Chapter 48 - Neurons, Synapses, and Signaling

Question 1

neuron

Answer 1

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.

Question 2

brain

Answer 2

Organ of the central nervous system where information is processed and integrated.

Question 3

ganglion

Answer 3

Clusters (functional groups) of nerve cell bodies in a centralized nervous system.

Question 4

central nervous system (CNS)

Answer 4

The portion of the nervous system where signal integration occurs; in vertebrate animals, the brain and spinal cord.

Question 5

peripheral nervous system (PNS)

Answer 5

The sensory and motor neurons that connect to the central nervous system.

Question 6

nerve

Answer 6

A fiber composed primarily of the bundled axons of PNS neurons.

Question 7

sensory neurons

Answer 7

A nerve cell that receives information from the internal or external environment and transmits signals to the central nervous system.

Question 8

interneurons

Answer 8

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.

Question 9

motor neurons

Answer 9

A protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.

Question 10

cell body

Answer 10

The part of a neuron that houses the nucleus and most other organelles.

Question 11

dendrite

Answer 11

One of usually numerous, short, highly branched extensions of a neuron that receive signals from other neurons.

Question 12

axon

Answer 12

A typically long extension, or process, of a neuron that carries nerve impulses away from the cell body toward target cells.

Question 13

synapse

Answer 13

The junction where a neuron communicates with another cell across a narrow gap via a neurotransmitter or an electrical coupling.

Question 14

neurotransmitter

Answer 14

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.

Question 15

glia (glial cells)

Answer 15

Cells of the nervous system that support, regulate, and augment the functions of neurons.

Question 16

membrane potential

Answer 16

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.

Question 17

resting potential

Answer 17

The membrane potential characteristic of a nonconducting excitable cell, with the inside of the cell more negative than the outside.

Question 18

ion channels

Answer 18

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

Question 19

equilibrium potential (<em>E</em>_ion)

Answer 19

The magnitude of a cell’s membrane voltage at equilibrium; calculated using the Nernst equation.

Question 20

gated ion channel

Answer 20

A gated channel for a specific ion. The opening or closing of such channels may alter a cell’s membrane potential.

Question 21

hyperpolarization

Answer 21

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.

Question 22

depolarization

Answer 22

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.

Question 23

graded potential

Answer 23

In a neuron, a shift in the membrane potential that has an amplitude proportional to signal strength and that decays as it spread.

Question 24

action potential

Answer 24

An electrical signal that propagates (travels) along the membrane of a neuron or other excitable cell as a nongraded (all-or-none) depolarization.

Question 25

voltage-gated ion channel

Answer 25

A specialized ion channel that opens or closes in response to changes in membrane potential.

Question 26

threshold

Answer 26

The potential that an excitable cell membrane must reach for an action potential to be initiated.

Question 27

refractory period

Answer 27

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.

Question 28

myelin sheath

Answer 28

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.

Question 29

oligodendrocytes

Answer 29

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the central nervous system.

Question 30

Schwann cellss

Answer 30

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the peripheral nervous system.

Question 31

node of Ranvier

Answer 31

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.

Question 32

saltatory conduction

Answer 32

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.

Question 33

ligand-gated ion channel

Answer 33

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.

Question 34

excitatory postsynaptic potential (EPSP)

Answer 34

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.

Question 35

inhibitory postsynaptic potential (IPSP)

Answer 35

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.

Question 36

temporal summation

Answer 36

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.

Question 37

spatial summation

Answer 37

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.

Question 38

acetylcholine

Answer 38

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.

Question 39

glutamate

Answer 39

An amino acid that functions as a neurotransmitter in the central nervous system.

Question 40

gamma-aminobutyric acid (GABA)

Answer 40

An amino acid that functions as a CNS neurotransmitter in the central nervous system of vertebrates.

Question 41

biogenic amine

Answer 41

A neurotransmitter derived from an amino acid.

Question 42

norepinephrine

Answer 42

A catecholamine that is chemically and functionally similar to epinephrine and acts as a hormone or neurotransmitter; also known as noradrenaline.

Question 43

dopamine

Answer 43

A neurotransmitter that is a catecholamine, like epinephrine and norepinephrine.

Question 44

serotonin

Answer 44

A neurotransmitter, synthesized from the amino acid tryptophan, that functions in the central nervous system.

Question 45

neuropeptide

Answer 45

A relatively short chain of amino acids that serves as a neurotransmitter.

Question 46

endorphin

Answer 46

Any of several hormones produced in the brain and anterior pituitary that inhibit pain perception.