Histology: The Nervous System Flashcards
(98 cards)
1
Q
What is the structural and functional unit of the nervous system?
A
The neuron
2
Q
What do the supporting cells in the nervous system do?
A
Provide physical Support and protection
insulate electrical activity of axons and synapses
assist in metabolic exchange between the vascular system and NS
3
Q
What are the 3 main parts of the neuron and their general functions?
A
Cell body (soma - supply station) Dentrites ( Reception or intake loci) Axon (the messenger)
4
Q
What part of the neuron produces proteins and provides metabolic function?
A
Soma
5
Q
What part of the neuron conducts information (electrical signals) from the soma to other neurons?
A
Axon
6
Q
What part of the neuron recieves connections (that provide electrical stimulation) from other neurons?
A
The dendrites
7
Q
Dedrites and axons are also known as….
A
processes of the cell body
8
Q
What is contained within the soma?
A
- nucleus with nucleolus
- a cytoplasm
- all cell organelles (rER, Golgi, lysomsome, mitochondria)
9
Q
What organelles may be apparent when using a light microscope to look at the soma?
A
rER (which produces a lot of proteins)
10
Q
Nissl bodies
A
clumps of rER clumped together in the cytoplasm
11
Q
What are the branches of dendrites called?
A
dendritic trees
12
Q
What are spines and where are they located?
A
loci for connections (synapses) with the end (terminals) of axons from other neurons
13
Q
What effect does down syndrome have on the dendrites?
A
Few dendritic spines
14
Q
T or F: organelles exist in the axon hillock?
A
False
15
Q
What are some physical characteristics of the axon?
A
- originates from axon hillock
- most covered by a lipid rich myelin sheath
16
Q
What is the job of the axon?
A
Conducts electrical info from soma to other neurons
17
Q
Where are action potentials in the axon generated?
A
in the initial part
18
Q
Characteristics of Pseudounipolar neurons
A
- Lack processes (dentrites of axon) on the cell soma
- Typically the nucleus is located in the center of soma
- Small nuclei of satellite cells surrounds the nucleus
19
Q
What are neurons classified by?
A
the number of processes (axons and dendrites) sticking out
20
Q
What’s another name for neurons and axons?
A
neuropil
21
Q
What is gray matter predominantly populated by?
A
cell bodies and neuropil
22
Q
What is white matter predominantly populated by?
A
mylinated axons
23
Q
What are synapses?
A
specialized junctions for transmission of nerve impulses from one neuron to anther neuron or to an effector
24
Q
What are the two types of synapse and which is most common in the mammalian brain?
A
Chemical synapses and Electrical
- Chemical = most important in the mammalian brain
25
What are the parts of a chemical synapse?
Presynaptic Bouton
Synaptic Cleft
Postsynaptic membrane
26
What is contained in the presynaptic bouton?
presynaptic density and synaptic vesicles with neurotrasmitters
27
What is the synaptic cleft?
a 20-30 mm space between pre and postsynaptic membranes
28
What is the postsynaptic membrane?
Posynaptic density and receptor sites with which the neurotransmitter interacts
29
What are the 3 types of synapses?
axosomatic
axodendritic
axoaxonic
30
Where does an axon terminal end in an axosomatic synapse?
on the soma
31
Where does an axon terminal end in an axodentritic synapse?
on a spine of the dendrite
32
Where does an axon terminal end in an axoaxonic synapse?
on another axon
33
What is the most common type of synapse in the brain?
Axodendritic - most synapses in the brain located on spines
34
What are the types of neurotransmitters?
excitatory
Inhibitory
Modulatory
35
What does an excitatory neurotransmitter do?
facilitates the postsynaptic neuron to fire a nerve impluse
36
What are examples of excitatory neurotransmitters?
glutamate and acetylcholine
37
What are inhibitory neurotransmitters?
Prevent the postsynaptic neuron from firing a nerve impulse
38
What are examples of inhibitory neurotransmitters?
Glycine and gamma-aminobutyric acid (GABA)
39
What are modulatory neurotransmitters?
influences how excitatory and inhibitory signals are integrated
40
What are examples of modulatory neurotransmitters?
Dopamine and seratonin
41
What is anterograde transport?
proteins synthesized in the soma are packed into cargo vescicles and transported along microtubules toward their destination in axons and dendrites
42
What is transported in anterograde transport?
```
sER
synaptic vesicles
sugars
amino acids
neurotransmitters
```
43
What is retrograde transport?
occurs when materials in the axon and dendrites are packed into cargo vesicles and transported along microtubules and intermediate filaments toward the soma
44
What materials are transported in retrograde transport that aren't transported in anterograde transport?
proteins and molecules endocytosed at the axon terminal
45
What happens to micotubules in alzheimer's disease?
- NORMALLY - microtubule polymers (made of tubulin dimers) in neuron is held together by protein tau.
- In AD tau is disassociated causing the formation of tangles
46
What are the types of supporting cells found in the nervous system?
```
Schwann cells
Oligodendrocytes
Astrocytes
Microglia
Ependymal Cells
Satellite cells
```
47
What do schwann cells do?
Provide myelination in the PNS
48
What do oligodendrocytes do?
myelination in the CNS
49
What are the two types of astrocytes and what do they do?
- Fibrous and protoplasmic
| - Provides general support and formation of blood-brain barrier
50
What do microglia do?
Act as Phagocytes
51
What do ependymal cells do?
