Spinal Cord Anatomy + Ascending and Descending Pathways Flashcards
1
Q
Which of the cranial meninges are also present in the spinal cord?
A
- Dura mater.
- Arachnoid mater.
- Pia mater.
i. e. all of them.
2
Q
The cranial meninges are continuous with the spinal meninges via what?
A
Foramen magnum.
3
Q
What suspends the spinal cord in the spinal canal?
A
the denticulate ligament.
4
Q
What forms the denticulate ligament?
A
Pial and arachnoid tissue.
- NB it occasionally attaches to dura at points along its length.
5
Q
What fills the subarachnoid space?
A
CSF
6
Q
What is the inner layer (core) of the spinal cord composed of?
A
Grey matter.
7
Q
What is the outer layer of the spinal cord composed of?
A
White matter.
8
Q
What does white matter consist of?
A
- Longitudinally oriented nerve fibres (Axons).
- Glial cells.
- Blood vessels.
9
Q
What does grey matter consist of?
A
- Neuronal soma.
- Cell processes.
- Synapses.
- Glia.
- Blood vessels.
10
Q
The small central canal extending the length of the spinal cord opens rostrally into what?
A
The 4th ventricle.
NB google says rostrally means towards anterior part of brain.
11
Q
The small central canal extending the length of the spinal cord opens caudally into what?
A
Nothing, caudally it is blind ending.
12
Q
What are the fasciculi/columns that make up the white matter of the spinal cord?
A
- Posterior fasciculi.
- Lateral fasciculi.
- Anterior fasciculi.
13
Q
Into what is grey matter divided?
A
The right: - Anterior horn. - Posterior horn. The left: - Anterior horn. - Posterior horn.
14
Q
The horizontal part of the “H” of the grey matter core of the spinal cord represents what?
A
The dorsal and ventral grey commisures that surround the central canal.
15
Q
At what spinal segments exists a smaller lateral horn containing the preganglionic sympathetic neurons?
A
T1-L2.
16
Q
What supplies blood to the spinal cord?
A
- Three major longitudinal arteries.
- Segmental arteries.
- Radicular arteries.
17
Q
Describe the segmental arteries that supply blood to the spinal cord.
A
Arteries derived from vertebral, intercostal and lumbar arteries.
18
Q
Describe the radicular arteries supplying blood to the spinal cord.
A
They travel along the dorsal and ventral roots.
19
Q
Describe the three major longitudinal arteries supplying blood to the spinal cord.
A
- ONE anterior.
- TWO posterior.
- Originate from vertebral arteries and run along the length of the spinal cord.
20
Q
An embolic occlusion in any of the arteries supplying the spinal cord may cause what?
A
Spinal cord infarction.
21
Q
The space in the spinal canal found between dura and bone is known as what?
A
Epidural space.
22
Q
What does the epidural space contain?
A
- Adipose.
- Anterior epidural venous plexus.
- Posterior epidural venous plexus.
23
Q
Why are sensations from the left side of the body represented on the right cortex and vice versa?
A
Sensory fibres cross in the midline.
24
Q
How does information from peripheries reach the somatosensory cortex?
A
Via the spinal cord.
- Except face and scalp.
25
What happens to the proportion of white matter as the spinal cord descends?
White matter occupies a smaller proportion of the cord as it descends.
26
In which regions of the spine is the spinal cord larger?
Cervical and lumbar regions.
i.e. it is therefore smaller in sacral and thoracic regions.
27
Where do the fibres of the Dorsal Column/Medial Lemniscus system cross?
Fibres cross in the medulla.
28
What is the function of the Dorsal column/Medial Lemniscus system?
To convey fine touch and conscious proprioception - particularly from upper limb.
29
Where is the primary motor cortex located?
Dorsal portion of frontal lobe.
30
This reflects the relative space occupied on the primary motor cortex by each part of the body.
Cortical motor homunculus.
31
Which tract is responsible for fine, precise movement - particularly of distal limb muscles e.g. digits?
Corticospinal tract.
32
This tract forms visible ridges - "pyramids" on the anterior surface of the medulla to form the pyramidal tract.
Corticospinal tract.
33
Where do the majority (85%) of fibres of the corticospinal tract cross?
In the caudal medulla at the decussation of the pyramids.
(the lower medulla).
34
Crossed fibres of the corticospinal tract form what?
The lateral corticospinal tract.
35
Uncrossed fibres of the corticospinal tract form what?
The ventral corticospinal tract.
| - These cross segmentally.
36
CVA of the internal capsule may have what effect?
Spastic paralysis with hyperflexion of the upper limbs - DECORTICATE POSTURING.
Due to lack of descending control of the corticospinal tract.
