Spinal Cord Flashcards
How many cervical nerves and vertebrae are there?
nerves: 8
vertebrae: 7
How many thoracic nerves and vertebrae are there?
nerves: 12
vertebrae: 12
How many lumbar nerves and vertebrae are there?
nerves: 5
vertebrae: 5
How many sacral nerves and vertebrae are there?
nerves: 5 nerves
vertebrae: 5
How many coccygeal nerves and vertebrae are there?
nerves: 1
vertebrae: 1
Which spinal cord segment(s) has/have there nerves below their respective vertebrae?
thoracic, lumbar, sacral, coccygeal
Which spinal cord segment(s) has/have there nerves above their respective vertebrae?
cervical
At which vertebral level does the spinal cord terminate?
L1/L2
What is the name of the structure where the spinal cord ends? At what level of the spinal cord is this structure located?
conus medullaris; L1/L2
Through which sulcus do the ventral roots leave the spinal cord?
anterolateral sulcus
Through which sulcus do the dorsal roots leave the spinal cord?
posterolateral sulcus
What is filum terminale?
pia mater that attaches to coccygeal bones
At which vertebral level does the dural sac end?
S2
Between which vertebral levels should you do a spinal tap to access CSF? Why?
- below L1/L2 so not spinal cord damage
- above S2 so still in dural sac (with CSF)
List the ascending pathways in white matter of the spinal cord.
- fasciculus gracilis
- fasciculus cuneatus
- posterior (dorsal) spinocerebellar tract
-spinothalamic and spinoreticular tract - anterior (ventral) spinocerebellar tract
List the descending pathways in white matter of the spinal cord.
- lateral (crossed) corticospinal (pyramidal) tract
- anterior (uncrossed) corticospinal tract
List the fibers in the white matter of the spinal cord that both ascends and descends.
dorsolateral fasciculus (of Lissauer)
Which levels of the spinal cord have an enlarged ventral horn?
cervical and lumbar
What is special about the cervical and lumber levels of the spinal cord? Why?
- more grey matter b/c cervical innervates arms and lumbar innervates legs
How many anterior spinal arteries are in the spinal cord?
1
How many posterior spinal arteries are in the spinal cord?
2
which spinal artery/arteries supplies almost all the grey matter in the spinal cord?
anterior spinal artery
Which spinal artery/arteries only supplies white matter in the spinal cord?
posterior spinal arteries and pial branches of the radicular artery
Where is the motor neuron in the spinal cord found?
ventral horn
Which rami are both sensory and motor?
ventral rami
What do the ventral rami supply?
- ventral/anterior trunk
- limbs
What do the dorsal rami supply?
dorsal/posterior trunk
What are segmental spinal nerves?
spinal nerves that arise from a certain spinal level and innervate somatic structures derived from the somites of the same level
Which levels of the spinal cord contain segmental nerves?
T2-T12
What is another name for the T2-T12 nerves?
intercostal nerves
What are non-segmental spinal nerves?
spinal nerves where the ventral primary rami fuse together to form a nerve plexus
Which spinal nerves does the phrenic nerve contain? Is this considered a segmental or non-segmental nerve?
- C3-C5
- non-segmental
TRUE or FALSE: all dorsal primary rami are non-segmental
FALSE –> all segmental
List the spinal nerve plexuses
- C1-C4: Cervical Plexus
- C5-T1: Brachial Plexus
- L1-L4: Lumbar Plexus
- L4-S2: Sacral Plexus
TRUE or FALSE: each spinal nerve supplies its own dermatome
TRUE
What are sensory spinal tracts?
- dorsal columns-medial lemniscal tract
- spinothalamic (anterolateral) tract
- spinocerebellar and cuneocerebellar tracts
What is the motor spinal tract?
corticospinal tract
What are the functions of the dorsal column-medial lemniscal tract? Is this tract sensory or motor? Ascending or descending?
- sensory
- ascending
- functions: discriminative touch (mechanoreception), conscious proprioception
In the dorsal columns-medial lemniscal pathway, which tract do the sensory axons enter the spinal cord at?
