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Definition
| 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. |
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| Any membrane capable of generating action potentials. The membrane of axons and muscle cells is excitable. |
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| resting membrane potential |
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Definition
| 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. |
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| An atom or molecule that has a net electrical charge because of a difference in the number of electrons and protons. |
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| 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. |
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| The covalent bond between the amino group of one amino acid and the carboxyl group of another. |
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| A string of amino acids held together by peptide bonds. |
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| A membrane-spanning protein that forms a pore that allows the passage of ions from one side of the membrane to the other. |
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Definition
| A property of ion channels that are selectively permeable to some ions and not to others. |
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Definition
| 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. |
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| A protein that transports ions across a membrane at the expense of metabolic energy. |
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| The temperature-dependent movement of molecules from regions of high concentration to regions of low concentration, resulting in a more even distribution. |
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Definition
| A difference in concentration from one region to another. Ionic concentration gradients across the neuronal membrane help determine the membrane potential. |
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Definition
| The rate of movement of electrical charge, represented by the symbol I and measured in amperes (amp). |
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Definition
| The force exerted on an electrically charged particle, represented by the symbol V and measured in volts; also called voltage or potential difference. |
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Definition
| The force exerted on an electrically charged particle, represented by the symbol V and measured in volts; also called electrical potential or potential difference. |
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Definition
| 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. |
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Definition
| 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. |
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Definition
| 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. |
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Definition
| The voltage across a cell membrane; represented by the symbol Vm. |
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Definition
| 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. |
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Term
| ionic equilibrium potential (equilibrium potential) |
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Definition
| The electrical potential difference that exactly balances an ionic concentration gradient, represented by the symbol Eion; also known as equilibrium potential. |
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Definition
| The difference between the real membrane potential, Vm, and the ionic equilibrium potential, Eion. |
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| A mathematical relationship used to calculate an ionic equilibrium potential. |
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| An ion pump that removes intracellular Na and concentrates intracellular K , using adenosine triphosphate as its energy source. |
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Definition
| An ion pump that removes cytosolic Ca2 . |
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Definition
| A mathematical relationship used to predict membrane potential from the concentrations and membrane permeabilities of ions. |
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Definition
| 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). |
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| A specialization of the walls of brain capillaries that limits the movement of blood-borne substances into the extracellular fluid of the brain. |
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