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.
where Vin is the potential on the inside of the cell and Vout the potential on the outside. 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. All electrical signaling involves brief changes from the resting membrane. potential due to alterations in the flow of electrical current across the cell membrane resulting from the opening and closing of ion channels.