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BIOL 3012 > 48 Chapter > Flashcards

48 Chapter Flashcards

1
Q

Neurons

A

The nerve cells that transfer information within the body

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2
Q

All neurons transmit electrical signals within the cell in an identical manner.

A

True

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3
Q

Brain

A

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

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4
Q

Ganglia (ganglion)

A

A cluster (functional group) of nerve cell bodies in a centralized nervous system

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5
Q

Cell body

A

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

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6
Q

Dendrite

A

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

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7
Q

Axon

A

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

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8
Q

Axon hillock

A

The cone-shaped base of an axon. Is typically where signals that travel down the axon are generated.

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9
Q

Synapse

A

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

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10
Q

Synaptic terminal

A

The part of each axon branch that form the synapse.

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11
Q

Neurotransmitter

A

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.

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12
Q

In describing a synapse, we refer to the transmitting neuron as the _______________ and the neuron, muscle, or gland cell that receives the signal as the _______________.

A

Presynaptic cell, postsynaptic cell

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13
Q

Glial cells, or glia

A

Cells of the nervous system that support, regulate, and augment the functions of neurons. Glia nourish neurons, insulate the axons of neurons, and regulate the extracellular fluid surrounding neurons.

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14
Q

Information processing by a nervous system occurs in three stages:

A

-Sensory input
-Integration: analyzing and interpreting the sensory input
-Motor output

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15
Q

Sensory neurons

A

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

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16
Q

Interneurons

A

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.

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17
Q

Motor neurons

A

A nerve cell that transmits signals from the brain or spinal cord to muscles or glands.

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18
Q

In many animals, the neurons that carry out integration are organized in a _______________

A

Central nervous system (CNS)

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19
Q

Central nervous system (CNS)

A

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

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20
Q

The neurons that carry information into and out of the CNS constitute the _______________.

A

Peripheral nervous system (PNS)

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21
Q

Peripheral nervous system (PNS)

A

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

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22
Q

Nerve

A

A fiber composed primarily of the bundled axons of neurons.

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23
Q

In neurons, as in other cells, ions are unequally distributed between the interior of cells and the surrounding fluid. As a result, the inside of a cell is negatively charged relative to the outside.

A
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24
Q

Membrane potential

A

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 substances.

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25
Q

Resting potential

A

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

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26
Q

Fundamentally, rapid changes in membrane potential are what enable us to see the intricate structure of a spiderweb, hear a song, or ride a bicycle.

A

True

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27
Q

In most neurons, the concentration of K+ is higher ___________, while the concentration of Na+ is _______________.

A

Inside the cell, higher outside

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28
Q

Sodium-potassium pump

A

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell. The sodium-potassium pump transports three Na+ out of the cell for every two K+ that it transports in.

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29
Q

Ion channels

A

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

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30
Q

Leak channels

A

Channel proteins that are always open

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31
Q

Diffusion of K+ through potassium channels that are always open is critical for establishing the resting potential.

A

True

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32
Q

Equilibrium potential (E ion)

A

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

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33
Q

Gated ion channels

A

Ion channels that open or close in response to stimuli.

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34
Q

Hyperpolarization

A

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.

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35
Q

Depolarization

A

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.
Is a reduction in the magnitude of the membrane potential.

36
Q

Graded potential

A

In a neuron, a shift in the membrane potential that has an amplitude proportional to signal strength and that decays as it spreads. The response to hyperpolarization or depolarization.

37
Q

Graded potentials induce a small electrical current that leaks out of the neuron as it flows along the membrane. Graded potentials thus decay with time and with distance from their source.

A

True

38
Q

If a depolarization shifts the membrane potential sufficiently, the result is a massive change in membrane voltage called _________________.

A

An action potential

39
Q

Action potential

A

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

40
Q

Unlike graded potentials, action potentials have a constant magnitude and can regenerate in adjacent regions of the membrane. Action potentials can therefore spread along axons, making them well suited for transmitting a signal over long distances.

A

True

41
Q

Voltage-gated ion channels

A

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

42
Q

Action potentials occur whenever a depolarization increases the membrane voltage to a particular value, called the _____________.

A

Threshold

43
Q

Threshold

A

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

44
Q

Because action potentials either occur fully or do not occur at all, they represent an all-or-none response to stimuli.

A

True

45
Q

The positive-feedback loop of channel opening and depolarization triggers an action potential whenever the membrane potential reaches threshold.

A

True

46
Q

Generation of Action Potentials
5 steps

A

Resting state
Depolarization
Rising phase of the action potential
Falling phase of the action potential
Undershoot

47
Q

Depolarization opens which channels? What opens first and what are its effects?

A

Depolarization opens both sodium and potassium voltages-gates channels. Sodium channels open first, initiating the action potential. As the action potential proceeds, sodium channels become inactivated: a loop of the channel protein moves, blocking ion flow through the opening. In contrast, potassium channels open more slowly than sodium channels, but remain open and functional until the end of the action potential.

48
Q

The “downtime” when a se one action potential cannot be initiated, because the sodium channels remain inactivated during the falling phase and the early part of the undershoot during the initial stimulus, is called the ________________

A

Refractory period

49
Q

Refractory period

A

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.

50
Q

Why does an action potential that starts at the axon hillock move along the axon toward the synaptic terminals?

