75 Questions
Which protein is involved in calcium-induced calcium release in cardiac muscle?
Troponin-C
What is the main role of the sodium-calcium exchanger in cardiac muscle?
To pump calcium out of the cell
What is the relationship between intracellular free calcium concentration and force generation in cardiac muscle?
As calcium concentration increases, force generation increases
Which factors influence the performance of the heart's contraction?
All of the above
What determines the strength of contraction of each myocardial cell?
Both A and B
What are the contractile elements responsible for active tension in the myocardial cell?
Actin and myosin
What is the role of the T-tubular system in excitation-contraction coupling?
Carry action potentials into the cell interior
Which of the following is true about the effect of ACh on Ca2+ current during the plateau of the action potential?
ACh decreases inward Ca2+ current
What is the effect of increasing intracellular Na+ on contractility?
Increases contractility
What happens to contractility when heart rate decreases?
Contractility decreases
Why can't cardiac muscle be tetanized?
The effective refractory period is too short
Which of the following is NOT a mechanism for relaxation in cardiac muscle?
Passive diffusion of Ca2+ out of the cell
Which term refers to the intrinsic ability of cardiac muscle to develop force at a given muscle length?
Contractility
What is the primary factor that determines the amount of Ca2+ released from the sarcoplasmic reticulum during excitation-contraction coupling?
The amount of Ca2+ previously stored in the SR
Which of the following is NOT a mechanism that impacts contractility in cardiac muscle?
Phosphorylation of TnI
Which protein plays a role in calcium-induced calcium release in cardiac muscle?
Troponin-C
What is the primary factor that determines the amount of calcium released from the sarcoplasmic reticulum during excitation-contraction coupling?
Troponin-C
What is the role of the sodium-calcium exchanger in cardiac muscle?
To pump calcium out of the cell
What determines the strength of contraction of each myocardial cell?
Intracellular free calcium concentration
What is the relationship between intracellular free calcium concentration and force generation in cardiac muscle?
Direct relationship
What are the contractile elements responsible for active tension in the myocardial cell?
Myosin and actin
Which of the following is NOT a mechanism for relaxation in cardiac muscle?
Ca2+ release from the sarcoplasmic reticulum
Which of the following is responsible for passive tension in the myocardial cell?
Titin
What is the function of the transverse-tubular (T-tubular) system in cardiac muscle?
Carry action potentials into the cell interior
Which of the following is true about the sliding filament mechanism in the myocardial cell?
Shortening occurs by the sliding of thick and thin filaments past each other
What is the role of troponin C in cardiac muscle contraction?
It binds to calcium ions, inducing a conformational change
Which of the following is NOT a characteristic of the myocardial cell?
Has a poorly developed T-tubular system in the ventricles
What is the main source of ATP production in cardiac muscle?
Mitochondria
What is the function of the sodium-calcium exchanger in cardiac muscle?
Remove calcium ions from the myoplasm to promote relaxation
Which of the following agents actively transports Ca2+ out of the cell when [Ca2+] is high?
Na+-Ca2+ exchanger (NCX)
Which term refers to the contractile strength of cardiac muscle?
Ionotropy
What is the primary mechanism for relaxation in cardiac muscle?
ATP-dependent Ca2+-pump (SERCA)
What factor determines the strength of contraction of each myocardial cell?
Intracellular Ca2+ concentration
Which protein is phosphorylated to stimulate the activity of the SERCA pump in cardiac muscle?
Phospholamban (PLB)
What effect does parasympathetic stimulation have on cardiac contractility?
Decreases contractility
What is the main role of the sodium-calcium exchanger (NCX) in cardiac muscle?
Transporting Na+ out of the cell
Which of the following mechanisms impacts contractility in cardiac muscle?
Increasing intracellular Na+
Which of the following is NOT a mechanism for relaxation in cardiac muscle?
Increasing intracellular Na+
What is the effect of decreasing the Na+ gradient across the sarcolemma on contractility?
