chapter 10: structure of the sarcomere

What is a sarcomere?

the smallest contractile unit of muscle cells, composed of repeating units within myofibrils that contribute to the striated appearance of muscle.

What are the main components of a sarcomere?

Thick filaments (myosin),

thin filaments (actin),

Z discs,

M line,

A band,

I band,

regulatory proteins (troponin and tropomyosin)

What is the function of the Z disc?

marks the boundary of a sarcomere and serves as an attachment point for actin filaments.

What is the role of myosin in muscle contraction?

What are the I band?

Light band containing only thin filaments.

what is the A band?

Dark band where thick and thin filaments overlap.

What is the function of the M line?

the center of the sarcomere where thick filaments are anchored.

What is titin and its role in muscle contraction?

an elastic protein that helps sarcomeres return to their resting length after stretching

How does calcium contribute to muscle contraction?

it binds to troponin, causing a conformational change that moves tropomyosin away from actin's binding sites, allowing myosin to attach.

What is the sliding filament theory?

theory states that muscle contraction occurs when myosin heads pull actin filaments toward the center of the sarcomere, shortening it.

What happens when a sarcomere shortens

The muscle contracts as the myofibrils and muscle fibers shorten due to the sliding of actin and myosin filaments.

What gives muscle cells their striated appearance?

The repeating sarcomere units within myofibrils create

What is titin and its role in muscle contraction?

an elastic protein that helps sarcomeres return to their resting length after stretching.