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Anatomy 6512 UNIT 1 > (H) Nervous Tissue Histology > Flashcards

(H) Nervous Tissue Histology Flashcards

1
Q

3 functions of nervous system

A
  1. gathers info (sensory input) via sensory receptors
  2. processes and interprets sensory input (integration) and decides what action should be taken
  3. produces response (motor output) activating effector organs
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2
Q

Nervous system can be structurally divided into:

A

central nervous system and peripheral nervous system

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3
Q

Central nervous system composed of:

A

brain and spinal cord

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4
Q

Central nervous system is important for what function?

A

integrative and control center of body

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5
Q

Peripheral nervous system is important for what function?

A

communicating lines between CNS and rest of body

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6
Q

Peripheral nervous system is composed of:

A

all nervous structures outside of brain/spinal cord

  1. cranial nerves (arise from brain) 12 pairs
  2. spinal nerves (arise from spinal cord) 31 pairs
  3. ganglia (groups of cell bodies in PNS)
  4. plexuses (intermingling of neuron cell processes from ventral rami of different cord levels)
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7
Q

What is the functional unit of nervous system?

A

nerve cells (aka neurons)

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8
Q

What 2 cell types are found in nervous tissue?

A
  1. nerve cells (aka neurons)

2. supporting cells (aka neuroglia aka glia)

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9
Q

Which cell type of nervous tissue is excitable/irritable?

A

neurons (aka nerve cells)

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10
Q

Which cell type of nervous tissue is smaller?

A

supporting cells (aka neuroglia or glia)

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11
Q

Which cell type is more numerous in nervous tissue?

A

supporting cells (aka neuroglia or glia)

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12
Q

Which is larger: neuron or neuroglia?

A

neuron

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13
Q

Which can carry a nerve impulse: neuron or neuroglia?

A

neuron

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14
Q

which can multiple/divide: neuron or neuroglia?

A

neuroglia

neurons are amitotic

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15
Q

3 special characteristics of neurons

A
  1. extreme longevity (can function 100+ years)
  2. most are amitotic (cannot divide)
  3. high metabolic rate (need large continuous supply of oxygen and glucose)
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16
Q

What is the basic structure of a neuron?

A
  1. neuron cell body

2. processes (dendrites and axons)

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17
Q

What is a perikaryon?

A

neuron cell body

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18
Q

What is the biosynthetic center of the neuron?

A

the neuron cell body (perikaryon)

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19
Q

What are nissl bodies and where are they found?

A

found in neuron cell body (perikaryon)

abundant free ribosomes clump together (= nissl bodies) which stain intensely basophilic

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20
Q

Is the neuron cell body (perikaryon) myelinated or unmyelinated?

A

always unmyelinated

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21
Q

Do AP take place on the perikaryon?

A

no

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22
Q

How many cell bodies can each neuron have?

A

1

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23
Q

Describe the nucleus of a neuron?

A

in perikaryon

site of nucleus and prominent nucleolus

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24
Q

Are there centrioles in the perikaryon?

A

no - think, they are amitotic

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25
Q

Are there regular organelles in the perikaryon?

A

yes

but no centrioles because neuron is amitotic

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26
Q

Microtubules and neurofibrils in the neuron cell body (perikaryon) serve what function?

A

maintain cell shape and assist in shipping in cell

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27
Q

What is the axon hillock of neuron?

A

Where axon attaches to cell body

Area most free of large cytoplasmic organelles

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28
Q

Clusters of cell bodies are called what in CNS vs PNS

A

clusters of cell bodies

CNS = nuclei
PNS = ganglia
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29
Q

What are the processes on a neuron?

A

dendrites and axons (nerve fibers)

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30
Q

How many dendrites can a neuron have?

A

many

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31
Q

What is the main function of a dendrite?

A

main receptive/main input region of neuron (so lots of surface area for that)

receive signals from other neurons and convey message to cell body

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32
Q

Dendrites are greatly branching which creates a ____

A

dendritic tree

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33
Q

Are there organelles in the dendrites?

A

Yes

Many organelles from cell body also extend into dendrites (except for golgi)

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34
Q

What are small branches of dendrites called?

A

dendritic spines

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35
Q

Are dendrites myelinated or unmyelinated?

A

always unmyelinated

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36
Q

Can dendrites generate/transmit AP?