Positive inotropic effect
What happens to contractility when heart rate increases?
Contractility increases
Which of the following is true about the effect of ACh on Ca2+ current during the plateau of the action potential?
ACh decreases inward Ca2+ current
What is the primary factor that determines the amount of Ca2+ released from the sarcoplasmic reticulum during excitation-contraction coupling?
Intracellular Ca2+ concentration
What is the main role of the sodium-calcium exchanger in cardiac muscle?
To decrease intracellular Ca2+ concentration
What determines the strength of contraction of each myocardial cell?
Intracellular Ca2+ concentration
What is the relationship between intracellular free calcium concentration and force generation in cardiac muscle?
Directly proportional
Which of the following is responsible for the passive tension in the myocardial cell?
Titin
What is the main source of ATP production in cardiac muscle?
Fatty acid oxidation
What is the role of the sodium-calcium exchanger (NCX) in cardiac muscle?
Transporting sodium out of the cell and calcium into the cell
What determines the strength of contraction of each myocardial cell?
The strength of contraction of all the individual myocardial cells
What is the primary factor that determines the amount of calcium released from the sarcoplasmic reticulum during excitation-contraction coupling?
The concentration of calcium in the cytoplasm
What happens to contractility when heart rate increases?
Contractility increases
What is the effect of increasing intracellular Na+ on contractility?
Contractility increases
Which of the following is NOT a mechanism for relaxation in cardiac muscle?
Active transport of Ca2+ into the cell by the Na+-Ca2+ exchanger
What is the primary mechanism for relaxation in cardiac muscle?
Active transport of Ca2+ out of the cell by the Na+-Ca2+ exchanger
What is the main role of the sodium-calcium exchanger (NCX) in cardiac muscle?
To transport Ca2+ into the cell in exchange for Na+
What happens to contractility when heart rate increases?
Contractility increases
What determines the strength of contraction of each myocardial cell?
The amount of Ca2+ released from the sarcoplasmic reticulum
What is the effect of increasing intracellular Na+ on contractility?
Contractility increases
Which of the following is responsible for passive tension in the myocardial cell?
The extracellular matrix
Which protein is involved in calcium-induced calcium release in cardiac muscle?
Troponin-C
What is the role of the sodium-calcium exchanger in cardiac muscle?
To pump sodium out of the cell and calcium into the cell
What is the primary factor that determines the amount of calcium released from the sarcoplasmic reticulum during excitation-contraction coupling?
Calcium-induced calcium release
What is the main role of the sodium-calcium exchanger in cardiac muscle?
To pump sodium out of the cell and calcium into the cell
What is the effect of increasing intracellular Na+ on contractility?
It increases contractility
What is the primary mechanism for relaxation in cardiac muscle?
Sarcoplasmic reticulum Ca2+ pump
What determines the strength of contraction of each myocardial cell?
Calcium concentration
Which of the following mechanisms impacts contractility in cardiac muscle?
Increasing heart rate
Which of the following is true about the effect of ACh on Ca2+ current during the plateau of the action potential?
ACh decreases inward Ca2+ current
What determines the strength of contraction of each myocardial cell?
Intracellular Ca2+ concentration
What is the primary mechanism for relaxation in cardiac muscle?
Decreased intracellular Ca2+
What is the main role of the sodium-calcium exchanger (NCX) in cardiac muscle?
Transporting Ca2+ out of the cell and Na+ into the cell
What is the effect of increasing intracellular Na+ on contractility?
Increases contractility
Why can't cardiac muscle be tetanized?
Due to the duration of the effective refractory period
What is the relationship between intracellular free calcium concentration and force generation in cardiac muscle?
Directly proportional
What is the main source of ATP production in cardiac muscle?
Fatty acid oxidation
This quiz tests your knowledge of the molecular events involved in muscle contraction and relaxation. Topics include myosin binding, ATP hydrolysis, excitation-contraction coupling, and calcium release.
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