Rigor mortis, the stiffening of muscles after death, occurs because
- A. calcium ions disappear from the sarcoplasm
- B. ATP is no longer available to detach the myosin heads from actin
- C. the muscle proteins are denatured by the fall in body temperature
- D. acetylcholine continues to be released at the neuromuscular junction
Explanation
ATP is needed not to form a cross bridge but to break one, so when respiration stops and ATP runs out the myosin heads stay locked on actin and the muscle cannot relax. Calcium in fact leaks out of the sarcoplasmic reticulum after death and floods the sarcoplasm, which is the opposite of the first option and is what allows the bridges to form in the first place.
Related questions
The functional contractile unit of a myofibril is the
During the contraction of a skeletal muscle, which of the following does NOT change in length?
According to the sliding filament theory, a muscle shortens because
Calcium ions start muscle contraction by binding to
The neurotransmitter released at the neuromuscular junction of skeletal muscle is