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.
How do ions affect membrane potential? Resting Membrane Potential (RMP) is the voltage (charge) difference across the cell membrane when the cell is at rest. RMP is a product of the distribution of charged particles (ions). There are positively charged ions called cations (e.g., Na+, K+, Mg2+, Ca2+) and negatively charged ions called anions (e.g., Cl- and proteins that act as anions).