Week 2 Objectives Flashcards
(60 cards)
1
Q
What are the 3 layers of the meninges?
A
- dura mater: pachymeninx
- arachnoid mater
- pia mater: fused to surface layer of brain
- arachnoid + pia are leptomeninges
2
Q
What are the spaces between the meninges called?
A
- -> between bone and dura mater: epidural space in spinal canal filled with fat (potential space in calvarium)
- -> between dura and arachnoid: subdural space (potential space)
- -> between arachnoid and pia mater: subarachnoid space (CSF)
3
Q
What is the order of the ventricular system?
A
- lateral ventricle in each cerebral cortex (2)(interventricular foramen)
- 3rd ventricle around interthalamic adhesion (mesencephalic aqueduct thru midbrain)
- 4th ventricle between pons/medulla (ventrally) and cerebellum (dorsally)
- lateral apertures to subarachnoid space for reabsorption OR central canal and subarchnoid space of spinal cord
4
Q
Which areas of the ventricles have choroid plexus?
A
Lateral and fourth ventricles
5
Q
What is the choroid plexus?
A
Highly vascularized area of pia mater that invaginates into the ventricle
- makes CSF (ultrafiltrate of blood thru blood-CSF barrier)
6
Q
What cells line the ventricles?
A
Ependymal cells with tight junctions
- will actively transport things in and out (cannot go around these cells)
- blood - CSF barrier
7
Q
What are the 2 major arterial blood supply vessels for the brain for the dog?
A
Internal carotid and basilar artery supply the circle of Willis to rostral, middle, caudal cerebral, rostral and caudal cerebellar, labyrinthine
8
Q
What is the major arterial blood supply to the brain of the cat?
A
Maxillary artery to middle meningeal artery and maxillary rete
- from external carotid
- have potential to compress maxillary artery with excessive jaw extension
9
Q
What cell layer does the notochord develop from?
A
Mesoderm
- defines midline
- signals the overyling ectoderm to become neuroectoderm
10
Q
What hormone does the notochord secrete?
A
Sonic hedgehog
- ventral from notochord/floor plate –> triggers motoneuron development on ventral aspect of developing spinal cord
11
Q
What cell layer does the neural tube develop from?
A
Neuroectoderm
- neural folds (lateral margins) fuse along midline, forming the neural tube and nerual canal
- neural crest cells separate at the junction of ectoderm and neuroectoderm as the neural tube is formed
12
Q
What are the four neurologic features that develop from the neural crest cells?
A
- dorsal root ganglia (sensory component of CNS)
- post ganglionic GVE axons (SANS, PANS) –> autonomic
- part of leptomeninges and lemnocytes
- Schwann cells
13
Q
What does the prosencephalon form?
A
- telencephalic vesicles –> form cerebral hemispheres
- diencephalon –> thalamus
- eyes
14
Q
What does the mesencephalon form?
A
- CN 3 and 4
- mesencephalic aqueduct
- alar plate proliferates to form tectum of midbrain
- crus cerebri ventrally
15
Q
Rhombencephalon
A
Caudal brainstem
- pons, cerebellum, medulla
- metencephalon and myelencephalon
16
Q
What cells are part of the germinal layer?
A
Ependymal cells
17
Q
What part of the brain is associated with the mantle layer?
A
Gray matter of spinal cord
- contains differentiated cells
- nuclei of brainstem, cortex of cerebellum and cerebrum, basal nuclei
18
Q
What part of the brain is associated with the marginal layer?
A
White matter of spine and brain
- where growing axonal processes form
19
Q
Where is gray matter found in the spinal cord?
A
Medial (inside)
- contains cell bodies
20
Q
Where is gray matter found in the cerebral cortex?
A
Gray matter is on the periphery
21
Q
Where is gray matter found in the cerebellum?
A
Gray matter is peripheral and central (outside)
22
Q
What two cells are formed from spongioblasts?
A
Migrate throughout mantle and marginal layer
- astrocytes
- oligodendrocytes
- both originate from neuroectoderm*
- microglia are monocytes from peripheral blood
23
Q
What happens if a neuron forming a peripheral nerve doesn’t reach its target?
A
Apoptosis
- start out with more neruons than what actually makes it to adulthood
24
Q
What myelinates a peripheral nerve axon vs a central tract axon?
A
Peripheral = Schwann cells (comes from neural crest cells) Central = Oligodendrocytes (comes from spongioblasts)
25
What are the 3 kinds of nerve injury?
- neuropraxia
- axonotmesis
- neurotmesis
26
Neuropraxia
Prevents transmission/conduction of electrical impulses
- most common
- causes: minor contusion/compression, disruption to blood supply, mild stretch
- should not need surgery
27
Axonotmesis
```
Characteristics:
- damage and breakdown of axon
- damage to myelin sheath
- preservation of schwann cells and endoneurium
- distal Wallerian degeneration occurs
Causes:
- crushing of the nerve
- severe stretch
Recovery:
- spontaneous regeneration with good functional recovery (3-6 months)
```
28
Neurotmesis
Most severe
Causes:
- laceration
- tearing force
Characteristics:
- complete anatomical severance, avulsion, or crushing of nerve
- axon, schwann cells and endoneurial tubes are completely disrupted
- distal Wallerian degeneration occurs
Recovery:
- some recovery after surgery
- spontaneous regeneration does not occur
29
What injuries are non-degenerative vs degenerative?
