Resting Membrane Potential Quiz - PDF

### The Resting Membrane Potential Measurements show that the interior of a nerve cell is negatively charged relative to the exterior in the resting state. There is an electrical potential of -70 millivolts (mV) between the inside and outside. This voltage across the membrane is known as the membr...

### The Resting Membrane Potential Measurements show that the interior of a nerve cell is negatively charged relative to the exterior in the resting state. There is an electrical potential of -70 millivolts (mV) between the inside and outside. This voltage across the membrane is known as the membrane potential. The membrane potential in an unstimulated nerve cell is called the resting potential. #### The Resting Potential Depends on Unequal Ion Distribution and Selective Permeability The resting potential is based on the unequal distribution of ions, which is caused by selective membrane permeability. The following ions contribute to the resting potential: * **Sodium Ions (Na+)** * **Potassium Ions (K+)** * ** Chloride Ions (Cl-)** * **Negatively charged organic ions (A-), mainly proteins** The membrane's permeability to these ions is different: * **K+ ions:** K+ ions can pass through the membrane almost unhindered. They have a permeability of 1. * **Cl- ions:** The membrane is more difficult for Cl- ions to pass through; their permeability is 43% of that of K+ ions. * **Na+ ions:** The permeability to Na+ ions is very low, only 4% of that of K+ ions, and organic ions cannot cross the membrane at all. #### Unequal Distribution of Ions Inside the nerve cell, there are many more K+ ions and organic negative ions and few Na+ ions and Cl- ions. Outside the cell, there are many Na+ and Cl- ions but only a few K+ ions and no organic negative ions. This results in a concentration gradient for all ions. #### Charge Gradient Simultaneously, there is a charge gradient between the inside of the cell and its exterior. #### K+ Ion Movement The two gradients lead to K+ ions diffusing out of the cell. Each K+ ion moving out also carries a positive charge, increasing the charge gradient. As a result, the attraction inside the cell increases, while the repulsion by the positive ions outside increases. #### Cl- Ion Movement The opposite is true for Cl- ions. #### Equilibrium The ion fluxes balance out, resulting in a steady state. The concentration gradients and the charge gradient work in opposition, creating an equilibrium. This means that the same number of K+ ions move from inside to outside as from outside to inside, and vice versa for Cl- ions. #### Maintaining the Resting Potential The resting potential is disrupted by the influx of Na+ ions. To maintain the resting potential, Na+-K+ pumps in the membrane constantly transport Na+ ions outside and K+ ions inside the cell using ATP. This ensures that the equilibrium and the function of the axon are maintained.