Line the ventricles of the brain and central canal of the spinal cord
52
What do satellite cells do?
Support and protect ganglion cells
53
How is compaction of the myelin sheath achieved?
By a transmembrane myelin-specific protein
54
What might a gene mutation in transmembrane myelin specific protein do?
cause demyelinating diseases
55
What is the junction between adjacent schwann cells?
node of ranvier - the only place the axon is exposed to the extracellular environment
56
Where is the schwann cell cytoplasm extruded to during tight wrapping?
- inner collar
- outer collar
- Schmidt-Lanterman Clefts
- Perinodal
57
What is the myelin sheath supported by?
the cytosol from the 4 cytoplasmic regions
58
T or F: Thicker axons tend to have thinner myelination?
False, myelination thickness is related to diameter
59
What envelopes unmyelinated axons?
Schwann cell cytoplasm
60
What cells play a role in cleaning up PNS debris after nerve injury and guide regrowth of PNS axons?
Schwann cellls
61
How does an action potential propagate along a myelinated axon?
Passive electronic spread under areas of myelination
| This trigger AP at next node of ranvier
62
What is wallerian degeneration?
When the area distal to a crushed or cut nerve degenerates causing muscle atrophy
63
What happens in regeneration of nerves after they are cut?
1. Proximal n. terminals send sprouts toward schwann cell tubes of degenerated spot
2. sprouts make it to the tube and reinnervate muscles that's undergone neurogenic rearragment
64
T or F: a single oligodendricyte can myelinate one or several axons.
T
65
T or F: many axons in the CNS are not myelinated?
T
66
Where can each type of astrocyte be found?
protoplasmic - gray matter
fibrous - white matter
Astrocytes = servants of CNS
67
How are astrocytes arranged in the CNS and how does this relate to their function?
- They contain radiating processes that contact axons and capillaries with perineural and perivascular feet
- This structure allows them to move metabolites to and from neurons in metabolic exchange (BLOOD BRAIN BARRIER)
68
T or F: astrocytes are responsible in 80% of brain tumors?
T
69
If your brain is injured or disease, what type of cell would you expect to see localize to the area?
microglia
70
What is the role of microglia in early development?
- they prune neural cell networks to help mold the brain's structure
- They remember infection challenges and go off if challenge occurs (could cause brain disorders later in life)
71
What part of the astrocyte is in contact with the blood vessel?
The perivascular feet
72
What part of the astrocyte is in contact with the neuron?
perineural feet
73
What type of astrocytes cause 80% of adult brain tumors?
Fibrous astrocytes
74
What kind of cell removes cellular debris after apoptosis?
microglia
75
What cells can be found surrounding a single unipolar neuron and what is their purpose?
- Satellite cells do this and control the extracelluar environment in the neuron
- Provide electrical insulation
76
What type of cells are satellite cells?
small cuboidal
77
what do ependymal cells look like?
- Cuboidal to columnar
| - apical surface covered with cillia and microvilli
78
What is the role of ependymal cells?
produce CSF by transport and secretion of material from adjacent capillary loops
79
What is the choroid plexus?
The combination of ependymal cells and capillary loops that are separated by pia mater
80
What are the larges neurons in the CNS?
motor neurons
81
What type of neurons innervate skeletal muscle and where are their cell bodies located, where do they finally synapse?
- somatic efferent neurons
- soma are found in ventral horn
- skeletal muscle
82
What type of neurons innervate blood vessels and glands?
Visceral efferent neurons
83
Where are the cell bodies for preganglionic GVE fibers located, what is their general path?
- lateral horn
- synapse in with postganglionic fiber in autonomic ganglion
- innervate visceral organs
84
T or F: Each muscle fiber can innervate multiple neurons?
True
85
T or F: each muscle fiber is innervated by only one neuron?
True
86
What is the neuromuscular junction?
The connection between axon terminal and muscle fiber
87
What are some key features of Dorsal root ganglia?
- Somas of dorsal root nerves are clustered
- They are also surrounded by satellite cells
- Axon bundles bypass the somas
88
What are some key features of autonomic ganglia?
- Multipolar nuerons
- not as tightly clustered as DRG
- Nuclei eccentrically located in cell soma
- fewer satellite cells surrounding cell bodies
- Axons run between cells
89
What cell becomes very active after neuron cell death in CNS?
microglia
90
Where are the venous sinuses formed and how?
Form between periosteal (superficial) and menigeal (deep) layers of the dura
91
T or F: only the dura mater is affected in menigitis?
False- all three layers are affected
92
What PNS layer is continuous with the dura mater and what type of tissue is this?
epineurium - dense CT
93
What PNS layer is continuous with the arachnoid and what type of tissue is this?
perineurium - squamous cells
94
What PNS layer is continuous with the pia mater and what type of tissue is this?
endoneurium - mostly schwann cells
95
T or F: capillaries are the only part of the CV system that actually exchange oxygen with the organ?
True
96
What forms the blood brain barrier (BBB), and how to astrocytes exhibit control over the BBB?
- complex tight junctions between endothelial cells of capillary form BBB
- Astrocytes release factors that increase the barrier properties and proteins for tights junctions
97
What substances can freely cross the BBB?
- O2 and CO2 (direct penetration)
| - glucose, aa, and vitamins transport across barrier by carrier proteins
98
How does HIV get through the BBB?
through a special type of white blood cell
