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Myelin (/ ˈ m aɪ. ə l ɪ n / MY-ə-lin) is a lipid-rich material that surrounds nerve cell axons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. [1] [2] The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However ...
A typical fat cell is 0.1 mm in diameter [2] with some being twice that size, and others half that size. However, these numerical estimates of fat cell size depend largely on the measurement method and the location of the adipose tissue. [2] The fat stored is in a semi-liquid state, and is composed primarily of triglycerides, and cholesteryl ester.
Electrical impulses carried by the sympathetic nervous system are converted to a chemical response in the adrenal gland. Chromaffin cells contained in the adrenal medulla act as postganglionic nerve fibers that release this chemical response into the blood as a circulating messenger. The sympathoadrenal system can activate and discharge ...
Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. [ 1 ] [ 2 ] It also contains the stromal vascular fraction ( SVF ) of cells including preadipocytes , fibroblasts , vascular endothelial cells and a variety of immune cells such as adipose tissue macrophages .
Due to their hydrophobic nature, lipids and lipid digestive derivatives must be transported in the globular form within the cell, blood, and tissue spaces. The formation of a fat globule starts within the membrane bilayer of the endoplasmic reticulum. It starts as a bud and detaches from the ER membrane to join other droplets.
White matter is the tissue through which messages pass between different areas of grey matter within the central nervous system. The white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons). This myelin is found in almost all long nerve fibers, and acts as an electrical insulation.
As an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon. In response to a signal from another neuron, sodium- (Na +) and potassium- (K +)–gated ion channels open and close as the membrane reaches its threshold potential.
(b) A functional electrical stimulation system injects electrical current into the cell. (c) The intact but dormant axon receives the stimulus and propagates an action potential to (d) the neuromuscular junction. (e) The corresponding muscle fibers contract and generate (f) muscle force. (g) A train of negative pulses is produced.