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A&P : Unit 2 > Chapter 12.1 : Nervous Tissue > Flashcards

Chapter 12.1 : Nervous Tissue Flashcards

1
Q

What two systems regulate homeostasis?

A

endocrine system and nervous system

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2
Q

Endocrine system

A

communicates by means of chemical messengers (hormones) secreted into to the blood // slow

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3
Q

Nervous system

A

employs electrical (action potentials) and
chemicals (neuro-transmitters) to send
messages between cell to cell // fast

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4
Q

The nervous system carries out its task in what three steps?

A

– sense organs (receptor) [1. receive information] about
changes in the body and the external environment then
transmits coded messages to the spinal cord and the
brain
– brain and spinal cord [2. processes this information],
relates it to past experiences, and determine what
response is appropriate to the circumstances
– brain and spinal cord [3. issue commands] to muscles and
gland cells to carry out such a response

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5
Q

What are the two anatomical divisions of the nervous system?

A

Central nervous system and peripheral nervous system

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6
Q

Central nervous system (CNS)

A

– brain and spinal cord enclosed in bony coverings
– enclosed by cranium and vertebral column
– nuclei – isolated “islands” of grey matter within CNS

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7
Q

nuclei

A

isolated “islands” of grey matter within CNS

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8
Q

Peripheral nervous system (PNS)

A

– all the nervous system except the brain and spinal cord
– composed of nerves and ganglia
* nerve – a bundle of nerve fibers (axons) wrapped in fibrous connective tissue
* ganglion – isolated “islands” of grey matter within PNS // soma outside CNS // a knot-like swelling in a nerve where neuron cell bodies are concentrated

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9
Q

nerve

A

a bundle of nerve fibers (axons) wrapped in fibrous connective
tissue

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10
Q

ganglion

A

isolated “islands” of grey matter within PNS // soma outside
CNS // a knot-like swelling in a nerve where neuron cell bodies are concentrated

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11
Q

How is the peripheral nervous system subdivided?

A

Somatic Nervous System, Autonomic Nervous System, and Enteric Nervous System.

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12
Q

Somatic refers to which parts of the body?

A

muscles, bones, joints, and the skin

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13
Q

Visceral refers to which parts of the body?

A

Internal organs

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14
Q

What is the target tissue of the somatic nervous system?

A

Skeletal muscle

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15
Q

What is the target tissue of the autonomic nervous system?

A

smooth muscle, cardiac muscle, and glands

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16
Q

What is the target tissue of the enteric nervous system?

A

Smooth muscle, glands, and endocrine cells of GI tract

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17
Q

Sensory division neurons

A

– carries sensory signals from receptors located in skeletal muscles and other tissues to the CNS
– informs the CNS of stimuli thoughout the body

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18
Q

somatic sensory neurons (division)

A

carries signals from receptors in the skin, muscles, bones,
and joints

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19
Q

visceral sensory neurons (division)

A

carries signals from the viscera of the thoracic and
abdominal cavities /// heart, lungs, stomach, blood
vessels, and urinary bladder

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20
Q

Motor Division Neurons

A

These signals originate in CNS and flow out to the
effectors

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21
Q

What are the two types of Motor division neurons?

A

somatic and visceral

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22
Q

Visceral motor neurons

A

by way of the Autonomic Nervous System = to glands, smooth muscle, and cardiac

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23
Q

Effectors

A

tissues that respond to commands
from the CNS

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24
Q

Somatic Motor Division (efferent fibers) signal originates from brain’s ________ ______

A

precentral gyrus

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25
Q

Visceral motor division (autonomic nervous system)

A

– carries signals to glands, cardiac muscle, and smooth muscle
– involuntary reflexes regulated by two division // also called
visceral reflexes (e.g. salavation, voiding urinary bladder)

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26
Q

What are the two divisions of the Visceral motor division (autonomic nervous system)

A

sympathetic division and parasympathetic division

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27
Q

sympathetic division

A

– tends to arouse body for action
– accelerating heart beat and respiration, while inhibiting
digestive and urinary systems

