BIOS 255 / BIOS255 EXAM 2
2026-2027 | Anatomy &
Physiology III Review |
Chamberlain | 100% Correct
Q&A | Grade A | Pass
Guaranteed
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PART A – MULTIPLE CHOICE (Q1–55)
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Q1 (Cardiovascular – Cardiac Muscle Action Potential):
Which ion is primarily responsible for the rapid depolarization (Phase 0) of a contractile cardiac
muscle cell action potential?
A. Calcium influx through L-type channels
B. Sodium influx through fast voltage-gated channels
C. Potassium efflux through delayed rectifier channels
D. Chloride influx through ligand-gated channels
[CORRECT] B
Rationale: The rapid depolarization of contractile cardiac cells (ventricular myocytes) is driven
by fast Na⁺ influx through voltage-gated Na⁺ channels, similar to skeletal muscle but with a
slower upstroke. Distractor A is wrong because Ca²⁺ influx (L-type channels) drives the plateau
phase (Phase 2), not rapid depolarization—students often confuse pacemaker cell physiology
(Ca²⁺-dependent upstroke) with contractile cells. Clinical pearl: Class I antiarrhythmics (e.g.,
lidocaine, flecainide) block these fast Na⁺ channels to treat ventricular arrhythmias.
Q2 (Cardiovascular – Pacemaker Action Potential):
During which phase of the SA nodal action potential does the funny current (I_f) play its primary
role?
, . Phase 0 – depolarization
A
B. Phase 1 – early repolarization
C. Phase 3 – repolarization
D. Phase 4 – spontaneous depolarization
[CORRECT] D
Rationale: The funny current (I_f) is a mixed Na⁺/K⁺ inward current activated by
hyperpolarization at the end of Phase 3, driving the spontaneous depolarization of Phase 4 in
pacemaker cells. Distractor A is wrong because Phase 0 in SA nodes is mediated by Ca²⁺ influx
(L-type channels), not the funny current—students frequently confuse the ionic basis of
pacemaker vs. contractile cell depolarization. Clinical pearl: Ivabradine selectively blocks I_f to
slow heart rate without affecting contractility, used in heart failure with reduced ejection fraction.
Q3 (Cardiovascular – ECG Interpretation):
A nurse is reviewing a 12-lead ECG and notes a PR interval of 0.24 seconds. The QRS
complex is narrow (0.08 seconds). Which condition is most consistent with these findings?
A. Third-degree AV block
B. First-degree AV block
C. Bundle branch block
D. Wolff-Parkinson-White syndrome
[CORRECT] B
Rationale: A prolonged PR interval (>0.20 seconds) with a preserved 1:1 relationship between P
waves and QRS complexes defines first-degree AV block, indicating delayed conduction
through the AV node. Distractor A is wrong because third-degree AV block shows complete AV
dissociation with no relationship between P waves and QRS complexes—students must
distinguish between delayed conduction vs. complete interruption. Clinical pearl: First-degree
AV block is often benign in athletes or with medications (beta-blockers, digoxin), but monitor for
progression to higher-degree blocks.
Q4 (Cardiovascular – ECG Waves):
The T wave on an ECG represents which of the following physiological events?
A. Atrial depolarization
B. Ventricular depolarization
C. Ventricular repolarization
D. Atrial repolarization
[CORRECT] C
Rationale: The T wave corresponds to ventricular repolarization, during which K⁺ efflux restores
the resting membrane potential; atrial repolarization is hidden within the QRS complex due to its
smaller muscle mass. Distractor B is wrong because ventricular depolarization is represented by
the QRS complex—students must memorize the wave-to-event correlations precisely. Clinical
pearl: T wave inversion or ST-segment elevation may indicate myocardial ischemia; always
correlate ECG findings with clinical presentation and troponin levels.
Q5 (Cardiovascular – Cardiac Cycle):
During which phase of the cardiac cycle does the aortic valve open?
A. Isovolumetric contraction
B. Rapid ejection
C. Isovolumetric relaxation
, . Rapid filling
D
[CORRECT] B
Rationale: The aortic valve opens at the beginning of ventricular ejection when intraventricular
pressure exceeds aortic pressure (~80 mmHg), marking the transition from isovolumetric
contraction to rapid ejection. Distractor A is wrong because during isovolumetric contraction, all
valves are closed while pressure builds—students often confuse the timing of valve events with
pressure changes. Clinical pearl: In aortic stenosis, the aortic valve opening is delayed and
reduced, producing a crescendo-decrescendo systolic murmur best heard at the right second
intercostal space.
Q6 (Cardiovascular – Heart Sounds):
The second heart sound (S2) is produced by closure of which valves?
