Which of these statements describes why you are able to repeatedly contract and relax your muscles of respiration, allowing you to breathe in and breathe out

Question

Quizplus · Accepted Answer

When a muscle cell is stimulated, calcium ions are released from the sarcoplasmic reticulum into the cytoplasm, allowing the myosin heads to bind to actin and cause muscle contraction. When the stimulation stops, there is no longer a local action potential, and calcium ions are actively transported back into the lateral sacs of the sarcoplasmic reticulum. This allows the myosin heads to release from actin and the muscle to relax. This process can repeat as needed, allowing for repeated contractions and relaxations of the muscles of respiration. Option A is incorrect because as soon as all the calcium ions are used up, muscle relaxation occurs, regardless of whether the lateral sacs of the sarcoplasmic reticulum are empty or not. Option B is incorrect because acetylcholinesterase breaks down acetylcholine to stop muscle stimulation, but it does not maintain the action of acetylcholine. Option D is incorrect because ATP is required for muscle contraction, not the other way around.

Which of These Statements Describes Why You Are Able to Repeatedly