Lecture 3: Cells of the Nervous System Flashcards
1
Q
Neurons are the _ of the nervous system
A
main signalling units
2
Q
Neuron:
A
from Greek, “sinew”,
“tendon”, “nerve”.
3
Q
Neuron: the term was introduced by:
A
German anatomist
Heinrich Waldeyer in 1891.Previously, Camillo Golgi had used
the term “nerve cell”
4
Q
Human brain: total number of neurons is estimated at
approximately
A
86 billion neurons (in humans)
5
Q
Most neurons are concentrated in the
A
cerebral cortex and
cerebellum
6
Q
Spinal Cord: contains about
A
197–222 million neurons (in
humans).
7
Q
Neuron counts in the Peripheral Nervous System:
SOMATIC , including sensory neurons (afferent) and motor neurons
(efferent):
A
UNKNOWN
8
Q
Neuron counts in the Peripheral Nervous System: AUTONOMIC: comprising sympathetic, parasympathetic, and enteric
divisions:
A
UNKNOWN
9
Q
Neuron counts in the Peripheral Nervous System: ENTERIC
A
contains about 168 million neurons (in humans).
10
Q
In the enteric nervous system (autonomic subdivision of the peripheral nervous system), neurons are clustered in:
A
The MYENTERIC (Auerbach’s) PLEXUS and SUBMUCOSAL (Meissner’s) PLEXUS of the gastrointestinal tracts
11
Q
Most neurons in the vertebrate nervous system have
A
several
main features in common.
12
Q
The cell body contains
A
the nucleus,
the storehouse of genetic information, and gives rise to two
types of cell processes, axons and dendrites.
13
Q
transmitting element of neurons
A
Axons
14
Q
Axons, the
transmitting element of neurons, can vary greatly in
A
length
15
Q
Some axons can extend more than __ in the body
A
3m
16
Q
Most axons in the
central nervous system are
A
very thin (between 0.2 and 20 µm in
diameter) compared with the diameter of the cell body (50 µm
or more)
17
Q
Many axons are insulated by
A
a fatty sheath of myelin
that is interrupted at regular intervals by the nodes of Ranvier.
18
Q
The action potential is the cell’s ___ signal
A
conducting
19
Q
The action potential, the cell’s conducting signal, is initiated
either at
A
the axon hillock, the initial segment of the axon, or in
some cases slightly farther down the axon at the first node of
Ranvier.
20
Q
Branches of the axon of one neuron (the presynaptic
neuron) transmit signals to another neuron (the postsynaptic
cell) at a site called:
A
the synapse
21
Q
The branches of a single axon
may form synapses with as many as
A
1000 other neurons
22
Q
the axon is the __ of the neuron
A
the output element of the neuron
23
Q
dendrites (apical and basal) are the __ of the neuron
A
input elements of the neuron.
24
Q
Together with the cell body, the dendrites receive
A
synaptic contacts from
other neurons
25
synapse:
signals called action potentials pass from an axon to a dendrite through junctions called synapses
A signal can have over 100000
26
dendrites :
signals come in through dendrites
These vast, tree-like branches grow up and out from the soma
Dendrites are thicker than axons and covered in synapses
27
Soma:
A cell's body, home of the nucleus.
If you stretched out all the DNA in just one of your cells, it would be at least 6 feet long
28
Axon:
Signals go out through axons, which branch many times and stretch vast distances.
Neurons send action potentials down their axons and through synapses they've formed to communicate with other cells.
The longest axons in your body reach from your toes to your spine
29
Spinous neurons are characterized by the presence of:
Numerous dendritic spines on their dendrites (aspinous neurons lack these spines)
30
aspinous neurons lack
dendritic spines on their dendrites
31
Most excitatory synapses in the brain form on __
dendritic spines
32
Most excitatory synapses in the brain form on dendritic spines, meaning:
spinous neurons generally
receive a larger number of excitatory inputs
compared to aspinous neurons.
