Accepted Answer

[Chapter 3, VII C]. The driving force is calculated from the Starling forces across the capillary wall. The net pressure $=\left(\mathrm{P}_{\mathrm{c}}-\mathrm{P}_{\mathrm{i}}\right)-\left(\pi_{\mathrm{c}}-\pi_{\mathrm{i}}\right)$. Therefore, net pressure $=$ $(32 \mathrm{~mm} \mathrm{Hg}-2 \mathrm{~mm} \mathrm{Hg})-(27 \mathrm{~mm} \mathrm{Hg})=+3 \mathrm{~mm} \mathrm{Hg}$. Because the sign of the net pressure is positive, filtration is favored.

Question 15

Which of the following substances has the lowest renal clearance?

Accepted Answer

[Chapter 5, III D]. Glucose has the lowest renal clearance of the substances listed, because at normal blood concentrations, it is filtered and completely reabsorbed. $\mathrm{Na}^{+}$is also extensively reabsorbed, and only a fraction of the filtered $\mathrm{Na}^{+}$is
excreted. $\mathrm{K}^{+}$is reabsorbed but also secreted. Creatinine, once filtered, is not reabsorbed at all. Para-aminohippuric acid (PAH) is filtered and secreted; therefore, it has the highest renal clearance of the substances listed.

Question 16

Atropine causes dry mouth by inhibiting which of the following receptors?

Accepted Answer

[Chapter 2, I C 2 b]. Atropine blocks cholinergic muscarinic receptors. Because saliva production is increased by stimulation of the parasympathetic nervous system, atropine treatment reduces saliva production and causes dry mouth.

Question 17

Which of the following transport mechanisms is inhibited by furosemide in the thick ascending limb?

Accepted Answer

[Chapter 5, IV C 2 ]. $\mathrm{Na}^{+}-\mathrm{K}^{+}-2 \mathrm{Cl}^{-}$cotransport is the mechanism in the luminal membrane of the thick ascending limb cells that is inhibited by loop diuretics such as furosemide. Other loop diuretics that inhibit this transporter are bumetanide and ethacrynic acid.

Question 18

Which of the following conditions decreases the likelihood of edema formation?

Accepted Answer

[Chapter 3, VII C; Table 3.2]. Constriction of arterioles causes decreased capillary hydrostatic pressure and, as a result, decreased net pressure (Starling forces) across the capillary wall; filtration is reduced, as is the tendency for edema. Venous constriction and standing cause increased capillary hydrostatic pressure and tend to cause increased filtration and edema. Nephrotic syndrome results in the excretion of plasma proteins in the urine and a decrease in the oncotic pressure of capillary blood, which also leads to increased filtration and edema. Inflammation causes local edema by dilating arterioles.

Question 19

Which of the following conditions causes hypoventilation?

Accepted Answer

[Chapter 4, IX A, B; Chapter 5 IX D]. Chronic obstructive pulmonary disease (COPD) causes hypoventilation. Strenuous exercise increases the ventilation rate to provide additional oxygen to the exercising muscle. Ascent to high altitude and anemia cause hypoxemia, which subsequently causes hyperventilation by stimulating peripheral chemoreceptors. The respiratory compensation for diabetic ketoacidosis is hyperventilation.

Question 20

A 28-year-old man who is receiving lithium treatment for bipolar disorder becomes polyuric. His urine osmolarity is $90 \mathrm{mOsm} / \mathrm{L}$; it remains at that level when he is given a nasal spray of dDAVP. Which diagnosis is correct?

Accepted Answer

[Chapter 5, VII C]. Lithium inhibits the G protein that couples the antidiuretic hormone ( $\mathrm{ADH})$ receptor to adenylate cyclase. The result is inability to concentrate the urine. Because the defect is in the target tissue for ADH (nephrogenic diabetes insipidus), exogenous ADH administered by nasal spray will not correct it.

Quiz 8: Comprehensive Examination

Which of the following is the first step in the biosynthetic pathway for thyroid hormones that is inhibited by propylthiouracil?

Arterial $\mathrm{pH}$ of 7.29 , arterial $\left[\mathrm{HCO}_{3}^{-}\right]$ of $14 \mathrm{mEq} / \mathrm{L}$ , increased urinary excretion of $\mathrm{NH}_{4}^{+}$ , and hyperventilation would be observed in a

Activation of which of the following receptors increases total peripheral resistance (TPR) ?

The receptor for this hormone has tyrosine kinase activity.

If an artery is partially occluded by an embolism such that its radius becomes one-half the preocclusion value, which of the following parameters will decrease by a factor of 16 ?

Which phase of the cardiac cycle is absent if there is no $\mathrm{P}$ wave on the electrocardiogram (ECG) ?

A receptor potential in the pacinian corpuscle

Compared with the base of the lung, in a person who is standing, the apex of the lung has

A 54-year-old man with a lung tumor has high circulating levels of antidiuretic hormone (ADH) , a serum osmolarity of $260 \mathrm{mOsm} / \mathrm{L}$ , and a negative free-water clearance $\left(\mathrm{C}_{\mathrm{H}_{2} \mathrm{O}}\right)$ . Which diagnosis is correct?

