RESTING MEMBRANE POTENTIAL Potential difference across the cell membrane at rest is called RMP All living cells has RMP RMP is negative inside with respect to outside Recording is done by using two microelectrodes One is inserted into the cell and other on the outer surface of membrane and both attached to meter Micro electrodes are made up of silver containing silver chlorideValues of RMP in different tissues: Nerve fiber and skeletal muscle= -90 mV Cardiac muscle = -85 - -90 mV Smooth muscle = -55 - -60 mV SA nodal fibers = -55 - -60 mV All the voltage gated channels are closed at RMP i.e. voltage gated Na, K, Ca Channels. Leak Channels i.e. Potassium Sodium leak channels are open at RMP Ligand Gated Channels also known as chemical gated channels open and close when a ligand binds with the receptors of channels. Ligand may be a neurotransmitter or a hormone e.g. Acetylcholine gated channels in the muscle membrane at the neuromuscular junction. Pumps are also present like sodium potassium ATPase pump, calcium pump. Generally in cell membrane there is Na K ATPase pump. Na K pump pumps actively Na and K Both leak channels and Na K pump are active at rest