24 September 2008 Pick up endocrine quiz from piano MC section counted 80% (avg missed 5.6, 82 ± 12) Trophic + Permissive effect counted 20% Overall Quiz 2 grade in Silver average = 78 ± 14, median = 80 n = 50 max = 100 (4 of these!) Reminder: Bring Androstenedione paper to lab this week.

Why is resting membrane potential closer to EK than ENa? Electrical and concentration gradient driving forces for Sodium and Potassium What would happen to membrane potential if suddenly PNa became very great? Graded potentials in dendrites and cell body, action potentials in axon because of the types of ion channels found in these membrane domains. How does the membrane potential change if 1)permeability to sodium increases 2) Permeability to potassium increases

Which ion moving in which direction (into or out of cell) is responsible for depolarization and overshoot? Which ion moving in which direction (into or out of cell) is responsible for repolarization and hyperpolarization? Can the membrane potential go more negative than -90 mV?

Graded potentials are conducted decrementally for only a few millimeters, die out over distance and time, and are proportional to the size of the stimulus.

To reset from inactivated state to closed state, membrane must repolarize. Compare and contrast voltage-gated Na and K channels based on time to open and duration of open time.

Why does the peak of the action potential not reach ENa? What accounts for the afterhyperpolarization? Explain the shape of the action potential based on the properties of Voltage-gated sodium and potassium channels (when and how long each type opens and closes.)

What happens when the membrane is depolarized by more than about 15 mV? How is the intensity of a stimulus encoded by action potential if all action potentials have the same size (amplitude)?

How does an action potential move along the axon? Why doesn’t the amplitude get smaller with distance? Why is the conduction of an action potential unidirectional? What is the absolute refractory period and is going on with voltage gated sodium channels that accounts for the relative refractory period? What is the relative refractory period and is going on with voltage gated sodium channels that accounts for the relative refractory period? Blocking Voltage-gated Sodium channels with Lidocaine. Axon Hillock Axon Who cares? Epidural injections to blunt the pain of childbirth.