1. capacitance
Capacitance (C) unit = F (Faraday)

2. t : time constant

3. Ex) Resting membrane potential

4. [Chapter 2] Classical Biophysics of the Squid Giant Axon
Action potential in nerve membrane → Electrically excitable
<History>
1902 • Bernstein's 'Membrane Hypothesis'
: The existence of a cell membrane
1905 • 'Self -stimulatory' Hermann : propagation in axons

5. 1936 Young: discovery of squid giant axon
Keneth S. Cole : membrane is a RC-circuit
Hermann (1905) : Cable theory:
electrical disturbance in a local circuit
→ spread passively to neighboring segment
1935 A.L. Hodgkin: depolarization spreads passively ∴ A. P. propagate eletrically
1936 Young: discovery of squid giant axon
1939 Cole & Curtis: measurement of membrane conductance

6. Hodgkin & Huxley, 1939; Curtis & Cole, 1940
An intracellular micropipette in squid giant axon
→ measurement of a full action potential
Overshoot: Potential is higher than 0mV; ⇒ Due to Na+
1949 Hodgkin & Katz :
Na+ hypothesis; Replacement of Na+ with choline or
glucose

7. Voltage clamp technique (1949)
(Marmont, Cole, Hodgkin, Huxley & Katz)
→ voltage clamp : control the membrane potential
cf. membrane → excitable
∴ membrane potential is not stable!
∴ To stabilize membrane potential → using voltage-clamp
⇒ This technique revolutionize the Biophysical areas.

8. Voltage clamp technique
• 세포의 크기가 작아야 보정해주는 current가 골고루 갈 수 있다.
∴ current를 측정하면 feedback Amp가 set voltage와 실제 unstable membrane voltage와의 difference를 전하의 input과 output을 통하여 보정해 준다.
◎ Advantage of using voltage-clamp technique
① 'hold' the membrane potential at the interested voltage
② To record membrane current

9. Voltage clamp in squid giant axon
1949 axial wire : To space-clamp
squid giant axon은 커서 Axon 자체에 wire를 꽃아 넣는다
Electrode 2개 필요 : recording용, 보정용
비교적 작은 cell에서 고루 분포하여 조절 가능, .

10. 1) Whole cell (단, cell이 작은 경우)
2) Xenopus oocyte는 크기가 크기 때문에 두 개의 electrode가 필요함
3) Single channel recording (=patch clamp)

11. Separation of INa & Ik

12. gion : Time and voltage dependent!
◎ Separation of INa & IK : Hodgkin & Huxley ⇒ Ionic conductance (g : conductance of ion) I = g*E  • RC-Circuit of membrane (Fig 2-10)
gion : Time and voltage dependent!

13. Na+ channel opens quickly and closes quickly.
K+ channel opens slowly!
So, gNa & gK are time dependent!!

14. ※ Measurement of Inactivation : 2 pulse protocol • Pre-pulse (or conditioning pulse) • Test-pulse : to measure un-inactivated current ⇒deactivated

15. ◎ : 2 kinetic processes (activation & inactivation)
① activation : • rapid, • voltage-dependent (fig 2-13)
② Inactivation : slow process that closes during depolarization
• Once inactivated, membrane should be hyperpolarized to remove
the inactivation (deactivation)
• Inactivation of Na+ ch → loss of excitability
① refractory period of excitable tissues
② loss of excitability due to anoxia or metabolic block
(Fig 2-15) Recovery from Sodium Inactivation