if a muscle cell receives a second stimulus while it is contracting will it respond to the second stimulus.explain
Yes, it will. See
http://www.cliffsnotes.com/study_guide/Muscle-Contraction.topicArticleId-22032,articleId-21923.html
To understand whether a muscle cell will respond to a second stimulus while it is contracting, let's first understand the basis of muscle contraction.
Muscle cells contract when they receive an electrical signal, called an action potential, from a nerve cell. This signal triggers the release of calcium ions within the muscle cell, which enables the interaction of proteins and leads to muscle contraction. Once the contraction is initiated, the muscle cell continues to contract until the calcium ions are removed and a relaxation signal is sent.
Now, coming to your question, if a muscle cell receives a second stimulus while it is already contracting, it will depend on the timing of the second stimulus.
If the second stimulus comes after the muscle cell has already relaxed and returned to its resting state, then the cell is likely to respond to the second stimulus by initiating another contraction. This is because the muscle cell is again stimulated, and the whole process of protein interaction leading to contraction will restart.
However, if the second stimulus occurs during the ongoing contraction, it is unlikely to elicit a response. This is because once the muscle cell is contracted, it goes through a refractory period where it becomes temporarily unresponsive to additional stimuli. During this period, the muscle cell is busy with contraction and cannot be stimulated again until it has completed the relaxation phase.
In summary, if a muscle cell receives a second stimulus while it is contracting, it will generally respond to the second stimulus only if the first contraction has already finished. If the muscle cell is still in the middle of a contraction, it will not respond until it has completed the relaxation phase and returned to its resting state.