Resting Potential

• When receptor is not being stimulated, neurone inside is less positive charged than outside; means there is a voltage (potential difference) across membrane
• Voltage is usually measured in millivolts (mV), it is know as resting potential and we say membrane is polarised as there is a charge difference; about -70mV
• Leaky K+ ion channels allow facilitated diffusion of K+ ions out of neurones down electrochemical gradient; so more positive ions move out so inside remains more negatively charged than outside
• Polarised membrane has a higher concentration of Na^+ ions outside axon and a higher concentration of K^+ ions inside axon
• Maintained by Na^+/K+ pumps (use ATP to move 3 Na^+ out and 2K^+ in), also voltage gated Na^+ channels are closed so ions cannot diffuse back into neurone (membrane is impermeable)