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28
Q

parasympathetic division

A

– tends to have calming effect
– slows heart rate and breathing
– stimulates digestive and urinary systems

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29
Q

Universal Properties of a Neuron

A
  • Excitability (irritability) /// respond to environmental
    changes called stimuli
  • Conductivity /// neurons respond to stimuli by
    producing electrical signals that are quickly
    conducted to other cells at distant locations
  • Secretion /// when electrical signal reaches end of
    nerve fiber, a chemical neurotransmitter is secreted
    that crosses the gap and stimulates the next cell
  • Note: The neuron’s function requires an electro-chemical
    form of communication! // its not just an electrical signal
    and not just a chemical signal but both which occurs at the
    synapse
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30
Q

neuron’s function requires an _______
form of communication!

A

electro-chemical

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31
Q

Neurons are defined by using either _______ or ______ criteria

A

structural ; functional

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32
Q

Soma

A

Control center of the neuron
also called neurosoma, cell body, or perikaryon

has a single, centrally located nucleus with large nucleolus

cytoplasm contains mitochondria, lysosomes, a Golgi complex, numerous inclusions, extensive rough endoplasmic reticulum, and a cytoskeleton.

The cytoskeleton consists of dense mesh of microtubules
and neurofibrils

compartmentalizes rough ER into dark staining Nissl
bodies

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33
Q

neurofibrils

A

bundles of actin filaments

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34
Q

Nissl bodies

A

compartmentalizes rough ER into dark staining

cytoskeleton of soma consists of dense mesh of microtubules
and neurofibrils

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35
Q

Do soma have centrioles?

A

no

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36
Q

Inclusions bodies

A

glycogen granules, lipid droplets,
melanin

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37
Q

Lipofuscin / inclusion bodies

A

(golden brown pigment
produced when lysosomes digest worn-out organelles)
* lipofuscin accumulates with age
* wear-and-tear granules
* most abundant in old neurons

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38
Q

Dendrites

A

Primary site for receiving signals from
other neurons = “the receptors”
* Transducers = receptors
* Stimulus creates local potential ///
graded potentials
* the more dendrites the neuron has, the
more information it can receive and
incorporate into decision making
* provide precise pathway for the reception
and processing of neural information

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39
Q

Axon is commonly called

A

nerve fiber

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40
Q

axon originates from a mound on one side of
the soma called the

A

axon hillock or trigger zone

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41
Q

axoplasm

A

cytoplasm of axon

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42
Q

axolemma

A

plasma membrane of axon

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43
Q

only ___ axon per neuron

A

1

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44
Q

axon collaterals

A

branches of axon

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45
Q

Schwann cells

A

myelin sheath enclose axon

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46
Q

terminal “arborization”

A

distal end of axon, complex of fine branches / like in a tree!

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47
Q

synaptic knob (terminal button)

A

little swelling that forms a junction (synapse) with the next cell. neuron to muscle or neuron to glandular tissue

Stores neurotransmitters

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48
Q

There are many types of neurotransmitters. Some are _________ others ________

A

stimulatory ; inhibitory

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49
Q

Neurotransmitters made in _____ and transported down ___ in
vesicles

A

soma ; axon

50
Q

Neurotransmitters released from synaptic knob via ________

A

exocytosis

51
Q

Synaptic knob forms part of the ______ // the presynaptic
membrane

A

synapse

52
Q

Explain the events at a chemical synapse:
synaptic transmission.

A
  1. An action potential in the presynaptic neuron triggers Ca2+ channels in the axon terminal to open.
  2. Influx of Ca2+ causes synaptic vesicles to release neurotransmitters into the synaptic cleft.
  3. Neurotransmitters bind to receptors on the postsynaptic neuron.
  4. Ion channels open, leading to a local potential and possibly an action
53
Q

Interneurons (association neurons)

A

are confined to the CNS.

receive signals from many neurons and carry
out the integrative function

54
Q

90% of all neurons are

A

interneurons

55
Q

multipolar neuron

A

– one axon and multiple dendrites
– most common
– most neurons in the brain and
spinal cord

56
Q

bipolar neuron

A

– one axon and one dendrite
– olfactory cells, retina, inner ear

57
Q

unipolar neuron

A

– single process
– sensory from skin and organs to
spinal cord

58
Q

anaxonic neuron

A

– many dendrites but no axon
– help in visual processes

59
Q

How many neurons are in the nervous system?