33
* Due to their spine structure, spinous neurons are
often associated with
greater synaptic plasticity,
allowing for more dynamic changes in neural
connections based on experience.
34
Due to their spine structure, spinous neurons are
often associated with greater synaptic plasticity,
allowing for
more dynamic changes in neural
connections based on experience.
35
Example neuron types:
Spinous:
Pyramidal neurons in the cerebral cortex
are a prominent example of spinous neurons
36
Example neuron types: Aspinous:
Some types of interneurons in the brain,
like certain stellate cells, are considered aspinous or
sparsely spinous.
37
Unipolar neurons, often referred to as
‘true’ unipolar neurons
38
Unipolar neurons, often referred to as ‘true’ unipolar neurons, feature:
a single process extending from the cell
body (soma), which then branches into dendrites or an axon.
39
In the context of human neurophysiology, the
term "unipolar" is sometimes mistakenly used in place of
pseudounipolar.
40
True unipolar neurons have
traditionally been considered as
absent in the mature vertebrate nervous system (specific developmental stages
may display neurons with only one process)
41
Unipolar neurons are predominantly observed in
invertebrates, where they
form a prevalent neuronal population
42
Bipolar neurons bear :
an oval shaped cell body possessing two processes: one axon and one process functioning
as a distant dendrite
43
In humans, bipolar neurons serve as
sensory neurons
44
In humans, bipolar neurons serve as sensory neurons and are primarily found in
special sensory organs such as the olfactory epithelium, retina and vestibulocochlear apparatus
45
Describe pathway of bipolar neurons:
The terminal ramifications in the periphery receive signals from the sensory organs and combine into one
process that reaches the cell body. The axon transfers the signal from the cell body to the central nervous
system (CNS) and distributes impulses to second order afferent neurons. Both processes exhibit axonal
characteristics and can be encased in a myelin sheath which increases the speed of impulse conduction.
46
In bipolar neurons, both processes exhibit __ and can be __
In bipolar neurons, both processes exhibit axonal characteristsics and can be encased in myelin sheath whih increases the speed of impulse conduction
47
Pseudounipolar neurons consist of:
one short process which splits into two other processes
48
pseudounipolar neurons serve as
sensory neurons
49
pseudounipolar neurons, along with bipolar neurons, constitute:
The entierety of the primary sensory neurons within the human PERIPHERAL NERVOUS SYSTEM (PNS)
50
Pseudounipolar neurons are found in :
All sensory ganglia of cranial and spinal nerves (except for olfactory epithelium, retins and vestibulocochlear apparatus)
51
Pseudounipolar neurons are found in all sensory GANGLIA of CRANIAL and SPINAL nerves except for (3) :
(1) Olfactory epithelium
(2) Retina
(3) Vestibulocochlear apparatus
52
Pseudounipolar neurons can be considered as variations of:
Bipolar neurons
53
PSEUDOUNIPOLAR MIDDLE PARAGRAPH:
***
54
The peripheral/ distal process of the pseudounipolar neuron axon terminates in the :
Periphery
55
The peripheral/ distal process of the pseudounipolar neuron terminates in the periphery, where :
the terminal ramification respond to a wide range of stimuli (thus functioning as distant dendrites)
56
The peripheral/distal process of the axon terminates in the
periphery, where the terminal ramifications respond to a wide
range of stimuli, thus functioning as :
Distant dendrites
57
The second branch of the pseudounipolar neuron is known as:
the central / proximal process
58
The second branch of the pseudounipolar neuron , known as the central / proximal process is usually __ , terminating in __
The second branch of the pseudounipolar neuron, known as the central/proximal process, is usually SHORTER, terminating in the CNS
59
The second branch of the pseudounipolar neuron, known as the central/proximal process, is usually SHORTER, terminating in the CNS, where:
they distribute impulses to second order afferent neurons
60
Nerve impulses in pseudounipolar neurons can pass from the peripheral to central processes without:
The involvement of the cell body in signal processing
61
The cell body of unipolar neurons mainly retains
Trophic functions (i.e. support, nourishement, maintenance of the neuron)
62
Anaxonic neurons are:
Small neurons which LACK AN AXON,or the axon cannot be distinguished
from its many dendrites
63
Anaxonic neurons * because they lack an axon * don't generate :
action potentials like typical neurons : they rely on graded potentials that influence neighbouring neurons, acting more like local interneurons
64
Since anaxonic axons lack axons and dont generate action potentionals, they rely on:
Graded potentials that influence neighbouring neurons, acting more like "local interneurons"
65
Can anaxonic axons release neurotransmitters?
