remains unchanged (i.e., whether the contraction is 10% or 20%), there-
fore the length of the I band is reduced from 1.0 to 0.5 μm and makes up
for the 0.5 μm reduction in length during the muscle contraction. The
processes of skeletal muscle contraction and relaxation are shown in the
image below and in the “High Yield Facts” section, p. 22.
222 Anatomy, Histology, and Cell Biology
The Sarcomere extends from Z disc (line) to Z disc.The H band is located between
the ends of the thin (actin) filaments.The A band is defined by the the width of the
thick (myosin) filaments.The I bands are not shown completely on the figure (see
High-Yield Facts) because they are found between adjacent A bands.
125.The answer is d.(Alberts, pp 961–965. Junqueira, p 192.)There is
some small amount of production of ATP after death through anaerobic
and phosphagen pathways. However, there is insufficient ATP to induce
the detachment of the myosin heads from actin. Ca^2 +ions continue to leak
from the extracellular fluid and the sarcoplasmic reticulum (answer a),
however, the sarcoplasmic reticulum is no longer able to retrieve the Ca^2 +
ions(answer b).Tropomyosin and troponin are disengaged from the
myosin active sites (answer c).Lactic acid is produced during rigor mortis
through anaerobic pathways. The high levels of lactic acid cause deteriora-
tion of the skeletal muscle and end the state of rigor mortis(answer e).