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The proof of concept of BOLD-contrast imaging was provided by Seiji Ogawa and Colleagues in 1990, following an experiment which demonstrated that an in vivo change of blood oxygenation could be detected with MRI. [6] In Ogawa's experiments, blood-oxygenation-level–dependent imaging of rodent brain slice contrast in different components of the ...
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 actin ( thin filaments ) during muscle contraction, while the two groups of filaments ...
The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. [2] [3] When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a ...
Signal enhancement by extravascular water protons, or SEEP, is a contrast mechanism for functional magnetic resonance imaging (fMRI), which is an alternative to the more commonly employed BOLD (blood-oxygen-level dependent) contrast. This mechanism for image contrast changes corresponding to changes in neuronal activity was first proposed by Dr ...
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 stretch reflex operates as a feedback mechanism to control muscle length by causing muscle contraction. In contrast, the tendon reflex operates as a negative feedback mechanism to control muscle tension. Although the tendon reflex is less sensitive than the stretch reflex, it can override the stretch reflex when tension is great, for ...
Cardiac muscle cells are joined to neighboring cells by intercalated discs, and when joined in a visible unit they are described as a cardiac muscle fiber. [8] Smooth muscle cells control involuntary movements such as the peristalsis contractions in the esophagus and stomach. Smooth muscle has no myofibrils or sarcomeres and is therefore non ...
A study of the developing leg muscle in a 12-day chick embryo using electron microscopy proposes a mechanism for the development of myofibrils. Developing muscle cells contain thick (myosin) filaments that are 160–170 Å in diameter and thin (actin)filaments that are 60–70 Å in diameter. Young myofibres contain a 7:1 ratio of thin to thick ...