yes
66
Anaxonic neurons release neurotransmitters, but unlike most
neurons:
They release them from their dendrites since they lack a distinct axon
67
Anaxonic neurons can typically be found:
where their modulatory functions are needed, such as in
the RETINA and OLFACTORY BULB
68
Dominant type of neurons in vertebrates:
multipolar neurons
69
Multipolar neurons are characterized by:
multiple processes: a single axon and numerous dendrites.
70
dendrites in multipolar neurons originate from:
different
regions of the cell body, displaying varying degrees of branching and directionality.
71
multipolar neurons are notable for:
their extensive diversity, manifesting in a wide range of sizes,
shapes and complexity within their dendritic tree.
72
multipolar neurons' cell bodies may measure:
as small as 5 μm
in diameter or reach as large as 100 μm (exemplified by giant pyramidal cells (of Betz))
73
The cell body of multipolat neurons can take on various forms including:
OVOID, SPHERICAL, PYRIFORM (pear -shaped) or fusiform (spindle -like shaped)
74
The axon of multipolar neurons may be:
short or long
75
common subtypes of multipolar neurons (4):
(1) Pyramidal
(2) Stellate
(3) Purkinje
(4) Granule
76
Pyramidal neurons (type of bipolar neuron) are characterized by their cell body, whose shape resembles:
a teardrop or rounded pyramid
77
pyramidal neurons: the dendrites emerge either:
From the top of the pyramid (apical dendrite) or from the base (basal dendrites)
78
Each pyramidal neuron usually possesses:
a single apical (top) dendrite that is longer than the basal dendrites and extends numerous dendritic branches
79
pyramidal neurons can be found in:
-cerebral cortex (layers III and V)
- subcortical structures (hippocampus and amygdala)
80
Where can pyramidal cells be found in the cerebral cortex?
Layers III (external pyramidal layer)
Layers V (internal pyramidal layer)
81
Due to the diversity of pyramidal neurons, there are:
subtypes of pyramidal neurons
82
largest example of pyramidal cells
Giant pyramidal cells (of Betz)
83
giant pyramidal cells (of Betz) are the largest example of pyramidal
cells; they are located in:
the motor cerebral cortex
84
giant pyramidal cells (of Betz) are the largest example of pyramidal
cells; they are located in the motor cerebral cortex and are
considered as:
the origin for the pyramidal tract controlling
voluntary movements (upper motor neurons).
85
Stellate cells are
SMALL multipolar neurons (look like stars)
86
Stellate cells are small multipolar neurons found
mainly in (4):
(1) INTERNAL GRANULAR LAYER IV of cortex (excitatory),
(2) cerebellar cortex (inhibitory)
(3) spinal cord (mixed)
(4)reticular formation (mixed)
87
Stellate cells have many :
local dendrites with equal lengths
(isodendritic) that radiate uniformly in all directions
and a short arbored axon.