37
The collective term for the motor systems existing outwith the pyramidal tract.
Extrapyramidal system.
38
Which tract is thought to mediate reflex head and neck movement due to visual stimuli?
Tectospinal tract.
- input mostly to cervical segments.
39
What forms the central core of the brainstem?
Reticular formation.
40
Composed of many nuclei receiving input from virtually all areas of CNS. Functions include influencing voluntary movement.
Reticular formation.
41
Fibres originate in areas of the reticular formation in the pons and medulla, from which they then descend.
Reticulospinal tract.
42
In general, fibres of the reticulospinal tract originating from the pons facilitate and inhibit what?
- Facilitate extensor movements.
| - Inhibit flexor movements.
43
In general, fibres of the reticulospinal tract originating from the medulla facilitate and inhibit what?
- Facilitate flexor movements.
| - Inhibit extensor movements.
44
The vestibulospinal tract conveys excitatory input to what?
"anti-gravity" extensor muscles.
45
Where do the fibres of the vestibulospinal tract originate?
Vestibular nuclei of pons and medulla.
NB these receive input from vestibular apparatus and cerebellum.
46
A tract thought to have an important role in those exhibiting decerebrate rigidity and paraplegia in extension.
Vestibulospinal tract.
47
Lesions where may cause a lack of descending cortical control of the vestibulospinal tract?
Lesions of the brainstem at the level of the midbrain.
48
Lesions of the brainstem at the level of the midbrain may cause reduced descending control of the vestibulospinal tract resulting in what?
Dominating extensor muscle tone and hyperextended spastic paralysis.
49
Lateral hemisection of the spinal cord gives rise to what condition?
Brown-Sequard's Syndrome.
50
List the signs/symptoms indicative of Brown-Sequard's Syndrome.
- Ipsilateral paralysis.
- Ipsilateral hyperreflexia and extensor plantar reflex.
- Ipsilateral loss of vibratory sense and proprioception.
- Contralateral loss of pain and temperature sense.
51
The spinal cord extends from where to terminate where?
- Extends from medulla oblongata.
| - Terminates at L1/L2.
52
What is the spinal cord made up of?
- Grey and white matter.
53
What is the "H-shape" of the spinal cord made up of?
Grey matter.
54
What is the "H-shape" of the spinal cord surrounded by?
White matter.
55
The dorsal (posterior) horns of the spinal cord receive what kind of information?
Somatosensory.
56
The ventral (anterior) horns of the spinal cord contain what?
Motor neurons for innervating muscles.
57
What is the lateral horn (interomediolateral grey column) of the spinal cord?
A triangular projection between the dorsal and ventral horns.
58
Where is the lateral horn (interomediolateral grey column) of the spinal cord present?
Only in the thoracic and upper lumbar segment of spinal cord.
59
What does the lateral horn of the spinal cord contain?
Autonomic neurons (sympathetic T1-L2).
60
Function of dorsal column-medial leminiscus pathway?
- Fine touch.
- Pressure.
- Vibration.
61
Describe the dorsal column-medial leminiscus pathway.
- Primary sensory fibres travel via posterior root ganglion > spinal cord to synapse with secondary neurons in medulla at nucleus cuneatus/nucleus gracilis.
- Fibres decussate to contralateral medial leminiscus > synapse in thalamus.
- Sensory signals relayed from thalamus to ipsilateral somatosensory cortex.
62
Function of spinothalamic tract?
Conveys pain and temperature.
63
Describe the spinothalmic tract pathway.
- Primary sensory axons enter spinal cord via posterior root ganglion > up for 1/2 segments at spinal cord periphery through tract of Lissauer to synapse in dorsal horn.
- Cross to contralateral side of spinal cord > synapse in thalamus.
- Sensory signals relayed from thalamus to ipsilateral somatosensory cortex.
64
Function of the spinocerebellar pathway?
Relays unconscious proprioceptive information to the cerebellum to coordinate posture + movement of lower + upper limb muscles.
65
Describe the Dorsal/Posterior Spinocerebellar pathway.
- Carries unconscious proprioceptive information (mostly from muscle spindles) from lower limbs.
- Synapses in dorsal nucleus of clarke > secondary neuron fibres ascend to ipsilateral cerebellum.
66
Where does the dorsal/posterior spinocerebellar pathway synapse?
Nucleus of Clarke.
67
After synapsing in the nucleus of Clarke, secondary neuron fibres of the dorsal/posterior spinocerebellar pathway ascend to where?
Ipsilateral cerebellum.
68
The dorsal/posterior spinocerebellar pathway carries what kind of information?
Unconscious proprioceptive info from lower limbs.
69
The cuneocerebellar pathway carries what kind of information?
Unconscious proprioceptive info from upper limbs.
