w-2 ion currents and action potentials

Question 1

____ contributes to action potential amplitude, but has little effect on resting membrane potential

Answer 1

Na+

Question 2

changes in channel conductance/opening:

Answer 2

1. channels activated by physical changes in the cell membrane
   * voltage activated (at a certain ion concentration it opens/closes)
   * stretch activated (mechanically pulled open/closed)
2. channels activated by ligands
   * extracellular activation (ligand binds on extracellular side and activates the channel)
   * intracellular activation (ligand binds on intracellular side and activates the channel)

Question 3

absolute refractory period:

Answer 3

• time window after AP during which no amount of stimulation can evoke another AP
• caused by inactivation of the sodium channels and slow deactivation of the potassium channels

Question 4

relative refractory period:

Answer 4

• time window during which another AP can be initiated with sufficiently increased depolarizing inputs
• the amount required to override the residual gk?? slowly decreases back to the normal threshhold

Question 5

where are Na+ and K+ channels localized?

Answer 5

The nodes of Ranvier