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19 Cards in this Set
- Front
- Back
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What is osmosis?
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Osmosis is the movement of solvent from the area of high solvent activity (low solute concentration) to an area of low solvent activity (high solute concentration) through a semipermiable membrane.
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The pressure of particles of a solute is proportional to what?
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The concentration of molecules bombarding the walls of its container - concentration of active particles.
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What is tonicity?
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Tonicity is the osmotic pressure produced by a solution across a membrane separating it from plasma. The influence of the osmolarity on the volume of cells.
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What is osmolyte?
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Anything in solution that will affect osmosis (e.g. Na+, Cl-, NaCl). I.e. molecules in dissolved form - some of the molecules may therefore still be in whole form as they do not dissociate in solution, like glucose. If 100% dissociated, the osmolarity of CaCl2 would be three times the molarity.
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What are controlled variables?
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Physiological parameters that need to remain at a constant level in order for the body to operate optimally. For example, body (core) temperature, oxygen saturation, glucose levels in the blood.
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What happens if the controlled variable deviates from the set-point?
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Effector mechanisms of the body, such as pulse rate, respiratory rate and skin temperature are altered to restore homeostasis.
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Name some of the properties of the internal environment that are regulated by homeostasis.
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- Blood pH;
- Core temperature; - Blood glucose concentration; - Arterial blood oxygen saturation. All of these are controlled variables. |
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What is the processor part in the negative feedback mechanism in the process of maintaining homeostasis?
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Integrating centre. The information about each variable is integrated and compared with the set-point. If the variable has deviated from the set-point the processor activates mechanisms that restore the variable back to set point.
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What are effector mechanisms?
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Mechanisms that are capable of producing a change in a particular variable in order to maintain in homeostasis.
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What are the main sources of osmotic gradient across cell membranes?
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The concentrations of Na and Cl ions in the ECF and K and organic metabolites in ICF.
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What are osmolyte particles?
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Dissolved particles that determine the osmotic pressure of the solution.
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Fill in the blanks:
When a ... such as glucose is dissolved in a ... such as water the product is called a ... . The concentration can be expressed in terms of ... i.e. the number of ... of ... per unit volume of ... . A ... is defined as the amount of a substance that contains the same number of particles as would be found in 12 g of the ... isotope i.e. Avogadro number. |
When a solute such as glucose is dissolved in a solvent such as water the product is called a solution. The concentration can be expressed in terms of molarity i.e. the number of moles of solute per unit volume of solution . A mole is defined as the amount of a substance that contains the same number of particles as would be found in 12 g of the Carbon - 12 isotope i.e. Avogadro number.
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Express 0.9% NaCl solution in weight per volume.
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0.9 g of NaCl per 100ml of water. Or 9g per litre.
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The higher the osmolarity the ... the activity of the solvent.
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lower
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Dissociation?
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A general process in which ionic compounds (complexes or salts, e.g. NaCl)
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Two solutions with the same effective osmotic pressures are called ..., but solutions with the same osmolarity is called ... .
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Two solutions with the same effective osmotic pressures are called isotonic, but solutions with the same osmolarity is called isosmotic.
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Reflection coefficient is different for different solutes. How does it affect the osmotic pressures?
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Lower the reflection coefficient (0 - total permeability, 1 - total impermeability), lower the effective osmotic pressure. So if uria has a RC of 0.024, but NaCl has 0.3, biological membrane is greater permeability to urea, than salt, so the effective osmotic pressure of a urea solution is lower than that of a salt solution of the same osmolarity.
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What is haematocrit or packed cell volume?
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The ratio of the volume of the cells to the total volume (i.e. both plasma and cells).
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What is haemolysed blood?
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The blood cells have burst abd the haemoglobin has dispersed throughout the fluid.
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