biomed Module11 obj.11-

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  1. Ions cannot flow freely across the _____ ________.  They must pass through ______ channels or be escorted by protein carriers.
    cell membrane, protein
  2. True or False 
    If a large number of positive charges accumulate outside a nerve cell, and the inside of the cell is negatively charged, the positive charges have a potential energy because the negative ions inside the cell attract them.
  3. Membrane Channels
    ion channels
    • the non-polar tails of lipid molecules prevent charged molecules like ions, from crossing the cell membrane
    • Ion channels allow ions to pass down their concentration gradient (from high concentration to low)
    • Some are open all the time -leakage channels
    • Some are gated - open and close on demand
  4. Voltage
    • interchangeably with potential
    • voltage describes the potential energy of particles
    • it is energy that is available but not released yet
    • the higher the voltage the more potential energy a particle has
  5. Conductor
    • holds electrons loosely 
    • Charges shift together from one end of the wire to the other
  6. True or false
    In metal wires, the electromagnetic wave that carries current moves at nearly the speed of light.
  7. See objective 12

    it was hard to put this on a card.
  8. Ohm's Law
    • Electric current flow is analogous to water flowing from a tank on the mountainside through a pipe.
    • Voltage = potential energy
    •    -Water: height of the tank above your house
    • Current = kinetic energy, flow of ions or electrons
    •    -Water: how many gallons per minute delivered by pipe.
    • Resistance = resistance to current flow
    •    -Water : how narrow is the pipe?
  9. True or false
    Ohm's Law says that voltage (V) is equal to the current (I) times the resistance (R)

    V= I x R

    See obj. 13 
  10. Selectively permeable
    • There are no channels for proteins, so protein is effectively trapped in the neuron
    • the channels for sodium, chloride, and potassium have special properties and there are no channels for phosphate or proteins
    • see obj 14
  11. What are the two forces that act on Ions?
    • concentration forces 
    • Electrical forces
  12. Concentration forces
    all atoms including sodium, potassium, chloride and calcium ions, want to move from where they are at high concentration to where they are at low concentraion
  13. Electrical forces 
    • Positive ions want to be where there are excess negative charges 
    • Negative ions want to be where there are excess negative charges
    • "Like repels Like" for electricity and magnetism
    • particles with opposite charges attract each other .
  14. Ions cannot move unless...
    they pass through a channel
  15. true or false
    Channels must be open for forces to operate
  16. At rest, the neuron is always negative inside relative to outside, so based on just electrical forces, ________ charged ions always want to flow in , and ________ charged ions always  want to flow out
    positively, negatively
  17. See objective 15

    concentration  and electrical forces: Potassium

    concentration and electrical forces: sodium
  18. Equalibrium
    the point at which the two forces (concentration and electrical) are equal and opposite.
  19. Equilibrium potential (Nernst potential)
    The voltage at which the concentration and electrical forces are exactly equal and opposite
  20. For K+, the equilibrium potential is about ...
  21. Sodium Equilibrium potential
    • it cant be negative
    • +20 mV for a typical neuron
    • see objective 16
  22. Resting Potential
    • the resting potential (resting voltage) of a neuron is maintained by leak channels
    • At rest, there are about 9K+ leak channels open for every 1 Na+ leak channel

    see objective 16
Card Set:
biomed Module11 obj.11-
2013-01-15 03:58:12
biomed module 11 obj

biomed module 11 obj. 11-
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