A

a trillion (10 to the 12th power) neurons

60
Q

How many neurons are in an organism?

A

50 trillion

61
Q

Neuroglia outnumber the neurons by as much as

A

50 to 1

62
Q

Neuroglia (also called glial cells)

A

– Support, protect, and enhance function of neurons
– Bind neurons together and form framework for nervous
tissue
– In fetus, guide migrating neurons to their destination
– If the surface of a mature neuron is not in synaptic contact
with another neuron then non-synaptic surface is covered
by glial cells /// prevents neurons from touching each
other /// gives precision to conduction pathways

63
Q

The CNS has how many types of glial cells? What are they?

A

4

oligodendrocytes
ependymal cells
microglia
astrocytes

64
Q

oligodendrocytes form _______ _______ in CNS

A

myelin sheaths

65
Q

each arm-like process on an oligodendrocytes wraps around a ______ ______, forming an insulating layer that ______ ___ signal conduction

A

nerve fiber ; speeds up

66
Q

ependymal cells ____ internal cavities of the brain

A

line

67
Q

ependymal cells are ______ epithelium with ___ on apical surface

A

cuboidal ; cilia

68
Q

ependymal cells ______ and _______ cerebrospinal fluid (CSF)

A

secrete ; circulate

69
Q

cerebrospinal fluid (CSF)

A

clear liquid that bathes the CNS

70
Q

microglia are

A

small, wandering macrophages

71
Q

microglia are formed by white blood cell called __________

A

monocytes

72
Q

microglia are thought to perform a complete ______ on the brain tissue several times a day

A

checkup

73
Q

microglia wander in search of cellular debris to _________

A

phagocytize

74
Q

Astrocytes are the most _______ glial cell in CNS

A

abundant

75
Q

What covers entire brain’s surface and most nonsynaptic
regions of the neurons in the gray matter of the CNS?

A

Astrocytes

76
Q

Astrocytes form a supportive _______ of nervous tissue

A

framework

77
Q

Astrocytes have extensions (perivascular feet) that
contact blood capillaries that stimulate them to
form a tight seal called the

A

blood-brain barrier

78
Q

Astrocytes convert blood glucose to ______ and supply this to the neurons for _______

A

lactate ; nourishment

79
Q

Nerve growth factors secreted by astrocytes promote
______ ______ and _______ _______

A

neuron growth ; synapse formation

80
Q

Astrocytes communicate electrically with neurons and may
influence ______ ______ // role in memory not
understood

A

synaptic signaling

81
Q

Astrocytes regulate chemical composition of tissue fluid by
absorbing excess ______________ and ____

A

neurotransmitters ; ions

82
Q

astrocytosis or sclerosis

A

when neuron is damaged, astrocytes form hardened scar tissue and fill space formerly occupied by the neuron

83
Q

Two types of glial cells occur in PNS. What are they?

A

Schwann cells and satellite cells

84
Q

Schwann cells

A
  • envelope nerve fibers in PNS
  • wind repeatedly around a nerve fiber
  • produces a myelin sheath similar to the ones
    produced by oligodendrocytes in CNS
  • assist in the regeneration of damaged fibers
85
Q

Satellite cells

A
  • surround the neurosomas in ganglia of the PNS
  • provide electrical insulation around the soma
  • regulate the chemical environment of the neurons
86
Q

an insulating layer around a nerve fiber

A

Myelin sheath

– formed by [oligodendrocytes] in CNS
– formed by [Schwann cells] in PNS
– consists of the plasma membrane of glial cells (20%
protein and 80 % lipid)

