Neuroscience Week 2: Organization and Cellular Components of the Nervous System Flashcards
(144 cards)
1
Q
Identify
A
2
Q
Superficial epineurium
A
The outer covering of the nerve
3
Q
Perineurium
A
- A mechanically strong sheath that is dense and forms a protective barrier around the nerve fascicle: a blood-nerve barrier.
- It encases two separate nerve fascicles.
4
Q
Endoneurium
A
A loose connective tissue.
5
Q
Deep epineurium
A
- Accounts for the connective tissue sandwiched between the nerve fascicles.
- We find vasculature in this region.
6
Q
Perineurial septa
A
Pass through the nerve fascicles and carry vasculature to the nerve fibers.
7
Q
NERVE FIBERS
A
Nerve fiber axon.
Myelin sheath surrounds myelinated axons.
Schwann cells: each myelinates at most one axon internode.
8
Q
Nerve Fascicles Histology
A
- Perineurium comprises a flattened form of epithelial cells. They are joined by special junctions, which helps it withstand tremendous pressure.
- Endoneurium comprises collagenous fibers.
- Superficial epineurium is a supporting coat: a cylindrical, dense connective tissue sheath.
- Deep epineurium lies between the fascicles.
9
Q
Identify
A
10
Q
Identify
A
11
Q
Identify
A
12
Q
Identify
A
13
Q
Identify
A
14
Q
Identify
A
15
Q
Endoneurium
A
Invests single nerve fiber layers (inflammatory infiltrate in Guillain-Barre Syndrome)
16
Q
Perineurium
A
(blood-nerve Permeability barrier)
Surrounds a fascicle of nerve fibers.
must be rejoined in microsurgery for limb reattachment
17
Q
Identify
A
18
Q
Resting membrane potential is?
A
At rest membrane potential is -60 to -80mV
19
Q
Myelin sheath in PNS
A
Schwann Cells
20
Q
Myelin Sheath in CNS
A
Oligodendrocytes
21
Q
Identify
A
22
Q
Identify
A
23
Q
Identify
A
24
Q
CNS Glial Cell types
A
- Astrocytes
- Microglial cells
- Ependymal cells
- Oligodendrocytes (“Macroglia”)
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PNS Glial Cell Types
* Satellite Cells
* Schwann Cells
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Astrocyte Function and Location
6 listed
* CNS
* Support and brace neurons
* Anchor neurons to supply lines
* Determine capillary permeability
* Guide neuron migration and synapse formation
* Mop up potassium and neurotransmitters
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Macroglia cell types
2 listed
* Astrocytes
* Oligodendrocytes
Both in CNS
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Microglial cells Function and location
CNS
* Monitor neuronal health
* Phagocytose pathogens and dead neurons
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Ependymal Cells Function and Location
* Form permeable barrier
* Cilia circulate CSF
CNS
30
Oligodendrocytes Function and Location
CNS
* Similar shape to astrocyte but few processes
* Create myelin sheath in CNS
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Satellite Cells Function and Location
Function in support like astrocytes
PNS
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Schwann Cells Function and Location
Create myelin sheath in PNS
PNS
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Nerve Type and Identify
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Nerve Type and Identify
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Nerve Type and Identify
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Nerve Types and Identify
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Dendrite Function
Relay impulses towards the cell body (soma)
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axon length
Axons can vary in length from microns to meters
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Protein synthesis in neurons
Protein synthesis is mainly carried out in the soma (including peptide neurotransmitters and enzymes for synthesis of chemical neurotransmitters
40
Anterograde axonal transport is
kinesin dependent and carries nutrients, enzymes, etc to the axonal terminal
Herpes Simplex/Herpes Zoster uses this mechanism for reactivation
41
Retrograde Axonal Transport is
Dynein-dependent and returns materials for lysis or recycling
Tetanus toxin and viruses (rabies, herpes simplex, and polio) are transported into the CNS by this mechanism
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Macroglia Embryological Origin
Neuroectoderm
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Microglia Embryological Origin
Mesoderm
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Ependymal Embryological Origin
Neuroectoderm
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Macroglia Glial cell types
4 listed
Astrocytes CNS
Oligodendrocytes CNS
Schwann Cells PNS (impaired in guillain-Barre Syndrome)
Capsular (satellite cells) PNS
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Microglia Glia cell types & Location
Microglia CNS
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Ependymal Glia cell types and Location
4 listed
* Ependymocytes (Ventricles and central canal of spinal cord)
* Tanycytes (floor of 3rd ventricle and part of hypothalamus)
* Choroidal epithelial cells (choroid plexus (CSF production))
* Muller Cells (Retina)
48
One Oligodendrocyte can interact with?
