Lecture 1 - Cells of the Nervous System Flashcards
(117 cards)
1
Q
How many neurons in our brain? How does this compare to that of a worm?
A
100 billion vs 302
2
Q
How many non-neural cells in our brain?
A
1000 billion
3
Q
What is the cell theory?
A
All tissues are composed of microscopic units called cells
4
Q
Describe multipolar neurons. Where are they found?
A
They have 2 or more primary neuritic processes on the cell body
CNS
5
Q
Describe pyramidal neurons. 2 types? What are there functions?
A
Triangular in shape and very favored.
Functions:
1. Spiny ones encode long-term info
2. Aspinous ones function as interneurons and modulate local information
6
Q
Where are purkinje cell neurons found?
A
Cerebellum
7
Q
Describe bipolar neurons. Where are they found?
A
Neurons with 2 opposing primary neurites.
Found in retina and inner ear
8
Q
What are bipolar neurons in the inner ear called?
A
Hair cells
9
Q
Describe unipolar neurons. What is their function?
A
Cell body is segregated from the single primary neurite.
Function as sensory/afferent neurons
10
Q
What stains are used to stain neurons?
A
Vital dyes:
- Golgi stain
- Nissi stain
- Weigart stain
11
Q
What lies below the 6 layers of the cerebral cortex?
A
Subcortical structures (eg corpus callosum) next to white matter
12
Q
What are the 3 basic elements of the neuron? Describe their location.
A
- Perikaryon
- Dendrites at the receiving end
- Axon at the transmitting end
13
Q
What are the neurites?
A
Structures that branch off the cell body: dendrites and axon
14
Q
What are 2 another names for perikaryon?
A
Cell body = soma
15
Q
What is another name for neurites?
A
Processes
16
Q
What are the different types of dendrites?
A
- Primary: directly coming off of the soma
- Secondary: branch off primary dendrites
- Tertiary: branch off secondary dendrites
AND SO ON…
17
Q
How do the dendrites’ diameter change as it gets further from the soma?
A
Decreases
18
Q
How many axons do most neurons have?
A
1
19
Q
Diameter of dendrite?
A
Thick/tapered
20
Q
Length of dendrite: limited or not?
A
Limited
21
Q
Branching of dendrites?
A
Many, acute
22
Q
Spines on dendrites?
A
Yes
23
Q
V-gated ion channels on dendrites?
A
Less
24
Q
Diameter of axon?
A
1 micrometer, uniform
25
Length of axon: limited or not?
NOPE
26
Branching of axon?
Few, not acute
27
Spines on axons?
NOPE
28
V-gated ion channels on axons?
More
29
What are considered the antennae of neurons?
Dendrites
30
How does the diameter of axons and dendrites affect them?
Thicker neurite will allow an AP to propagate more quickly
31
What determines the length of the axon that goes from the bottom of one's spinal cord to the end of a toe?
Length of the leg!
32
What is the function of dendritic spines?
To elaborate postsynaptic surfaces by increasing the surface area to volume ratio of neurons
33
What is the main component of dendritic spines?
Actin (microfilament)
34
Is the shape/diameter of dendritic spines critical? For what?
YUP
| Critical for higher functioning
35
How do dendritic spines change with maturation?
They morph into the mature mushroom morphology
36
Where do we store a lot of info in our neurons?
Mature dendritic spines
37
3 neuron cytoskeletal elements?
1. Microtubules
2. Microfilaments
3. Neurofilaments
38
What is another name for neurofilaments?
Intermediate filaments
39
Microtubules: size?
20 nm
40
Microfilaments: size?
5 nm
41
Neurofilaments: size?
10 nm
42
Microtubules: structure?
Globular tubulin protein which is hollow and longitudinal
43
Microfilaments: structure?
Actin protein
44
Neurofilaments: structure?
Long NF proteins
45
Microtubules: location?
Everywhere EXCEPT axon terminal or dendritic spine
46
Microfilaments: location?
Throughout
47
Neurofilaments: location?
Throughout
48
Do neurons have a cytoskeleton?
YUP
49
What is the role of Microtubule Associated Proteins (MAPs)?
They govern changes in neuron shape and size overtime
50
What are the 4 major MAPs?
1. MAP-2
2. Tau
3. Kinesin
4. Dynein
51
MAP-2: 2 locations?
1. Dendrites
| 2. Soma
52
Tau: 1 location?
Axon
53
Kinesin: 2 locations?
1. Axon
| 2. Dendrites
54
Dynein: 2 locations?
1. Axon
| 2. Dendrites
55
MAP-2: function?
Stabilizes the shape of the mature neuron
56
Tau: function?
Stabilizes the shape of the mature neuron
57
Which MAP is defective in neurodegenerative disorders like Parkinsons and Alzheimers?
Tau
58
Dynein: function? What is this called?
Motor protein ATPase that transport proteins, nutrients, etc. intracellularly in vesicles from synaptic terminals to the cell body to be recycled = retrograde transport
59
Kinesin: function? What is this called?
Motor protein ATPase that transport proteins, nutrients, etc in vesicles intracellularly from cell body to synaptic terminal = anterograde transport
60
What is axoplasmic transport referred to as? Why?
Activity dependent transport because it uses ATP
61
Describe the flow on conduction.
Usually unidirectional but bidirectionality can have some functions as well
62
What do you call a neuron with dendritic spines?
Spinous = spiny
63
What do you call a neuron without dendritic spines?
Aspinous = non-spiny
64
What are the 4 components of the axon?
1. Axon hillock
2. Initial segment
3. Axon proper
4. Axon terminal
65
Describe the structure and location of the axon hillock.
Conical shape transition from soma to axon
66
Function of axon hillock?
