Lecture 2

• Tumor


  When cell cycle regulation is disrupted, abnormal cell division occurs
• Cancer


  When boundaries of the tumor break through tissue and into bloodstream, attacking nutrients across body
• Intercellular Fluid


  • LOW Na + Cl
  • HIGH K
  • HIGH Viscosity
  • MORE Electronegativity
• Extracellular Fluid


  • HIGH Na + Cl
  • LOW K
  • LOW Viscosity
  • LESS Electronegativity
• Ions Crossing Membrane


  • Diffusion - NO protein assistance
  • No transport
  • Facilitated Transport - movement with help of membrane protein
• Facilitated Transport


  • Passive Transport - Concentration Gradient [high] to [low]
  • Active Transport - Against Concentration Gradient [low] to [high]
• Active Transport


  • Primary Active Transport: 'pump' protein uses ATP - Na and K Gradients
  • Secondary Active Transport: cotransport protein (eg. Na drags protein when pumped) - Cl Gradient (aka cotransport with K)
  • Vesicular Transport: for larger particles
• Graded Potential


  Dendrites, small localized
• Graded Potential


  • Affect Size: # Ion Channels that Open à More Permeability
  • Affect Size: Direction + Amplitude
• Action Potential


  Axon, generated by opening and closing of Voltage-Gated Ion Channels
• Voltage-Gated Ion Channels


  • Voltage-Gated Na Channel: RAPID - Activation Gate: opens in response to depolarization - Inactivation Gate: starts open then closes
  • Voltage-Gated K Channel: SLOW - Activation Gate: responds to Vm crossing threshold (but after a delay) - Repolarization it opens
• Action Potentials


  • All-or-None (Threshold)
  • Propagation: when they travel across axon it does not get weaker
  • Stereotyped Dimensions
  • All-or-None (Refractory)
• Refractory Period


  • Absolute Refractory Period: a second AP CANNOT be triggered
  • Relative Refractory Period: a larger than normal stimulus can trigger 2nd AP
• Resting Membrane Potential


  The total resting membrane potential of all ions
• Equilibrium Potential Eion


  • No Net Movement occurs across the membrane (Diffusion = Electro)
  • Each ion moves membrane toward its own equilibrium
• Electrochemical Gradient


  • Diffusive Forces: Uncharged molecule moves passively
  • Electromotive Forces: Charged molecules move
• Ions move across membrane

  According to Electrochemical Gradient (Diffusive + Electro Force)
• Neuron Transmembrane Potential (Vm)

  • Membrane Potentials are generated by ION CHANNELS
  • Ion Channels - fastest
  • Cotransporter
  • ATP-Powered Pump - slowest
• Excitable Cells


  Neurons + Myocytes
• Ion Channels: Gating


  • Non-Gated (Leak) Ion Channel: Always opened, Create Resting Membrane Potential
  • Gated Channels: Open and Close depending on 'Gating' Factors - Ligand-Gating - Binding of Neurotransmitters (eg. Ach)
  • Voltage Gating - Activation Gate, electrical change
  • Mechanical-Gating - Applied Pressure
• Ion Pumps


  • Make a small DIRECT effect on Resting Membrane Potential
  • Transmembrane Potential is MAINTAINED by Ion Pumps
• All new cells come from the division of preexisting cells
• During differentiation, cells specialize into different functions (epithelial, connective, muscle, neural)