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Anatomy & Physiology > Chapter 11 > Flashcards

Chapter 11 Flashcards

1
Q

peripheral nervous system (PNS)

A

it includes sensory receptors, nerves, ganglia, and plexuses. The sensory division of the PNS detects stimuli and transmits information in the form of action potentials to the CNS.

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2
Q

central nervous system (CNS)

A

consists of the brain and spinal cord.

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3
Q

Sensory receptors

A

endings of neurons, or separate, specialized cells that detect temperature, pain, touch, pressure, light, sound, odor, and other stimuli.

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4
Q

nerve

A

bundle of axons and their sheaths; it connects the CNS to sensory receptors, muscles, and glands.

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5
Q

cranial nerves/ spinal nerves

A

12 pairs originate the brain, and 31 pairs of spinal nerves originate from the spinal cord

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6
Q

ganglion

A

a collection of neuron cell bodies located outside the CNS.

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7
Q

plexus

A

an extensive network of axons and, in some cases, neuron cell bodies, located outside the CNS.

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8
Q

The PNS has two functional subdivisions: The sensory division (afferent (toward) division) and the motor division (efferent (away) division)

A
  • sensory - transmits electrical signals, called action potentials, from the sensory receptors to the CNS. The cell bodies of sensory neurons are located in dorsal root ganglia near the spinal cord or in ganglia near the origin of certain cranial nerves.
  • motor division - transmits action potentials from the CNS to effector organs, such as muscles and glands.
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9
Q

The motor division is divided into the somatic nervous system (SNS) and the autonomic nervous system (ANS).

A

-somatic nervous system controls conscious activities -ANS controls subconscious activities.

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10
Q

synapse

A

junction of a neuron with another cell; axons extend through nerves to form connections with skeletal muscle cells.

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11
Q

The ANS is subdivided into the sympathetic division and the parasympathetic division.

A

In general, the sympathetic division is most active during physical activity, whereas the parasympathetic division regulates resting functions, such as digesting food or emptying the urinary bladder.

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12
Q

enteric nervous system (ENS)

A

consists of plexuses within the wall of the digestive tract; enteric neurons monitor and control the digestive tract independently of the CNS through local reflexes.

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13
Q

The two types of cells that make up the nervous system are neurons and nonneural cells.

A

Neurons receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs. Nonneural cells are called neuroglia cells, and they support and protect neurons and perform other functions.

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14
Q

neuron cell body

A

cell body

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15
Q

Nissl bodies

A

The neurofilaments separate abundant ER which are located primarily in the cell body and dendrites; primary site of protein synthesis in neurons.

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16
Q

dendritic spines

A

Many dendrite surfaces have small extensions called dendritic spines, where axons of other neurons form syn- apses with the dendrites.

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17
Q

axon hillock

A

In most neurons, a single axon arises from this cone-shaped area of the neuron cell body

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18
Q

initial segment

A

beginning of the axon

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19
Q

trigger zone

A

Action potentials are generated at the trigger zone, which consists of the axon hillock and the part of the axon nearest the cell body.

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20
Q

axoplasm/axolemma

A

The cytoplasm of an axon is sometimes called the axoplasm, and its plasma membrane is called the axolemma.

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21
Q

presynaptic terminals

A

Axons terminate by branching to form small extensions with enlarged ends

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22
Q

neurotransmitters

A

Within the presynaptic terminals are these numerous small vesicles that contain chemicals

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23
Q

Sensory neurons (or afferent neurons)

A

conduct action potentials toward the CNS

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24
Q

motor neurons (or efferent neurons)

A

conduct action potentials away from the CNS toward muscles or glands.

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25
Q

Interneurons

A

conduct action potentials from one neuron to another within the CNS

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26
Q

Multipolar neurons

A

have many dendrites and a single axon.

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27
Q

Bipolar neurons

A

have two processes: one dendrite and one axon

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28
Q

Pseudo-unipolar neurons

A

have a single process extending from the cell body; This process divides into two branches a short distance from the cell body. One branch extends to the CNS, and the other extends to the periphery and has dendritelike sensory receptors.

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29
Q

Astrocytes

A

neuroglia that are star- shaped because cytoplasmic processes extend from the cell body. These extensions widen and spread out to form foot processes, which cover the surfaces of blood vessels, neurons, and the pia mater.

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30
Q

blood-brain barrier

A

endothelial cells with their tight junctions form the blood-brain barrier, which determines what substances can pass from the blood into the nervous tissue of the brain and spinal cord.

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31
Q

reactive astrocytosis

A

Almost all injuries to CNS tissue induce reactive astrocytosis, in which astrocytes wall off the injury site and help limit the spread of inflammation to the surrounding healthy tissue.

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32
Q

Ependymal cells

A

line the ventricles (cavities) of the brain and the central canal of the spinal cord

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33
Q

choroid plexuses

A

formed by specialized ependymal cells and blood vessels, which are located within certain regions of the ventricles; secrete the cerebrospinal fluid that circulates through the ventricles of the brain

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34
Q

Microglia

A

neuroglia in the CNS that become mobile and phagocytic in response to inflammation. They phagocytize necrotic tissue, microorganisms, and other foreign substances that invade the CNS.

