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Test Review Questions and Electrical Conduction in Axons

Test Review Questions and Electrical Conduction in Axons. 17 February 2012. Voltage Clamp: Vm is stepped to +100mV, Na+ flows outward. Why?. At 100mV, there is more Na inside the cell than outside At 100mV, Na+ ions flow down their electrochemical gradient

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Test Review Questions and Electrical Conduction in Axons

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  1. Test Review Questions and Electrical Conduction in Axons 17 February 2012

  2. Voltage Clamp: Vm is stepped to +100mV, Na+ flows outward. Why? • At 100mV, there is more Na inside the cell than outside • At 100mV, Na+ ions flow down their electrochemical gradient • The cell membrane is damaged when it is depolarized beyond about +80mV • At highly depolarized potentials, sodium channels do not inactivate

  3. The rising phase of the action potential is primarily caused by: • Potassium entering the cell • Chloride leaving the cell • Sodium entering the cell • Potassium leaving the cell • The activation of the sodium/potassium pump

  4. Which of the following is TRUE about the voltage gated K+ channel? • It is made up of 4 homogenous subunits. • It is made up of a single protein 1830 amino acids long. • It is made up of 5 subunits: 2 alpha and one beta, gamma and delta. • It is sensitive to tetrodotoxin. • More than one of the above.

  5. What is measured using the Voltage Clamp method? • Membrane voltage • Changes in membrane voltage • Movement of ions • Opening of ion channels • Action potential threshold • None of the above

  6. Does the Na/K pump contribute to the RMP? • Yes, it is responsible for most of the RMP • Yes, but only a small portion of the RMP • No

  7. What happens to the RMP when extracellular [K] increases? • Stays the same • Depolarizes • Hyperpolarizes • Becomes stabilized • None of the above

  8. Which of the following is TRUE? • Potassium channels are only open at positive Vm • Sodium channels are only open at positive Vm • At rest, the membrane is impermeable to ions • Action potentials depend on passive spread of voltage • None of the above are true

  9. Which of these determines whether ions flow across the membrane? • The membrane voltage • The concentration of ions • The permeability of the membrane • All of the above are important • None of the above

  10. A reduction in extracellular [Ca2+]: • Increases membrane excitability • Decreases membrane excitability • Does not affect membrane excitability • Polarizes the membrane potential • Depolarizes the membrane potential

  11. Ion currents following depolarization Increased Na conductance comes from? Why does it stop? Increased K conductance comes from? Why does it stop?

  12. C B D A Ionic Basis of the Action Potential Na+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ Na+/K+ pump Na+ Na+ Na+ Na+ Na+ Na+ E

  13. Events that comprise an action potential • Voltage-gated Na+ channels open • Na+ rushes into the cell • Vm gets more positive; steps 1 & 2 continue • Voltage-gated K+ channels open • K+ rushes out of cell; Na+ channels inactivate • Vm gets more negative; steps 3 & 4 continue • K+ channels close • Na+/K+ pump and K+ leak channels restore resting Vm

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