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Smooth muscle differs from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling. However, smooth muscle tissue tends to demonstrate greater elasticity and function within a larger length-tension curve than striated muscle. This ability to stretch and still maintain ...
Since smooth muscle does not contain a troponin complex, as striated muscle does, this mechanism is the main pathway for regulating smooth muscle contraction. Reducing intracellular calcium concentration inactivates MLCK but does not stop smooth muscle contraction since the myosin light chain has been physically modified through phosphorylation ...
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]
Airway tone, short for airway smooth muscle tone, is the degree of sustained contractile activation of airway smooth muscle. [1] The airways have a tone baseline, and consequently a baseline level of contraction of their smooth musculature.
The α 1-adrenergic receptor has several general functions in common with the α 2-adrenergic receptor, but also has specific effects of its own. α 1-receptors primarily mediate smooth muscle contraction, but have important functions elsewhere as well. [3]
They are located in the smooth muscles of the blood vessels, as well as in the lungs. Because the M 3 receptor is G q -coupled and mediates an increase in intracellular calcium, it typically causes contraction of smooth muscle, such as that observed during bronchoconstriction and bladder voiding . [ 32 ]
The smooth muscle of the blood vessels reacts to the stretching of the muscle by opening ion channels, which cause the muscle to depolarize, leading to muscle contraction. This significantly reduces the volume of blood able to pass through the lumen, which reduces blood flow through the blood vessel.
Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with. All skeletal muscle and many smooth muscle contractions are facilitated by the neurotransmitter acetylcholine .