87
Q

production of the myelin sheath

A

Myelination

88
Q

Myelination begins the ____ week of fetal development

A

14th

  • proceeds rapidly during infancy
  • completed in late adolescence
  • dietary fat is important to nervous system
    development (Danger! Trans Fat!)
89
Q

Schwann cell

A

spirals repeatedly around a single nerve fiber

lays down as many as a hundred layers of its own membrane

no cytoplasm between the membranes

90
Q

neurilemma

A

thick outermost coil of myelin sheath ///
contains nucleus and most of its cytoplasm

91
Q

external to neurilemma is basal lamina and a thin layer of
fibrous connective tissue

A

endoneurium

92
Q

oligodendrocytes cannot ______ around nerve fibers like
Schwann cells

A

migrate

93
Q

nerve fibers in CNS have no _______ or
_______

A

neurilemma ; endoneurium

94
Q

Many Schwann cells and oligodendrocytes are needed to cover one ____

A

nerve fiber

95
Q

mesaxon

A

neurilemma wrapping of unmyelinated nerve fibers

96
Q

Speed at which a nerve signal travels along a nerve fiber depends on two factors

A

Diameter of fiber
- larger fibers have more surface area and conduct signals
more rapidly
Presence or absence of myelin / amount of myelination
- myelin further speeds signal conduction
Temperature (lower speed when cooled)
-

97
Q

slow signals supply

A

the stomach and dilate pupil where speed is less of an issue

98
Q

fast signals of the nerve fiber supply

A

skeletal muscles and transport sensory signals for vision and balance

99
Q

regeneration of a damaged peripheral nerve fiber can occur only if ….

A

– The soma is not damaged but intact
– Neurilemma must be intact

100
Q

axon distal to the injury cannot survive and they

A

degenerate

macrophages engulf tissue debris inside tubular Schwan cells
distal to point of damage

101
Q

due to loss of nerve growth factor from neuron’s
target cell,

A

the soma swells, ER breaks up, and nucleus
moves off center

102
Q

Peripheral Motor Nerves are not able to regenerate their

A

cell bodies

103
Q

axon stump sprouts multiple ________ _______

A

growth processes

104
Q

regeneration tube

A

formed by Schwann cells, basal lamina, and the neurilemma
near the injury

105
Q

regeneration tube guides the growing sprout back to the original target cells and

A

re-establishes synaptic contact

106
Q

In regeneration of peripheral motor nerve axons, the nucleus

A

returns to normal shape

107
Q

regeneration of damaged nerve fibers in the CNS may

A

not occur

108
Q

Denervation Atrophy

A

Atrophy of muscle due to loss of nerve contact by damaged nerve

109
Q

nervous pathway are a series of cells separated by
gaps called ________.

A

synapses

110
Q

nerve growth factor (NGF) are what and do what 2 things?

A

a protein secreted by a gland, muscle, and glial cells and picked up by the axon terminals of the neurons.
– prevents apoptosis (programmed cell death) in growing neurons
– enables growing neurons to make contact with their target cells

111
Q

many proteins made in soma must be transported to

A

axon terminal

112
Q

axonal transport

A

two-way passage of proteins, organelles,
and other material along an axon

anterograde transport and retrograde transport

113
Q

microtubules

A

guide materials along axon

114
Q

motor proteins

A

carry materials “on their backs” while
they “crawl” along microtubules

115
Q

kinesin

A

motor proteins in anterograde transport

116
Q

dynein

A

motor proteins in retrograde transport

117
Q

fast axonal transport

A

rabies, herpes simplex, tetanus, polio viruses

118
Q

slow axonal transport

A

damaged nerve fibers regenerate at a speed governed by slow axonal transport

119
Q

tumors

A

mature neurons have little or no capacity for mitosis and seldom form tumors

120
Q

current science tells us certain neurons do have the capacity to
undergo mitosis however

A

most neurons are in G zero

121
Q

brain tumors arise from:

A

A&P : Unit 2 (7 decks)

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