The Sarcomere

Flashcards about the Sarcomere

Sarcomere

Fundamental unit of muscle contraction in striated muscle, responsible for contraction and relaxation of muscle fibers.

Z-Disk (Z-line)

Boundaries of the sarcomere, anchoring thin filaments and maintaining its structural integrity.

Thick Filaments

Motor protein primarily composed of myosin, crucial for muscle contraction through ATP hydrolysis.

Thin Filaments

Composed mainly of actin along with tropomyosin and troponin, regulating the interaction between actin and myosin.

M-Line

Anchors thick filaments in the center of the sarcomere.

A-Band

Portion of the sarcomere containing the entire length of thick filaments and overlaps with thin filaments, appearing dark under a microscope.

I-Band

Region containing only thin filaments, bisected by the Z-disk, appearing lighter under a microscope.

H-Zone

Central region of the A-band with no overlap between thick and thin filaments.

Excitation-Contraction Coupling

Process initiated by a neural signal, triggering calcium ion release from the sarcoplasmic reticulum into the muscle fiber cytoplasm.

Myosin

Motor protein with a tail, neck, and two heads containing ATPase activity, essential for muscle contraction.

Actin

Globular and filamentous forms, forms the backbone of thin filaments.

Tropomyosin

Blocks active sites on actin, preventing myosin binding during muscle relaxation.

Troponin C

Binds calcium ions, triggering a conformational change that allows myosin to bind to actin.

Dystrophin

Links actin cytoskeleton to the extracellular matrix via the sarcolemma

Z-line

What marks the boundary of each sarcomere?

I-band

What region of the sarcomere contains only thin filaments (actin)?

A-band

What band contains the entire length of thick filaments (myosin)?

Thick filaments

In the sarcomere, what area does the M-line stabilize?

Z-Line

What structure appears as a zigzag and maintains structural integrity of the sarcomere?

Troponin

What is the complex of three subunits that consists of Troponin C, Troponin T, and Troponin I?

Cross-Bridges

What are formed when myosin heads bind to actin; essential for generating tension and movement during contraction?

Hinge Region

What part of the Myosin allows pivoting motion of myosin head and is critical to sliding filament mechanism?