Tonicity
Tonicity ( Greek τόνος tónos , tension, tension '), also referred to as "effective osmolarity ", is a qualitative measure of the difference in osmotic pressure between two solutions based on a cell type (with its respective semi-permeability ). In contrast to osmolarity, tonicity has no unit .
meaning
The term tonicity is often used in biological medicine and biochemistry to describe the behavior of cells (the cytoplasm is "solution I") that are surrounded by a liquid ("solution II") through their cell membrane ("semipermeable membrane"). are separated. Since the tonicity is described as the difference in osmotic pressure, it is only caused by dissolved substances which - if an equilibrium is established - can not cross the membrane . Dissolved substances that can move freely through the membrane have no effect on tonicity.
Typical systems in which the term tonicity plays a role and is used are e.g. B. blood cells in serum , prokaryotes in fermentation medium , eukaryotic animal, plant or fungal cells in a purely chemically composed buffer or a complex composed nutrient medium and artificial membrane vesicles ( liposomes ) - z. B. in reconstitution experiments - in physiological buffers.
Terms
The tonicity is named in different terms: hypertonic, isotonic and hypotonic.
Hypertonicity
The term hypertonic ( syn. Hypertonic ; Greek ὑπέρ , over 'and tónos , tension, tension') means in biochemistry and biology:
- A solution has a higher osmotic pressure than a comparison medium.
- A cell (more precisely: the cytoplasm , the medium inside a cell) has a higher osmotic pressure than the medium surrounding it (the fluid outside the cell).
Isotonicity
The term isotonic (syn. Isotonic ; from the Greek ἴσος ísos 'equal' and τόνος tónos 'tension, tension') means in biochemistry and biology:
- A solution has the same osmotic pressure as a comparison medium.
- A cell (more precisely: the cytoplasm, the medium inside a cell) has the same osmotic pressure as the medium surrounding it (the fluid outside the cell).
In medicine, isotonic means:
- A solution has the same osmotic pressure as human blood.
Hypotonicity
The term hypotonic (syn. Hypotonic ; Greek ὑπό hypo 'under' and τόνος tónos 'tension, tension') means in biochemistry and biology:
- A solution has a lower osmotic pressure than a comparison medium.
- A cell (more precisely: the cytoplasm, the medium within a cell) has a lower osmotic pressure than the medium surrounding it (the fluid outside the cell).
Other meanings in medicine
Hypertension, hypertonic, hypertonic
- Technical term for high blood pressure
- Technical term for the tension of the muscles, d. H. the muscle tone is unphysiologically increased .
Isotonic
- Technical term: The muscle shortens without any change in force ("tensioned").
Hypotension, hypotonic
- Technical term for low blood pressure
- Technical term for the tension of the muscles, d. H. the muscle tone is unphysiologically low.
Web links
literature
- Dee U. Silverthorn: Physiologie , 4th updated edition, Pearson Studium, Munich et al. 2009, ISBN 978-3-8273-7333-5 , pp. 236-238 .
Individual evidence
- ^ Hans Walter Striebel: The operative intensive care medicine. Safety in clinical practice. Schattauer, Stuttgart et al. 2008, ISBN 978-3-7945-2480-8 , p. 123 .
- ↑ Gary Gill: Cytopreparation. Springer Science & Business Media, 2012, ISBN 978-1-461-44933-1 , p. 37.