~50 axons
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Oligodendrocyte Function
* Formation and maintenance of CNS myelin (axonal insulation)
* There are interruptions in myelin important for impulse conduction
* One Oligodendrocyte can interact with ~50 axons
* Produces neurotrophic factors such as NGF
*
50
Oligodendrocytes in MS
Damaged in Multiple Sclerosis
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Microglia Functions and Caveat
* Immune Cells of the CNS
* Phagocytosis of debris after injury or disease
* May contribute to the pathophysiology of neurodegenerative disorders such as Alzheimers disease
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Oligodendrocytes derived from
Neuroectoderm
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Microglia derived from
Bone Marrow (mesoderm)
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Microglia in HIV
Fuse as multinucleated giant cells in HIV
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Astrocyte Function
* Respond to injury (reactive gliosis)
* Produce neurotrophic factors for neuronal survival
* Optimize interstitial space composition for synaptic transmission
* Remove some neurotransmitters from the synaptic cleft (glutamate and GABA)
* Vascular end feed couple neuronal activity with blood flow and support endothelial cells forming the blood-brain barrier
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Astrocyte histological marker for pathoglogy
Glial Fibrillary Acidic Protein (GFAP)
Common in astrocytic tumors
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GFAP AKA
Glial Fibrillary Acidic Protein
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Glial Fibrillary Acidic Protein
Histological marker for pathology in astrocytic tumors
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Astrocyte neoplasms prevalence and identifying components
* Common source of tumors
* Histological marker for pathology is Glial Fibrillary Acidic Protein
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Blood-brain Barrier Function
* Provides protective separation of the circulating blood from the CNS extracellular fluid, limiting the penetration of agents including (bacteria, drugs, toxins)
* Is a biochemical barrier for selective transport in/out of CNS
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Properties which allow for better BBB penetration
* ↑ Lipid solubility
* ↓ molecular weight
* ↓ charge (non-polar)
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How do polar molecules transport across BBB?
* Transporters can facilitate the entrance of polar molecules
* (glucose and Amino Acids via facilitated transport that does not require energy)
* Insulin and transferrin use active transport and require energy
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The blood-brain barrier is mediated by?
tight junctions between capillary endothelial cells as well as a surrounding layer of astrocyte end-feet
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Parts of the brain without a normal BBB
Some parts of the brain, the circumventricular organs lack a normal BBB and have fenestrated capillaries
These include regions that sample the blood such as the
* area postrema vomiting center,
* paraventricular nuclei including the organum vasculosum lamina terminalis (OVLT) for osmolarity regulation, and neurohypophysis for antidiuretic hormone secretion
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The BBB can open in?
Stroke, tumors, trauma, infections, epilepsy, MS, Neurodegenerative diseases, etc.
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Acute Neuronal injury cause examples
Can be hypoxia-ischemia or hypoglycemia which → necrosis or apoptosis
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Acute neuronal injury is characterized by?
Is characterized by intense cytoplasmic eosinophilia (due to Nissi body destruction; known as red neurons) and nuclear pyknosis (irreversible chromatin condensation)
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subacute and chronic Neuronal Injury is characterized by?