Lissauer’s tract (dorsolateral fasciculus)
Where does the synapse occur in the dorsal columns-medial lemniscal pathway?
medulla and thalamus
Which spinal pathway is the pain pathway?
spinothalamic tract
What does a lesion to the spinothalamic pathway cause?
contralateral analgesia
Where does the synapse occur in the spinothalamic tract?
substantia gelatinosa and thalamus
Is the spinothalamic tract sensory or motor?
sensory
Is the corticospinal tract sensory or motor?
motor
What is the function of the corticospinal tract?
conscious movement (skeletal movement)
What is another name for the lateral corticospinal tract?
pyramidal tract
What is the spinocerebellar tract responsible for?
- constant proprioception
- lower limb and joint position
Where is the synapse in the spinocerebellar tract?
below L2 (Clarke’s nucleus)
Is the spinocerebellar tract sensory or motor?
sensory
What is the cuneocerebellar tract responsible for?
- constant proprioception
- upper limb and joint position
Is the cuneocerebellar tract sensory or motor?
sensory
Where is the synapse in the cuneocerebellar tract?
accessory cuneate nucleus
In the dorsal column-medial lemniscal pathway, what do the gracile and cuneate tracts innervate?
gracile: lower limb
cuneate: upper limb
List the cerebellar peduncles.
- superior cerebellar peduncle
- middle cerebellar peduncle
- inferior cerebellar peduncle
What do cerebellar peduncles do?
axon tracts that connect cerebellum to brain
Which artery in the spinal cord allows for sacral sparing?
pial branches of radicular artery
What would a cortical lesion (e.g. medial cerebral artery stroke) of the dorsal columns-medial lemniscal pathway cause?
contralateral loss of discriminative touch
What would a cortical lesion (e.g. medial cerebral artery stroke) of the spinothalamic tract cause?
contralateral analgesia
What would a cortical lesion (e.g. medial cerebral artery stroke) of the corticospinal tract cause?
contralateral hemiplegia
What would a brainstem lesion to the dorsal columns-medial lemniscal pathway cause?
contralateral loss of discriminative touch
What would a brainstem lesion to the spinothalamic tract cause?
contralateral analgesia
What would a brainstem lesion to the corticospinal tract cause?
contralateral hemiplegia
What would a lesion to the medulla cause in the dorsal columns-medial lemniscal pathway?
ipsilateral loss of discriminative touch
What would a lesion to the medulla cause in the spinothalamic tract?
contralateral analgesia
What would a lesion to the medulla cause in the corticospinal tract?
contralateral hemiplegia
What would a spinal cord hemisection to the spinothalamic tract cause?
contralateral analgesia
What would a spinal cord hemisection to the corticospinal tract cause?
ipsilateral hemiplegia and ataxia
What would a spinal cord hemisection to the dorsal columns-medial lemniscal pathway cause?
ipsilateral loss of discriminative touch
What would a peripheral nerve lesion to the dorsal columns-medial lemniscal pathway cause?
ipsilateral loss of discriminative touch
What would a peripheral nerve lesion to the spinothalamic tract cause?
ipsilateral analgesia
What would a peripheral nerve lesion to the corticospinal tract cause?
ipsilateral hemiplegia and ataxia
If a lesion is above the thoracic level, it affects:
a) lower limb
b) upper limb
c) both
b) upper limb
Lesions to the cuneocerebellar and spinocerebellar tracts are:
a) ipsilateral
b) contralateral
c) both
a) ipsilateral
Describe the knee-jerk reflex steps.
- hammer strike deforms patellar tendon to cause muscle stretch
- sensory nerve (proprioceptive A-alpha nerve) initiates AP and sends signal back to spinal cord (L2-L4)
3a. synapses on quads lower motor nerve and causes muscle stretch
3b. synapse on interneuron which goes on to synapse onto opposing hamstring muscle, causing OPPOSING mm to relax - knee jerk
What is the opposing muscle to the quadriceps?
hamstrings
Describe the events of the withdrawal refelx.
- ipsilateral leg (stimulus): hamstrings contract and quadriceps relax to lift leg
- contralateral leg (no stimulus): hamstrings relax and quadriceps contract to support weight of body
- contralateral muscles of hip and abdomen contract
What structures of the brain is the withdrawal reflex mediated by?
cerebellum and cerebral cortex