Definition: A portion of a line which starts at a point and goes off in a particular direction to infinity. Try this Adjust the ray below by dragging an orange dot and see how the ray AB behaves. Point A is the ray's endpoint.
Plant cell cross-section, showing the membrane. Animal cell cross-section, showing the membrane. Resting membrane potential is the difference in voltage of the fluids inside a cell and outside a cell, which is usually between -70 to -80 millivolts (mV). View slideshow of images above.
Resting membrane potential. The neuron maintains a resting membrane potential. This potential is based on the concentration gradient of ions that is created by an energy-dependent sodium-potassium ATPase pump. This pump moves 2 potassium ions into the neuron in exchange for 3 sodium ions moving out of the cell.Therefore, this pump directly creates a slight electrical potential, with the outside of the cell being slightly positive.his potential is based on the concentration gradient of ions that is created by an energy-dependent sodium-potassium ATPase pump. This pump moves 2 potassium ions into the neuron in exchange for 3 sodium ions moving out of the cell.