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Cell Bio Exam 2 > Nervous Tissue I > Flashcards

Nervous Tissue I Flashcards

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1
Q

What is the basic structural and functional unit of the nervous system?

A

neuron

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2
Q

Other names for the cell body?

A

soma, perikaryon

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3
Q

What is the trophic, metabolic center of the cell?

A

cell body

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4
Q

What are the three shapes cell bodies of neurons may take?

A

spherical
ovoid
angular

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5
Q

What is the membrane of the cell body specialized for?

A

impulse generation

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6
Q

What organelles would you find in the cell body of a neuron?

A

GA, mitochondria, nissl bodies, free ribosomes

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7
Q

What are nissl bodies?

A

stacks of rER

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8
Q

Describe the nucleus of a neuron.

A

Large, clear, and euchromatic with a dense nucleolus

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9
Q

Why don’t neurons form tumors?

A

In adults there is no mitosis

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10
Q

Can neurons divide?

A

In general, NO

But, in the adult brain some neural stem cells retain the ability to regenerate and may migrate to the site of injury

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11
Q

What filaments are found in the cell bodies of neurons?

A

neurofilaments (intermediate), microfilaments (actin) and microtubules

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12
Q

What is lipofuscin? what color does it stain?

A

lysosomal enzymatic residue

Accumulation of degraded cell organelles and debris present in long-lived cells such as organelles

yellowish-brown pigment

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13
Q

What is the axon hillock? how does it stain?

A

The funnel-shaped origin of the axon

pale staining due to a lack of rER

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14
Q

What is chomatolysis?

A

dissolution of nissl substance following injury

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15
Q

What increases the receptive area of neurons?

A

dendrites

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16
Q

Are dendrites myelinated?

A

Never

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17
Q

What is the function of dendrites?

A

They receive information from receptor cells and transmit this information to the cell body

membrane specialized for impulse generation

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18
Q

What is the function of axons?

A

Relay action potentials away from the cell ody to the axon terminals and then transmit them to other neurons, smooth, skeletal, or cardiac muscle cells, or gland cells

membrane specialized for impulse conduction

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19
Q

What organelles might be found in the axon?

A

NO rER

may contain mitochondria, microtubules, neurofilaments, vesicles, and sER

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20
Q

What is the axolemma?

A

the axon cell membrane

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21
Q

What is the axoplasm?

A

the axon cytoplasm

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22
Q

What is the initial segment of the axon? why is it important?

A

Segment of axon distal to the axon hillock and proximal to where myelination begins

Action potential is initiated here

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23
Q

Describe the cell membrane of the initial segment of the axon.

A

Dense undercoating with numerous ion channels

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24
Q

Where are collateral branches located?

