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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
Visceral motor division (autonomic nervous system)
– 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)
26
What are the two divisions of the Visceral motor division (autonomic nervous system)
sympathetic division and parasympathetic division
27
sympathetic division
– tends to arouse body for action – accelerating heart beat and respiration, while inhibiting digestive and urinary systems
28
parasympathetic division
– tends to have calming effect – slows heart rate and breathing – stimulates digestive and urinary systems
29
Universal Properties of a Neuron
* 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
30
neuron’s function requires an _______ form of communication!
electro-chemical
31
Neurons are defined by using either _______ or ______ criteria
structural ; functional
32
Soma
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
33
neurofibrils
bundles of actin filaments
34
Nissl bodies
compartmentalizes rough ER into dark staining cytoskeleton of soma consists of dense mesh of microtubules and neurofibrils
35
Do soma have centrioles?
no
36
Inclusions bodies
glycogen granules, lipid droplets, melanin
37
Lipofuscin / inclusion bodies
(golden brown pigment produced when lysosomes digest worn-out organelles) * lipofuscin accumulates with age * wear-and-tear granules * most abundant in old neurons
38
Dendrites
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
39
Axon is commonly called
nerve fiber
40
axon originates from a mound on one side of the soma called the
axon hillock or trigger zone
41
axoplasm
cytoplasm of axon
42
axolemma
plasma membrane of axon
43
only ___ axon per neuron
1
44
axon collaterals
branches of axon
45
Schwann cells
myelin sheath enclose axon
46
terminal “arborization”
distal end of axon, complex of fine branches / like in a tree!
47
synaptic knob (terminal button)
little swelling that forms a junction (synapse) with the next cell. neuron to muscle or neuron to glandular tissue Stores neurotransmitters
48
There are many types of neurotransmitters. Some are _________ others ________
stimulatory ; inhibitory
49
Neurotransmitters made in _____ and transported down ___ in vesicles
soma ; axon
50
Neurotransmitters released from synaptic knob via ________
exocytosis
51
Synaptic knob forms part of the ______ // the presynaptic membrane
synapse
52
Explain the events at a chemical synapse: synaptic transmission.
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
Interneurons (association neurons)
are confined to the CNS. receive signals from many neurons and carry out the integrative function
54
90% of all neurons are
interneurons
55
multipolar neuron
– one axon and multiple dendrites – most common – most neurons in the brain and spinal cord
56
bipolar neuron
– one axon and one dendrite – olfactory cells, retina, inner ear
57
unipolar neuron
– single process – sensory from skin and organs to spinal cord
58
anaxonic neuron
– many dendrites but no axon – help in visual processes
59
How many neurons are in the nervous system?
a trillion (10 to the 12th power) neurons
60
How many neurons are in an organism?
50 trillion
61
Neuroglia outnumber the neurons by as much as
50 to 1
62
Neuroglia (also called glial cells)
– 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
The CNS has how many types of glial cells? What are they?
4 oligodendrocytes ependymal cells microglia astrocytes
64
oligodendrocytes form _______ _______ in CNS
myelin sheaths
65
each arm-like process on an oligodendrocytes wraps around a ______ ______, forming an insulating layer that ______ ___ signal conduction
nerve fiber ; speeds up
66
ependymal cells ____ internal cavities of the brain
line
67
ependymal cells are ______ epithelium with ___ on apical surface
cuboidal ; cilia
68
ependymal cells ______ and _______ cerebrospinal fluid (CSF)
secrete ; circulate
69
cerebrospinal fluid (CSF)
clear liquid that bathes the CNS
70
microglia are
small, wandering macrophages
71
microglia are formed by white blood cell called __________
monocytes
72
microglia are thought to perform a complete ______ on the brain tissue several times a day
checkup
73
microglia wander in search of cellular debris to _________
phagocytize
74
Astrocytes are the most _______ glial cell in CNS
abundant
75
What covers entire brain's surface and most nonsynaptic regions of the neurons in the gray matter of the CNS?