88
Isodendritic
dendrites with equal lengths --> STELLATE CELLS
89
In cortical layer IV, stellate cells mainly receive input from
the thalamus
90
In cortical layer IV, they mainly receive input from
the thalamus and are considered to be
high-fidelity
translators of thalamic input, maintaining strict
topographic organization and accurately and
efficiently convey sensory information received from
the thalamus to other parts of the cerebral cortex
91
Granule cells are
small oval-shaped
multipolar interneurons
92
Granule cells exert:
different functions and
neurochemical characteristics depending on
their location
93
granule cells are found in the (3):
(1) cerebellum (excitatory, NT: glutamate),
(2) the olfactory bulb (inhibitory, NT: GABA)
(3) the dentate gyrus (excitatory, NT: glutamate)
94
Granule cells in the CEREBELLUM:
- excitatory
- NT: glutamate
95
Granule cells in OLFACTORY BULB:
- Inhibitory
-NT: GABA
96
Granule cells in Dentate Gyrus:
- Excitatory
-NT: glutamate
97
Granule cells, particularly in the dentate gyrus, show
adult NEUROGENESIS
98
Granule cells, particularly in the dentate
gyrus, show adult neurogenesis, meaning
new granule cells can form throughout life,
contributing to learning and memory.
99
Purkinje cells are located in
the CEREBELLUM
100
Purkinje cells are located in the cerebellum, between
the molecular and granular layers
101
Purkinje neurons have:
large pear-shaped cell bodies and
characteristic fan-shaped dendritic trees which fill
the molecular layer.
102
Purkinje neurons are the only:
ONLY PROJECTION (EFFERENT) NEURONS OF THE CEREBELLAR CORTEX (all other neurons in the
cerebellum are intrinsic) and their axons
terminate in the cerebellar nuclei
103
Purkinje neurons are the only projections (efferent) neurons of the. erebellar cortex, their axons terminate in:
cerebellar nuclei
104
Purkinje neurons have an __ role, using __ as a neurotransmitter
they have an
inhibitory role, using gamma-aminobutyric acid
(GABA) as a neurotransmitter.
105
Multi-polar neurons come in
many shapes…
106
Multi-polar neurons: Classification by shape: Golgi types:Golgi type I neurons have
very long axons
that connect different parts of the system
107
Multi-polar neurons: Classification by shape: Golgi types:Golgi type II:
also known as
microneurons, have only short axons or
sometimes none
108
page 24
109
From a functional point of view, neurons can be classified
into (3) :
(1) Motor neurons
(2) Sensory neurons
(3) interneurons
110
Motor neurons:
facilitate the transmission of signals
from the CNS to effector organs, such as muscles and
glands.
111
Sensory neurons:
receive input from the periphery
and convey it to the CNS.
112
Interneurons
most neurons in the CNS can be
classified as neither motor nor sensory; since they
integrate, combine, process and further transmit the
signals received towards other brain regions, they can
be characterized as short axon (a.k.a. local
circuit) or long axon (projection, association or
commissural) interneurons
113
26/27
114
Afferent neurons
receiving information from other
brain areas.
115
Efferent (or projection) neurons
are considered
the principal neurons of every brain region, extending
their axons beyond the borders of the specific area
establishing connections with neurons of other regions
in the CNS.
116
Local circuit neurons (or intrinsic neurons or short axon interneurons)
have
shorter axons and connect with other neurons in their
close proximity, exerting their role as mediators
between other neurons of the same CNS area. These
neurons are also called SHORT AXON INTERNEURONS
117
Regarding their connections, nerve cells of every CNS area
can further be classified into (3):
(1) Afferent neurons
(2) Efferent (or projection) neurons
(3) Local circuit neurons
118
Excitatory Neurons:
facilitate the transmission of signals
that induce depolarization in neighboring neurons. This
depolarization increases the likelihood of generating an
action potential, subsequently activating the neurons.
119
Inhibitory Neurons:
Constituting a relatively small fraction
of the neural population, inhibitory neurons are
distinguished by their diverse expression of molecular
markers and firing properties. They form intricate circuits
that provide inhibition for a wide array of stimuli while also
regulating the activity of excitatory neurons.
120
Modulatory neurons:
Modulatory neurons release
neurotransmitters or neuromodulators to inflyence the
activity of other neurons.
