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.
In most resting neurons, the potential difference across the membrane is about 30303030 to 90909090 mV\text{mV}mVm, V (a mV\text{mV}mVm, V is 1/10001/10001/10001, slash, 1000 of a volt), with the inside of the cell more negative than the outside.