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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]
The sliding filament theory is a widely accepted explanation of the mechanism that underlies muscle contraction. [6] This model shows the four main and significant steps of the sliding filament theory as well as with a detailed visual.
The endplate potential is thus responsible for setting up an action potential in the muscle fiber which triggers muscle contraction. The transmission from nerve to muscle is so rapid because each quantum of acetylcholine reaches the endplate in millimolar concentrations, high enough to combine with a receptor with a low affinity, which then ...
Reciprocally, a muscle that shortens without changing force (isotonic contraction) will show a horizontal line 'work loop'. Finally, a muscle can behave like a spring which extends linearly as a force is applied. This final case would yield a slanted straight line 'work loop' where the line slope is the spring stiffness. [12]
The stretch reflex (myotatic reflex), or more accurately "muscle stretch reflex", is a muscle contraction in response to stretching a muscle. The function of the reflex is generally thought to be maintaining the muscle at a constant length but the response is often coordinated across multiple muscles and even joints. [1]
The myosin head is the part of the thick myofilament made up of myosin that acts in muscle contraction, by sliding over thin myofilaments of actin.Myosin is the major component of the thick filaments and most myosin molecules are composed of a head, neck, and tail domain; the myosin head binds to thin filamentous actin, and uses ATP hydrolysis to generate force and "walk" along the thin filament.
The acetylcholine molecules then bind to nicotinic ion-channel receptors on the muscle cell membrane, causing the ion channels to open. Sodium ions then flow into the muscle cell, initiating a sequence of steps that finally produce muscle contraction. Factors that decrease release of acetylcholine (and thereby affecting P-type calcium channels ...
In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas , they provoke release of insulin . [ a ] Action potentials in neurons are also known as " nerve impulses " or " spikes ", and the temporal sequence of action potentials generated by a neuron is called ...