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The skeletal muscle pump. The skeletal muscle pump or musculovenous pump is a collection of skeletal muscles that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart, [1] but may also play a role in arterial blood flow.
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
This protein is found as a pentamer and is a major substrate for the cAMP-dependent protein kinase in cardiac muscle. In the unphosphorylated state, phospholamban is an inhibitor of cardiac muscle sarcoplasmic reticulum Ca 2+ -ATPase ( SERCA2 ) [ 7 ] which transports calcium from cytosol into the sarcoplasmic reticulum .
Cardiac excitation-contraction coupling (Cardiac EC coupling) describes the series of events, from the production of an electrical impulse (action potential) to the contraction of muscles in the heart. [1] This process is of vital importance as it allows for the heart to beat in a controlled manner, without the need for conscious input.
Thickness is defined as the area between the aponeuroses of the muscle. A low gear ratio occurs when the contraction velocity of the whole muscle and individual fibers is approximately the same, resulting in a gear ratio of 1. Conditions resulting in a low gear ratio include high force and low velocity contraction of the whole muscle.
This shape change causes the cytosolic side of the pump to open, allowing the two Ca 2+ to enter. The cytosolic side of the pump then closes and the sarcoplasmic reticulum side opens, releasing the Ca 2+ into the SR. [6] A protein found in cardiac muscle, called phospholamban (PLB) has been shown to prevent SERCA from working. It does this by ...
The absolute refractory period for cardiac contractile muscle lasts approximately 200 ms, and the relative refractory period lasts approximately 50 ms, for a total of 250 ms. This extended period is critical, since the heart muscle must contract to pump blood effectively and the contraction must follow the electrical events.
There are several mechanisms directly linked to the terminal cisternae which facilitate excitation-contraction coupling. When excitation of the membrane arrives at the T-tubule nearest the muscle fiber, a dihydropyridine channel (DHP channel) is activated. [2] This is similar to a voltage-gated calcium channel, but is not actually an ionotropic ...