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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]
See media help. The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. [ 1] It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, called systole. [ 1]
Sliding filament theory: A sarcomere in relaxed (above) and contracted (below) positions. The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement. [ 1] According to the sliding filament theory, the myosin ( thick filaments) of muscle fibers slide past the ...
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.
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in controlling hemorrhage and reducing acute blood loss.
The cardiac conduction system ( CCS, also called the electrical conduction system of the heart) [ 1] transmits the signals generated by the sinoatrial node – the heart 's pacemaker, to cause the heart muscle to contract, and pump blood through the body's circulatory system. The pacemaking signal travels through the right atrium to the ...
Neuromuscular junction. A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [ 1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction . Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
Hemostasis. In biology, hemostasis or haemostasis is a process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel (the opposite of hemostasis is hemorrhage ). It is the first stage of wound healing. Hemostasis involves three major steps: vasoconstriction.