(H) Nervous Tissue Histology Flashcards
1
Q
3 functions of nervous system
A
- gathers info (sensory input) via sensory receptors
- processes and interprets sensory input (integration) and decides what action should be taken
- produces response (motor output) activating effector organs
2
Q
Nervous system can be structurally divided into:
A
central nervous system and peripheral nervous system
3
Q
Central nervous system composed of:
A
brain and spinal cord
4
Q
Central nervous system is important for what function?
A
integrative and control center of body
5
Q
Peripheral nervous system is important for what function?
A
communicating lines between CNS and rest of body
6
Q
Peripheral nervous system is composed of:
A
all nervous structures outside of brain/spinal cord
- cranial nerves (arise from brain) 12 pairs
- spinal nerves (arise from spinal cord) 31 pairs
- ganglia (groups of cell bodies in PNS)
- plexuses (intermingling of neuron cell processes from ventral rami of different cord levels)
7
Q
What is the functional unit of nervous system?
A
nerve cells (aka neurons)
8
Q
What 2 cell types are found in nervous tissue?
A
- nerve cells (aka neurons)
2. supporting cells (aka neuroglia aka glia)
9
Q
Which cell type of nervous tissue is excitable/irritable?
A
neurons (aka nerve cells)
10
Q
Which cell type of nervous tissue is smaller?
A
supporting cells (aka neuroglia or glia)
11
Q
Which cell type is more numerous in nervous tissue?
A
supporting cells (aka neuroglia or glia)
12
Q
Which is larger: neuron or neuroglia?
A
neuron
13
Q
Which can carry a nerve impulse: neuron or neuroglia?
A
neuron
14
Q
which can multiple/divide: neuron or neuroglia?
A
neuroglia
neurons are amitotic
15
Q
3 special characteristics of neurons
A
- extreme longevity (can function 100+ years)
- most are amitotic (cannot divide)
- high metabolic rate (need large continuous supply of oxygen and glucose)
16
Q
What is the basic structure of a neuron?
A
- neuron cell body
2. processes (dendrites and axons)
17
Q
What is a perikaryon?
A
neuron cell body
18
Q
What is the biosynthetic center of the neuron?
A
the neuron cell body (perikaryon)
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
20
Q
Is the neuron cell body (perikaryon) myelinated or unmyelinated?
A
always unmyelinated
21
Q
Do AP take place on the perikaryon?
A
no
22
Q
How many cell bodies can each neuron have?
A
1
23
Q
Describe the nucleus of a neuron?
A
in perikaryon
site of nucleus and prominent nucleolus
24
Q
Are there centrioles in the perikaryon?
A
no - think, they are amitotic
25
Are there regular organelles in the perikaryon?
yes
but no centrioles because neuron is amitotic
26
Microtubules and neurofibrils in the neuron cell body (perikaryon) serve what function?
maintain cell shape and assist in shipping in cell
27
What is the axon hillock of neuron?
Where axon attaches to cell body
Area most free of large cytoplasmic organelles
28
Clusters of cell bodies are called what in CNS vs PNS
clusters of cell bodies
```
CNS = nuclei
PNS = ganglia
```
29
What are the processes on a neuron?
dendrites and axons (nerve fibers)
30
How many dendrites can a neuron have?
many
31
What is the main function of a dendrite?
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
32
Dendrites are greatly branching which creates a ____
dendritic tree
33
Are there organelles in the dendrites?
Yes
| Many organelles from cell body also extend into dendrites (except for golgi)
34
What are small branches of dendrites called?
dendritic spines
35
Are dendrites myelinated or unmyelinated?
always unmyelinated
36
Can dendrites generate/transmit AP?
no
37
What is the main function of an axon/nerve fiber?
```
conducting region of a neuron
function - to generate/transit AP
```
38
How many axons can a neuron have?
1
| but that 1 can branch into several once it leaves the cell body
39
Is an axon long or short?
can be either
40
A nerve impulse is generated at the ______ of an axon.
trigger zone aka initial segment
this is between the axon hillock and axon
41
What is the trigger zone aka initial segment?
this is where the nerve impulse is generated in the axon of neuron
between axon hillock and axon
42
AP of axon travels to _____
axon terminal aka:
synaptic knob
end bulb
bouton terminal
43
What cells myelinate the axon in PNS vs CNS?