A. Tricuspid and mitral valves
B. Pulmonary and aortic valves
C. Mitral and aortic valves
D. Tricuspid and pulmonary valves
[CORRECT] B
Rationale: S2 ("dub") results from closure of the semilunar valves (aortic and pulmonary) at the
end of ventricular systole, marking the beginning of diastole; the aortic component typically
precedes the pulmonary component. Distractor A is wrong because tricuspid and mitral valve
closure produces S1 ("lub")—students must distinguish between atrioventricular valve closure
(S1) and semilunar valve closure (S2). Clinical pearl: Splitting of S2 during inspiration is normal
(physiologic splitting) due to delayed pulmonary valve closure; fixed splitting suggests an atrial
septal defect.
Q7 (Cardiovascular – Cardiac Output):
A patient has a heart rate of 72 bpm and a stroke volume of 70 mL/beat. What is the cardiac
output?
A. 4.2 L/min
B. 5.04 L/min
C. 6.2 L/min
D. 3.8 L/min
[CORRECT] B
Rationale: Cardiac output (CO) = Stroke Volume (SV) × Heart Rate (HR) = 70 mL × 72
beats/min = 5,040 mL/min = 5.04 L/min, which is within the normal range of 4–8 L/min for a
resting adult. Distractor A is wrong because it incorrectly divides 70 by 72 or misplaces decimal
points—students must ensure consistent units (convert mL to L). Clinical pearl: In sepsis, CO
may increase (high-output failure) despite hypotension due to vasodilation and reduced
afterload; always assess CO in context of systemic vascular resistance.
Q8 (Cardiovascular – Stroke Volume Regulation):
According to the Frank-Starling law, an increase in which of the following will increase stroke
volume?
A. Afterload
B. Contractility
C. End-diastolic volume (preload)
D. Heart rate
, [CORRECT] C
Rationale: The Frank-Starling law states that stroke volume increases with increased
end-diastolic volume (preload/ventricular filling) due to greater sarcomere stretch and optimized
actin-myosin overlap, up to a physiological limit. Distractor A is wrong because increased
afterload (e.g., hypertension, aortic stenosis) actually decreases stroke volume by increasing
resistance to ejection—students must not confuse preload (filling) with afterload (resistance).
Clinical pearl: In heart failure with preserved ejection fraction (HFpEF), the Frank-Starling
mechanism is impaired; diuretics may reduce preload excessively and worsen output.
Q9 (Cardiovascular – Blood Pressure):
A patient's blood pressure is recorded as 128/82 mmHg. According to the 2017 ACC/AHA
hypertension guidelines, how is this classified?
A. Normal
B. Elevated
C. Stage 1 hypertension
D. Stage 2 hypertension
[CORRECT] C
Rationale: The 2017 ACC/AHA guidelines define Stage 1 hypertension as systolic 130–139
mmHg or diastolic 80–89 mmHg; this patient's diastolic of 82 mmHg meets criteria regardless of
systolic value. Distractor B is wrong because "elevated" is defined as systolic 120–129 mmHg
with diastolic <80 mmHg—students must use the higher category when systolic and diastolic fall
in different stages. Clinical pearl: These guidelines lowered thresholds from previous JNC-7
standards, increasing hypertension prevalence; lifestyle modification is first-line for Stage 1
without cardiovascular disease.
Q10 (Cardiovascular – MAP Calculation):
A patient has a blood pressure of 110/70 mmHg. What is the approximate mean arterial
pressure (MAP)?
A. 80 mmHg
B. 90 mmHg
C. 83 mmHg
D. 75 mmHg
[CORRECT] C
Rationale: MAP ≈ Diastolic BP + 1/3(Systolic BP − Diastolic BP) = 70 + 1/3(110 − 70) = 70 +
13.3 = 83.3 mmHg, or alternatively (SBP + 2×DBP)/3 = (110 + 140)/3 = 83.3 mmHg. Distractor A
is wrong because it uses a simple average (110+70)/2 = 90, ignoring the greater time spent in
diastole—students must remember diastole occupies approximately 2/3 of the cardiac cycle.
Clinical pearl: MAP must be ≥65 mmHg for adequate tissue perfusion; in shock, vasopressors
(norepinephrine) are titrated to maintain MAP ≥65.
Q11 (Cardiovascular – Baroreceptor Reflex):
A patient suddenly stands up from a supine position. Which immediate physiological response
occurs to prevent orthostatic hypotension?
