Unit IV Flashcards
(107 cards)
1
Q
What are the length, weight, and max diameter of an average adult spinal cord?
A
40-45cm long (16-18in); 27-35gm (1oz); 1.2cm diameter
2
Q
What portion of the spinal cord is the longest and why?
A
Cervical enlargement due to the fibers that innervate the upper extremities
3
Q
What are the superior and inferior borders of the average adult spinal cord?
A
Superior border: superior most ventral root of C1
Inferior border: between vertebral levels L1 and L2
4
Q
What nervous structures are found within the vertebral canal and which system does each belong to?
A
Spinal cord: CNS
Dorsal and ventral rootlets: PNS
Dorsal root ganglia: PNS
Spinal Nerves: PNS
5
Q
Where do the following cervical nerves exit the vertebral canal? C1, C2, C7, C8
A
C1: occiput and atlas
C2: atlas and axis
C7: C6 and C7
C8: C7 and T1
6
Q
What is the name of the openings between the vertebra through which spinal roots pass?
A
Intervertebral Foramen (IVF)
7
Q
T/F? The 12th thoracic nerve exits the vertebral canal between T11 and T12.
A
False, between T12 and L1
8
Q
What spinal nerve exits the vertebral canal between L5 and S1?
A
L5
9
Q
Where do spinal nerves S1-S4 leave the protection of the axial skeleton?
A
Through their respective dorsal and ventral sacral foramina
10
Q
Where do S5 and Co1 nerves exit the vertebral canal?
A
Through the sacral hiatus
11
Q
T/F? During embryonic development, the cord and vertebra are approximately the same length.
A
True
12
Q
What is the cauda equina?
A
Spinal nerves of the lumbar sacral and coccygeal segments that pass down the vertebral canal and exit at their respective vertebral levels.
13
Q
Are cord levels and vertebral levels the same thing?
A
No, vertebral levels correspond to the vertebra and cord levels correspond to where each cord level’s spinal nerves exit the vertebral canal.
14
Q
What cord levels are protected by the first lumbar vertebra?
A
S4, S5, Co1
15
Q
Between what vertebral levels is the cervical enlargement of the cord found?
A
C3-T2
16
Q
Where is the lumbar enlargement found?
A
T9-T12
17
Q
What is the terminal ventricle?
A
A very small expansion of the insignificant central canal found in the conus medullaris.
18
Q
Clinically, what is the significance of the terminal ventricle?
A
The most common place for an ependymoma.
19
Q
T/F? Grey and white matter are both found at all cord levels.
A
True
20
Q
T/F? Grey and white matter are found in equal amounts at all cord levels.
A
False
21
Q
What is another name for white matter?
A
Substantia Alba
22
Q
Define a funiculus
A
A longitudinal bundle of white matter fiber that can be anatomically observed.
23
Q
What is the composition of grey matter?
A
Dense concentration of neuron cell bodies and dendrites, support glial cells and some myelin, dense capillary beds.
24
Q
Where in grey matter would myelin be present and what type of cell would it compose?
A
Found on some axon trunks; composed of intrafasicular oligodendrocytes
25
Rexed established how many different lamina?
Ten
26
Explain the composition of white matter.
Dense concentration of neuron fibers (axons), neurological support and covering cells, and a moderate amount of blood vessels.
27
The diameter of axons varies from ___ to ___ in the white matter of the cord?
0.5microns; 30microns
28
Define a fasciculi.
Small bundle of functionally related axons.
29
How do the fibers of a fasciculi associate with one another during development.
Surface proteins. NCAMs
30
T/F? Fasciculi are observable by PET scans.
True
31
T/F? Fasciculi are observable by general staining techniques.
False
32
How does sensory input enter the spinal cord?
A dorsal root ganglion axon at the dorsal lateral sulcus.
33
One DRG averages how many neurons?
Between 50,000 and 100,000 neurons
34
Where will MOST of the DRG axons synapse after entering the cord?
Dorsal grey horn
35
Approximately how many recognized fasciculi are there in the spinal cord?
24
36
T/F? All fasciculi or tracts are bilateral.
True
37
T/F? All tracts are found at all cord levels
False
38
What part of the cord contains the gracilis and cuneatus tracts?
posterior funiculus
39
The axons that form the gracilis and cuneatus tracts come from where?
DRGs
40
Which is more medial, gracilis or cuneatus?
Gracilis
41
Gracilis and Cuneatus are found at what cord levels?
