Lecture 7 (Action Potentials)

Question 1

Action Potantials

Answer 1

• all or nothing e- signals
• depend on voltage gated Na+ and K+ channels
• at trigger zone
  
  • usually axon initial segment
  • in afferent neurons - sensory dend

Question 2

Na+ Voltage Gated Channels

Answer 2

• Voltage Sensor
  
  • transmembrane segment e/ + amino acids
  • Depol = outward movement + opening
• Rapid Inactivation
  
  • Inactivation gate
    
    • hinge to close before V,m reaches E,Na

Question 3

Positive Feedback Loop Na+ Gated Channel

Answer 3

• Open Na+ gate = explosive depol

-> rising phase action potential

• triggered by threshold level depol

Question 4

Voltage Gated K+ Channels

Answer 4

= open w/ delay to Na_

• Resp for repol (falling phase)
• reset Na+ gate

Question 5

Refractory Period

Answer 5

• right after act pot = no more act pot
• Absolute
  -from Na+ channel inact = impossible
• Relative
  • difficult - not imp -> act pot