Physiology 5th Ed.

Challenge Yourself Answers

Chapter 1

1 Solution B, negative; or Solution A, positive

2 150 mmol/L urea

3 Increases

4 Upstroke of the action potential

5 25 quanta

6 Botulinus toxin

7 Action potential in nerve fiber; opening Ca2+ channels in presynaptic terminal; ACh release from presynaptic terminal; binding of ACh to nicotinic receptors; opening ligand-gated ion channels; MEPP; EPP; action potential in muscle fiber

8 Approximately equal to (Hint: Passive tension is negligible in this range.)

9 Substance P, vasopressin

10 Double (Hint: ΔC = 10 − 1 = 9. If both sides doubled, ΔC = 20 − 2 = 18.)

11 L-Dopa, dopamine, norepinephrine

12 Increasing nerve diameter: increases; increasing internal resistance (Ri): decreases; increasing membrane resistance (Rm): increases; decreasing membrane capacitance (Cm): increases; increasing length constant: increases; increasing time constant: decreases.

13 Depolarizes; causes muscle weakness by closing inactivation gates on Na+ channels so that they are unavailable to carry Na+ current for upstroke of muscle action potential

14 Conformational change in myosin that reduces its affinity for actin

15 Nicotinic receptor antagonist; inhibitor of choline reuptake; inhibitor of ACh release

16 Water flows from A to B. (Hint: Calculated πeff of Solution B is higher than that of Solution A, and water flows from low to high πeff.)

Chapter 2

1 Dilation of airways; relaxation of bladder wall

2 Muscarinic; sphincter

3 Ganglia in or near target tissues (Hints: All postganglionic neurons have nicotinic receptors; sweat glands have sympathetic cholinergic innervation; all preganglionic neurons are cholinergic.)

4 Inhibits (or blocks); β1 receptors

5 Effect of epinephrine to increase cardiac contractility; effect of epinephrine to increase heart rate

6 Phenylethanolamine-N-methyltransferase

7 α1-adrenergic agonist (would constrict vascular smooth muscle, further elevating blood pressure); β1-adrenergic agonist (would increase heart rate and contractility, further elevating blood pressure)

8 Muscarinic, contraction, muscarinic, relaxation

9 αq binds to GDP, αq binds to GTP, activation of phospholipase C, generation of IP3, release of Ca2+ from intracellular stores, activation of protein kinase

10 Slowing of conduction velocity in AV node; gastric acid secretion; erection; sweating on a hot day

Chapter 3

1 Right optic nerve

2 To the left (Hint: Postrotatory nystagmus is in the opposite direction of the original rotation.)

3 One

4 Knee-jerk reflex; stretch reflex (Hint: Knee-jerk is an example of stretch reflex.)

5 Phasic

6 Light; conversion of 11-cis rhodopsin to all-trans rhodopsin; transducin; decreased cyclic GMP; closure of Na+ channels; hyperpolarization; release of neurotransmitter

7 More negative; decreases likelihood of action potentials

8 Golgi tendon organs: activated

Ia afferent fibers: unchanged (Hint: Ia afferents are involved in the stretch reflex.)

Ib afferent fibers: activated

Inhibitory interneurons: activated

α motoneurons: inhibited

9 Protein; glucose; K+

10 Initial rotation to the right—right canal is activated; head stops rotating—left canal is activated.

11 Wider; more compliant; lower

Chapter 4

1 mm Hg/mL/min or mm Hg/L/min

2 800 milliseconds (Hint: 60 seconds in a minute)

3 Ventricular action potential; Ca2+ release from sarcoplasmic reticulum; Ca2+ binding to troponin C; tension; Ca2+ accumulation by sarcoplasmic reticulum

4 0.50 (Hint: Heart rate is not needed for the calculation.)

5 Isovolumetric relaxation (Hint: Ventricle is filling during atrial systole.)

6 Increased; increased

7 77 mL (Hint: First, calculate stroke volume from cardiac output and heart rate; then use calculated stroke volume and stated end-diastolic volume to calculate end-systolic volume.)

8 Net filtration; driving force is 9 mm Hg

9 All will decrease.

10 End-diastolic volume (or preload)

11 Increased phosphorylation of phospholamban; increased action potential duration

12 Phase 0

13 Excitability

14 Increased heart rate (Hint: Each change, by itself, leads to increased heart rate.)

15 Heart rate; resistance of cutaneous vascular beds; angiotensin II levels (Hint: Unstressed volume decreases due to venoconstriction.)

