They are removed from circulation by macrophages (also known as white blood cells). These macrophages are produced by stem cells in bone marrow.
<span>Drowsiness. Nausea. Dry mouth. Insomnia. Diarrhea. <span>Nervousness, agitation or restlessness.</span></span>
Answer: Refractory period of the cardiac action potential
Explanation:
Unlike the skeletal muscle which can be reactivated before it reaches a contraction, cardiac muscle must wait before it is almost completely relaxed to be activated again (because of its long refractory period), so one cannot make an increase in strength of contraction with a high frequency of stimulations.