Questions and Answers
What are the reasons why there is unequal distribution of ions in and out of the cell?
Selective permeability of the cell membrane, activity of Na+/K+ pump.
What is the role of the Na+/K+ pump?
The major extracellular cation is potassium.
False
Match the following cations to their typical location:
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What major ions are found in greater concentration inside the cell?
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What do the initials RMP stand for?
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The mnemonic PISO stands for _____ In, Sodium Out.
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What are the different types of membrane potentials?
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Study Notes
Cell Membrane
- Composed of a phospholipid bilayer that is selectively permeable.
- Maintains the difference in ionic composition inside versus outside the cell.
Ionic Composition and Gradient
- Unequal distribution of ions is due to selective permeability and the activity of the Na+/K+ pump.
- This pump uses ATP to transport Na+ out and K+ into the cell, creating ionic and voltage gradients.
- Inside the cell, key ions include K+, Mg2+, phosphate, sulfate, and amino acids.
- Outside the cell, major ions include Na+, Ca2+, Cl-, and HCO3-.
Resting Membrane Potential (RMP)
- RMP is the electrical potential difference across the plasma membrane at rest, typically around -70 mV.
- Maintained by the Na+/K+ pump and the differential permeability to ions.
Action Potential (AP)
- AP is a rapid change in membrane potential; initiated when local potentials reach a threshold.
- Phases of action potential include depolarization, repolarization, and hyperpolarization.
- Periods include absolute and relative refractory periods where the membrane is less responsive to stimuli.
Ion Channels
- Two main types:
- Leak channels: Allow passive flow of ions based on concentration gradients.
- Gated channels: Open in response to specific stimuli (voltage, ligand, etc.).
Major Concepts
- Electrogenic Pump: Generates electrical gradients by moving charged ions across the membrane.
- PISO Mnemonic: Helps remember major ion movements – Potassium In, Sodium Out.
Summary of Abbreviations
- EG: Electrical Gradient
- CG: Concentration Gradient
- mV: Millivolt
- RMP: Resting Membrane Potential
- Na+/K+ Pump: Sodium Potassium Pump
- AP: Action Potential
- LP: Local Potential
Learning Objectives
- Understand cell membrane structure and protein channel types.
- Differentiate between leak and gated channels, local and action potentials.
- Discuss ionic events during local and action potentials.
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Description
Test your knowledge on cell electrophysiology in this quiz covering the ionic composition and gradient. Explore the mechanisms of ion distribution across cell membranes and their physiological implications. Ideal for students of physiology seeking to reinforce their understanding.
