lecture 3 - golfetti

Compartments Major body cavities Cranial cavity Pleural sac + pericardial sac = thoracic cavity Diaphragm Abdominal cavity + pelvic cavity = abdominopelvic cavity fluid compartments intracellular fluid (icf) or cytosol extracellular fluid (ecf): between cells. Plasma intracellular compartments membranous organelles Cytoplasm cytosol: semigelatinous intracellular fluid medium for suspension of organelles ions, nutrients, enzymes, wastes, etc. inclusions organelles perform specialized tasks there are membranous and non-membranous organelles Membranes allow specific body functions to be confined to a specific location the cell membrane separates the cell from its surroundings. This allows cellular specialization membranes within cells separate some of the cellular organelles. This allows specialization within the cell continuity of membranes between adjoining cells (tight junctions) can separate two extracellular compartments. These separations play a critical role in organ function Cell membrane the plasma membrane is a lipid bilayer with the hydrophobic fatty acid chain pointing toward the center and the hydrophilic head groups oriented toward the extracellular space and cytoplasm Membrane lipids major lipids of membrane: phospholipids or phosphoglycerides phospholipids: amphiphatic molecules charged hydrophilic head two non polar hydrophobic fatty chains this arrange is crucial for formation of bilayer: hydrophobic fatty acyl chains forming the core hydrophilic exposed to surface Membrane composition: lipids and proteins membranes proteins: classified as integral membrane protein ? some bilayer ? also called transmembrane lipid anchored membrane protein peripheral proteins Cytoskeleton strength support shape transport cell to cell links protein fibers: microfilaments, intermediate, microtubules cell-to-cell junctions: desmosomes, tight junctions, gap junctions, etc utilize CAMs (cell adhering membranes) tight junctions anchoring junctions (desmosomes) gap junctions tight junctions complete barrier (brick wall) fusion of adjacent cell membranes via claudin and acculdin found in blood-brain barrier, GI tract, kidneys Anchoring junctions cell to cell or cell to connective tissue matrix anchoring junctions (CAMs: cadherins) desmosomes adherens junctions cell matrix attachments (CAMs: integrins) hemidesmosomes spot desmosomes or focal adhesions gap junctions cylindrical proteins from channels can open and close electrical synapses rapid transfer of signals in cardiac and smooth muscle mechanism of membrane transport small solutes can cross membranes either by simple diffusion or by a carrier mediated process. Whenever a carrier is involved, the movement is called ?transport? simple diffusion occurs by molecular dispersion. Diffusion occurs across the lipid membrane itself, through proteins, through ion channels and pores diffusion across the lipid membrane: smaller and less polar molecules are more lipid soluble and can diffuse directly through lipid membranes. Larger molecules and ions cannot easily cross the membrane itself. The relevant size depends in part on the sphere of hydration diffusion is the net movement of substances from an area of higher concentration to an area of lower concentration. This movement occurs as a result of the random and constant motion characteristic of all molecules, (atoms or ions) and is independent from the motion of other molecules water channels: diffusion of solutes through channel proteins in the plasma membrane. Water can pass freely through the plasma membrane without the aid of specialized proteins (though facilitated by aquaporins) solute carriers (facilitated diffusion) membrane transporters com more than 40 different types identified. Diffusion with a protein carrier and large polar molecules (glucose). There are 3 major groups: (1) function groups (Uniporters ? GLUT 2) single molecule across the membrane. (2) symporters: couple movements of two molecules (3) antiporters: couple transport across membrane. Molecules and ions are transported in opposite directions active transport is the movement of particles from an area of lower concentration to an area of higher concentration ? against the concentration gradient powered by cell energy (ATP) solute ?pumps? : Na+/K+ pump. Creates gradients, creates polarity Osmosis is the diffusion of water molecules across a selectively permeable membrane. When water moves into a body by osmosis, hydrostatic pressure or osmotic pressure may build up inside the body osmotic pressure is determined by the number of molecules in that solution. It is not dependable on factors as size of the molecules, mass, or chemical nature osmotic pressure is calculated by van?t Hoff?s Law and is measured in atm Equation 1-7: pi = nCRT N = number of dissociable particles per molecule C = total solute concentration R = gas constant T = temperature in K Osmolarity refers to the osmotic pressure generated by the dissolved solute molecules in 1 L of solvent (mOsm/L) Osmolality refers to numbers of molecules dissolved in 1 kg of solvent (Osm/kg H2O). however because of dilute nature of physiological solutions, when water is the solvent osmolality is expressed as mmol/kg H2O Osmolarity and osmolality reflect the number of moles of solute particles in a solution. Solution contained a 140 mmoles NaCl per 1 kg water, its molarity is equal to 140 mmol/kg. osmolality would be 280 mOsm/kg because we would count the free-floating ions Na+ and Cl- separately Volume is temperature dependent: as T increases, V increases Equation 1-8: Osmolarity = concentration x number of dissociable particles Tonicity ? hypertonic, hypotonic, isotonic related to the effect of the solution on the volume of a cell isotonic solutions do not change the volume of a cell hypotonic solutions cause a cell to swell hypertonic solutions cause a cell to shrink takes into consideration the ability of molecules in solution to cross membranes the osmotic concentration of solutions administered clinically is generally compared to the osmotic concentration of plasma. The osmotic concentration depends on the gram molecular weight of the solute and its dissociability