Contains proteins that determine which information is propagated to post synaptic cells
67
What is the initial segment of the axon closely associated with?
The axon hillock
68
What is the function of the initial segment of the axon?
Site of signal integration and generation of AP through Na+ and K+ VG channels
69
Describe the structure of the axon proper.
Uniform width
70
Function of axon proper?
Signal propagation through Na+ and K+ VG channels
71
What are axon collaterals? Function?
Axon branches off primary axon which influence neighboring neurons
72
What does it mean when an axon collateral is able to inhibit a neighboring neuron?
It is firing faster and more easily than the neighboring neuron
73
Describe the structure of the axon terminal.
Enlargement of the axon where microtubules terminate
74
What is another name for the axon terminal?
Presynaptic bouton
75
What does the synapse contain?
Axon terminal + synaptic cleft + postsynaptic dendrite
76
How big is the synaptic cleft?
20 nm
77
What is the function of the axon terminal?
Convert the electrical signal into a chemical one by using calcium VG channels and many membrane proteins to release synaptic vesicles containing NTs into the cleft
78
What does the absence of microtubules at the axon terminal mean?
Less plasticity
79
What is the site of neurotransmission?
Axon terminal
80
What % of our brain cells are neurons?
10%
81
What are nonelectrically stimulated brain cells called?
Glial cells
82
What are the 6 types of glial cells? Are they in CNS or PNS?
```
CNS:
1. Astrocytes
2. Ependymal cells
3. Microglia
4. Oligodendrocytes
PNS:
5. Satellite cells
6. Schwann cells
```
83
Which glial cells are most prevalent in the CNS?
Astrocytes
84
Where are astrocytes found?
Wrapped around capillaries on cortex or cerebellum, or ventral Tegmental Area or other brain structures
85
Astrocytes: main/overall function?
Supporting structure connecting the circulatory and nervous systems so that nutrients can be propagated to neurons
86
Ependymal cells: function?
Produce and circulate cerebrospinal fluid which contains waste and essential molecules by rapidly beating their apical cilia in a circular motion through the brain ventricles/central canal of spinal cord
87
Which glial cell most resembles a neuron morphologically? How do they differ?
Microglial cell
| But they do not have VG channels so are electrically silent
88
Describe the structure of ependymal cells.
Squamous with apical cilia
89
What is the function of microglial cells?
Immune cells of CNS
90
What is the RMP of microglial cells? How does this compare to other NS cells? What is it mainly due to?
- 90 mV (more negative than normal)
| Leakage K+ channels
91
What are we discovering more and more about neurological disorders?
They have an immune component
92
Oligodendrocytes: function?
Produce concentric layers of myelin sheath in CNS to insulate axons and reduce the current leakage to increase conduction velocity
93
Schwann cells: function?
Produce concentric layers of myelin sheath in PNS to insulate axons and reduce the current leakage to increase conduction velocity
94
Oligodendrocytes: location?
Wrapped multiple times around naked axons in CNS
95
Schwann cells: location?
Wrapped multiple times around naked axons in PNS
96
How many oligodendrocytes per neuron axon?
Many
97
How many neuron axons per oligodendrocytes?
Many
98
What are satellite cells compared to? What does this mean for their function?
Astrocytes + microglial cells of PNS = structural and immune functions of PNS
99
Where are satellite cells found?
Form a ring around somas of neurons of the PNS
100
What are 3 diseases that have issues with neuron myelination?
1. ALS
2. Guillain-Barre
3. Multiple Sclerosis
101
How many Schwann cells per neuron axon?
Many
102
How many neuron axons per Schwann cell?
One
103
What are the Schwann cells separated by on an axon?
Nodes of Ranvier
104
Are all neurons myelinated?
NOPE
105
Where are the mitochondria located in the neuron axon?
In the axoplasm of myelinated portions
106
What protein do astrocytes express? What is it?
GFAP = Glia fibrillary acidic protein: intermediate filament found ONLY in astrocytes
107
What is another name for astrocytes?
Astroglia
108
What is special about astrocytes?
They are very dynamic and can change shape and size in response to many stimuli
109
What are the 9 functions of astrocytes?
1. Regulate the BBB by effecting endothelial cells and angiogenic factors that regulate the passage or not of molecules to the brain
2. Brain glycogen reserves
3. Regulate extracellular ions (K+, Na+, H+, water)
4. Uptake and regulate NTs (eg: GABA, serotonin)
5. Regulate glutamate by converting it to glutamine (glutamate sponges from synapse)
6. Express neurotrophic factors to contribute to learning, memory, and development to promote neuronal survival and myelanation
7. Synaptogenesis and neurogenesis by secreting and modifying the extracellular matrix
8. Immune modulation (w/ microglia)
9. Remove cellular debris from dead or dying neurons
110
How do astrocytes contribute to the maturation of dendritic spines?
By secreting and modifying the extracellular matrix
111
What does the BBB consist of?
Endothelial cells entirely wrapped around lumen forming tight junctions with themselves
112
What are pericytes?
Cells that interact closely with endothelial cells of the BBB to regulate the opening/closing of the blood vessels aka the capillary lumen diameter
113
What covers the lumen, endothelial cell, and pericytes of the BBB?
Basal lamina
114
What are astrocytic foot processes?
Parts of astrocytes found around the capillaries of the BBB containing specialized membrane transporters to allow the passage of some LIPID SOLUBLE molecules to the brain tissue
115
What is rapid anesthesia provided by? Why?
Gases because lipid-soluble (uncharged) so can pass the BBB
116
Can local anesthetics pass the BBB? Why?
NOPE because not lipid soluble
117
Where are Golgi apparati found in neurons?
Soma and axons