They modify the SENSITIVITY or
RESPONSIVENESS of neurons to other signals and DO NOT DIRECTLY STIMULATE action potentials. They play a crucial role
in regulating neural circuits and shaping overall brain
function.
121
modulatory neurons modify:
the sensitivity or responsiveness of neurons to other signals
122
modulatory neurons do not:
directly stimulate action potentials
123
modulatory neurons play a crucial role in:
regulating neural circuits and shaping overall brain function
124
Neurons can also be categorized according to the
neurotransmitters which they release. Some common types are
the:
Glutamatergic
Cholinergic
GABAergic
Dopaminergic
neurons.
125
Glutamatergic neurons
produce and secrete glutamate, which
is the main excitatory neurotransmitter of the CNS
126
Pyramidal
neurons are principally categorized as
glutamatergic.
127
Cholinergic neurons secrete:
acetylcholine.
128
Cholinergic neurons are located
both in the PNS and the CNS
129
GABAergic neurons are
inhibitory neurons. Their neurotransmitter is
GABA, the main inhibitory neurotransmitter of the CNS.
130
examples of gabaergic neurons:
Purkinje cells and many
interneurons
131
Dopaminergic neurons produce and release
the monoamine
neurotransmitter dopamine
132
Dopaminergic neurons are mainly located in the (3):
(1) midbrain
(2) hypothalamus
(3) olfactory bulb
133
Examples of glutamatergic neurons (7):
(1) Pyramidal Neurons
(2) Spiny Stellate Cells
(3) Granule Cells
(4) Mossy Cells
(5) Retinal bipolar cells (on bipolar cells)
(6) Mitral and Tufted Cells
(7) Thalamocortical Neurons
134
Examples of glutamatergicl neurons: pyramidal neurons: Type / Location / Function
135
Examples of glutamatergic neurons: spiny stellate cells
136
Examples of glutamatergic neurons: granule cells
137
Examples of glutamatergic neurons: mossy cells
138
Examples of glutamatergic neurons: retinal bipolar cells (on bipolar cells)
139
Examples of glutamatergic neurons: mitral and tufted cells
140
Examples of glutamatergic neurons: thalamocortical neurons
141
Examples of GABAergic neurons: Basket cells
142
Examples of GABAergic neurons:
stellate cells
143
Examples of GABAergic neurons: purkinje cells
144
Examples of GABAergic neurons: medium spiny neurons (MSNs)
145
Examples of GABAergic neurons: PV+ interneurons
146
Examples of GABAergic neurons (SST + interneurons)
147
Examples of GABAergic neurons: Chandelier cells
148
Cholinergic neurons : type:
Excitatory or modulatory neurons
149
Cholinergic neurons: location:
Found in various regions, including:
* Basal forebrain (e.g., nucleus basalis of Meynert,
medial septum).
* Brainstem (e.g., pedunculopontine nucleus,
laterodorsal tegmental nucleus).
* Spinal cord (e.g., motor neurons in the ventral
horn).
150
151
Cholinergic neurons function:
Release acetylcholine (ACh) to modulate
synaptic activity and influence processes
152
cholinergic neurons:Function: Release acetylcholine (ACh) to modulate
synaptic activity and influence processes like:
* Arousal, attention, and learning (via basal forebrain
projections to the cortex and hippocampus).
* Motor control (via brainstem projections to the
spinal cord and basal ganglia).
* Autonomic nervous system regulation (via spinal
and peripheral cholinergic neurons).
153
Myasthenia gravis is
a neuromuscular
disease leading to fluctuating muscle
weakness and fatigability during simple activities.
154
Cholinergic neurons & myasthenia gravis: weakness is typially caused by:
circulating antibodies that block acetylcholine
receptors at the postsynaptic neuromuscular
junction, inhibiting the stimulative effect of the
neurotransmitter acetylcholine.