```
Non-degenerative:
- neuropraxia: transient block
Degenerative:
- axonotmesis: lesion in continuity
- neurotmesis: division of a nerve
```
30
Wallerian degeneration
Severing of the axon from the cell body (axotomy)
- can be physical or chemical
- target in chemical axotomy is axon transport system
In peripheral neurons: damage happens in the middle, regeneration can occur but depends
31
Distal stump
- severed ends close
- distal stump destroys itself by Ca sensitive proteases
- macrophages eat myelin debris
- can have target cell/organ effects
32
Proximal part of neuron
- chromatolysis occurs --> swelling of cell body, dendrite disconnection, increased synthesis of material for growth cones and for axon structure
- Schwann cells dedifferentiate to a premyelinating state --> macrophages signal schwann cells to replicate
33
What do new Schwann cells produce?
- cell adhesion molecules
- basal lamina components (ECM)
- neurotrophins (NGF and BDNF)
34
What do macrophages do?
Signal Schwann cells to replicate via interleukin 1 and they eat myelin debris
- produce inflammatory cytokines and chemokines
- attract peripheral immune cells causing damage to nearby intact tissue (short term)
- activate astrocytes
35
What does the cell body/neuron do?
Cell body responds to axotomy, initiating chromatolysis
- swelling of cell body
- dendrite disconnection
- increased synthesis of material for growth cones and for axon structure
- proximal stump spouts neurites
36
Is glutamate excitatory or inhibitory?
Excitatory
| - is the number 1 excitatory neurotransmitter in the brain (calcium)
37
What does it allow in the cell?
Calcium
38
Why does the CNS not show regeneration of the axons like the PNS?
Damage in CNS promotes neuronal cell death (apoptosis or necrosis)
- CNS neurons do not show chromatolysis changes --> reduced expression of regenerative associated genes
- oligodendrocytes form myelin and produce inhibitors of neurite outgrowth --> NogoA, MAG, OMgp
39
What cell is the macrophage of the CNS?
Microglia
- clear debris, but not fast
- produce inflammatory cytokines
40
Which is better at encouraging axonal repair: schwann cells or oligodendrocytes?
Schwann cells
41
Astrocytes prevent axonal growth by forming what?
A glial scar where axon used to be
- physically prevents growth cone navigation
- scar also contains chondroitin sulfate proteoglycans which inhibit regenerative growth
42
What 2 locations in the adult brain are neural stem cells found?
```
Subventricular zone (olfactory bulb)
- in the wall of the lateral ventricle
Subgranular zone (hippocampus)
```
43
If you loose a motor neuron, what are two processes that another motor neuron help fill the deficit?
Rerouting
- re-establishing an existing nervous connection via an alternative pathway
Collateral sprouting
- growth of new axon or dendrite fibers to enable new neural connections to be formed
44
What 2 structures keep the nucleus pulposus from entering the spinal canal?
Dorsal annulus fibrosus and dorsal longitudinal ligament
| - also have intercaptial ligament from T1 - T10
45
Where do the sympathetic neruons live the spinal cord? How do their axons get to the sympathetic trunk?
Gray matter
- communicating branch off ventral nerve root
- thoracolumbar spinal cord
46
How many cervical vertebrae vs how many cervical spinal cord segments are there?
7 cervical vertebrae
| 8 cervical spinal cord segments
47
How many thoracic vertebra/spinal cord segments are there?
13 in dog/cat
| 18 horse
48
How many lumbar vertebra/spinal cord segments are there?
7 lumbar vertebra
| 7 lumbar spinal segments
49
How many sacral vertebra/spinal cord segments are there?
3 sacral vertebra in dog/cat (fused)
| 4-5 in large animals
50
What are the 4 functional divisions of the spinal cord? What delineates them?
```
C1-C5
- in front of cervical intumescence
C6-T2
- cervical intumescence (nerves coming off forelimb)
T3-L3
- between cervical and lumbar intumescence
L4-S1
- lumbar intumescence
```
51
What named nerve is required to be functional to support weight in the forelimb and hind limb? What spinal cord segments do they originate from?
Forelimb: radial nerve
- originates from C7, C8, T1 (T2)
Hindlimb: femoral nerve -
- originates from L4-L5 (L6)
52
What does the dorsal spinal artery supply?
Dorsal funiculus (white matter) and dorsal horn (gray matter)
53
What do the branches of the ventral spinal artery supply?
Central branches to ventral and intermediate gray matter
| Other branches to ventral and lateral white matter
54
Axon transport system
Keeps the axon alive by removing waste material back to cell body
- neuron and bringing food from the cell body/neuron
55
To perform a myelogram, you would inject a contrast agent into which space?
Cerebellomedullary cistern or lumbar cistern
| - L4-5 or L5-6
56
What space can this be performed at in the dog?
Subarachnoid
| - spaces vary depending on the contrast/test being performed
57
Which sequence on MRI do we run after IV contrast administration?
T1
58
Which MRI scan is best for anatomy?
T1
59
Which MRI is best for pathology, because edema is bright?
T2
60
Which of the following regarding an MRI is true?
- fat is bright on T1 and T2
- CSF is bright on T1 and T2
- CSF is bright on T1 and dark on T2
- Fat is dark on T1 and T2
Fat is bright on T1 and T2