A

no

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37
Q

What is the main function of an axon/nerve fiber?

A 
conducting region of a neuron
function - to generate/transit AP
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38
Q

How many axons can a neuron have?

A

1

but that 1 can branch into several once it leaves the cell body

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39
Q

Is an axon long or short?

A

can be either

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40
Q

A nerve impulse is generated at the ______ of an axon.

A

trigger zone aka initial segment

this is between the axon hillock and axon

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41
Q

What is the trigger zone aka initial segment?

A

this is where the nerve impulse is generated in the axon of neuron

between axon hillock and axon

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42
Q

AP of axon travels to _____

A

axon terminal aka:
synaptic knob
end bulb
bouton terminal

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43
Q

What cells myelinate the axon in PNS vs CNS?

A 
CNS = Oligodenderocytes
PNS = Schwann Cells
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44
Q

What is axonal transport of axon?

A

bidirectional movement along microtubules of axon

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45
Q

What is anterograde transport of axon?

A

transport from cell body toward axon terminal

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46
Q

What is retrograde transport of axon?

A

transport from axon terminal toward cell body

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47
Q

How are neurons categorized based on structure?

A

multipolar neurons
bipolar neurons
unipolar neurons

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48
Q

Which neuron type is the major neuron type in the CNS?

of multipolar, bipolar and unipolar

A

multipolar

49
Q

Which neuron type is the rarest?

of multipolar, bipolar and unipolar

A

bipolar

50
Q

Which neuron type is the major type in the PNS?

A

unipolar

51
Q

How are neurons categorized based on function?

A

sensory (afferent) neurons
motor (efferent) neurons
associated neurons (interneurons)

52
Q

Sensory (afferent) neurons conduct AP in what direction?

A

towards CNS

53
Q

Motor (efferent) neurons conduct AP in what direction?

A

away from CNS

54
Q

Associated neurons/interneurons are found where?

A

between sensory and motor neurons

55
Q

Multipolar neurons can be what kind of functional neuron?

of sensory, motor or interneuron

A

motor neurons or interneurons

56
Q

Bipolar neurons can be what kind of functional neuron?

of sensory, motor or interneuron

A

sensory neurons for SPECIAL sensaton

57
Q

Unipolar neurons can be what kind of functional neuron?

of sensory, motor or interneuron

A

sensory neurons for GENERAL sensation

58
Q

What are the 5 classifications of synapses based on neuronal components involved?

A
  1. axodendritic synapse (axon terminal and dendrite)
  2. axosomatic synapse (axon terminal and cell body)
  3. axoaxonic synaopse (bw axon terminals)
  4. dendrodendritic synapse (bw dendrites)
  5. dendrosomatic synapse (bw dendrites and cell body)
59
Q

What are the 2 most common classifications of synapses based on neuronal components involved?

A

axodendritic synapse and axosomatic synapse

60
Q

How do electrical synapses conduct AP?

A

AP is conducted directly through gap junctions (which connect cytosols) so this is DIRECT COMMUNICATION

61
Q

Which is faster: electrical synapse or chemical synapse?

A

electrical synapse

62
Q

Describe the synaptic cleft in a chemical synapse?

A

cells are close but not touching
synapotic cleft is space between presynaptic and postsynpaitc neuron
can be 20-30 nm wide
take electrical signal –> chem singal –> electrical signal

63
Q

Can chemical synapses be a two way transfer?

A

no. chemical synapses are ONE WAY transfer.

64
Q

Where do chemical synapses take place?

A

axon terminals

65
Q

In chemical synapse, presynaptic neurons contain ______ that are released via exocytosis.

A

contain vesicles filled with neurotransmitters

66
Q

In chemical synapse, postsynaptic neuron contain ____ receptors which the neurotransmitters bind to

A

ligand-gated receptors

67
Q

In a chemical synapse, presynaptic neuron carries nerve impulse and it arrives at the ____

A

synaptic end bulb of presynaptic axon

68
Q

In a chemical synapse, ______ causes voltage-gated calcium channels to open in the pre-synaptic neuron

A

depolarization

69
Q

In a chemical synapse, once calcium is released, it signals for release of _____. Describe this release.

