Chapter 5

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Author:
igarett
ID:
157486
Filename:
Chapter 5
Updated:
2012-06-05 21:57:14
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Allen Physiology Cells
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Physio
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  1. Explain the concentration gradients across cells at rest.
    • Usually, the inside of a cell membrane holds a more negative charge at rest because of the high concentration of Potassium (K+) ions in comparisson to the outside.
    • There is a higher concentration of Sodium and Calcium outside the cell membrane.
  2. Describe permeability differences across cell membrane at rest.
    When a cell is at rest, most of the protien channels within the membrane are closed. However, there are occasional potassium channels that remain open, allowing K+ ions to flow freely in and out of the membrane.
  3. What is the purpose and action of Na-K ATPase pumps?
    • To restore the "normal" concentration gradient within cells
    • These pumps constantly pump 3Na+ ions out & 2K+ ions inside the cell which contributes to the general overall more negative inner charge.
  4. What is the biggest reason why the inside of the cell has a negative charge compared to the outside?
    The presence of Protien anions (Pr-) within the ICF greatly contributes to the negative inner charge.
  5. Which ion is about 10,000 times more concentrated outside the cell membrane in the ECF?
    Calcium (Ca++)
  6. Cell membranes at rest are more permeable to which ion? and by how much?
    Membranes at rest are 40x more permeable to K+ ions compared to Na+ ions, becaus they have more "open leakage channels" for potassium.
  7. Why is the Resting Membrane Potential -70mV value?
    The actual value reflects which ion is mostly moving across the membrane at any given time. (Which happens to be K+)
  8. What is the equillibrium potential for K+?
    -90mV
  9. What is the equillibrium potential for Na+?
    +60 mV
  10. Depolarization-
    Inside verses outside the cell becomes LESS NEGATIVE.
  11. Hyperpolarization-
    Inside verses outside the cell becomes MORE NEGATIVE.
  12. Repolarization-
    Returning to the resting membrane potential from either direction.

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