Vertebrate striated muscle contraction is controlled (regulated) by the action of the proteins troponin and tropomyosin on the actin filaments. Nervous stimulation causes a depolarisation of the muscle membrane (sarcolemma) which triggers the release of calcium ions from the sarcoplasmic reticulum.
n. 1  Abnormally fast or deep respiration, which results in the loss of carbon dioxide from the blood, thereby causing a fall in blood pressure, tingling of the extremities, and sometimes fainting.
Labored breathing is distinguished from shortness of breath or dyspnea, which is the sensation of respiratory distress rather than a physical presentation. Still, many simply define dyspnea as difficulty in breathing without further specification, which may confuse it with e.g. labored breathing or tachypnea (rapid breathing). Labored breathing has occasionally been included in the definition of dyspnea as well.