A. Decreased sympathetic outflow to the heart
B. Increased parasympathetic outflow to the heart
C. Increased sympathetic outflow to arterioles and veins
D. Decreased renin release from the juxtaglomerular apparatus
2026-2027 | Anatomy &
Physiology III Review |
Chamberlain | 100% Correct
Q&A | Grade A | Pass
Guaranteed
=======================================================================
=
========
PART A – MULTIPLE CHOICE (Q1–55)
========================================================================
========
Q1 (Cardiovascular – Cardiac Muscle Action Potential):
Which ion is primarily responsible for the rapid depolarization (Phase 0) of a contractile cardiac
muscle cell action potential?
A. Calcium influx through L-type channels
B. Sodium influx through fast voltage-gated channels
C. Potassium efflux through delayed rectifier channels
D. Chloride influx through ligand-gated channels
[CORRECT] B
Rationale: The rapid depolarization of contractile cardiac cells (ventricular myocytes) is driven
by fast Na⁺ influx through voltage-gated Na⁺ channels, similar to skeletal muscle but with a
slower upstroke. Distractor A is wrong because Ca²⁺ influx (L-type channels) drives the plateau
phase (Phase 2), not rapid depolarization—students often confuse pacemaker cell physiology
(Ca²⁺-dependent upstroke) with contractile cells. Clinical pearl: Class I antiarrhythmics (e.g.,
lidocaine, flecainide) block these fast Na⁺ channels to treat ventricular arrhythmias.
Q2 (Cardiovascular – Pacemaker Action Potential):
During which phase of the SA nodal action potential does the funny current (I_f) play its primary
role?
, . Phase 0 – depolarization
A
B. Phase 1 – early repolarization
C. Phase 3 – repolarization
D. Phase 4 – spontaneous depolarization
[CORRECT] D
Rationale: The funny current (I_f) is a mixed Na⁺/K⁺ inward current activated by
hyperpolarization at the end of Phase 3, driving the spontaneous depolarization of Phase 4 in
pacemaker cells. Distractor A is wrong because Phase 0 in SA nodes is mediated by Ca²⁺ influx
(L-type channels), not the funny current—students frequently confuse the ionic basis of
pacemaker vs. contractile cell depolarization. Clinical pearl: Ivabradine selectively blocks I_f to
slow heart rate without affecting contractility, used in heart failure with reduced ejection fraction.
Q3 (Cardiovascular – ECG Interpretation):
A nurse is reviewing a 12-lead ECG and notes a PR interval of 0.24 seconds. The QRS
complex is narrow (0.08 seconds). Which condition is most consistent with these findings?
A. Third-degree AV block
B. First-degree AV block
C. Bundle branch block
D. Wolff-Parkinson-White syndrome
[CORRECT] B
Rationale: A prolonged PR interval (>0.20 seconds) with a preserved 1:1 relationship between P
waves and QRS complexes defines first-degree AV block, indicating delayed conduction
through the AV node. Distractor A is wrong because third-degree AV block shows complete AV
dissociation with no relationship between P waves and QRS complexes—students must
distinguish between delayed conduction vs. complete interruption. Clinical pearl: First-degree
AV block is often benign in athletes or with medications (beta-blockers, digoxin), but monitor for
progression to higher-degree blocks.
Q4 (Cardiovascular – ECG Waves):
The T wave on an ECG represents which of the following physiological events?
A. Atrial depolarization
B. Ventricular depolarization
C. Ventricular repolarization
D. Atrial repolarization
[CORRECT] C
Rationale: The T wave corresponds to ventricular repolarization, during which K⁺ efflux restores
the resting membrane potential; atrial repolarization is hidden within the QRS complex due to its
smaller muscle mass. Distractor B is wrong because ventricular depolarization is represented by
the QRS complex—students must memorize the wave-to-event correlations precisely. Clinical
pearl: T wave inversion or ST-segment elevation may indicate myocardial ischemia; always
correlate ECG findings with clinical presentation and troponin levels.
Q5 (Cardiovascular – Cardiac Cycle):
During which phase of the cardiac cycle does the aortic valve open?
A. Isovolumetric contraction
B. Rapid ejection
C. Isovolumetric relaxation
, . Rapid filling
D
[CORRECT] B
Rationale: The aortic valve opens at the beginning of ventricular ejection when intraventricular
pressure exceeds aortic pressure (~80 mmHg), marking the transition from isovolumetric
contraction to rapid ejection. Distractor A is wrong because during isovolumetric contraction, all
valves are closed while pressure builds—students often confuse the timing of valve events with
pressure changes. Clinical pearl: In aortic stenosis, the aortic valve opening is delayed and
reduced, producing a crescendo-decrescendo systolic murmur best heard at the right second
intercostal space.
Q6 (Cardiovascular – Heart Sounds):
The second heart sound (S2) is produced by closure of which valves?