16 Decreased radius (Hint: T = P × r. Thus, if P increases, r must decrease to maintain a constant wall tension.)

17 Pulmonary (Hint: Pulmonary blood flow is 100% of cardiac output.)

18 Increased contractility (Hints: End-diastolic volume is preload, and aortic pressure is afterload.)

19 Rapid ventricular ejection

20 Decreased; decreased

21 Decreased cardiac output caused by increased aortic pressure (Hint: Pressure work is more costly than volume work.)

22 Total resistance decreases from 3.33 to 2.5.

23 Blood vessel A (Hint: Velocity = flow/area.)

24 Dicrotic notch: arterial pressure trace

 β1 receptors: sinoatrial node and ventricular muscle

 Lmax: Length-tension curve

 Radius to the fourth power: resistance of blood vessels or resistance equation

 Phospholamban: sarcoplasmic reticulum

 Negative dromotropic effect: AV node

 Pulse pressure: arteries or arterial pressure

 Normal automaticity: SA node

 Ejection fraction: ventricle

25 Rapid ventricular ejection, isovolumetric ventricular relaxation

26 Diameter of splanchnic arterioles, TPR

27 End-systolic volume

28 Sympathetic effect to increase contractility

Chapter 5

1 1500 mL

2 Milliliters or liters (Hint: FEV1 is the volume expired in the first second of forced expiration, not a fractional volume.)

3 547.5 mm Hg (Hint: [740 − 47] × 0.79.)

4 39.3 mL/min/mm Hg (Hint 1: VCO = DL × ΔP. Hint 2: PCO in room air = [PB − 47 mm Hg] × 0.001, and PCO in blood is initially zero.)

5 Increased H+ concentration, increased PCO2, increased 2,3-diphosphoglycerate (DPG) concentration (Hint: Increased P50 = right shift.)

6 None of changes listed causes a change in O2-binding capacity of hemoglobin. (Hint: O2-binding capacity is the milliliter of O2 bound to 1 g of hemoglobin at 100% saturation. Right- and left-shifts change the percent saturation but do not alter the amount of O2 that can be bound at 100% saturation.)

7 PO2 is decreased and PCO2 is increased.

8 PAo2

9 Blood flow, ventilation, PCO2

10 imagedefects, fibrosis, right-to-left shunt

11 Inspiratory capacity

12 Vital capacity, FEV1 (Hint: FEV1/FVC is decreased in obstructive but increased in restrictive.)

13 3.5 L/minute (Hints: Calculate VD first as 200 mL. Several of the given values are not needed for the calculation.)

14 FRC increases.

15 Airway pressure = +15 cm H2O and intrapleural pressure = +20 cm H2O.

16 High altitude

17 Decreased PIO2, decreased PAO2, decreased PaO2, hyperventilation, decreased PaCO2, increased pH

18 FEV1: forced vital capacity curve or measurement

image = 0: lung region where there is airway obstruction, or shunt

PA > Pa: apex of lung

Afterload of right ventricle: pulmonary artery or pulmonary arterial pressure

γ chains: fetal hemoglobin

P50: O2-hemoglobin dissociation curve

Slope of pressure-volume curve: compliance

Normal pressure lower than PB: intrapleural space

DL: alveolar/pulmonary capillary barrier

PO2 < 60 mm Hg stimulates breathing: peripheral chemoreceptors, or carotid bodies

19 Equal to systemic arterial PO2

20 Decrease

Chapter 6

1 Efferent arteriole

2 At all plasma glucose concentrations below threshold

3 Oncotic pressure is increased. (Hint: More fluid filtered out of glomerular capillaries leads to increased plasma protein concentration.)

4 Below Tm (Hint: Below Tm, the assumption that renal vein PAH ≈ 0 is correct.)

5 306.7 mOsm/L (Hints: New total body water = 45 L; NaCl dissociates into two particles; new total body osmoles = 13,800 mOsm.)

6 Unchanged (Hint: If GFR is constant and urine flow rate increases, urine inulin concentration decreases.)

7 Increased

8 Bowman’s space or early proximal convoluted tubule (Hint: [TF/P]inulin is lowest before any water reabsorption has occurred.)

9 Bowman’s space or early proximal convoluted tubule

10 Decreased (Hint: Na+-K+-2Cl cotransporter is required for countercurrent multiplication, which establishes corticopapillary gradient.)

11 Central diabetes insipidus

12 Decreased

13 mg/min (or amount/time)

14 Decreased

15 Lack of insulin, spironolactone, hyperosmolarity

16 Inhibition of Na+-phosphate cotransport, decreased urinary Ca2+ excretion

17 Net reabsorption, 1100 mg/min

18 Midpoint of distal convoluted tubule or early distal tubule

19 Clearance of PAH below Tm (Hints: Clearance of glucose below threshold is zero; clearance of inulin is GFR; clearance of PAH below Tm is RPF.)

