Lecture 1.7: Ion Gradients & The Resting Membrane Potential II

What does it mean that Chemical and Electrical forces for K+

are nearly in balance?

Outwardly-directed K+ gradient results in an inside-negative electrical potential.

The ‘electrical potential difference’ (PD)

is measured in…

Volts

Resting membrane potential is…

K+ -dominated, inside-negative membrane potential is a characteristic of ALL cells at ‘ rest ’.

Changes in ‘Membrane Permeability’ can produce large changes in the…

Membrane potential

Membrane permeability to an ion (K+ or Na+).

Opens channels for that ion.

What are the Keys to manipulation of Membrane Potential when considering channel mediated ion permeability to generate electrical signals?

1. Maintain (stable) Na+ and K+ gradients (Na/K ATPase)

2. Vary the activity of specific ion channels

What are the three steps for ion channels for manipulation of membrane permeability?

1. Integral membrane proteins

2. Channels can be ‘open’ or ‘closed’

3. Some channels are routinely open

How do mechanically gated channels work?

They open when membrane gets stretched.

How do voltage gated channels work?

They open when the membrane potential gets less negative (depolarized).

How do you chemically (‘ligand’) gated channels work?

They open when a signal molecule binds to the channel protein.