A. Tricuspid and mitral valves
B. Pulmonary and aortic valves
C. Mitral and aortic valves
D. Tricuspid and pulmonary valves
[CORRECT] B
Rationale: S2 ("dub") results from closure of the semilunar valves (aortic and pulmonary) at the
end of ventricular systole, marking the beginning of diastole; the aortic component typically
precedes the pulmonary component. Distractor A is wrong because tricuspid and mitral valve
closure produces S1 ("lub")—students must distinguish between atrioventricular valve closure
(S1) and semilunar valve closure (S2). Clinical pearl: Splitting of S2 during inspiration is normal
(physiologic splitting) due to delayed pulmonary valve closure; fixed splitting suggests an atrial
septal defect.
Q7 (Cardiovascular – Cardiac Output):
A patient has a heart rate of 72 bpm and a stroke volume of 70 mL/beat. What is the cardiac
output?
A. 4.2 L/min
B. 5.04 L/min
C. 6.2 L/min
D. 3.8 L/min
[CORRECT] B
Rationale: Cardiac output (CO) = Stroke Volume (SV) × Heart Rate (HR) = 70 mL × 72
beats/min = 5,040 mL/min = 5.04 L/min, which is within the normal range of 4–8 L/min for a
resting adult. Distractor A is wrong because it incorrectly divides 70 by 72 or misplaces decimal
points—students must ensure consistent units (convert mL to L). Clinical pearl: In sepsis, CO
may increase (high-output failure) despite hypotension due to vasodilation and reduced
afterload; always assess CO in context of systemic vascular resistance.
Q8 (Cardiovascular – Stroke Volume Regulation):
According to the Frank-Starling law, an increase in which of the following will increase stroke
volume?
A. Afterload
B. Contractility
C. End-diastolic volume (preload)
D. Heart rate
, [CORRECT] C
Rationale: The Frank-Starling law states that stroke volume increases with increased
end-diastolic volume (preload/ventricular filling) due to greater sarcomere stretch and optimized
actin-myosin overlap, up to a physiological limit. Distractor A is wrong because increased
afterload (e.g., hypertension, aortic stenosis) actually decreases stroke volume by increasing
resistance to ejection—students must not confuse preload (filling) with afterload (resistance).
Clinical pearl: In heart failure with preserved ejection fraction (HFpEF), the Frank-Starling
mechanism is impaired; diuretics may reduce preload excessively and worsen output.
Q9 (Cardiovascular – Blood Pressure):
A patient's blood pressure is recorded as 128/82 mmHg. According to the 2017 ACC/AHA
hypertension guidelines, how is this classified?
A. Normal
B. Elevated
C. Stage 1 hypertension
D. Stage 2 hypertension
[CORRECT] C
Rationale: The 2017 ACC/AHA guidelines define Stage 1 hypertension as systolic 130–139
mmHg or diastolic 80–89 mmHg; this patient's diastolic of 82 mmHg meets criteria regardless of
systolic value. Distractor B is wrong because "elevated" is defined as systolic 120–129 mmHg
with diastolic <80 mmHg—students must use the higher category when systolic and diastolic fall
in different stages. Clinical pearl: These guidelines lowered thresholds from previous JNC-7
standards, increasing hypertension prevalence; lifestyle modification is first-line for Stage 1
without cardiovascular disease.
Q10 (Cardiovascular – MAP Calculation):
A patient has a blood pressure of 110/70 mmHg. What is the approximate mean arterial
pressure (MAP)?
A. 80 mmHg
B. 90 mmHg
C. 83 mmHg
D. 75 mmHg
[CORRECT] C
Rationale: MAP ≈ Diastolic BP + 1/3(Systolic BP − Diastolic BP) = 70 + 1/3(110 − 70) = 70 +
13.3 = 83.3 mmHg, or alternatively (SBP + 2×DBP)/3 = (110 + 140)/3 = 83.3 mmHg. Distractor A
is wrong because it uses a simple average (110+70)/2 = 90, ignoring the greater time spent in
diastole—students must remember diastole occupies approximately 2/3 of the cardiac cycle.
Clinical pearl: MAP must be ≥65 mmHg for adequate tissue perfusion; in shock, vasopressors
(norepinephrine) are titrated to maintain MAP ≥65.
Q11 (Cardiovascular – Baroreceptor Reflex):
A patient suddenly stands up from a supine position. Which immediate physiological response
occurs to prevent orthostatic hypotension?
A. Decreased sympathetic outflow to the heart
B. Increased parasympathetic outflow to the heart
C. Increased sympathetic outflow to arterioles and veins
D. Decreased renin release from the juxtaglomerular apparatus