20 K+ on a very high-potassium diet, inulin, Na+, HCO3, glucose (below threshold)

Chapter 7

1 Weak acid “A”

2 7.9 mEq/L

3 Increased (Hint: compensatory hyperventilation for metabolic acidosis.)

4 Diarrhea, salicylate overdose, chronic renal failure

5 Loop diuretics, thiazide diuretics (Hint: Carbonic anhydrase inhibitors and K+-sparing diuretics produce metabolic acidosis.)

6 Metabolic acidosis; anion gap is 29 mEq/L.

7 mOsm/L

8 Vomiting, morphine overdose, obstructive lung disease, hyperaldosteronism

9 Filtration of HCO3 across glomerular capillaries; Na+-H+ exchange; conversion of HCO3 to H2CO3; conversion of H2CO3 to CO2 and H2O; conversion of H2CO3 to H+ and HCO3; facilitated diffusion of HCO3

10 70 mEq/day

11 The patient with chronic respiratory acidosis will have the higher HCO3 and the higher pH (closer to normal).

12 No; metabolic acidosis and respiratory acidosis

13 Decreases (toward normal)

14 Filtered load of HPO4−2 (Hints: Amount of H+ in the urine is determined by urinary buffers; urine pH is free H+ concentration, not amount of H+. Most NH3 in urine is synthesized in proximal tubule cells, not filtered.)

15 Diabetic ketoacidosis

Chapter 8

1 Contraction of the gallbladder, stimulation of HCO3 secretion, stimulation of pancreatic enzyme secretion

2 Decreased intracellular cyclic AMP levels

3 Less negative (Hint: Membrane potentials are expressed as intracellular potential with respect to extracellular potential.)

4 Absorption of more solute than water

5 Increases cyclic AMP levels, activates αs subunit of GTP-binding protein

6 Sucrose

7 Emulsification of lipids in the intestinal lumen, action of pancreatic lipase, micelles, formation of cholesterol ester, chylomicrons

8 HCO3

9 Trypsinogen to trypsin, procarboxypeptidase to carboxypeptidase

10 Duodenum

11 Gastrin secretion: G cells or gastric antrum

Na+–bile salt cotransport: ileum

H+-K+ ATPase: gastric parietal cells

Intrinsic factor secretion: gastric parietal cells

Omeprazole action: H+-K+ ATPase in gastric parietal cells

Na+-glucose cotransporter: apical (luminal) membrane of intestinal epithelial cells

Secondary bile acids (or bile salts): intestinal lumen

12 Inhibition of H+-K+ ATPase

13 Increased body fat, increased insulin levels

14 Contraction of circular muscle, action of acetylcholine on circular muscle

Chapter 9

1 Cortisol: Decreased

ACTH: Increased

Blood glucose: Decreased

2 ADH: Increased

Urine osmolarity: Decreased, or dilute or hyposmotic

3 Serum K+: Decreased

Blood pressure: Increased

Renin: Decreased (Hint: Increased blood pressure inhibits renin secretion.)

4 ACTH: Increased

Cortisol: Increased

Blood glucose: Increased

5 Serum Ca2+: Decreased

Serum phosphate: Increased

Urinary cyclic AMP: Decreased

6 Prolactin: Increased

ADH: Decreased

Serum osmolarity: Increased (Hint: due to decreased ADH)

PTH: No change

7 T4: Decreased

TSH: Increased

Basal metabolic rate: Decreased

T3 resin uptake: Decreased (Hint: due to decreased T3 levels)

8 ACTH: Increased

Cortisol: Decreased

Deoxycorticosterone (DOC): Decreased

Aldosterone: Decreased

Dehydroepiandrosterone (DHEA): Increased (Hint: shunting of intermediates toward adrenal androgens)

Urinary 17-ketosteroids: Increased

9 ACTH: Decreased

Cortisol: Decreased (Hint: decreased secretion of endogenous cortisol)

10 Serum Ca2+: Increased

PTH: Decreased (Hint: Increased serum Ca2+ inhibits endogenous PTH secretion.)

11 Blood pressure: Increased (Hint: Mineralocorticoids accumulate to left of block.)

Blood glucose: Decreased

DHEA: Decreased

Aldosterone: Decreased (Hint: Excess deoxycorticosterone and corticosterone cause increased blood pressure, which inhibits renin secretion.)

Chapter 10

1 Hypothalamic dysfunction

2 Cholesterol to pregnenolone

3 21β-hydroxylase


5 Placenta; fetal liver; fetal adrenal cortex

6 Days 5–14

7 Days 26–28

8 Testes; muscle mass; epididymis; deepening of the voice

9 Male phenotype, testes, vagina

10 Testosterone → 17β-estradiol