Physiology Ch. 6

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rleighn25
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99225
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Physiology Ch. 6
Updated:
2011-08-31 18:43:51
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physiology cells
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Interactions between cells and the extracellular environment
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  1. Extracellular environment
    Located outside the cell
  2. Body Fluids
    • 33% of the body's water located in extracellular environment
    • of this 20% is the blood plasma, 80% is the interstitial fluid
  3. Extracellular matrix
    The cells of the organs are suspended with the extracellular material (matrix) of connective tissues that contain protein fibers of collagen and elastin
  4. Transport across the plasma membrane
    Plasma (cell )membrane is semi-permeable or selectively permeable
  5. 2 Categories for transport based upon mediation
    • Carrier-mediated
    • Non carrier-mediated
  6. 2 categories for transport based upon energy requirements
    • Passive transport
    • Active transport
  7. Carrier-mediated transport
    Transport of molecules across cell membrane that is mediated by protein carriers within the membrane
  8. Active transport
    • Active net movement against (up) a concentration gradient
    • Requires metabolic energy (ie: from lower to higher concentration)
  9. Types of Active transport
    • Primary active transport
    • Sodium-potassium pump
    • Secondary active transport
  10. Bulk transport
    Use of exocytosis and endocytosis
  11. Diffusion
    • Random molecular motion
    • Net diffusion of an ion/molecule always occurs in the direction of lower concentration
  12. Rate of diffusion- the greater the concentration the faster the diffusion
    • Magnitude of concentration difference across membrane
    • Permeability of the membrane to the molecule/substance
    • Temperature of the solution
    • Surface area of the membrane
    • Presence of ion channels/gates (ex: Na+, K+)
  13. Facilitated diffusion
    Passive net movement down a concentration gradient (high to low) ex: transport of glucose from the blood across plasma membrane
  14. Osmosis
    The net diffusion of solvent (water) across a membrane (high to low)
  15. 2 requirements for Osmosis
    • Concentration difference present on the 2 sides of a selectively permeable membrane
    • Membrane must be relatively impermeable to the solute
  16. Osmotic pressure
    Amount of pressure/force that would be required to prevent osmosis from occuring
  17. Membrane Potential
    • As a result of the permeability properties across the cell membrane a membrane potential can be present
    • The membrane potential is the difference in charge across the cell membrane (outside vs inside)
    • Unequal distribution of charges between the inside and outside of the cell, causes each cell to act as a tiny battery
  18. Inside membrane potential
    • Cellular proteins and phosphate groups are negatively charged
    • K+ is positively charged
  19. Outside membrane potential
    • Na+ is positively charged
    • Cl is negatively charged
  20. Equilibrium Potential
    • The membrane potential that would exactly balance the diffusion gradient and prevent the net movement of a particular ion is known as the equilibrium potential
    • Magnitude of difference in charge on the 2 sides of the membrane
  21. Equilibrium potential for K+
    • -90mV
    • No k+ movement within or outside the cell
  22. Equilibrium potential for Na+
    • 60 mV
    • no movement
  23. Resting Membrane Potential (RMP)- The membrane potential of a resting cell
    • Resting membrane potential is less than equilibrium potential (Ek) because some Na+ can also enter the cell
    • The slow rate of Na+ efflux is accompanied by slow rate of K+ influx
  24. Resting Membrane Potential depends upon 2 factors
    • Ratio of the concentrations of each ion on the 2 sides of the plasma membrane
    • Specific permeability of membrane to each different ion
  25. RMP of most cells range from:
    -65 to -85 mV
  26. RMP of a neuron nerve cell:
    -70mV

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