155
Myasthenia is treated
with:
(1) immunosuppressants
(2) cholinesterase inhibitors
(3) thymectomy (removing thymus gland)
156
Dopaminergic neurons type:
modulatory
157
dopaminergic neruons are found in
(1) midbrain : Substantia Nigra Pars Compacta (SNc), ventral tegmental area (VTA),
(2) Hypothalamus: Arcuate nucleus
158
Human dopamine pathways: Substantia nigra pars compacta (SNc): Projects to
the
striatum, forming the nigrostriatal pathway.
159
Human dopamine pathways: VTA projects to:
the cortex and limbic regions via the mesocortical and mesolimbic pathways
160
Human dopamine pathways: Arcuate nucleus: projects to :
the median eminence, regulating hormone release in the pituary
161
Dopaminergic neurons release dopamine to regulate various processes including:
(1) motor control
(2) reward and motivation
(3) Cognition and executive function
(4) Endocrine regulation
162
Dopaminergic neurons: Function: Release dopamine (DA) to regulate various processes, including: Motor control:
Via the nigrostriatal pathway, dysfunction
contributes to Parkinson’s disease
163
Dopaminergic neurons: Function: Release dopamine (DA) to regulate various processes, including: reward and motivation:
Through the mesolimbic pathway, critical
for reinforcement and addiction.
164
Dopaminergic neurons: Function: Release dopamine (DA) to regulate various processes, including:Dopaminergic neurons: Function: Release dopamine (DA) to regulate various processes, including: cognition and executive function:
Via the mesocortical pathway,
implicated in attention and decision-making.
165
Dopaminergic neurons: Function: Release dopamine (DA) to regulate various processes, including:Dopaminergic neurons: Function: Release dopamine (DA) to regulate various processes, including: Endocrine regulation:
Modulates prolactin secretion in the
pituitary gland.
166
Multiple sclerosis:
Axon loss is a factor in the neurological
symptoms of multiple sclerosis.
167
Stroke:
Physical damage to the brain from a stroke can kill
or disable neurons.
168
Traumatic brain injury:
Physical damage to the brain from
an injury, such as a hit to the head, can kill or disable
neurons.
169
Neurodegenerative diseases:
Axons can be damaged in
the early stages of neurodegenerative diseases like
Alzheimer's disease, Parkinson's disease, and motor neuron
disease.
170
Peripheral neuropathies:
Axon loss can contribute to
neurological symptoms of peripheral neuropathies
171
Diffuse axonal injury (DAI) is a
type of traumatic brain injury that occurs when the brain rapidly shifts within the skull, causing widespread damage to the long connecting nerve fibers (axons), leading to disruptions in brain communication and potentially resulting in coma, cognitive impairment, or physical disabilities
172
Axons can be damaged by:
nerve injury, or by the earliest
stages of neurodegenerative diseases.
173
Damaged axons can prevent
neurons from communicating
properly.
174
The adult brain can sometimes repair itself by
reverting
injured cortical neurons to an embryonic state, allowing them
to regrow axons.
175
Imaging techniques for diagnosing axonal injury
*Magnetic resonance imaging (MRI), particularly diffuse tensor
imaging (DTI), is the preferred imaging technique for
diagnosing diffuse axonal injury.
176
Glia cells
* Non-neuronal cells in the nervous system.
* Perform many support functions.
* Do not produce electrical impulses.
177
Glial cells far outnumber neurons:
there are between 10 and 50 times
more glia than neurons in the central nervous system of vertebrates.
178
Despite their name, glia cells do not
commonly hold nerve cells
together. Rather, they surround the cell bodies, axons, and dendrites of
neurons.
179
glia are not directly involved in
information
processing, but they are thought to have at least seven other vital roles
180
most numerous of glial cells
Astrocytes
181
astrocyte shape:
Irregular, roughly star-shaped cell bodies.
182
astrocytes have long __ some of which terminate in __
LONG PROCESSES (brances, some ofwhich terminate in END-FEET)
183
Astrocytes : end feet: role:
* Some astrocytes form end-feet on the surfaces of
neurons in the brain and spinal cord and may play a role
in bringing nutrients to these cells.