A

release of neurotransmitters (which are stored in teh synaptic vesicles of the presynaptic neuron)

these neurotransmitters exit via exocytosis into the synaptic cleft

70
Q

In a chemical synapse, the neurotransmitters diffuse across the ____ and bind to ____

A

neurotransmitters diffuse across the synaptic cleft and bind to neurotransmitter receptors on the postsynaptic neuron membrane.

Each of these receptors is part of ligand-gated channel

71
Q

In a chemical synapse, once the neurotransmitter has opened the ligand-gated channel on the postsynaptic neuron membrane, ________

A

this allows ions to flow across the post synaptic neuron membrane

72
Q

In a chemical synapse, ions flowing across the post synaptic neuron membrane produces ____

A

post synaptic potential (type of graded potential)

this can be a depolarization or hyperpolarization

73
Q

What are the 3 ways that neurotransmitters can be removed from the postsynaptic receptors?

A
  1. degradation by enzymes
  2. reuptake by astrocytes or presynaptic terminal
  3. diffusion away from synapse
74
Q

What are the 6 types of neuroglia and where are they each found?

A

4 in CNS: astrocyte, microglia, ependymal cells and oligodendrocytes

2 in PNS: schwann cells and satellite cells

75
Q

Neuroglia: oligodendrocytes (CNS)

what is the main function? how does it do this?

A

produce myelin sheath (electrical insulation)

each oligodendrocyte extends over several processes; each wraps around a section of axon producing a sheath

can form 1 segment of mylin (internodal segment)

76
Q

Neuroglia: oligodendrocytes (CNS)

predominent glia cell found in _____

A

white matter

77
Q

Neuroglia: oligodendrocytes (CNS)

Describe histologically

A

small cell with condensed, rounded nucleus with unstained cytoplasm next to nucleus (bc lots of golgi complex)

cells often aligned in rows in between axons

78
Q

Which type of neuroglia is the largest?

A

astrocytes (in CNS)

79
Q

Neuroglia: astrocytes (CNS)

found in ____ matter

A

both white and gray

80
Q

Neuroglia: astrocytes (CNS)

What is it’s major function?

A

control ionic environment of neurons

81
Q

Which neuroglia are connected to each other via gap junctions? What does this do?

A

astrocytes (in CNS)

this forms a network of cells in CNS

82
Q

Which neuroglia has perivascular feet?

A

astrocytes (in CNS)

perivascular feet are at the end of processes
they cover capillary endothelial cells and contribute to blood brain barrier
can regular vasodilation of blood vessels, transfer of O2, ions, etc.

83
Q

Which neuroglia covers capillary endothelial cells and contributes to the blood brain barrier?

A

astrocytes (specifically the perivascular feet of astrocytes)

in CNS

84
Q

What is the role of perivascular feet in astrocyte neuroglia (CNS)?

A

perivascular feet are at the end of astrocyte processes

they cover capillary endothelial cells and contribute to blood brain barrier

they regular vasodilation of blood vessels, transfer O2, transfer ions, etc.

85
Q

What are some minor roles of astrocyte neuroglia?

A

assistance in formation of CNS during embryo/fetal development (through scaffolding)

can get rid of excess neurotransmitters

can form cellular scar tissue when CNS is damaged

86
Q

Astrocyte neuroglia are best visualized in what staining method?

A

immunostaining

87
Q

Astrocytes are joined to each other via ____

A

gap junctions (which forms a network of cells in the CNS)

88
Q

Ependymal cell neuroglia are joined to each other via ____

A

junctional complexes (which creates a barrier)

89
Q

Describe ependymal cell neuroglia physically and where they are found

A

low columnar/ cuboidal cells that line space in CNS

have cilia that extend into space containing CSF, cilia help CSF flow

90
Q

What type of neuroglia are modified in ventricles to be a part of the choroid plexus?

A

ependymal cells (in CNS)

choroid plexus helps produce CSF by transport/secretion of materials derived from plasma of capillary loops

91
Q

Are microglia neuroglia (CNS) in white matter or gray matter?

A

evenly distributed between white and gray matter

92
Q

Which neuroglia can be identified histologically by their dense staining and elongated nuclei?

A

microglia (CNS)

93
Q

Describe microglia neuroglia (CNS) physically

A

small cells with short irregular processes w/ spikes (need special staining to see)

nuclei are dense staining and ELONGATED

94
Q

Which neuroglia can migrate?