A

near the hillock

branches off of the main axon

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25
What are the terminal arborizations?
terminal axonal branches
26
What are terminal buttons? what are other names for terminal buttons?
aka axon terminals or end bulbs The dilated ends of arborizations which form synapses *some prtn synthesis may occur here
27
Which direction is anterograde transport? retrograde?
anterograde is away from the cell body retrograde is toward the cell body
28
What is the microtubule-associated motor protein involved in anterograde transport?
kinesin
29
What is the microtubule-associated motor protein involved in retrograde transport?
dynein
30
What molecules are transported via the slow anterograde transport system?
tubulin molecules, actin molecules, and neurofilament proteins moves .2-.4 mm/day
31
Which transport system do viruses and toxins use?
Retrograde transport enter the nerve endings and travel to the CNS
32
What molecules are carried via the fast transport system? which direction?
bidirectional! membranous organelles such as sER, synaptic vesicles and mitochondira; sugars; aa; nucelotides; NT; and calcium **requires ATP**
33
What are bipolar neurons associated with?
special senses Can be found in the retina, inner ear, and nose
34
What anatomical classification would motor neurons and interneurons fall under?
multipolar neurons *multipolar is the most common type of neuron
35
Where would you find unipolar neurons?
enclosed in CN sensory ganglia and dorsal root ganglia
36
Do impulses enter the cell body of unipolar cells?
No | Impulses are transmitted down the axon, bypassing the cell body
37
Where do skeletal motor (somatic efferent) neurons go?
to skeletal muscle fibers
38
Where do visceral motor (visceral efferent) neurons go?
to smooth muscle, cardiac muscle, or glands *Autonomic
39
What do somatic afferent neurons receive?
Sensory stimuli from the environment
40
What do visceral afferent neurons receive?
Sensory stimuli from the viscera
41
Where are the interneurons located?
confined to the CNS | 99.9% of neurons!- multipolar
42
What is the function of neuroglia cells?
both physical and physiological support protecting nerve cells
43
Which is more numerous- neuroglia or neurons?
neuroglia (3-4 neuroglial cells per neuron)
44
Can neuroglial cells form tumors?
YES because unlike neurons they divide
45
Does the CNS contain connective tissue?
NO | the only connective tissue found in the brain is associated with blood vessels
46
What are the defining physical features of astrocytes?
largest of glial cells with "vascular feet", "pedicles"
47
What are the functions of astorglial cells? (5)
1) Ensheathe all blood vessels covered by basal lamina 2) Assist in the formation of the Blood-Brain-Barrier 3) Surround periphery of brain and spinal cord forming a layer deep to pia mater 4) Form scar tissue following nerve tissue injury (tissue repair) 5) Monitor the ionic and chemical composition in extracellular space around nerve cells
48
Where are protoplasmic astrocytes found?
Primarily in gray matter, granular cytoplasm, processes cover synapses, neurons and blood vessels
49
Where are fibrous astrocytes found?
Primarily in white matter, associated with blood vessels and pia mater, cover the nodes of ranvier and synapses Long thin processes are light staining
50
How prevalent are fibrous astrocytomas?
Fibrous astrocytomas make up about 80% of primary brain tumors in the adult
51
Where are oligodendrocytes found?
In white matter they form rows and each oligo myelinates one or more than one axon
52
Which cells are known as the CNS housekeepers?
Microglia because they are phagocytic
53
Describe microglia.
Small cell bodies, elongated nuclei (other glia have round), condensed chromatin Present in both gray and white matter
54
Which cells line the brain and spinal cord cavities?
cuboidal-columnar ependymal cells They have motile cilia which move the CSF They also cover the choroid plexus which forms CSF
55
What are other important features of Ependymal cells?
abundant mitochondria, apical GA, sparse rER, gap junctions and zonula adherens
56
Where is an ependymoma located?
A tumor growing in the fourth ventricle Compresses surrounding structures as it expands 5% of primary brain tumors
57
Describe an unmyelinated axon in the CNS.
not covered by glia (wear their birthday suit)
58
Describe an unmyelinated axon in the PNS.
occupy a groove of a Schwann cell One Schwann cell may envelop many axons
59
Are there nodes of Ranvier along unmyelinated axons?
Nope
60
If an axon is myelinated within the CNS, it is myelinated by ....
oligodendrocytes
61
If an axon is myelinated within the PNS, it is myelinated by ....
Schwann cells
62
Is myelin a substance that is 'secreted' on the axon by a cell?
NO | Myelin is formed by concentric layers of cell membranes (myelin sheath) which have a high lipid content
63
What is the function of myelin?
Myelin increases impulse conduction and insulates axons
64
What is a node of Ranvier?
The unmyelinated segment of an axon between two Schwann cells or oligodendrocytes
65
If an immature Schwann cell is in close proximity to a large-diameter axon, what will it develop into?
A myelinating cell small-diameter--> nonmyelinating cells
66
Define mesaxon.
Fused cell membranes
67
What is an internodal segment?
Insulated (myelin-covered) segments of axon
68
Where are schwann cells derived from?
neural crest
69
Where would you expect to find nerve coverings?
ONLY associated with NERVES in the PNS
70
Which nerve covering encloses individual axons?
Endonerium
71
What synthesizes the endonerium?
schwann cells
72
Describe the endoneurium.
Delicate layer of loose connective tissue with collagen fibrils
73
What is the order of coverings of a myelinated peripheral nerve? (hint: 5)
``` myelin sheath basal lamina endoneurium perineurium epineurium ```
74
Which covering layer surrounds a nerve bundle?
perineurium
75
Which covering surrounds a 'gross nerve'?
epineurium A dense irregular connective tissue (fibrous coat) with elastic fibers which covers several nerve bundles, which together form the gross nerve
76
What is the name for cytoplasm trapped in concentric layers of cell membranes of Schwann cells myelinating an axon?
Schmidt-Lanterman cleft
77
What is the function of Satellite cells?
support cells that surround the cell bodies of neurons housed in ganglia analogous function to schwann cells
78
Do Satellite cells form myelin?
NO
79
What is optic neuritis?
Inflammation of the optic nerve symptoms: visual loss affecting one eye, pain when moving eye, papilledema
80
What is the most common cause of optic neuritis?
multiple sclerosis or other demyelinating disease
81
What is MS?
autoimmune disease causing progressive demyelination of white matter in the CNS resulting in decreased velocity of impulse propagation in affected axons Possible root cause is immune system responding to an oligodendropathy

Cell Bio Exam 2 (9 decks)

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