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35
Q

Oligodendrocytes

A

have cytoplasmic extensions that can surround axons; form an insulating material called myelin sheath

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36
Q

Schwann cells

A

neuroglia in the PNS that wrap around axons; form a myelin sheath around a portion of only one axon

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37
Q

Satellite cells

A

surround neuron cell bodies in sensory ganglia; provide support and nutrition to the neuron cell bodies, protect neurons from heavy-metal poisons by absorbing them and reducing their access to the neuron cell bodies.

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38
Q

myelinated axons

A

in myelinated axons, the extensions from Schwann cells or oligodendrocytes repeatedly wrap around a segment of an axon to form a series of tightly wrapped membranes rich in phospholipids, with little cytoplasm sandwiched between the membrane layers

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39
Q

nodes of Ranvier

A

interruptions in the myelin sheath

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40
Q

Unmyelinated axons

A

rest in invaginations of the Schwann cells or oligodendrocytes

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41
Q

Gray matter

A

consists of groups of neuron cell bodies and their dendrites, where there is very little myelin.

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42
Q

cortex/nuclei

A

In the CNS, gray matter on the surface of the brain is called the cortex, and clusters of gray matter located deeper within the brain are called nuclei.

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43
Q

ganglion

A

a cluster of neuron cell bodies in the PNS

44
Q

White matter

A

consists of bundles of parallel axons with their myelin sheaths, which are whitish in color.

45
Q

White matter of the CNS

A

forms nerve tracts, or conduction pathways, which propagate action potentials from one area of the CNS to another. In the PNS, bundles of axons and their connective tissue sheaths are called nerves

46
Q

sodium-potassium pump

A

The differences in K+ and Na+ concentrations across the plasma membrane are maintained primarily by the action of this

47
Q

Leak ion channels

A

nongated ion channels; are always open and are responsible for the permeability of the plasma membrane to ions when the plasma membrane is unstimulated, or at rest

48
Q

Gated ion channels

A

closed until opened by specific signals. By opening and closing, these channels can change the permeability of the plasma membrane.

49
Q

ligand

A

a molecule, such as a neurotransmitter or a hormone, that binds to a receptor.

50
Q

receptor

A

a protein or glycoprotein that has a receptor site to which a ligand can bind; located in plasma membrane

51
Q

Ligand-gated ion channels

A

receptors that have an extracellular receptor site and a membrane- spanning part that forms an ion channel.

52
Q

Voltage-gated ion channels

A

These channels open and close in response to small voltage changes across the plasma membrane.

53
Q

other gated ion channels

A

Gated ion channels that respond to stimuli other than ligands or voltage changes are present in specialized electrically excitable tissues.

54
Q

polarized

A

opposite charges, or poles, across the membrane.

55
Q

potential difference

A

The electrical charge difference across the plasma membrane

56
Q

resting membrane potential

A

In an unstimulated, or resting, cell, this is the potential difference

57
Q

Depolarization

A

decrease in the membrane potential caused by a decrease in the charge difference, or polarity, across the plasma membrane

58
Q

hyperpolarization

A

an increase in the membrane potential caused by an increase in the charge difference across the plasma membrane; occurs when the inside of the plasma membrane becomes more negative relative to the outside

59
Q

graded potential

A

a change in the membrane potential that is localized to one area of the plasma membrane; can result from (1) chemical signals binding to their receptors, (2) changes in the voltage across the plasma membrane, (3) mechanical stimulation, (4) temperature changes, or (5) spontaneous changes in membrane permeability

60
Q

Summation

A

Summation of graded potentials can occur when the effects produced by one graded potential are added onto the effects produced by another graded potential, which can lead to an action potential

61
Q

action potential

A

an electrical signal conducted from a neuron to its target

62
Q

threshold

A

a series of permeability changes results in an action potential

63
Q

depolarization phase

A

the membrane potential moves away from the resting state and becomes more positive

64
Q

repolarization phase

A

the membrane potential returns toward the resting state and becomes more negative

65
Q

afterpotential

A

After the repolarization phase, the plasma membrane may be slightly hyperpolarized for a short period

66
Q

activation gates and inactivation gates

A

Each voltage-gated Na+ channel has two voltage-sensitive gates; at rest, NA closed but when reaches threshold NA open and can diffuse; at rest K are closed but when reaches threshold K open but diffuse slower than NA

67
Q

refractory period

A

Once an action potential is produced at a given point on the plasma membrane, the sensitivity of that area to further stimulation decreases for a time called the refractory period.

68
Q

absolute refractory period

A

The first part of the refractory period, during which complete insensitivity exists to another stimulus

69
Q

relative refractory period

A

The second part of the refractory period that follows the absolute refractory period; when the membrane is more permeable to K1 because many voltage-gated K1 channels are open; ends when the voltage-gated K1 channels close

70
Q

action potential frequency

A

the number of action potentials produced per unit of time in response to a stimulus.