```
CNS = Oligodenderocytes
PNS = Schwann Cells
```
44
What is axonal transport of axon?
bidirectional movement along microtubules of axon
45
What is anterograde transport of axon?
transport from cell body toward axon terminal
46
What is retrograde transport of axon?
transport from axon terminal toward cell body
47
How are neurons categorized based on structure?
multipolar neurons
bipolar neurons
unipolar neurons
48
Which neuron type is the major neuron type in the CNS?
| of multipolar, bipolar and unipolar
multipolar
49
Which neuron type is the rarest?
| of multipolar, bipolar and unipolar
bipolar
50
Which neuron type is the major type in the PNS?
unipolar
51
How are neurons categorized based on function?
sensory (afferent) neurons
motor (efferent) neurons
associated neurons (interneurons)
52
Sensory (afferent) neurons conduct AP in what direction?
towards CNS
53
Motor (efferent) neurons conduct AP in what direction?
away from CNS
54
Associated neurons/interneurons are found where?
between sensory and motor neurons
55
Multipolar neurons can be what kind of functional neuron?
| of sensory, motor or interneuron
motor neurons or interneurons
56
Bipolar neurons can be what kind of functional neuron?
| of sensory, motor or interneuron
sensory neurons for SPECIAL sensaton
57
Unipolar neurons can be what kind of functional neuron?
| of sensory, motor or interneuron
sensory neurons for GENERAL sensation
58
What are the 5 classifications of synapses based on neuronal components involved?
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
What are the 2 most common classifications of synapses based on neuronal components involved?
axodendritic synapse and axosomatic synapse
60
How do electrical synapses conduct AP?
AP is conducted directly through gap junctions (which connect cytosols) so this is DIRECT COMMUNICATION
61
Which is faster: electrical synapse or chemical synapse?
electrical synapse
62
Describe the synaptic cleft in a chemical synapse?
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
Can chemical synapses be a two way transfer?
no. chemical synapses are ONE WAY transfer.
64
Where do chemical synapses take place?
axon terminals
65
In chemical synapse, presynaptic neurons contain ______ that are released via exocytosis.
contain vesicles filled with neurotransmitters
66
In chemical synapse, postsynaptic neuron contain ____ receptors which the neurotransmitters bind to
ligand-gated receptors
67
In a chemical synapse, presynaptic neuron carries nerve impulse and it arrives at the ____
synaptic end bulb of presynaptic axon
68
In a chemical synapse, ______ causes voltage-gated calcium channels to open in the pre-synaptic neuron
depolarization
69
In a chemical synapse, once calcium is released, it signals for release of _____. Describe this release.
release of neurotransmitters (which are stored in teh synaptic vesicles of the presynaptic neuron)
these neurotransmitters exit via exocytosis into the synaptic cleft
70
In a chemical synapse, the neurotransmitters diffuse across the ____ and bind to ____
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
In a chemical synapse, once the neurotransmitter has opened the ligand-gated channel on the postsynaptic neuron membrane, ________
this allows ions to flow across the post synaptic neuron membrane
72
In a chemical synapse, ions flowing across the post synaptic neuron membrane produces ____
post synaptic potential (type of graded potential)
this can be a depolarization or hyperpolarization
73
What are the 3 ways that neurotransmitters can be removed from the postsynaptic receptors?
1. degradation by enzymes
2. reuptake by astrocytes or presynaptic terminal
3. diffusion away from synapse
74
What are the 6 types of neuroglia and where are they each found?
4 in CNS: astrocyte, microglia, ependymal cells and oligodendrocytes
2 in PNS: schwann cells and satellite cells
75
Neuroglia: oligodendrocytes (CNS)
what is the main function? how does it do this?
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
Neuroglia: oligodendrocytes (CNS)
predominent glia cell found in _____
white matter
77
Neuroglia: oligodendrocytes (CNS)
Describe histologically
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
Which type of neuroglia is the largest?
astrocytes (in CNS)
79
Neuroglia: astrocytes (CNS)
found in ____ matter
both white and gray
80
Neuroglia: astrocytes (CNS)
What is it's major function?
control ionic environment of neurons
81
Which neuroglia are connected to each other via gap junctions? What does this do?
astrocytes (in CNS)
this forms a network of cells in CNS
82
Which neuroglia has perivascular feet?
