February 28th

II. Cells
     B. Neurons
     3. Dendrites

III. The Nerve Impulse: how does a neuron initiate and propagate an electrical impulse?
      A. The Resting Potential: setting up the potential for a neuron to "fire".
          Cl - 10x
          Na+ 10x  (sodium can leak in, just as potassium can leak out)
  
(K+ 30x)  (large (-) polypeptides ) potassium can leak out~
- Resting Charge (-70mv) neutral/balance between negative and positive charges

Na+/K+ Pump:
      1.  K+ is at a 30 times greater concentration inside of the neuron. it can leak out and does.
      2. Large (-) polypeptides- made by neurons and they are highly concentrated inside the neuron. these want to hold K+ in so, K+ has two forces acting upon it.
        a. Diffusion- wants it out
        b. Electrical Attraction- wants it in.        }when these two forces are equal it makes the net flow of K+ zero and the inside or Resting Charge of the neuron will be at -70mv.
     3. Na+ - is at a 10x greater concentration. outside and it really wants to flow in because both forces want to move it in. (arrow) Na+ can leak in through gated channels and does, Na+/K+ pumps must constantly be at work to keep the resting charge and concentration of Na+ and K+ where they need to be
    4. Cl-is also at 10x concentration outside and the external environment is electrically neutral.