70
Where does the cuneocerebellar pathway relay its information from and to?
- from upper limbs to ipsilateral cerebellum.
71
What kind of information does the ventral/anterior spinocerebellar pathway carry?
Unconscious proprioceptive info (mainly from golgi tendon organs) from lower limbs.
72
How does information from lower limbs reach the cerebellum in the ventral/anterior spinocerebellar pathway?
Fibres decussate twice in order to reach the ipsilateral cerebellum.
73
The spinocerebellar tract transmits unconscious proprioceptive information to which cerebellum?
Ipsilateral.
74
The spinothalamic tract transmits pain/ temperature information to which somatosensory cortex?
Contralateral.
75
The dorsal column-medial leminiscus pathway transmits fine touch/pressure/vibration information to which somatosensory cortex?
Contralateral.
76
Corticospinal tracts are responsible for what?
Voluntary movements.
77
Corticospinal tracts originate form where?
Motor cortex (precentral gyrus) and descend to pyramid of medulla.
78
The majority of fibres of the corticospinal tracts decussate where?
Pyramid of medulla - pyramidal decussation.
79
After decussating at pyramid of medulla, fibres of the corticospinal tracts descend via what?
The lateral corticospinal tract.
80
The lateral corticospinal tracts supply what?
The distal extremities.
81
Undecussated fibres (minority) of the corticospinal tracts descend via what?
Anterior corticospinal tract.
82
Where do undecussated fibres of the anterior corticospinal tract decussate?
At level of desired destination via the anterior white commisure.
83
Fibres of the anterior corticospinal tract decussate to supply what?
Proximal and axial muscles.
84
Corticobulbar tracts contain what?
UMN of cranial nerves.
85
Function of corticobulbar tracts?
- Innervate face, head and neck.
| - Innervate cranial motor nuclei bilaterally (except hypoglossal and lower facial nuclei).
86
Corticobulbar tracts innervate cranial motor nuclei bilaterally except what and why?
- Hypoglossal and lower facial nuclei.
| - Innervated contralaterally only.
87
Clinical significance of innervation of facial nerve?
- UMN lesion > CENTRAL FACIAL PALSY.
| - LMN lesion > Bell's palsy.
88
What is central facial palsy?
UMN lesion of facial nerve causes paralysis of lower half of face unilaterally with forehead muscles unaffected.
89
What is Bell's palsy?
LMN lesion of facial nerve causes ipsilateral paralysis of half the face including the forehead.
90
Vestibulospinal tract originates from where?
Vestibular nucleus in the pons.
91
Vestibulospinal tract controls what?
- Balance and posture.
92
How does the vestibulospinal tract control balance and posture?
By innervating anti-gravity muscles.
- Leg extensors.
- Arm flexors.
93
Origin of reticulospinal tracts?
Reticular formation in medulla and pons.
94
Pontine reticulospinal tract facilitates what?
- Voluntary/reflex responses and increases tone.
95
The medullary reticulosponal tract inhibits what?
- Voluntary/reflex responses and decreases tone.
96
Origin of the rubrospinal tract?
Red nucleus in the midbrain.
97
Function of the rubrospinal tract?
Upper body:
- Excite flexor muscles.
- Inhibit extensor muscles.
98
Origin of tecto-spinal tract?
Superior colliculus in midbrain.
99
Function of tecto-spinal tract?
Co-ordinates movements of head and neck to vision stimuli.
100
Name the layers (7) traversed by a needle during lumbar puncture.
1. Skin.
2. Fascia.
3. Supraspinous ligament.
4. Interspinous ligament.
5. Ligamentum flavum.
6. Epidural space.
7. Dura.
101
Give the function of the anterior longitudinal ligament of the spine.
Connects the anterolateral aspects of vertebral bodies and intervertebral discs.
102
Give the location of the posterior longitudinal ligament of the spine.
Runs within the vertebral canal posterior to the vertebral bodies.
103
Give the function of the ligamentum flavum of the spine.
Aids maintenance of upright posture and assists straightening the spine after flexion.
104
How did ligamentum flavum get its name?
It is rich in elastin and thus appears yellow.
105
Give the location of ligamentum flavum.
Runs vertically connecting the lamina of adjacent vertebrae.
106
Give the location of the supraspinous ligament.
Runs along tips of spinous processes.
107
Give the location of the interspinous ligament.
Runs between spinous processes.
108
Which spinal tract is responsible for:
| fine touch, pressure and vibration?
DCML pathway.
109
Which spinal tract is responsible for:
| pain and temperature?
Spinothalamic tract.
110
Which spinal tract is responsible for:
| exciting flexor muscles and inhibiting extensor muscles of the upper body?
Rubrospinal tract.
