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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]
In physiology, medicine, and anatomy, muscle tone (residual muscle tension or tonus) is the continuous and passive partial contraction of the muscles, or the muscle's resistance to passive stretch during resting state. [1] [2] It helps to maintain posture and declines during REM sleep. [3]
An impulse from a nerve cell causes calcium release and brings about a single, short muscle contraction called a muscle twitch. If there is a problem at the neuromuscular junction, a very prolonged contraction may occur, such as the muscle contractions that result from tetanus. Also, a loss of function at the junction can produce paralysis. [5]
Uterine muscle contractions are induced via a G-protein pathway stemming from the oxytocin receptor (OXTR), the binding and activation site of oxytocin. [7] When oxytocin binds to its associated receptors in the uterus, a cascade is initiated that results in an increase in calcium and subsequently an increase in muscle contractions.
A cramp is a sudden, involuntary, painful skeletal muscle contraction [1] [2] or overshortening associated with electrical activity; [3] while generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the affected muscle.
[1] [3] One muscle may be normal while the other is atrophic or hypertrophic; alternately, one muscle may be hypertrophic while the other is atrophic. [3] A decrease in muscle tone leads to continuous disuse and eventually muscular atrophy. The constant contraction of the agonist muscle with minimal resistance can result in a contracture.
I set a goal to transform 50 percent of my body weight into muscle within a year. So, I took Orangetheory circuit training classes three times a week, working on both strength training and cardio.
The perineum muscles play roles in urination in both sexes, ejaculation in men, and vaginal contraction in women. [1] Pelvic floor dysfunction is a term used for a variety of disorders that occur when pelvic floor muscles and ligaments are impaired. The condition affects up to 50 percent of women who have given birth. [2]