Astrocytes
76
Astrocytes form a supportive _______ of nervous tissue
framework
77
Astrocytes have extensions (perivascular feet) that contact blood capillaries that stimulate them to form a tight seal called the
blood-brain barrier
78
Astrocytes convert blood glucose to ______ and supply this to the neurons for _______
lactate ; nourishment
79
Nerve growth factors secreted by astrocytes promote ______ ______ and _______ _______
neuron growth ; synapse formation
80
Astrocytes communicate electrically with neurons and may influence ______ ______ // role in memory not understood
synaptic signaling
81
Astrocytes regulate chemical composition of tissue fluid by absorbing excess ______________ and ____
neurotransmitters ; ions
82
astrocytosis or sclerosis
when neuron is damaged, astrocytes form hardened scar tissue and fill space formerly occupied by the neuron
83
Two types of glial cells occur in PNS. What are they?
Schwann cells and satellite cells
84
Schwann cells
* 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
Satellite cells
* surround the neurosomas in ganglia of the PNS * provide electrical insulation around the soma * regulate the chemical environment of the neurons
86
an insulating layer around a nerve fiber
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
production of the myelin sheath
Myelination
88
Myelination begins the ____ week of fetal development
14th * proceeds rapidly during infancy * completed in late adolescence * dietary fat is important to nervous system development (Danger! Trans Fat!)
89
Schwann cell
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
neurilemma
thick outermost coil of myelin sheath /// contains nucleus and most of its cytoplasm
91
external to neurilemma is basal lamina and a thin layer of fibrous connective tissue
endoneurium
92
oligodendrocytes cannot ______ around nerve fibers like Schwann cells
migrate
93
nerve fibers in CNS have no _______ or _______
neurilemma ; endoneurium
94
Many Schwann cells and oligodendrocytes are needed to cover one ____
nerve fiber
95
mesaxon
neurilemma wrapping of unmyelinated nerve fibers
96
Speed at which a nerve signal travels along a nerve fiber depends on two factors
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
slow signals supply
the stomach and dilate pupil where speed is less of an issue
98
fast signals of the nerve fiber supply
skeletal muscles and transport sensory signals for vision and balance
99
regeneration of a damaged peripheral nerve fiber can occur only if ….
– The soma is not damaged but intact – Neurilemma must be intact
100
axon distal to the injury cannot survive and they
degenerate macrophages engulf tissue debris inside tubular Schwan cells distal to point of damage
101
due to loss of nerve growth factor from neuron’s target cell,
the soma swells, ER breaks up, and nucleus moves off center
102
Peripheral Motor Nerves are not able to regenerate their
cell bodies
103
axon stump sprouts multiple ________ _______
growth processes
104
regeneration tube
formed by Schwann cells, basal lamina, and the neurilemma near the injury
105
regeneration tube guides the growing sprout back to the original target cells and
re-establishes synaptic contact
106
In regeneration of peripheral motor nerve axons, the nucleus
returns to normal shape
107
regeneration of damaged nerve fibers in the CNS may
not occur
108
Denervation Atrophy
Atrophy of muscle due to loss of nerve contact by damaged nerve
109
nervous pathway are a series of cells separated by gaps called ________.
synapses
110
nerve growth factor (NGF) are what and do what 2 things?
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
many proteins made in soma must be transported to
axon terminal
112
axonal transport
two-way passage of proteins, organelles, and other material along an axon anterograde transport and retrograde transport
113
microtubules
guide materials along axon
114
motor proteins
carry materials “on their backs” while they “crawl” along microtubules
115
kinesin
motor proteins in anterograde transport
116
dynein
motor proteins in retrograde transport
117
fast axonal transport
rabies, herpes simplex, tetanus, polio viruses
118
slow axonal transport
damaged nerve fibers regenerate at a speed governed by slow axonal transport
119
tumors
mature neurons have little or no capacity for mitosis and seldom form tumors
120
current science tells us certain neurons do have the capacity to undergo mitosis however
most neurons are in G zero
121
brain tumors arise from:

A&P : Unit 2 (7 decks)

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