End-organ resistance to which of the following hormones results in polyuria and elevated serum osmolarity?

Which diuretic causes increased urinary excretion of $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ and decreased urinary excretion of $\mathrm{Ca}^{2+}$ ?

Arterial $\mathrm{PCO}_{2}$ of $72 \mathrm{~mm} \mathrm{Hg}$ , arterial $\left[\mathrm{HCO}_{3}^{-}\right]$ of $38 \mathrm{mEq} / \mathrm{L}$ , and increased $\mathrm{H}^{+}$ excretion would be observed in a

Which of the following substances has the lowest renal clearance?

Atropine causes dry mouth by inhibiting which of the following receptors?

Which of the following transport mechanisms is inhibited by furosemide in the thick ascending limb?

Which of the following conditions decreases the likelihood of edema formation?

Which of the following conditions causes hypoventilation?

A 28-year-old man who is receiving lithium treatment for bipolar disorder becomes polyuric. His urine osmolarity is $90 \mathrm{mOsm} / \mathrm{L}$ ; it remains at that level when he is given a nasal spray of dDAVP. Which diagnosis is correct?

Quiz 8: Comprehensive Examination

Use the diagram of an action potential to answer the following questions. -The action potential shown corresponds to which portion of an electrocardiogram (ECG) ?

Which of the following is the first step in the biosynthetic pathway for thyroid hormones that is inhibited by propylthiouracil?

Arterial pH\mathrm{pH}pH of 7.29 , arterial [HCO3−]\left[\mathrm{HCO}_{3}^{-}\right][HCO3−​] of 14mEq/L14 \mathrm{mEq} / \mathrm{L}14mEq/L , increased urinary excretion of NH4+\mathrm{NH}_{4}^{+}NH4+​ , and hyperventilation would be observed in a

Activation of which of the following receptors increases total peripheral resistance (TPR) ?

The receptor for this hormone has tyrosine kinase activity.

If an artery is partially occluded by an embolism such that its radius becomes one-half the preocclusion value, which of the following parameters will decrease by a factor of 16 ?

Which phase of the cardiac cycle is absent if there is no P\mathrm{P}P wave on the electrocardiogram (ECG) ?

A receptor potential in the pacinian corpuscle

Compared with the base of the lung, in a person who is standing, the apex of the lung has

End-organ resistance to which of the following hormones results in polyuria and elevated serum osmolarity?

Which diuretic causes increased urinary excretion of Na+\mathrm{Na}^{+}Na+ and K+\mathrm{K}^{+}K+ and decreased urinary excretion of Ca2+\mathrm{Ca}^{2+}Ca2+ ?

Arterial PCO2\mathrm{PCO}_{2}PCO2​ of 72 mmHg72 \mathrm{~mm} \mathrm{Hg}72 mmHg , arterial [HCO3−]\left[\mathrm{HCO}_{3}^{-}\right][HCO3−​] of 38mEq/L38 \mathrm{mEq} / \mathrm{L}38mEq/L , and increased H+\mathrm{H}^{+}H+ excretion would be observed in a

Which of the following substances has the lowest renal clearance?

Atropine causes dry mouth by inhibiting which of the following receptors?

Which of the following transport mechanisms is inhibited by furosemide in the thick ascending limb?

Which of the following conditions decreases the likelihood of edema formation?

Which of the following conditions causes hypoventilation?

A 28-year-old man who is receiving lithium treatment for bipolar disorder becomes polyuric. His urine osmolarity is 90mOsm/L90 \mathrm{mOsm} / \mathrm{L}90mOsm/L ; it remains at that level when he is given a nasal spray of dDAVP. Which diagnosis is correct?

Arterial $\mathrm{pH}$ of 7.29 , arterial $\left[\mathrm{HCO}_{3}^{-}\right]$ of $14 \mathrm{mEq} / \mathrm{L}$ , increased urinary excretion of $\mathrm{NH}_{4}^{+}$ , and hyperventilation would be observed in a

Which phase of the cardiac cycle is absent if there is no $\mathrm{P}$ wave on the electrocardiogram (ECG) ?

Which diuretic causes increased urinary excretion of $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ and decreased urinary excretion of $\mathrm{Ca}^{2+}$ ?

Arterial $\mathrm{PCO}_{2}$ of $72 \mathrm{~mm} \mathrm{Hg}$ , arterial $\left[\mathrm{HCO}_{3}^{-}\right]$ of $38 \mathrm{mEq} / \mathrm{L}$ , and increased $\mathrm{H}^{+}$ excretion would be observed in a

A 28-year-old man who is receiving lithium treatment for bipolar disorder becomes polyuric. His urine osmolarity is $90 \mathrm{mOsm} / \mathrm{L}$ ; it remains at that level when he is given a nasal spray of dDAVP. Which diagnosis is correct?