11 Questions
What is the role of mucopolysaccharides within the T tubules of cardiac muscle fibers?
Binding calcium ions
Why does a heart placed in a calcium-free solution stop beating?
T tubules allow percolation of extracellular fluid containing calcium ions
How does the strength of cardiac muscle contraction relate to extracellular fluid calcium concentration?
It is greatly influenced by extracellular fluid calcium concentration
Why is skeletal muscle contraction less affected by changes in extracellular fluid calcium concentration compared to cardiac muscle contraction?
Skeletal muscle relies mainly on intracellular calcium ions for contraction
How are calcium ions removed from cardiac muscle cells?
By a sodium-calcium exchanger
What is the main difference in calcium ion release between skeletal muscle and cardiac muscle?
In cardiac muscle, calcium ions also diffuse from T tubules in addition to being released from the sarcoplasmic reticulum.
What triggers the release of calcium into the sarcoplasm in cardiac muscle?
Activation of calcium release channels in the sarcoplasmic reticulum membrane by calcium entering the cell.
Why would the strength of cardiac muscle contraction be reduced without calcium from the T tubules?
Sarcoplasmic reticulum of cardiac muscle does not store enough calcium for full contraction.
What is the role of troponin in initiating contraction in both skeletal and cardiac muscles?
Interacting with calcium ions to initiate cross-bridge formation.
What happens when voltage-dependent calcium channels in T tubules open during an action potential?
Calcium ions diffuse into the sarcoplasm from the T tubules.
Why are the T tubules in cardiac muscle larger in diameter compared to those in skeletal muscle?
To allow for a greater volume of diffusion of calcium ions into the sarcoplasm.
Test your knowledge on the mechanism of excitation-contraction coupling in smooth muscle, focusing on the unique aspects of calcium ion movement. Explore how calcium ions are released into the sarcoplasm from the cisternae of the sarcoplasmic reticulum and diffuse into the sarcoplasm from the T tubules.
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