Ion channels - Quick Reference

Types of ion channels

• Voltage-gated

• Ligand-gated

• Mechanosensitive

• Leak (background)

Gating mechanisms

• Activation and inactivation gates

• Voltage-dependent gating

• Ligand-dependent gating

• Mechanosensitive gating

Ion selectivity

• Specific ions: Na⁺, K⁺, Ca²⁺, Cl⁻

• Pore size, dehydration energy, and charge determine selectivity

• Selectivity filter

Functional roles

• Generate and propagate action potentials

• Synaptic transmission

• Muscle contraction

• Maintain resting membrane potential

Key concepts and equations

• Resting potential set by leak channels and gradients (typical around -70 mV)

• Nernst equation: E{ion} = \frac{RT}{zF}\ln\left(\frac{[ \mathrm{ion} \]{out}}{[ \mathrm{ion} \]_{in}}\right)

• Goldman-Hodgkin-Katz equation: Em = \frac{RT}{F} \ln\left(\frac{PK [K^+]{out} + P{Na} [Na^+]{out} + P{Cl} [Cl^-]{in}}\frac{PK [K^+]{in} + P{Na} [Na^+]{in} + P{Cl} [Cl^-]_{out}}\right)

• Common ions to know: Na⁺, K⁺, Ca²⁺, Cl⁻

Quick reference

• Ion types: Na⁺, K⁺, Ca²⁺, Cl⁻

• Typical resting potential: ~ -70 mV

• Gating modalities: voltage-, ligand-, mechanical-gated