Chapter 3 Key Terms and Definitions
University of Pennsylvania
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| 888948596 | action potential | A brief fluctuation in membrane potential caused by the rapid opening and closing of voltage-gated ion channels; also known as spike, nerve impulse, or discharge. Action potentials sweep like a wave along axons to transfer information from one place to another in the nervous system. | |
| 888948597 | excitable membrane | Any membrane capable of generating action potentials. The membrane of axons and muscle cells is excitable. | |
| 888948598 | resting membrane potential | The membrane potential, or membrane voltage, maintained by a cell when it is not generating action potentials; also called resting potential. Neurons have a resting membrane potential of about -65 mV. | |
| 888948599 | ion | An atom or molecule that has a net electrical charge because of a difference in the number of electrons and protons. | |
| 888948600 | cation | A positively charged ion. | |
| 888948601 | anion | A negatively charged ion. | |
| 888948602 | phospholipid bilayer | The arrangement of phospholipid molecules that forms the basic structure of the cell membrane. The core of the bilayer is lipid, creating a barrier to water and to water-soluble ions and molecules. | |
| 888948603 | peptide bond | The covalent bond between the amino group of one amino acid and the carboxyl group of another. | |
| 888948604 | polypeptide | A string of amino acids held together by peptide bonds. | |
| 888948605 | ion channel | A membrane-spanning protein that forms a pore that allows the passage of ions from one side of the membrane to the other. | |
| 888948606 | ion selectivity | A property of ion channels that are selectively permeable to some ions and not to others. | |
| 888948607 | gating | A property of many ion channels, making them open or closed in response to specific signals, such as membrane voltage or the presence of neurotransmitters. | |
| 888948608 | ion pump | A protein that transports ions across a membrane at the expense of metabolic energy. | |
| 888948609 | diffusion | The temperature-dependent movement of molecules from regions of high concentration to regions of low concentration, resulting in a more even distribution. | |
| 888948610 | concentration gradient | A difference in concentration from one region to another. Ionic concentration gradients across the neuronal membrane help determine the membrane potential. | |
| 888948611 | electrical current | The rate of movement of electrical charge, represented by the symbol I and measured in amperes (amp). | |
| 888948612 | electrical potential | The force exerted on an electrically charged particle, represented by the symbol V and measured in volts; also called voltage or potential difference. | |
| 888948613 | voltage | The force exerted on an electrically charged particle, represented by the symbol V and measured in volts; also called electrical potential or potential difference. | |
| 888948614 | electrical conductance | The relative ability of an electrical charge to migrate from one point to another, represented by the symbol g and measured in siemens (S). Conductance is the inverse of resistance and is related to electrical current and voltage by Ohm's law. | |
| 888948615 | electrical resistance | The relative inability of an electrical charge to migrate from one point to another, represented by the symbol R and measured in ohms (W). Resistance is the inverse of conductance and is related to electrical current and voltage by Ohm's law. | |
| 888948616 | Ohm's law | The relationship between electrical current (I), voltage (V), and conductance (g): I = gV. Because electrical conductance is the inverse of resistance (R), Ohm's law may also be written: V = IR. | |
| 888948617 | membrane potential | The voltage across a cell membrane; represented by the symbol Vm. | |
| 888948618 | microelectrode | A probe used to measure the electrical activity of cells. Microelectrodes have a very fine tip and can be fashioned from etched metal or glass pipettes filled with electrically conductive solutions. | |
| 888948619 | ionic equilibrium potential (equilibrium potential) | The electrical potential difference that exactly balances an ionic concentration gradient, represented by the symbol Eion; also known as equilibrium potential. | |
| 888948620 | ionic driving force | The difference between the real membrane potential, Vm, and the ionic equilibrium potential, Eion. | |
| 888948621 | Nernst equation | A mathematical relationship used to calculate an ionic equilibrium potential. | |
| 888948622 | sodium-potassium pump | An ion pump that removes intracellular Na+ and concentrates intracellular K+, using adenosine triphosphate as its energy source. | |
| 888948623 | calcium pump | An ion pump that removes cytosolic Ca2+. | |
| 888948624 | Goldman equation | A mathematical relationship used to predict membrane potential from the concentrations and membrane permeabilities of ions. | |
| 888948625 | depolarization | A change in membrane potential, taking it from the value at rest (e.g., -65 mV) to a less negative value (e.g., 0 mV). | |
| 888948626 | blood-brain barrier | A specialization of the walls of brain capillaries that limits the movement of bloodborne substances into the extracellular fluid of the brain. |
