Term
| absolute refractory phase |
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Definition
| A brief period of complete insensitivity to stimuli. |
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Term
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Definition
| A neurotransmitter that is produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain. |
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Term
| acetylcholinesterase (AChE) |
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Definition
| An enzyme that inactivates the transmitter acetylcholine. |
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Term
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Definition
| Also called spike. A rapid reversal of the membrane potential that momentarily makes the inside of the membrane positive with respect to the outside. |
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Term
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Definition
| The positive or negative change in membrane potential that may follow an action potential. |
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Term
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Definition
| A molecule, usually a drug, that binds a receptor molecule and initiates a response like that of another molecule, usually a neurotransmitter. |
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Term
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Definition
| The fact that the size (amplitude) of the action potential is independent of the size of the stimulus. |
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Term
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Definition
| A negatively charged ion, such as a protein or a chloride ion. |
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Term
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Definition
| A molecule, usually a drug, that interferes with or prevents the action of a neurotransmitter. |
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Term
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Definition
| In epilepsy, the unusual sensations or premonition that may precede the beginning of a seizure. |
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Term
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Definition
| A synapse at which a presynaptic axon terminal synapses onto the axon terminal of another neuron. |
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Term
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Definition
| A synapse at which a presynaptic axon terminal synapses onto a dendrite of the postsynaptic neuron, either via a dendritic spine or directly onto the dendrite itself. |
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Term
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Definition
| A synapse at which a presynaptic axon terminal synapses onto the cell body (soma) of the postsynaptic neuron. |
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Term
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Definition
| The cone-shaped area on the cell body from which the axon originates. |
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Term
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Definition
| A neurotoxin, isolated from the venom of the banded krait, that selectively blocks acetylcholine receptors. |
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Term
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Definition
| A calcium atom that carries a double positive charge because it has lost two electrons. |
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Term
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Definition
| A positively charged ion, such as a potassium or sodium ion. |
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Term
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Definition
| A chlorine atom that carries a negative charge because it has gained one electron. |
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Term
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Definition
| Referring to cells that use acetylcholine as their synaptic transmitter. |
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Term
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Definition
| In epilepsy, a type of seizure that doesn’t involve the entire brain, and therefore can cause a wide variety of symptoms. |
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Term
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Definition
| The chemical breakdown of a neurotransmitter into inactive metabolites. |
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Term
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Definition
| A decrease in membrane potential (the interior of the neuron becomes less negative). |
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Term
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Definition
| The spontaneous spread of molecules until a uniform concentration is achieved. |
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Term
| electroencephalogram (EEG) |
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Definition
| A recording of gross electrical activity of the brain via large electrodes placed on the scalp. |
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Term
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Definition
| A brain disorder marked by major, sudden changes in the electrophysiological state of the brain that are referred to as seizures. |
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Term
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Definition
| The point at which the movement of ions across the cell membrane is balanced, as the electrostatic pressure pulling ions in one direction is offset by the diffusion force pushing them in the opposite direction. |
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Term
| event-related potential (ERP) |
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Definition
| Also called evoked potential. Averaged EEG recordings measuring brain responses to repeated presentations of a stimulus. Components of the ERP tend to be reliable because the background noise of the cortex has been averaged out. |
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Term
| excitatory postsynaptic potential (EPSP) |
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Definition
| A depolarizing potential in the postsynaptic neuron that is caused by excitatory presynaptic potentials. EPSPs increase the probability that the postsynaptic neuron will fire an action potential. |
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Term
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Definition
| The fluid in the spaces between cells (interstitial fluid) and in the vascular system. |
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Term
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Definition
| An increase in membrane potential (the interior of the neuron becomes even more negative). |
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Term
| inhibitory postsynaptic potential (IPSP) |
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Definition
| A hyperpolarizing potential in the postsynaptic neuron that is caused by inhibitory connections. IPSPs decrease the probability that the postsynaptic neuron will fi re an action potential. |
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Term
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Definition
| Also called cytoplasm. The watery solution found within cells. |
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Term
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Definition
| An atom or molecule that has acquired an electrical charge by gaining or losing one or more electrons |
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Term
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Definition
| A pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open. |
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Term
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Definition
| An electrical potential that is initiated by stimulation at a specific site, which is a graded response that spreads passively across the cell membrane, decreasing in strength with time and distance. |
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Term
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Definition
| An especially small electrode used to record electrical potentials in living cells. |
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Term
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Definition
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Term
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Definition
| Literally, “many scars”; a disorder characterized by the widespread degeneration of myelin. |
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Term
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Definition
| The fatty insulation around an axon, formed by glial cells. This sheath boosts the speed at which nerve impulses are conducted. |
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Term
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Definition
| The study of the life processes of neurons. |
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Term
| neurotransmitter receptor |
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Definition
| Also called receptor. A protein that captures and reacts to molecules of a neurotransmitter or hormone. |
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Term
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Definition
| A gap between successive segments of the myelin sheath where the axon membrane is exposed. |
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Term
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Definition
| Also called absence attack. A seizure that is characterized by a spike-and-wave EEG and often involves a loss of awareness and inability to recall events surrounding the seizure. |
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Term
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Definition
| Exhibiting a difference in electrical charge between the inside and outside of the cell. |
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Term
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Definition
| Referring to the region of a synapse that receives and responds to neurotransmitter. |
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Term
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Definition
| A local potential that is initiated by stimulation at a synapse, which can vary in amplitude, and spreads passively across the cell membrane, decreasing in strength with time and distance. |
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Term
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Definition
| A potassium atom that carries a positive charge because it has lost one electron. |
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Term
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Definition
| Referring to the region of a synapse that releases neurotransmitter. |
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Term
| relative refractory phase |
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Definition
| A period of reduced sensitivity during which only strong stimulation produces an action potential. |
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Term
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Definition
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Term
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Definition
| A difference in electrical potential across the membrane of a nerve cell during an inactive period. |
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Term
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Definition
| The process by which released synaptic transmitter molecules are taken up and reused by the presynaptic neuron, thus stopping synaptic activity. |
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Term
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Definition
| The form of conduction that is characteristic of myelinated axons, in which the action potential jumps from one node of Ranvier to the next. |
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Term
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Definition
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Term
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Definition
| The property of a membrane that allows some substances to pass through, but not others. |
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Term
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Definition
| The energetically expensive mechanism that pushes sodium ions out of a cell, and potassium ions in. |
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Term
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Definition
| A sodium atom that carries a positive charge because it has lost one electron. |
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Term
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Definition
| The summation of postsynaptic potentials that reach the axon hillock from different locations across the cell body. If this summation reaches threshold, an action potential is triggered. |
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Term
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Definition
| The space between the presynaptic and postsynaptic neurons at a synapse. This gap measures about 20–40 nm. |
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Term
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Definition
| The brief delay between the arrival of an action potential at the axon terminal and the creation of a postsynaptic potential. |
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Term
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Definition
| The summation of postsynaptic potentials that reach the axon hillock at different times. The closer in time the potentials occur, the more complete the summation is. |
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Term
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Definition
| The stimulus intensity that is just adequate to trigger an action potential at the axon hillock. |
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Term
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Definition
| A specialized receptor in the presynaptic membrane that recognizes transmitter molecules and returns them to the presynaptic neuron for reuse. |
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Term
| voltage-gated Na+ channel |
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Definition
| A Na+-selective channel that opens or closes in response to changes in the voltage of the local membrane potential; it mediates the action potential. |
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