Muscle Contraction and Sarcomere Shortening Quiz

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What is the functional unit of the myofibril in a cardiac muscle fiber?

M-line

Z-line

Sarcomere (correct)

I-band

What is the role of the intercalated discs in cardiac muscle fibers?

Act as sites for energy production

Regulate oxygen intake

Allow for rapid communication between adjacent cells (correct)

Store excess calcium ions

What gives cardiac muscle fibers their striated appearance?

Golgi apparatus

Mitochondria

Myofibrils (correct)

Endoplasmic reticulum

How are cardiac muscle fibers different from skeletal muscle fibers?

Presence of T-tubules and intercalated discs in cardiac muscle fibers Signup and view all the answers

What is the significance of the central nucleus in a cardiac myocyte?

Provides genetic material for protein synthesis Signup and view all the answers

Which cellular structure is responsible for storing and releasing intracellular calcium ions during muscle contraction?

Sarcoplasmic reticulum Signup and view all the answers

What is the role of tropomyosin in muscle contraction?

Inhibit the interaction between actin and myosin Signup and view all the answers

Which subunit of troponin binds the entire troponin molecule to tropomyosin?

TnT Signup and view all the answers

What induces a conformational shift in tropomyosin, exposing the active sites on the actin filament?

Binding of calcium by TnC Signup and view all the answers

What is the composition of each myosin molecule?

Two globular heads and a rod-like tail Signup and view all the answers

What is the function of the myosin heads during muscle contraction?

Bind ATP and G-actin forming cross bridges Signup and view all the answers

How does binding of calcium ions contribute to muscle contraction?

Exposes active sites on G-actin for myosin binding Signup and view all the answers

What is the main function of the Transverse (T) tubule in a cardiac myocyte?

Propagation of electrical changes into the sarcoplasm Signup and view all the answers

How does the Transverse (T) tubule contribute to Excitation-Contraction Coupling in a cardiac myocyte?

By propagating electrical changes into the sarcoplasm Signup and view all the answers

What is the role of the dilated terminal of the sarcoplasmic reticulum in a cardiac myocyte?

Storage of calcium during muscle relaxation Signup and view all the answers

Where do 25% of intracellular Calcium ions enter from, in a cardiac myocyte?

T tubules through voltage gated Ca channels Signup and view all the answers

What distinguishes the sarcoplasmic reticulum in cardiac muscle from that in skeletal muscle?

Presence of T tubules and dyads Signup and view all the answers

How does the wide diameter of the T tubule impact calcium handling in a cardiac myocyte?

Increases influx of calcium ions from extracellular fluid Signup and view all the answers