Muscle

Question 1

sarcomere

Answer 1

• composed of overlapping filaments of actin and myosin as well as structural and binding proteins (eg, titin, α-actinin).
• single sarcomere is defined as the distance between two Z lines.
• Thin (actin) filaments are bound to structural proteins at the Z line.
• The unbound ends of the actin filaments project into the middle of the sarcomere, where they interact with thick (myosin) filaments during muscle contraction.
• Myosin and actin filaments overlap at the segment of the sarcomere between the H and I bands.

Question 2

A band

Answer 2

• myosin filaments in the sarcomere
• In this region, there are myosin filaments overlapped with actin filaments as well as non-overlapped myosin filaments.
• always remains the same length during muscle contraction.

Question 3

M line

Answer 3

lies at the center of the A band and is where myosin filaments anchor to structural elements in the center of the sarcomere.

Question 4

I band and H band

Answer 4

• I band is the region of the sarcomere in which actin does not overlap with myosin
• H band is the region in which myosin does not overlap with actin.
• During muscle contraction, both H and I bands decrease in length.