Chapter 6 Neuronal Signaling and the Structure of the Nervous System Section B Membrane Potential
Chapter 6 Neuronal Signaling and the Structure of the Nervous System Section B Membrane Potential
opyright The McGrew-Hill Com penies.inc.Perm lssion requlred for reproduction or display Figure 6-7 Electrical force ⊙ Force increases with the Force increases with quantity of charge decreasing distance of charge separation ⊕ ⊕】 >⊙ ⊕ ⊕ Opposite charges attract each other and will move toward each other if not separated by some barrier
Opposite charges attract each other and will move toward each other if not separated by some barrier. Figure 6-7
Section B Membrane Potential Resting membrane potential -Potential difference under resting conditions ·Graded potential -Transient change,short distance ·Action potential -Transient change,long distance
• Resting membrane potential – Potential difference under resting conditions • Graded potential – Transient change, short distance • Action potential – Transient change, long distance Section B Membrane Potential
Copyright The McGraw-Hill Companles,nc.Permission requred for reproduction or display. Figure 6-8 Voltmete Extracellular fluid Resting membrane potential Time
Figure 6-8
opyrght OThe McGraw-Hill Com panie Figure 6-9 d for reproduction or display. Extracellular fluid 4 Cell Only a very thin shell of charge difference is needed to establish a membrane potential
Only a very thin shell of charge difference is needed to establish a membrane potential. Figure 6-9
Copyright The McGra CopyrightThe McGraw-Hill Companies,Inc.Permission required for reproduction or display. Distribution of Major Mobile Ions TABLE 6-2 Across the Plasma Membrane of a Typical Nerve Cell Concentration,mmol/L ION EXTRACELLULAR INTRACELLULAR Na 150 6 CI 110 7 K 5 150 A more accurate measure of electrical driving force can be obtained using mEq/L which factors in ion valence.Since all the ions in this table have a valence of 1,the mEq/L is the same as the mmol/L concentration
Copyright The McGraw-Hil Companles,Inc.Pe or c Begin: a) Compartment 1 Compartment 2 K+in Compartment 2, 0.15M 0.15M Nat in Compartment 1; KCI BUT only K+can move. lon movement: K'crosses into Compartment 1; Na Na*stays in Compartment 1. (d) K+ Figure 6-10 Na At the potassium e K K equilibrium potential: buildup of positive charge Na* in Compartment 1 produces an electrical potential that exactly offsets the K*chemical concentration gradient
Figure 6-10 Begin: K+ in Compartment 2, Na+ in Compartment 1; BUT only K+ can move. Ion movement: K+ crosses into Compartment 1; Na+ stays in Compartment 1. buildup of positive charge in Compartment 1 produces an electrical potential that exactly offsets the K+ chemical concentration gradient. At the potassium equilibrium potential:
Copyright The McGraw-Hil Com n or display Begin: (a) Compartment 1 Compartment 2 K+in Compartment 2, 0.15M 0.15M Na*in Compartment 1; BUT only Na+can move. NaCl KCI lon movement: (b) Na'crosses into Na* Compartment 2; but K+stays in Compartment 2. (c) Na Na' At the sodium K equilibrium potential: buildup of positive charge in Compartment 2 produces an electrical potential that exactly offsets the Na*chemical concentration gradient
Begin: K+ in Compartment 2, Na+ in Compartment 1; BUT only Na+ can move. Ion movement: Na+ crosses into Compartment 2; but K+ stays in Compartment 2. buildup of positive charge in Compartment 2 produces an electrical potential that exactly offsets the Na+ chemical concentration gradient. At the sodium equilibrium potential:
Copy n or displa Figure 6-13 Establishment of resting 个 membrane potential: Na+/K+pump establishes concentration gradient generating a small negative potential;pump uses up to 40%of the ATP produced by that cell!
Establishment of resting membrane potential: Na+/K+ pump establishes concentration gradient generating a small negative potential; pump uses up to 40% of the ATP produced by that cell! Figure 6-13
Copyright The McGraw-Hill Companles,Inc.Permlaslon requlred tor reproduction or display. Figure 6-14 Overshoot refers to the development of a charge reversal. +60 A cell is “polarized' Repolarization is because movement back its interior toward the is more resting potential. negative than its exterior. -70 Resting potential Depolarization occurs Time Hyperpolarization is when ion the development of movement even more negative reduces the charge inside the cell. charge imbalance
Depolarization occurs when ion movement reduces the charge imbalance. A cell is “polarized” because its interior is more negative than its exterior. Overshoot refers to the development of a charge reversal. Repolarization is movement back toward the resting potential. Hyperpolarization is the development of even more negative charge inside the cell. Figure 6-14