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.
The membrane potential of a cell at rest is called the resting membrane potential. Since, by convention, the potential outside the cell is defined as zero, the. resting potential (Vr) is equal to Vin. Its usual range in neurons is -60 mV to -70 mV.