Test Bank For Costanzo Physiology, 8th Edition
Authors: By Linda S. Costanzo, PhD
,Costanzo Physiology (8th Edition)
Chapter 1: Cellular Physiology
MCQs (1–30)
Q1. Membrane Potential (Nernst Concept)
A neuron has high intracellular K⁺ and low extracellular K⁺. Which factor MOST directly
determines the equilibrium potential for K⁺?
A. Membrane permeability to Na⁺
B. Ratio of intracellular to extracellular K⁺
C. Absolute intracellular K⁺ concentration only
D. ATP availability
Correct Answer: B
Explanation:
• Nernst equation:
EK=RTzFln[K+]out[K+]inE_K = \frac{RT}{zF} \ln \frac{[K^+]_{out}}{[K^+]_{in}}EK =zFRT
ln[K+]in [K+]out
• Depends on concentration ratio, not absolute values.
Why others are wrong:
• A: permeability affects membrane potential (Goldman), not equilibrium potential
• C: ignores extracellular concentration
• D: ATP affects pumps, not equilibrium directly
Clinical correlation:
Hyperkalemia reduces gradient → depolarization → arrhythmias.
Q2. Goldman Equation Concept
,Which condition will DEPOLARIZE resting membrane potential?
A. Increased extracellular K⁺
B. Decreased extracellular Na⁺
C. Increased intracellular Cl⁻
D. Decreased membrane Na⁺ permeability
Answer: A
Explanation:
• Increased extracellular K⁺ → reduces K⁺ efflux → less negative membrane potential
Wrong:
• B: minimal effect at rest
• C: Cl⁻ effect depends on gradient but stabilizing
• D: reduces depolarizing influence, hyperpolarizes
Clinical:
Hyperkalemia → cardiac arrhythmias, peaked T waves.
Q3. Action Potential Upstroke
Rapid depolarization is caused by:
A. K⁺ efflux
B. Na⁺ influx
C. Ca²⁺ efflux
D. Cl⁻ influx
Answer: B
Explanation:
Voltage-gated Na⁺ channels open → Na⁺ influx → depolarization.
Wrong:
• A: repolarization
• C: not involved in neuronal AP upstroke
, • D: inhibitory stabilization
Clinical:
Local anesthetics block Na⁺ channels → prevent AP.
Q4. Cardiac Contractility
Increased intracellular Ca²⁺ in cardiac muscle leads to:
A. Decreased stroke volume
B. Increased contractility
C. Decreased preload
D. Increased afterload
Answer: B
Explanation:
Ca²⁺ binds troponin C → increased actin-myosin cross-bridge formation.
Wrong:
• A: opposite effect
• C: preload is venous return
• D: afterload = arterial resistance
Clinical:
Digoxin increases Ca²⁺ → positive inotropy.
Q5. Pressure-Volume Loop
A rightward shift of the PV loop indicates:
A. Decreased preload
B. Increased preload
C. Decreased contractility
D. Increased afterload
Answer: B
Authors: By Linda S. Costanzo, PhD
,Costanzo Physiology (8th Edition)
Chapter 1: Cellular Physiology
MCQs (1–30)
Q1. Membrane Potential (Nernst Concept)
A neuron has high intracellular K⁺ and low extracellular K⁺. Which factor MOST directly
determines the equilibrium potential for K⁺?
A. Membrane permeability to Na⁺
B. Ratio of intracellular to extracellular K⁺
C. Absolute intracellular K⁺ concentration only
D. ATP availability
Correct Answer: B
Explanation:
• Nernst equation:
EK=RTzFln[K+]out[K+]inE_K = \frac{RT}{zF} \ln \frac{[K^+]_{out}}{[K^+]_{in}}EK =zFRT
ln[K+]in [K+]out
• Depends on concentration ratio, not absolute values.
Why others are wrong:
• A: permeability affects membrane potential (Goldman), not equilibrium potential
• C: ignores extracellular concentration
• D: ATP affects pumps, not equilibrium directly
Clinical correlation:
Hyperkalemia reduces gradient → depolarization → arrhythmias.
Q2. Goldman Equation Concept
,Which condition will DEPOLARIZE resting membrane potential?
A. Increased extracellular K⁺
B. Decreased extracellular Na⁺
C. Increased intracellular Cl⁻
D. Decreased membrane Na⁺ permeability
Answer: A
Explanation:
• Increased extracellular K⁺ → reduces K⁺ efflux → less negative membrane potential
Wrong:
• B: minimal effect at rest
• C: Cl⁻ effect depends on gradient but stabilizing
• D: reduces depolarizing influence, hyperpolarizes
Clinical:
Hyperkalemia → cardiac arrhythmias, peaked T waves.
Q3. Action Potential Upstroke
Rapid depolarization is caused by:
A. K⁺ efflux
B. Na⁺ influx
C. Ca²⁺ efflux
D. Cl⁻ influx
Answer: B
Explanation:
Voltage-gated Na⁺ channels open → Na⁺ influx → depolarization.
Wrong:
• A: repolarization
• C: not involved in neuronal AP upstroke
, • D: inhibitory stabilization
Clinical:
Local anesthetics block Na⁺ channels → prevent AP.
Q4. Cardiac Contractility
Increased intracellular Ca²⁺ in cardiac muscle leads to:
A. Decreased stroke volume
B. Increased contractility
C. Decreased preload
D. Increased afterload
Answer: B
Explanation:
Ca²⁺ binds troponin C → increased actin-myosin cross-bridge formation.
Wrong:
• A: opposite effect
• C: preload is venous return
• D: afterload = arterial resistance
Clinical:
Digoxin increases Ca²⁺ → positive inotropy.
Q5. Pressure-Volume Loop
A rightward shift of the PV loop indicates:
A. Decreased preload
B. Increased preload
C. Decreased contractility
D. Increased afterload
Answer: B