* Other astrocytes place end-feet on the brain's blood
vessels and cause the vessel's endothelial (lining) cells to
form tight junctions, thus creating the protective blood-
brain barrier.
184
Astrocytes help to:
maintain the right potassium ion concentration in
the extracellular space between neurons
(( When a nerve cell fires, potassium ions flow out of the
cell. Repetitive firing may create an excess of
extracellular potassium that could interfere with
signaling between cells in the vicinity. Because
astrocytes are highly permeable to potassium, they can
take up the excess potassium and so protect those
neighboring neurons))
185
Astrocytes take up:
neurotransmitters from synaptic zones after release
and thereby help regulate synaptic activities by removing
transmitters.
186
Microglia are
immune cells in the brain that help maintain
brain health and repair damage. They are a key part of the
brain's immune system, and they also play a role in brain
development and aging.
187
Microglia function:
(1) eliminate harmful substances
(2) Regulate brain development
(3) Mediate inflammation
(4) present antigens
(5) Sustain the blood-brain barrier
(6) Repair injuries
188
Ependymal cells
Glial ciliated cells that line the brain's ventricles and spinal cord central canal
189
Ependymal cells regulate:
the flow of cerebrospinal fluid (CSF) and other substances in and out of
the brain
190
Myelin-forming cells
Schwann cells and oligodendrocytes are glial cells
that produce myelin sheaths in the peripheral and
central nervous systems (PNS and CNS)
191
Myelin
insulates
xons, which allows for faster impulses
to travel
192
Schwann cells are mainly in the
PNS
193
oligodendrocytes are mainly in the
CNS
194
Schwann cells
myelinate (how many axons at a time) :
one axon at a time
195
oligodendrocytes can myelinate up to:
60 axons
196
Capacity for replication: Oligodendrocytes are
terminally differentiated and cannot replicate
after injury. Schwann cells can invade the CNS to
form new myelin sheaths.
197
Myelin disorders
Myelin disorders are diseases that damage the myelin sheath, which insulates nerves.
Damaged myelin can slow or stop nerve impulses, causing neurological issues.
198
Multiple sclerosis (MS):
An autoimmune disease that damages the myelin in the brain,
spinal cord, and optic nerve. It's the most common demyelinating disorder.
199
Acute disseminated encephalomyelitis (ADEM):
A brief but widespread inflammation that
damages the myelin in the brain and spinal cord.
200
Neuromyelitis optica (Devic's disease):
An autoimmune disease that causes inflammation
and myelin loss around the spinal cord and optic nerve.
201
Transverse myelitis:
Can be an early sign of MS or a relapse.
202
Balo's disease:
A rare and potentially fatal form of MS
203
Leukodystrophy:
A demyelinating disease that affects the central nervous system.
204
Symptoms of myelin disorders:
Trouble walking or seeing, Changes in bladder and
bowel function, and Fatigue
205
Causes of myelin disorders:
* Infections
* Immune disorders
* Metabolic disorders
* Nutritional deficiencies
* Poisons
* Drugs or medications
* Excessive alcohol use
* Viral infections
* Loss of oxygen
* Physical compression
206
Radial Glial Cells
Arise from neuroepithelial cells after
neurogenesis. Function as neuronal
progenitors and scaffolds for migrating
neurons. Retained in the cerebellum
(e.g., Bergmann glia, regulating synaptic
plasticity) and retina (e.g., Müller cells,
supporting neurons)
207
Satellite Glial Cells
Small cells surrounding neurons in
sensory, sympathetic, and
parasympathetic ganglia. Regulate the
external chemical environment and are
involved in injury and inflammation (e.g., chronic pain).
207
Enteric Glial Cells
Found in the intrinsic ganglia of the
digestive system. Support homeostasis
and regulate digestive processes,
including muscular activity.
