The sheath of fatty tissue composed of 70-80% lipid and 20-30% protein, derived from glial cells, that wraps around the axons of neurons in the central and peripheral nervous system, whose purpose is to increase transmission speed and reliability. The combined length of myelinated nerve fibers in the adult brain has been estimated to achieve …
Category Archives: Uncategorized
Mutual gaze
The simultaneous gaze of partnerstoward each other, which may or may not involve direct eye contact. It can serve a number of different functions:as means of communicating intimacy or a request for help, as well as aggressionand the intention to be dominant. Thenthere are distinctive cultural differences in how mutual gaze is deployed insocial situations. …
Mutation (biology)
A term originally devised by Hugo M. de Vries (1848-1935) in 1901, it refers to a random alteration in the arrangement or amount of genetic material in a cell that may cause it and all cells derived from it to differ in structure and function. An organism affected by a mutation is called a mutant. …
Mutation (speech)
See Adolescent voice change.
Mutagens
Broadly speaking, any substance, natural or man-made, that results in a mutation that alter the sequence or structure of DNA. Radiation, in the form of x-rays, was the first mutagen to be identified in 1927 by Hermann J. Muller (1890-1967) in fruit flies. Nitrogen mustard (the main component of mustard gas) was then identified …
Mutant
Usually an organism phenotypically affected in one or more characteristics by a mutation in a particular gene or chromosome. A mutant is not the same as an organism with a developmental abnormality, the latter arising during morphogenesis. Furthermore, a mutant may prove to be lethal in one condition, but not under another. …
Musculoskeletal system
In the human, the complex of about 800 muscles, 200 bones, more than 100 joints, and a host of ligaments and tendons. The ligaments connect and constrain two or more bones or cartilages at a moveable joint. The inelastic tendons connect muscles with moveable structures such as a bone and ensure that the force exerted …
Muscle tone (or power)
The degree of activation or tension in skeletal (striated) muscle. Sometimes referred to active muscle power, it is the product of force and velocity generated by a muscle (the muscle model of Archibald V. Hill (1886-1977, also referred to Hill’s equation for muscle tension-velocitycurve essential addresses this relationship). Also referred to as residual muscle tension, …
Muscle wasting in the right arm, together with contractures in the fingers, as a consequence of denervation. See Action potential, Fasciculation, Fibrillation, Motor unit, Muscle tone (or power), Peripheral nervous system, Reflex, Synapse
asting in the right arm, together with contractors in the fingers, as a consequence of denervation. See Action potential, Fasciculation, Fibrillation, Motor unit, Muscle tone (or power), Peripheral nervous system, Reflex, Synapse
Muscle spindle
A specialized sensory mechanoreceptor of up to 20 muscle fibers with a wrapped neuritis that is stretch sensitive, embedded in muscle, and relaying information regarding muscle length and change of length (i.e., stretch). The muscle fibers within the spindle are referred to as intrafusal muscle fibers, while those that move the bones are extrafusal muscle …