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
Which neuroglia covers capillary endothelial cells and contributes to the blood brain barrier?
astrocytes (specifically the perivascular feet of astrocytes)
in CNS
84
What is the role of perivascular feet in astrocyte neuroglia (CNS)?
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
What are some minor roles of astrocyte neuroglia?
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
Astrocyte neuroglia are best visualized in what staining method?
immunostaining
87
Astrocytes are joined to each other via ____
gap junctions (which forms a network of cells in the CNS)
88
Ependymal cell neuroglia are joined to each other via ____
junctional complexes (which creates a barrier)
89
Describe ependymal cell neuroglia physically and where they are found
low columnar/ cuboidal cells that line space in CNS
have cilia that extend into space containing CSF, cilia help CSF flow
90
What type of neuroglia are modified in ventricles to be a part of the choroid plexus?
ependymal cells (in CNS)
choroid plexus helps produce CSF by transport/secretion of materials derived from plasma of capillary loops
91
Are microglia neuroglia (CNS) in white matter or gray matter?
evenly distributed between white and gray matter
92
Which neuroglia can be identified histologically by their dense staining and elongated nuclei?
microglia (CNS)
93
Describe microglia neuroglia (CNS) physically
small cells with short irregular processes w/ spikes (need special staining to see)
nuclei are dense staining and ELONGATED
94
Which neuroglia can migrate?
microglia (CNS)
95
Which neuroglia is a major mechanism for immune defense in the CNS?
microglia (CNS)
We analyze microglial tissue for damaged cells / invading microorganisms in CNS
96
Microglia (CNS) originate from ____
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
What happens to microglia (CNS) when activated?
they assume morphological characteristic of macrophages
| they proliferate, become phagocytotic, act as antigen-presenting in areas of injury/disease
98
Schwann cells aka _____
neurolemmocytes (neuroglia in the PNS)
99
What is the main function of schwann cells (PNS)?
schwann cells aka neurolemmocytes
myelinate axons in PNS
one schwann cell produces myelin around 1 segment (internodal segment)
100
What is a neurolemmocyte?
neurolemmocyte aka schwann cell (neuroglia in PNS)
101
What do sattelite neuroglia cells do (PNS?)
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
What is white matter primarily composed of? Why is it white?
myelinated axons and some neuroglia
white because of phospholipids (fatty) myelin
103
What is gray matter primarily composed of? Why is it gray?
neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia
gray due to Nissl bodies and lack of myelin
104
Clusters of cell bodies called:
In CNS = ______
in PNS = ______
Bundles of neuronal axons called:
In CNS = _____
in PNS = ______
Cell bodies:
CNS = Nuclei
PNS = Ganglia
Neuronal axons:
CNS = Tract
PNS = Nerve
105
What is a nerve? What are the 5 components of a nerve?
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
What are the 3 connective tissue coverings associated with nerves?
Endoneurium
Perineurium
Epineurium
107
What does the endoneurium surround?
surrounds axon alone (if unmyelinated)
| or surrounds axon and myelin sheath (if myelinated)
108
What does the perineurium surround?
| what does this create?
surrounds several endoneurium-wrapped axons together
this creates a FASICLE
109
What does the epineurium surround?
| what does this create?
surrounds several fasicles and blood vessels and lymph vessels together
this creates NERVE
110
What are the 2 functions of myelinated nerve fibers?
1. protect and electrically insulate axons from other axons
| 2. increases speed of nerve impulse transmission
111
Which conduct impulses faster: myelinated or unmyelinated axons?
myelinated axons
112
How must myelinated axons be stained?
osmium-fixed to preserve plasma membrane composing the myelin sheath
113
The rate of impulse propagation is dependent on:
1. axon diameter
| 2. myelination
114
What are the 2 types of conducting impulse propagation?
continuous conduction (for unmyelinated axons)
saltatory conduction (for myelinated axons)
115
Describe continuous conduction
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
Describe saltatory conduction
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
Which is faster: continuous conduction or saltatory conduction?
saltatory conduction
118
Are unmyelinated axons in PNS associated with schwann cells?
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
