Chapter 3: The Resting Membrane Potential

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Chapter 3 The Resting Membrane Potential

• I. Intra- and Extracellular Fluid
• II. Neuronal Membrane
• III. Ion Movement
• IV. Resting Potential

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I. Intra- and Extracellular Fluid

• A. Water (3.2)
• 1. polar covalent bond
• 2. polar solvent

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I. Intra- and Extracellular Fluid

• B. Ions (3.2)
• 1. ionic bond
• 2. spheres of hydration
• C. Cations
• 1. Na, K, Ca
• D. Anions
• 1. Cl-

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II. Neuronal Membrane

• A. Phospholipid Bilayer
• 1. Lipid (3.3)
• a. C-H nonpolar covalent bonds
• 1) hydrophobic tail
• b. polar phosphate head (P-O3)
• 1) hydrophilic

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II. Neuronal Membrane

• B. Proteins (3.6)
• 1. integral peripheral
• 2. 1-2-3-4 structure

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II. Neuronal Membrane

• C. Ion Channels (3.7)
• 1. integral proteins
• 2. hydrophobic hydrophilic regions
• a. hydrophobicity chart
• 3. specificity
• a. size
• b. charge
• 4. gating
• D. Ion Pumps

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III. Ion Movement

• A. Electrochemical Gradient (3.8, 3.9)
• 1. concentration gradient
• 2. electrical potential

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III. Ion Movement

• B. Diffusion (3.8)
• 1. via ion channels

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III. Ion Movement

• C. Current (I amperes) (3.10b)
• 1. conductance (g siemens-S)
• 2. driven by voltage (V volts)
• 3. resistance (R ohms-W)
• 4. Ohms Law I gV
• a. current ions
• b. I requires g V

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IV. Resting Potential

• A. Vm membrane potential (3.11)
• 1. microelectrode
• 2. voltmeter
• 3. ground
• B. Vm -65 mV

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IV. Resting Potential

• B. Equilibrium Potential (3.12)
• 1. in gt out
• 2. K channels always open
• 3. elec. grad. conc. grad.
• 4. Eion -80 mV

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IV. Resting Potential

• C. Nernst Equation
• 1. calculate Eion (e.g., EK, ENa) need to know
• a. temperature
• b. ion charge
• c. ion inside
• d. ion outside

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IV. Resting Potential

• D. Ion Pumps
• 1. Na-K ATPase (3.16)
• a. 3 Na out
• b. 2 K in
• c. ATP -gt ADP
• 2. Ca pump
• a. Ca out

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IV. Resting Potential

• E. Membrane Permeabilities
• 1. freely permeable to K
• 2. slightly permeable to Na
• F. Goldman Equation
• 1. calculates resting potential
• G. Resting Potential
• 1. -65 mV
• a. polarized
• 2. depolarized
• 3. hyperpolarized

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IV. Resting Potential

• H. K outside
• 1. affects resting potential
• 2. increase -gt depolarization
• 3. regulated
• a. BBB
• b. astrocytes K buffering
• 1) K pumps (uptake)
• 2) K channels