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.
An arrhythmia (also called dysrhythmia) refers to what is usually an irregular heartbeat. The heart rate can be fast, slow, or irregular, taking into consideration age and activity. For example, a newborn's heart beats much faster than a 5-year-old child's heart. A fast heart rate is called tachycardia. A slow heart rate is called bradycardia. Some irregular heartbeats are normal: Sinus arrhythmia is the normal variation in heart rate that accompanies breathing in and out.