Quiz 13: Cardiac Muscle
Biology
Q 1Q 1
Contraction of cardiac muscle typically requires:
A)Ca++ influx through voltage-gated Ca++ channels to trigger a rise in cytosolic [Ca++].
B)Ca++ influx through voltage-gated Ca++ channels,which is sufficient to support contraction.
C)Activation of myosin light-chain kinase (MLCK).
D)Phosphorylation of myosin heavy chain.
E)Ca++ influx through the Na+-Ca++ antiporter.
Free
Multiple Choice
A
Q 2Q 2
Relaxation of cardiac muscle typically requires:
A)Myosin light-chain dephosphorylation.
B)Activation of the ryanodine receptor.
C)Ca++ uptake by the sarcoplasmic reticulum (SR).
D)Phosphorylation of phospholamban.
E)Activation of the dihydropyridine receptor.
Free
Multiple Choice
C
Q 3Q 3
The force of contraction of cardiac muscle is typically increased by:
A)An increase in Ca++ extrusion by the Na+-Ca++ antiporter in cardiac muscle.
B)An increase in myosin phosphorylation in cardiac muscle.
C)A decrease in cytosolic [Ca++] in the cardiac muscle.
D)β-Adrenergic stimulation of the cardiac muscle.
E)Recruitment of more cardiac muscle cells.
Free
Multiple Choice
D
Q 4Q 4
Epinephrine increases the force of contraction of cardiac muscle by:
A)Increasing the amount of Ca++ in the SR for release to the cytosol.
B)Increasing the level of myosin light-chain phosphorylation.
C)Inhibiting the ryanodine receptor.
D)Increasing Ca++ extrusion through the sarcolemmal Ca++ pump.
E)Shortening the duration of the action potential.
Free
Multiple Choice
Q 5Q 5
Stretching cardiac muscle results in an increase in the force of contraction as a result of:
A)Activation of K+ channels.
B)An increase in the sensitivity of actin-myosin interactions to Ca++.
C)Phosphorylation of the ryanodine receptor.
D)Increased phosphorylation of troponin I.
E)Increased Ca++ influx through the Na+-Ca++ antiporter.
Free
Multiple Choice
Q 6Q 6
Calsequestrin in cardiac muscle:
A)Acts as a high-affinity Ca++ buffer in the cytosol.
B)Acts as a low-affinity Ca++ buffer in the SR lumen,near the ryanodine receptor.
C)Promotes Ca++ accumulation by the mitochondria.
D)Increases the Ca++ affinity of the sarcolemmal Ca++ pump.
E)Facilitates myosin binding to the actin thin filament.
Free
Multiple Choice
Q 7Q 7
Cardiac muscle cells in the atria are capable of contracting spontaneously because of a spontaneous depolarization that results from:
A)An inward current through a hyperpolarization-activated channel.
B)Cyclic changes in the activity of Na+,K+-ATPase.
C)Slow leak of Ca++ through the dihydropyridine receptor.
D)Cyclic changes in the activity of the sarcolemmal Ca++ pump.
E)Cyclic changes in the activity of SERCA.
Free
Multiple Choice
Q 8Q 8
Mutations in the cardiac ryanodine receptor have been associated with cardiac arrhythmias.Specifically,a mutation in the cardiac ryanodine receptor that increases Ca++ efflux from the SR promotes the development of delayed afterdepolarizations by:
A)Decreasing the activity of calcineurin.
B)Increasing Ca++ efflux through the Na+-Ca++ antiporter.
C)Increasing mitochondrial Ca++ uptake.
D)Decreasing actin-myosin interactions.
E)Increasing the activity of K+ channels.
Free
Multiple Choice
Q 9Q 9
The mechanisms underlying the development of cardiac hypertrophy are complex,although relaxation abnormalities that result in chronic elevation of cytosolic Ca++ level appear to promote the development of hypertrophy through:
A)Stimulation of the sarcolemmal Ca++ pump.
B)Ca++ binding to troponin I.
C)Activation of calcineurin.
D)Inhibition of Ca++/calmodulin-dependent protein kinase.
E)Opening of Ca++-activated K+ channels.
Free
Multiple Choice