neurons at rest

• when a neuron isnt transmitting an action potential, it is said to be at rest.
• If a neuron is at rest, it is still actively pumping ions across the membrane; sodium/potassium pumps use ATP to pump 3 sodium ions out and 2 potassium ions in.
• The gated sodium ion channels are kept closed. However, some of the potassium ions are kept open, therefore the plasma membrane is more permeable to potassium ions than sodium. Potassium ions tend to diffuse out of the cell, the cytoplasm also contains large inorganic anions. Hence, the interior of the cell is maintained at a negative potential compared with the outside.
• The cell membrane is said to be polarised, the potential difference across the cell membrane is about -60 mV. this is called the resting potential.
• where does ion exchange take place across a neuron?

  The nodes of Ranvier
• why does ion exchange take place at the nodes of ranvier?

  The myelin sheet is impermeable to ions.