Starts with excitable tissues and the two types of excitable membrane, then explains how ion diffusion creates membrane potentials, introducing the Nernst and Goldman-Hodgkin-Katz equations. Breaks the nerve resting potential into potassium, sodium and pump contributions, then walks through the stages of the action potential and the gating behaviour of voltage-gated sodium and potassium channels, ending with a summary of conductance changes.
Topic 4 of 17 in the MU Pleven syllabus for Physiology (Medicine, Year 2). The free AceMed note covers it in 6 sections, about 1,658 words (11 min of reading), with 16 flashcards.
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TOPIC 4. BASIC PHYSICS OF MEMBRANE POTENTIALS. RESTING MEMBRANE POTENTIAL OF NERVES. GENERATION OF ACTION POTENTIAL.
INTRODUCTION.
BASIC PHYSICS OF MEMBRANE POTENTIALS.
RESTING MEMBRANE POTENTIAL OF NERVES.
GENERATION OF ACTION POTENTIAL.
SUMMARY OF GENERATION OF ACTION POTENTIAL
INTRODUCTION.
Excitable tissues.
EXCITATION → process of changes in the cells under effect of applied stimulus.
IRRITABILITY → basic function of protoplasm, however, the nerve cells and muscle fibers are specialized excitable cells of the body capable of conducting (transmitting) excitations along their membrane.
There are 2 types of excitable membranes:
ELECTRO-EXCITABLE → generate action potentials.
ELECTRO-UNEXCITABLE (ligand excitable) → sensory receptors and postsynaptic membranes that generate acute local potentials.
Membrane potentials and action potentials.
Electrical potentials exist across the membranes of virtually all cells of the body.
Some cells, such as nerve and muscle cells, are capable of generating rapidly changing electrochemical impulses at their membranes, and these impulses are used to transmit signals along the nerve or muscle membranes.
In other types of cells, such as glandular cells, macrophages, and ciliated cells, local changes in membrane potentials also activate many of the cells’ functions.
The present discussion is concerned with membrane potentials generated both at rest and during action by nerve and muscle cells.
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