Neuronal death (apoptosis) and reactive gliosis (e.g. as it occurs in neurodegenerative disorders)
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Axonal Reaction description
Response of neuronal cell body to axonal damage
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Neuronal inclusions common causes
4 listed
* Can be caused by aging → (lipofuscin)
* metabolic disorders (storage material)
* viral diseases (inclusion bodies)
* neurodegenerative diseases (aggregated proteins)
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Astrocytes function in NS injury
2 listed
* Repair and scar formation
* they initially develop an enlarged vesicular nucleus and eosinophilic cytoplasm (gemistocytic astrocytes) culminating in tissue gliosis
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Gemistocytic astrocytes
Astrocytes in NS injury
Repair and scar formation
they initially develop an enlarged vesicular nucleus and eosinophilic cytoplasm (gemistocytic astrocytes) culminating in tissue gliosis
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When Astrocytes are directly damaged they...
When directly damaged they can
* form elongated eosinophilic structures (Rosenthal fibers) as seen in gliosis and tumors
* Copora amylacea in advanced age (lamellated polyglucosan bodies)
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Gliosis
Gliosis is a nonspecific reactive change of glial cells in response to damage to the central nervous system (CNS). In most cases, gliosis involves the proliferation or hypertrophy of several different types of glial cells, including astrocytes, microglia, and oligodendrocytes.
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Microglia in injury
Following injury they proliferate and develop elongated nuclei, form aggregates around necrotic foci (microglial nodules) and aggregate around dying neurons (neuronophagia)
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Oligodendrocyte in injury
cell death is characteristic of demyelinating disorders
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Ependymal Cells in injury
do not regenerate, scar formed by subependymal astrocytes (forming ependymal granulations)
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Schwann Cells in injury
a central role in peripheral nerve regeneration
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Neurapraxia common causes
is usually caused by a mild injury (eg, ischemia, mechanical compression, metabolic or toxic factors) that results in focal demyelination. The axon distal to the injury is intact, and there is nerve continuity across the site of injury.
80
Axonotmesis common causes and description
4 listed
* typically occurs as a result of crush injuries, nerve stretch injuries (eg, motor vehicle accidents, falls) or percussion injuries (eg, gunshot wounds).
* The axon is locally, but irreversibly damaged, and the myelin sheath is similarly involved.
* However, the surrounding stroma, including the endoneurium and perineurium, remains intact.
* undergoes Wallerian degeneration
81
Neurotmesis common causes and description
most often occurs in association with severe lesions, such as sharp injuries, traction injuries, percussion, or exposure to neurotoxic substances. The axon, myelin sheath, and surrounding stroma are all irreversibly damaged. The external continuity of the injured nerve is usually disrupted.
82
Sequence of morphological changes after injury to a Myelinated PNS axon
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Sequence of Morphological changes after CNS injury
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Types of ion-channels
85
Gated ion channels basic function
* transduce chemical signals into electrical signals
* allow for rapid responses
86
Ions flow along?
Concentration gradient and electric potential (electrochemical gradient)
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Sodium and potassium channels
88
Action potentials
89
Refractory periods
* Absolute refractory period
* Relative refractory period
90
Absolute refractory period
91
Relatively refractory period
When sodium channels are reset and some potassium channels are still open the membrane potential is more negative than resting potential and more difficult to overcome to initiate another potential
92
Resting state
all gated ion channels are closed
93
Depolarization
Na+ channels are open
K+ channels are closed
94
Repolarization
Na+ channles inactivated
K+ channels open
95
Hyperpolarization
* Na+ remain closed but are reset
* K+ channels still open
96
Properties of action potentials
97
Nonsaltatory conduction in unmyelinated axon
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Saltatory conduction in myelinated axons
99
more myelinated axon
100
Voltage-gated Na+ channels in myelinated and unmyelinated axons
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Question 1
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Question 2
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Question 3
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Question 4
105
Question 5
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Question 6
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Question 7
108
Question 8
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Question 9
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Question 10
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Question 11
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Question 12
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Question 13
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Question 14
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Question 15
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Question 16
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Question 17
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Corpora Amylacea description
astrocytes form lamellated polyglucosan bodies in advanced age
119
Cells that determine capillary permeability in the CNS
Astrocytes
120
Herpes Simplex/Herpes Zoster uses this mechanism for reactivation
Anterograde axonal transport mediated by kinesin
121
Tetanus toxin and viruses (rabies, herpes simplex, and polio) are transported into the CNS by this mechanism
Retrograde axonal transport and is mediated by Dynein
122
What are Muller Cells and where are they?