```
Gracilis = all cord levels
Cuneatus = T6 and above
```
42
The fibers from gracilis synapse where?
Nucleus gracilis of the M.O.
43
The fibers from the cuneatus synapse where?
Nucleus cuneatus of the M.O.
44
Gracilis and cuneatus are major pathways carrying what sensations?
2 pt. touch discrimination, vibratory sensation, and kinesthetic sense
45
T/F? Gracilis and cuneatus are both ipsilateral tracts.
True
46
A sensory neuron carrying vibratory sensation enters the cord at T2, what tract does it enter?
Cuneatus
47
T/F? The anterior and lateral spinothalamic tract axons come from DRGs.
False, dorsal grey horn neurons
48
In a cross section of the cord where would you find the anterior and lateral spinothalamic tracts?
Anterior and lateral funiculi respectively
49
At what cord levels are the anterior and lateral spinothalamic tracts found?
Both at all cord levels
50
T/F? Both spinothalamic tracts cross the cord?
True
51
Explain how both spinothalamic tracts cross the cord.
Anterior gradually works its way across the cord
| Lateral abruptly crosses the cord
52
What is the function of each of the spinothalamic tracts?
Anterior is light touch reception
| Lateral is pain and thermal sensation
53
Fibers from the spinothalamics terminate where?
Thalamus (VPL)
54
What tracts are located along the anterior and posterior periphery of the lateral funiculus?
Anterior and posterior spinocerebellar tracts
55
Where do the axons that make up the posterior spinocerebellar tracts come from?
Clark's Nucleus (C8-L3)
56
Fibers for the anterior spinocerebellar tracts originate where?
Anterior - in the cords lumbosacral grey laminae.
57
Explain the ascension of the posterior spinocerebellar tract.
The fibers pass ipsilaterally up the cord, through the inferior cerebellar peduncle, and into the cerebellum on the same side as input.
58
Explain the ascension of the anterior spinocerebellar tract.
Most fibers cross the cord in the lumbosacral region, pass up to the superior cerebellar peduncle, enter the cerebellar lobe and then cross (second time) back to the lobe of the cerebellum on the same side as the input.
59
Explain the functions of each spinocerebellar tract
Anterior: proprioception of movements in the lower limb
Posterior: proprioception of fine movements of individual muscles
60
What nucleus carries all fine movement proprioceptive input below the C8 cord level?
Clark's nucleus
61
How does fine movement proprioception from the lower lumbar and sacral cord levels get to Clark's nucleus?
These fibers are carried in the tract of gracilis up to cord level L2, L3 where they synapse in Clark's nucleus.
62
How do fine proprioceptive fibers from the pectoral girdle and upper extremity reach the cerebellum?
DRGs enter the cord and ascend to the M.O.'s accessory cuneate nucleus where they synapse. The appropriate fibers then leave the nucleus, form the cuneocerebellar tract and enter the cerebellum.
63
The cuneocerebellar tract enters the cerebellum through what structure?
Inferior cerebellar peduncle
64
What descending tract is essential for beginning and maintaining precise voluntary skilled muscle movements?
Lateral corticospinal tract
65
What is the function of the anterior corticospinal tract?
Function is unclear
66
Which of the 2 corticospinal tracts contains 75-95% of the corticospinal fibers?
Lateral
67
Where do the anterior corticospinal tract fibers cross and where does the tract terminate?
Fibers cross at the cord level and the tract terminates by T6
68
Where do the lateral corticospinal tract fibers cross and where does the tract terminate?
Fibers cross in the pyramids of the M.O. and the tract runs the entire length of the cord
69
What is unique about the corticospinal tracts?
They are the only fibers that run from the cerebral cortex uninterrupted to the cord
70
How many corticospinal fibers are found on each side of the body and what are the fibers' diameters?
One million on each side. 2-25microns in diameter
71
Do the descending spinal tracts increase or decrease in size as they descend the cord?
Decrease
72
On a percentage, where does the corticospinal tract drop off its fibers as it descends the cord?
55% in cervical enlargement; 20% in the middle thoracic levels; 25% in the lumbar enlargement
73
In what lamina does most of the corticospinal fibers synapse in?