A

microglia (CNS)

95
Q

Which neuroglia is a major mechanism for immune defense in the CNS?

A

microglia (CNS)

We analyze microglial tissue for damaged cells / invading microorganisms in CNS

96
Q

Microglia (CNS) originate from ____

A

monocytes (which originate from bone marrow) and enter CNS in development

*aka microglia migrate to the CNS in development
(so they are capable of migration)

97
Q

What happens to microglia (CNS) when activated?

A

they assume morphological characteristic of macrophages

they proliferate, become phagocytotic, act as antigen-presenting in areas of injury/disease

98
Q

Schwann cells aka _____

A

neurolemmocytes (neuroglia in the PNS)

99
Q

What is the main function of schwann cells (PNS)?

A

schwann cells aka neurolemmocytes

myelinate axons in PNS
one schwann cell produces myelin around 1 segment (internodal segment)

100
Q

What is a neurolemmocyte?

A

neurolemmocyte aka schwann cell (neuroglia in PNS)

101
Q

What do sattelite neuroglia cells do (PNS?)

A

create a covering layer over the large neuronal cell bodies in PNS ganglia

exact role still unknown but it has a supportive role for neuron cell bodies of PNS ganglia

102
Q

What is white matter primarily composed of? Why is it white?

A

myelinated axons and some neuroglia

white because of phospholipids (fatty) myelin

103
Q

What is gray matter primarily composed of? Why is it gray?

A

neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia

gray due to Nissl bodies and lack of myelin

104
Q

Clusters of cell bodies called:
In CNS = ______
in PNS = ______

Bundles of neuronal axons called:
In CNS = _____
in PNS = ______

A

Cell bodies:
CNS = Nuclei
PNS = Ganglia

Neuronal axons:
CNS = Tract
PNS = Nerve

105
Q

What is a nerve? What are the 5 components of a nerve?

A

nerve = collection of axons in PNS

composed of

  1. neuron processes (axon)
  2. schwann cells (if myelinated)
  3. connective tissue
  4. blood vessels
  5. lymphatic vessels
106
Q

What are the 3 connective tissue coverings associated with nerves?

A

Endoneurium
Perineurium
Epineurium

107
Q

What does the endoneurium surround?

A

surrounds axon alone (if unmyelinated)

or surrounds axon and myelin sheath (if myelinated)

108
Q

What does the perineurium surround?

what does this create?

A

surrounds several endoneurium-wrapped axons together

this creates a FASICLE

109
Q

What does the epineurium surround?

what does this create?

A

surrounds several fasicles and blood vessels and lymph vessels together

this creates NERVE

110
Q

What are the 2 functions of myelinated nerve fibers?

A
  1. protect and electrically insulate axons from other axons

2. increases speed of nerve impulse transmission

111
Q

Which conduct impulses faster: myelinated or unmyelinated axons?

A

myelinated axons

112
Q

How must myelinated axons be stained?

A

osmium-fixed to preserve plasma membrane composing the myelin sheath

113
Q

The rate of impulse propagation is dependent on:

A
  1. axon diameter

2. myelination

114
Q

What are the 2 types of conducting impulse propagation?

A

continuous conduction (for unmyelinated axons)

saltatory conduction (for myelinated axons)

115
Q

Describe continuous conduction

A

AP generated at trigger zone (bw axon hillock and axon)

causes flow of ions down axon

plasma membrane is LEAKY so ion flow can only go so far before it needs to be regenerated

so regeneration of AP occurs CONTINUOUSLY until the axon terminal

116
Q

Describe saltatory conduction

A

AP generated at trigger zone (bw axon hillock and axon)

Because myelinated (insulated), ions can go further w/o being regenerated

Regeneration takes place at the NODES OF RANVIER

117
Q

Which is faster: continuous conduction or saltatory conduction?

A

saltatory conduction

118
Q

Are unmyelinated axons in PNS associated with schwann cells?

A

YES!
unmyelinated axons “snuggle up” and surrounded by cytoplasm of schwann cell (like bean bag)

but schwann cell does not wrap around axons (doesn’t make sheath) aka unmyelinated axons in PNS still undergo continuous conduction

Anatomy 6512 UNIT 1 (6 decks)

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