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Tonicity. In chemical biology, tonicity is a measure of the effective osmotic pressure gradient; the water potential of two solutions separated by a partially-permeable cell membrane. Tonicity depends on the relative concentration of selective membrane-impermeable solutes across a cell membrane which determine the direction and extent of ...
In physiology, medicine, and anatomy, muscle tone ( residual muscle tension or tonus) is the continuous and passive partial contraction of the muscles, or the muscle's resistance to passive stretch during resting state. [1] [2] It helps to maintain posture and declines during REM sleep. [3] Muscle tone is regulated by the activity of the motor ...
Tonic (physiology) Tonic in physiology refers to a physiological response which is slow and may be graded. This term is typically used in opposition to a fast response. For instance, tonic muscles are contrasted by the more typical and much faster twitch muscles, while tonic sensory nerve endings are contrasted to the much faster phasic sensory ...
Vasopressin regulates the tonicity of body fluids. It is released from the posterior pituitary in response to hypertonicity and causes the kidneys to reabsorb solute-free water and return it to the circulation from the tubules of the nephron, thus returning the tonicity of the body fluids toward normal.
Osmolarity vs. tonicity Osmolarity and tonicity are related but distinct concepts. Thus, the terms ending in -osmotic (isosmotic, hyperosmotic, hypoosmotic) are not synonymous with the terms ending in -tonic (isotonic, hypertonic, hypotonic).
A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction [2] evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate. [3] [4] During this state, a motor unit has been ...
Osmotic shock Tonicity concept related to the transport of water towards the more concentrated aqueous solution ( osmotic transport ): In isotonic solutions, water flows equally into and out of the cell ( equilibrium ). In hypertonic solutions water flows out of the cell and the cell shrinks ( plasmolysis ). In hypotonic solutions, water flows into the cell and the cell swells ( turgescence ).
A red blood cell in a hypertonic solution, causing water to move out of the cell. Hemolysis or haemolysis ( / hiːˈmɒlɪsɪs / ), [1] also known by several other names, is the rupturing ( lysis) of red blood cells (erythrocytes) and the release of their contents ( cytoplasm) into surrounding fluid (e.g. blood plasma ).