Physiology 3140A Lecture Notes - Lecture 4: Resting Potential, Goldman Equation, Reversal Potential
22 May 2018
School
Department
Course
Professor
Physiology 3140
Dr. Bai
Lecture 4
Resting Membrane Potential
- Equilibrium potential and directions of ionic current flow
- Current-voltage (I-V) relationship
- Goldman equation and resting membrane potential
Why do we need to know the equilibrium potential?
- Equilibrium potential and membrane potential determine the direction and magnitude of ion
movement (current)
- conductance = how many channels are opening
Current-Voltage Relationship
- this is the IV curve for the equation
- current-voltage relationship creates a linear line
- anything above the X axis, is outward current
- anything below the X axis is a inward current (-ive)
- there is a point where the current reverses (called the reversal potential)
o goes from inward to outward current or vice versa
- G is constant (slope)
- if there is a single type of ion responsible for the current-voltage relationship, the Em=Ex
- but if you have more than one type of ion, this does not apply
- if for any reason, the cell is extremely hyperpolarized to -100mV, and the same channel current
now becomes negative (in the inward current)
o the amplitude of this current is -11 multiplied by the conductance
- to calculate conductance(slope):
o use the triangle from the x intercept and y intercept
o divide 0.8nA (y intercept) by -89mV (x intercept)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Equilibrium potential and directions of ionic current flow. Equilibrium potential and membrane potential determine the direction and magnitude of ion movement (current) conductance = how many channels are opening. Cell membrane permeable to multiple ions all ions contribute to the membrane potential. Membrane potential em depends on permeability (p) to k+ ions. Good but not the best description of the resting membrane potential bc doesn"t take into consideration for other ion contributions. Nai = intracellular na+ concentration condition than in nernst equation. Membrane potential em depends on 3 ions: na+, k+ & cl- permeability"s (p) more common. Goldman equation reduces to nernst equation when there is only one permeable ion k+ Goldman equation reduces to nernst equation when there is only one permeable ion cl- Driving force for ion x can be described by ohm"s law. Ix = gx (em- ex), where gx = conductance: em = membrane potential, ex = reversal potential for ion x.