an ependymal cell in the retina
123
What are Tanycytes and where are they located?
Tanycytes are ependymal cells located on the floor of the 3rd ventricle and are part of the hypothalamus
124
What are Choroidal epithelial cells and where are they located?
ependymal cells and are located in the choroid plexus and are responsible for CSF production
125
What are Ependymocytes and where are they located?
Ependymocytes are ependymal cells and are located in ventricles and the central canal the of spinal cord
126
cells that produce neurotrophic factors such as NGF
2 listed
* Oligodendrocytes
* Astrocytes
127
Cell that may contribute to the pathophysiology of neurodegenerative disorders such as Alzheimers disease
Microglia
128
Fuse as multinucleated giant cells in HIV
Microglia
129
Insulin transport across the BBB
Active transport that requires energy
130
Transferrin transport across the BBB
uses active transport and requires energy
131
glucose transport across the BBB
Facilitated transport and does not require energy
132
Amino Acid transport across the BBB
Facilitated transport and does not require energy
133
organum vasculosum lamina terminalis (OVLT) function and caveat
2 listed
* for osmolarity regulation, and neurohypophysis for antidiuretic hormone secretion
* not covered by the BBB
134
What is nuclear pyknosis?
(irreversible chromatin condensation)
135
What is lipofuscin?
* lipofuscin is a nuclear inclusion in the CNS as a result of aging
* more precisely, fine yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion. It is considered to be one of the aging or "wear-and-tear" pigments, found in the liver, kidney, heart muscle, retina, adrenals, nerve cells, and ganglion cells.
136
What are ependymal granulations and where are they located?
When ependymal cells are damaged they do not regenerate and a scar is formed by subependymal astrocytes (forming ependymal granulations)
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Neurapraxia prognosis
An excellent recovery is expected and may occur within hours, days, weeks, or at the maximum, a few months
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Axonotmesis prognosis
Overall, partial recovery is the expected outcome, but the time course is significantly protracted as compared with neurapraxia.
139
Wallerian degeneration description and involved in?
* Involved in Axonotmesis
* Proximal to the lesion, the cell body undergoes changes including swelling and chromatolysis, which resolves with time. Distal to the lesion, the axon degenerates, and the myelin sheath involutes; this process is known as Wallerian degeneration.
140
Neurotmesis prognosis
* No significant regeneration occurs with such a lesion, unless surgical re-anastomosis is performed.
* Spontaneous reversal of the changes is impossible as the nerve regenerates in a disorganized proliferation of axons, Schwann cells, and perineural cells within a collagenous stroma called a neuroma.
* With surgical intervention (scarring debridement and approximation of the nerve ends or interposing of a nerve graft), the axon may grow along the endoneurial tubes of the distal segments.
* This process may take months to years until a useful function is achieved. In neurotmesis, muscle recovery can only occur by axonal regeneration.
141
Action potential ion channels: Resting state
all gated ion channels are closed
142
Action potential ion channels: Depolarization
* Na+ channels open
* K+ channels closed
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Action potential ion channels: Repolarization
* Na+ channels inactivated
* K+ channels open
144
Action potential ion channels: Hyperpolarization
* Na+ channels reset and closed
* K+ channels still open