71
Q

subthreshold stimulus

A

any stimulus not strong enough to produce a graded potential that reaches threshold.

72
Q

threshold stimulus

A

produces a graded potential that is just strong enough to reach threshold and cause the production of a single action potential.

73
Q

maximal stimulus

A

just strong enough to produce a maximum frequency of action potentials.

74
Q

submaximal stimulus

A

includes all stimuli between threshold and the maximal stimulus strength.

75
Q

supramaximal stimulus

A

any stimulus stronger than a maximal stimulus.

76
Q

propagate

A

spread

77
Q

Hypokalemia

A

a lower than normal concentration of K in the blood or extracellular fluid. Reduced extracellular K+ concentrations cause hyperpolarization of the resting membrane potential

78
Q

Hypocalcemia

A

a lower than normal concentration of Ca2+ in the blood or extracellular fluid.

79
Q

tetany

A

uncontrolled contraction of skeletal muscles

80
Q

local current or an ionic current

A

The movement of positively charged ions

81
Q

continuous conduction

A

action potential conduction in unmyelinated axons

82
Q

saltatory conduction

A

In a myelinated axon, an action potential is conducted from one node of Ranvier to another

83
Q

Nerve fibers (axons)

A

classified according to their size and myelination.

84
Q

presynaptic cell

A

The cell that transmits a signal toward the synapse

85
Q

postsynaptic cell

A

the cell that receives the signal

86
Q

Electrical synapses

A

gap junctions that allow a local current to flow between adjacent cells

87
Q

connexons

A

at these gap junctions, the membranes of adjacent cells are separated by these gap spanned by tubular proteins

88
Q

The essential components of a chemical synapse are:

A

the presynaptic terminal, the synaptic cleft, and the postsynaptic membrane

89
Q

presynaptic terminal

A

consists of the end of an axon

90
Q

synaptic cleft

A

space separating the axon ending and the cell with which it synapses

91
Q

postsynaptic cell

A

The membrane of the postsynaptic cell opposed to the presynaptic terminal; typically other neurons, muscle cells, or gland cells.

92
Q

synaptic vesicles

A

contain neurotrans- mitters, such as acetylcholine

93
Q

acetylcholinesterase

A

in the neuromuscular junction, the neurotransmitter acetylcholine is broken down by the enzyme acetylcholinesterase to acetic acid and choline

94
Q

monoamine oxidase

A

This enzyme inactivates some of the norepinephrine.

95
Q

catechol-O-methyltransferase

A

Norepinephrine in the circulation is taken up primarily by liver and kidney cells, where the enzymes monoamine oxidase and catechol-O-methyltransferase convert it into inactive metabolites.

96
Q

Neuromodulators

A

substances released from neurons that influence the likelihood of an action potential being produced in the postsynaptic cell.

97
Q

excitatory post- synaptic potential (EPSP)

A

When depolarization occurs, the response is stimulatory, and the graded potential is called an excitatory post- synaptic potential; important because the depolarization might reach threshold, thereby producing an action potential and a response from the cell.

98
Q

inhibitory postsynaptic potential (IPSP)

A

When the combination of a neurotransmitter with its receptor results in hyperpolarization of the postsynaptic membrane, the response is inhibitory, and the local hyperpolarization is called an inhibitory postsynaptic potential; important because they decrease the likelihood of producing action potentials by moving the membrane potential farther from threshold.

99
Q

inhibitory neurons

A

Neurons releasing neurotransmitter substances that cause IPSPs

100
Q

axoaxonic synapses

A

Many of the synapses of the CNS are axoaxonic synapses, meaning that the axon of one neuron synapses with the presynaptic terminal (axon) of another

101
Q

presynaptic inhibition

A

the amount of neurotransmitter released from the presynaptic terminal decreases.

102
Q

presynaptic facilitation

A

the amount of neurotransmitter released from the presynaptic terminal increases.

103
Q

Spatial summation

A

occurs when multiple action potentials arrive simultaneously at two different presynaptic terminals that synapse with the same postsynaptic neuron.

104
Q

Temporal summation

A

results when two or more action potentials arrive in very close succession at a single presynaptic terminal.

105
Q

convergent pathways

A

In convergent pathways, many neurons converge and synapse with a smaller number of neurons; Convergence allows different parts of the nervous system to activate or inhibit the activity of neurons.

106
Q

divergent pathways

A

in divergent pathways, a smaller number of presynaptic neurons synapse with a larger number of postsynaptic neurons to allow information transmitted in one neuronal pathway to diverge into two or more pathways; allow one part of the nervous system to affect more than one other part of the nervous system.

107
Q

Oscillating circuits

A

have neurons arranged in a circular fashion, which allows action potentials entering the circuit to cause a neuron farther along in the circuit to produce an action potential more than once; This response, called afterdischarge, prolongs the response to a stimulus.

Anatomy & Physiology (10 decks)

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