Lamina VII
74
Trace an impulse from the cerebral cortex, through the corticospinal tracts, and out to somatic musculature.
cerebral cortex -> corticospinal tract -> lamina VII -> lamina IX -> somatic musculature
75
What are Betz cells and what part of the brain are they from?
very small percentage of the lateral corticospinal axons that come from the precentral gyrus and terminate directly in lamina IX
76
What is a lower motor neuron?
neurons that originate in the spinal cord or brain stem and innervate somatic musculature
77
What is an upper motor neuron?
neurons from higher brain centers that influence lower motor neurons
78
What are clinical signs of upper motor neuron leisons?
loss of lower motor neuron control resulting in spastic movement, hypersensitivity, positive Babinski, voluntary paralysis
79
What are clinical signs of lower motor neuron leisons?
loss of nerve supply to muscle cells resulting in hypononia, hyporeflexia, atrophy, flaccid paralysis
80
What is a pyramidal neuron?
upper motor neurons involved with initiation of skilled voluntary movements
81
What is an extrapyramidal neuron and what actions do they influence?
upper motor neurons that influence posture, muscle tone, reflexes and allow voluntary movements to be smooth and effective
82
Name three examples of extrapyramidal neurons
tectospinal, rubrospinal, vestibulospinal
83
What tract's function is extrapyramidal "posture reflex enhancement dealing with sight and auditory stimuli"?
tectospinal
84
What is the origin and termination of the tectospinal tract?
originates in the superior colliculus of the midbrain's tectum and terminates in the upper four cervical cord levels
85
Are tectospinal fibers ipsilateral or contralateral and if they do, where do they cross?
contralateral crossing gradually in the brain stem
86
What tract consists of extrapyramidal fibers dealing with "muscle tone control in contralateral flexor musculature"?
rubrospinal tract
87
Where do the rubrospinal tract fibers originate and synapse?
fibers originate in the nucleus ruber of the midbrain's tectum, cross the cord as they descend, and synapse in all cord levels
88
What tract's function is "muscle tone and postural adjustment in ipsilateral extensor musculature"?
vestibulospinal tract
89
Where do the vestibulospinal tract fibers originate and at what cord level are they found?
originate in Dieter's nucleus of the M.O. and are found at all cord levels
90
T/F? The vestibulospinal tract fibers are contralateral.
false, ipsilateral
91
Does the tectospinal, rubrospinal, or vestibulospinal tract "enhance spinal reflex capability"?
vestibulospinal
92
What are fasciculi proprii tracts, where are they found, and what do they do?
the propriospinal system containing fibers that originate and terminate in the cord; found scattered around the grey horns and contain fibers that "usually extend short distances up and down the cord:; this system is extremely important to the coordination of spinal reflexes
93
What is unique about these fibers in embryonic development?
first fibers to myelinate, at about 10th week
94
What is another name for the dorsalateral tracts and where are they found?
dorsalateral tracts of Lissauer found between Lamina I and the posterior lateral sulcus of the cord
95
The dorsalateral tracts are primarily composed of what?
Small diameter collateral fibers off the posterior root axons...running short distances up or down the cord and synapsing in lamina II of the grey horns
96
Where is the most likely location for a total transection of the spinal cord to occur and why?
Vertebral levels C5/C6 and T12/L1 due to vertebral mobility and maximum cord size at these points
97
What is a spinal shock?
Complete neural inactivity below a total transection injury. Usually lasts 1-6 weeks
98
What is Brown-sequard syndrome?
Total loss of either the right or left side of the cord
99
What is Tabes dorsalis?
A bacterial tertiary syphilis that attacks the DRG axons that contribute to the fasciculus gracilis resulting in a wasting of the dorsal funiculus
100
What is M.S. and what is another name for it?
A demyelinating disease in which glial cells harden; "Charcot's disease"
101
Where does the demyelination in M.S. occur and what causes it?
Randomly attacks the cord, cerebellum, and cerebrum but not PNS structures; unknown cause
102
What is the proper name for Combined Systems Disease, and what causes it?
Pernicious anemia; caused by deficiency of B12
103
What areas of the cord are most vulnerable to pernicious anemia?
Posterior funiculus fibers and corticospinal tracts
104
In what condition does the cord's central canal begin to enlarge resulting in a loss of pain sensation?
Syringomyelia
105
How does poliomyelitis affect the body?
Virus that alters the cytoplasm of the neurons cell body resulting in swelling of the neuron, nuclear displacement, chromatolysis until the cell dies
106
What percentage of CNS tumors occur in spinal cord tissue and what is the most common type of tumor?
10% of CNS tumors occur in the cord tissue; ependymoma
107
What is the most common tumor in the vertebral canal and what areas areDe most commonly affected?
meningiomas, 50% occurring in the thoracic area where the dentate ligaments attach to the dura
