Resting Membrane Potential and Ion Concentration Quiz

Ion Distribution Across the Cell Membrane

• There is a higher concentration of Na+ (145 mmol/L) outside the cell than inside (14 mmol/L)
• There is a higher concentration of K+ (140 mmol/L) inside the cell than outside (5 mmol/L)
• The total concentration of positive ions inside and outside the cell is 165 mmol/L

Resting Membrane Potential (RMP)

• The RMP is the voltage across a cell membrane during the resting stage
• In neuromuscular tissues, the RMP of a typical neuron is about −70 mV, with the interior of the cell negative in charge to the outside
• The basis for the RMP is the unequal distribution of ions, particularly K+ and Na+, on either side of the plasma membrane

Action Potential

• The propagation of an electrical signal would constitute unusual activity
• Depolarization is due to the net flow of positive charges into the cell or negative charges to regions outside the cell
• Repolarization is a stage of an action potential in which the cell experiences a decrease in voltage due to the efflux of potassium (K+) ions along its electrochemical gradient
• Hyperpolarization is due to the net flow of negative charges into the cell or positive charges to outside the cell, resulting in a polarized state

Types of Cell Membrane Excitations

• There are two types of axon excitations: graded potentials and action potentials
• Graded potentials are minor perturbations in the membrane potential due to the binding of neurotransmitters, the stimulation of sensory reception, or spontaneous ion leakage through the cell membrane
• Successive graded potentials can add to one another, but they only propagate short distances along the membrane before decaying
• Action potentials are qualitatively different from graded potentials, with relatively large depolarizations above the resting value of −70 mV to a threshold of about −55 mV