Osmosis and Membrane Process Flashcards
Osmolality
measurement of solute concentration in fluid
High osmolality = high solute concentration
Range of serum osmolality varies in species
Increased osmolality of blood triggers
Desire to drink
Release of antidiuretic hormone
Decreased osmolality of blood
Inhibits desire to drink
Inhibits release of antidiuretic hormone
Serum osmolality tests may be ordered to asses
Hydration status
High osmolality if dehydrated
Hyperglycaemia
Functioning of hypothalamus
Poisoning by ethylene glycol
Antifreeze poisoning
Series of oxidation reactions in liver and kidneys metabolize ethylene glycol
Toxic metabolites cause metabolic acidocis and nephrotoxosis
Oxalate is cytotoxic
Isotonic fluid therapy
Osmolality comparable to that of normal blood
extracellular fluid has same concentration of dissolved substances as intracellular fluid
Example : 0.9% NaCl (normal saline)
Hypertonic fluids
Osmolality is greater than that of blood
Extracellular fluid has higher concentration of solutes than the cytoplasm
Water leaves the cell, causing the cell to shrink and become shrivelled
Hypotonic fluids
Osmolality is less than that of blood
Higher concentration of solutes in the cytoplasm than in the extracellular fluid
Water flows into the cell and causes it to swell and possibly to break
Electrolytes are
Small and most abundant solute in body
Greatest ability to cause fluid shifts between compartments
Concentration in body fluids is expressed as milliequivalents per litre
Osmolality and water
Any change in the concentration of any solute incurs movement of water from one compartment to another
Water crosses cell membrane
or
Water crosses capillary walls
Edema is a
Abnormal, excess accumulation of fluid in tissue
Common sign of abnormal movement of fluid from vascular space into interstitial space
Pulmonary edema
Fluid leaking into lungs
Cutaneous edema
Leaking into skin
Crystalloid fluid
Composed of water rich with electrolytes
hypotonic or isotonic
Solutes are small
Able to cross the vascular wall
Good for rehydrating extravascular spaces and correcting acid/base imbalances
Colloid fluid
Heavy molecules suspended in isotonic crystalloid
Solutes too large to cross vascular wall
“hold” fluid in intravascular space
Passive process
Requires no energy
Active process
Require energy to be used
Three types of membrane permeability
Freely permeable
Impermeable
Selectively permeable
Diffusion
Kinetic movement of molecules from higher to lower concentration
Concentration gradient
Factors determining whether molecule may pass through cell membrane:
Molecular size
Lipid solubility
Molecular charge
Channels allow certain ions to pass through
Facilitated diffusion
Selective carrier proteins assist in movement of molecules from higher to lower concentration
Process limited by the number of carrier proteins available
Passive processes
Requires no energy from cell
Example
Glucose moves into muscle and fat cells
Osmosis
Passive movement of water through a semipermeable membrane from area of low solute concentration to higher solute concentration
Example
water moves from stomach into bloodstream
Concentration balance = equilibrium
Osmotic pressure – force of water moving from one side of membrane to the other because of differences in solute concentration
Normally extracellular fluid has the same concentration of dissolved solutes as intracellular fluid
Oncotic pressure
Difference between:
osmotic pressure of blood
osmotic pressure of interstitial fluid or lymph
Important force in maintaining fluid balance
Filtration
Based on a pressure gradient
Liquids may be pushed through membrane if pressure on one side is greater than that on the other side
Hydrostatic pressure – caused by beating heart
Example: filtration of blood in kidneys
Dialysis
Example of use of basic scientific principles to help resolve a clinical problem
Dialysis is a type of diffusion used most commonly in animals with acute kidney failure
To remove toxins the animal’s blood is circulated through an artificial kidney with semipermeable filaments
An electrolyte solution called dialysate is driven through the artificial kidney in the opposite direction of the blood
Small solutes move out of the blood into the dialysate
Move from higher solute concentration to a lower one
Reasons why molecules can’t enter cells by passive root
Not lipid soluble
Too large to pass through a membrane pore
Going against the concentration gradient
Active transport 2 types
Synport system
Antiport system
Cytosis two types
Endocytosis
Exocytosis
All cells actively carry these electrolytes
Na+
K+
Ca2+
Mg2+
Symport system
All substances are moved in the same direction
Antiport system
some substances moved in one direction
others moved in the opposite direction
Cytosis
Mechanism for bringing nutrients into the cell and ejecting waste
Endocytosis
Transports large particles or liquids into the cell by engulfing them
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Phagocytosis
Cells engulf solid material
Vesicle formed called a phagosome
Macrophage – debris, dead cells, invaders
Phagosome fuses with lysosomes for digestion
White blood cell – bacteria, viruses
Macrophages and WBC can move by ameboid motion
Pseudopodia
Pinocytosis
Cells engulf liquid material
Involves only minute infolding of plasma membrane
Important in cells lining small intestine and renal tubules
Receptor mediated endocytosis
Very specific process
Occurs in cells with specific proteins in their plasma membranes
Ligands bind to specific receptors
Vesicle is formed = coated pit
Insulin binding to insulin receptors
Exocytosis
Cells export intracellular substances into the extracellular space
Substances packaged in vesicles by ER and Golgi body
Vesicles move through cytoplasm to cell surface, fuse with plasma membrane, and release contents into extracellular fluid
Excretion – waste products
Secretion – manufactured molecules
Neurons release packages of acetylcholine
Endothelial cells lining trachea secrete mucus
Mass cells release thousands of granules of histamine during allergic reactions
Principle ions of membrane potential
K+ and Na+
Normally more what inside cell
K+
What is more concentrated outside of the cell
Na+
Every cycle of active trasnport
3 Na+ exit for every 2 K+ entering
changes that can alter resting membrane potential
Environmental tonicity
Osmotic pressure
Temperature
Contact with neighboring cells
Changes that alter resting membrane potential can alter the flow of
metabolites
Alters behavior of some structural and enzymatic proteins
Example = muscle cells – contract due to changes in membrane potential
Treatment for anti freeze poisoning
IV fluid therapy to restore hydration, correct electroyte imbalances, promote kidney function and excretion of ethylene glycol
Sodium bicarbonate often included to counteract excessive acid levels
Solution of diluted ethanol often given as treatment
Works by competing with ethylene glycol for binding site on the enzyme that converts ethylene glycol into toxic metabolites
Ethylene glycol can be eliminated from the body unchanged
Elements in electrolytes
Calcium
Chloride
Magnesium
Phosphorus
Potassium
Sodium
What happens if oncotic pressure is disturbed
If levels of protein in plasma decrease, balance is disrupted
Subcutaneous edema
Fluid leaks into skin
Ascites
Fluid leaks into abdomen
Factors determining whether molecules may pass through the cell membrane
Molecular size
Lipid solubility
Molecular charge
Channels allow certain ions to pass through
