Chapter 48 - Neurons, Synapses, and Signaling Flashcards
neuron
A nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its plasma membrane.
brain
Organ of the central nervous system where information is processed and integrated.
ganglion
Clusters (functional groups) of nerve cell bodies in a centralized nervous system.
central nervous system (CNS)
The portion of the nervous system where signal integration occurs; in vertebrate animals, the brain and spinal cord.
peripheral nervous system (PNS)
The sensory and motor neurons that connect to the central nervous system.
nerve
A fiber composed primarily of the bundled axons of PNS neurons.
sensory neurons
A nerve cell that receives information from the internal or external environment and transmits signals to the central nervous system.
interneurons
An association neuron; a nerve cell within the central nervous system that forms synapses with sensory and/or motor neurons and integrates sensory input and motor output.
motor neurons
A protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.
cell body
The part of a neuron that houses the nucleus and most other organelles.
dendrite
One of usually numerous, short, highly branched extensions of a neuron that receive signals from other neurons.
axon
A typically long extension, or process, of a neuron that carries nerve impulses away from the cell body toward target cells.
synapse
The junction where a neuron communicates with another cell across a narrow gap via a neurotransmitter or an electrical coupling.
neurotransmitter
A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response.
glia (glial cells)
Cells of the nervous system that support, regulate, and augment the functions of neurons.
membrane potential
The difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substance.
resting potential
The membrane potential characteristic of a nonconducting excitable cell, with the inside of the cell more negative than the outside.
ion channels
A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.
equilibrium potential (<em>E</em>ion)
The magnitude of a cell’s membrane voltage at equilibrium; calculated using the Nernst equation.
gated ion channel
A gated channel for a specific ion. The opening or closing of such channels may alter a cell’s membrane potential.
hyperpolarization
A change in a cell’s membrane potential such that the inside of the membrane becomes more negative relative to the outside. Hyperpolarization reduces the chance that a neuron will transmit a nerve impulse.
depolarization
A change in a cell’s membrane potential such that the inside of the membrane is made less negative relative to the outside. For example, a neuron membrane is depolarized if a stimulus decreases its voltage from the resting potential of -70 mV in the direction of zero voltage.
graded potential
In a neuron, a shift in the membrane potential that has an amplitude proportional to signal strength and that decays as it spread.
action potential
An electrical signal that propagates (travels) along the membrane of a neuron or other excitable cell as a nongraded (all-or-none) depolarization.
voltage-gated ion channel
A specialized ion channel that opens or closes in response to changes in membrane potential.
threshold
The potential that an excitable cell membrane must reach for an action potential to be initiated.
refractory period
The short time immediately after an action potential in which the neuron cannot respond to another stimulus, owing to the inactivation of voltage-gated sodium channels.
myelin sheath
Wrapped around the axon of a neuron, an insulating coat of cell membranes from Schwann cells or oligodendrocytes. It is interrupted by nodes of Ranvier, where action potentials are generated.
oligodendrocytes
A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the central nervous system.
Schwann cellss
A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the peripheral nervous system.
node of Ranvier
Gap in the myelin sheath of certain axons where an action potential may be generated. In salutatory conduction, an action potential is regenerated at each node. appearing to “jump” along the axon from node to node.
saltatory conduction
Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.
ligand-gated ion channel
A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand), allowing or blocking the flow of specific ions; also called an ionotropic receptor.
excitatory postsynaptic potential (EPSP)
An electrical change (depolarization) in the membrane of a postsynaptic cell caused by the binding of an excitatory neurotransmitter from a presynaptic cell to a postsynaptic receptor; makes it more likely for a postsynaptic cell to generate an action potential.
inhibitory postsynaptic potential (IPSP)
An electrical change (usually hyperpolarization) in the membrane of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from a presynaptic cell to a postsynaptic receptor; makes it more difficult for a postsynaptic neuron to generate an action potential.
temporal summation
A phenomenon of neural integration in which the membrane potential of the postsynaptic cell in a chemical synapse is determined by the combined effect of EPSPs or IPSPs produced in rapid succession.
spatial summation
A phenomenon of neural integration in which the membrane potential of the postsynaptic cell is determined by the combined effect of EPSPs or IPSPs produced nearly simultaneously by different synapses.
acetylcholine
One of the most common neurotransmitters; functions by binding to receptors and altering the permeability fo the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane.
glutamate
An amino acid that functions as a neurotransmitter in the central nervous system.
gamma-aminobutyric acid (GABA)
An amino acid that functions as a CNS neurotransmitter in the central nervous system of vertebrates.
biogenic amine
A neurotransmitter derived from an amino acid.
norepinephrine
A catecholamine that is chemically and functionally similar to epinephrine and acts as a hormone or neurotransmitter; also known as noradrenaline.
dopamine
A neurotransmitter that is a catecholamine, like epinephrine and norepinephrine.
serotonin
A neurotransmitter, synthesized from the amino acid tryptophan, that functions in the central nervous system.
neuropeptide
A relatively short chain of amino acids that serves as a neurotransmitter.
endorphin
Any of several hormones produced in the brain and anterior pituitary that inhibit pain perception.
