Search results
Results from the WOW.Com Content Network
An example of normal spontaneous depolarization is the constant contractions of cardiac muscle, causing the heart to beat. Usually, intentional movement of the involved muscle causes fasciculations to cease immediately, but they may return once the muscle is at rest again. Tics must also be distinguished from fasciculations.
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]
The muscle which can 'cancel' or to some degree reverse the action of the muscle. Muscle synergies are noted in parentheses when relevant. O (Occurrences) Number of times that the named muscle row occurs in a standard human body. Here it may also be denoted when a given muscles only occurs in a male or a female body.
The origin of a muscle is the bone, typically proximal, which has greater mass and is more stable during a contraction than a muscle's insertion. [14] For example, with the latissimus dorsi muscle, the origin site is the torso, and the insertion is the arm. When this muscle contracts, normally the arm moves due to having less mass than the torso.
When necessary, the maximal number of motor units in a muscle can be recruited simultaneously, producing the maximum force of contraction for that muscle, but this cannot last for very long because of the energy requirements to sustain the contraction. To prevent complete muscle fatigue, motor units are generally not all simultaneously active ...
Only skeletal and smooth muscles are part of the musculoskeletal system and only the muscles can move the body. Cardiac muscles are found in the heart and are used only to circulate blood; like the smooth muscles, these muscles are not under conscious control. Skeletal muscles are attached to bones and arranged in opposing groups around joints. [8]
A secondary cause of muscle atrophy is that denervated muscles are no longer supplied with trophic factors from the α-MNs that innervate them. Alpha motor neuron lesions also result in abnormal EMG potentials (e.g., fibrillation potentials) and fasciculations, the latter being spontaneous, involuntary muscle contractions.
The rapid influx of calcium into the cell signals for the cells to contract. When the calcium intake travels through an entire muscle, it will trigger a united muscular contraction. This process is known as excitation-contraction coupling. [2] This contraction pushes blood inside the heart and from the heart to other regions of the body.