A

Immediately behind the traveling zone of depolarization caused by Na+ inflow is a zone of repolarization caused by K+ outflow. In the repolarized zone, the sodium channels remain inactivated. Consequently, the inward current that depolarizes the axon membrane ahead of the action potential cannot produce another action potential behind it. This prevents action potentials from traveling back toward the cell body.

51
Q

Myelin sheath

A

Is an insulating coat of cell membranes wrapped around the axon of vertebrate neurons. Myelin sheaths are formed by Shwann cells or oligodendrocytes; it is interrupted by nodes of Ranvier, where action potentials are generated.

52
Q

Myelin sheaths are produced by two types of glia:

A

Oligodendrocytes in the CNS
Schwann cells in the PNS

53
Q

Oligodendrocytes

A

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

54
Q

Schwann cells

A

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

55
Q

node of Ranvier

A

A gap in the myelin sheath of certain axons where an action potential may be generated. In saltatory conduction, an action potential is regenerated at each node, appearing to “jump” along the axon from node to node.

56
Q

Saltatory conduction

A

A mechanism for propagating action potentials in which 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.

57
Q

In most cases, action potentials are not transmitted from neurons to other cells. However information is transmitted, and this transmission occurs at synaptic terminals.

A
58
Q

Electrical synapses

A

Are synapses that contain gap junctions which do allow electrical current to flow directly from one neuron to another. They synchronize the activity of neurons responsible for certain rapid, unvarying behaviors.

59
Q

Chemical synapses involve the release of a chemical neurotransmitter by the presynaptic neuron.

A

True

60
Q

Synaptic vesicles

A

Membrane-enclosed compartments that package the neurotransmitter at chemical synapses.

61
Q

Explain a chemical synapse

A

The action potential depolarizes the pre synaptic membrane which opens voltage-gated channels, triggering an influx of Ca2+. The elevated Ca+2 concentration causes synaptic vesicles to fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft. Then the neurotransmitter binds to ligand-gated ion channels in the postsynaptic membrane, triggering a response.

62
Q

Synaptic cleft

A

The gap that separates the presynaptic neuron from the postsynaptic cell.

63
Q

Ligand-gated ion channel, or ionotropic receptor

A

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.

64
Q

Postsynaptic potential

A

A graded potentials in the postsynaptic cell caused by the binding of the neurotransmitter (the receptor’s ligand) to a particular part of the ligand-gated ion channel, which opens the channel and allows specific ions to diffuse across the postsynaptic membrane.

65
Q

Excitatory postsynaptic potential (EPSP)

A

An electrical charge (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.

66
Q

Inhibitory postsynaptic potential (IPSP)

A

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. Occurs when the ligand-gated ion channel is selectively permeable for only K+ or Cl-.

67
Q

As a graded potential, a postsynaptic potential becomes smaller with distance from the synapse. Therefore, by the time a single EPSP reaches the axon hillock, it is usually too small to trigger an action potential.

A

True

68
Q

Temporal summation

A

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.

69
Q

Spatial summation

A

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.

70
Q

The axon hillock is the neuron’s integrating center, the region where the membrane potential at any instant represents the summed effect of all EPSPs and IPSPs.

A

True

71
Q

Metabotropic receptor

A

Is a neurotransmitter receptor which is not part of an ion channel. So named because the resulting opening or closing of ion channels depends on one or more metabolic steps.

72
Q

How is neurotransmitter signaling terminated?

A

Both receptor activation and postsynaptic response cease when neurotransmitter molecules are cleared from the synaptic cleft. The removal of neurotransmitters can occur by simple diffusion or by other mechanisms. For example, enzymatic breakdown of neurotransmitter in the synaptic cleft or the reuptake of neurotransmitter by presynaptic neuron.

73
Q

Acetylcholine

A

One of the most common neurotransmitters; functions in muscle stimulation, memory formation, and learning.

74
Q

Neuromuscular junction

A

The site where a motor neuron forms a synapse with a skeletal muscle cell.

75
Q

In vertebrates, there are two major classes of acetylcholine receptors:

A

One is a ligand-gates ion channel, which functions at the vertebrate neuromuscular junction. The other is a metabotropic acetylcholine receptor found in the CNS and heart.

76
Q

Acetylcholinesterase

A

An enzyme in the synaptic cleft that hydrolyzes the neurotransmitter.

77
Q

Four classes of neurotransmitters:
(Excluding acetylcholine)

A

Amino acids
Biogenic amines
Neuropeptides
Gases

78
Q

Glutamate

A

An amino acid that functions as a neurotransmitter in the CNS

79
Q

Gamma-aminobutyric acid (GABA)

A

An amino acid that functions as a CNS neurotransmitter in the CNS of vertebrates. Functions in most inhibitory synapses in the brain.

80
Q

Glycine

A

An amino acid that functions as a neurotransmitter and acts at inhibitory synapses in parts of the CNS that lie outside of the brain.

81
Q

Biogenic amines

A

A neurotransmitter derived from an amino acid.

82
Q

Norepinephrine

A

A Biogenic amine made from tyrosine. Is an excitatory neurotransmitter in the autonomic nervous system, a branch of the PNS

83
Q

Dopamine

A

A neurotransmitter that is a catecholamine, like epinephrine and norepinephrine. Is derived from tyrosine.

84
Q

Serotonin

A

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

85
Q

Neuropeptides

A

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

86
Q

Endorphins

A

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

BIOL 3012 (14 decks)

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