Spinal tracts Flashcards
What is the difference between an UMN lesion and a LMN lesion?
UMN lesion- affect upper motor neurons running from precentral gyrus to the anterior horn cell in spinal cord
- hypertonia (spastic, clonus), hyper-reflexia, upward plantar reflex, weakness (pyramidal pattern)
LMN lesion- affects lower motor neurons running from the anterior horn cell in spinal cord to the muscle that is to be supplied
- weakness (wasting, fasciculations), hypotonia, hypo-reflexia, plantar reflex down-going
Describe the myotomes of the shoulder?
o Abduction: C5, C6
o Adduction: C6, C7, C8
Describe the myotomes of the elbow?
o Flexion: C5, C6
o Extension: C7, C8
Describe the myotomes of the wrist?
o Flexion: C6, C7
o Extension: C7, C8
Describe the myotomes of the fingers?
o Flexion: C7, C8
o Extension: C7, C8
o Abduction; C8, T1
o Adduction: C8, T1
What is the function of the corticospinal tract?
Function: voluntary movement of contralateral limbs, reflexes
Describe the pathway of the corticospinal tract?
A descending tract
Primary motor cortex (precentral gyrus)
- > descends through internal capsule (anterior 2/3 of posterior limb)
- > cerebral peduncles -> anterior medulla -> decussation at pyramids of medulla (90%)
- > lateral corticospinal tract (10% not decussating are the anterior corticospinal tract)
- > ventral horn -> anterior horn cells
- > exit (become 2nd order neurons) -> NMJ -> innervate muscle
What is the function of the spinothalamic tract?
Function: pain and temperature (lateral), and crude touch (anterior pathway) from extremities and trunk
Describe the pathway of the spinothalamic tract?
Ascending tract
- First order neurons: pain and temp sensory nerve endings -> cell bodies in dorsal root ganglia -> enter spinal cord (via A-delta and C dorsal root fibers) -> synapse in dorsal horn
- Second order neurons: cell body in dorsal horn grey matter -> axons cross ventral white commissure (decussating in spinal cord)-> form spinothalamic tract in ventral part of lateral funiculus -> ascends spinal cord -> brain stem -> thalamus (ventral posterolateral nucleus (VPL))
- Third order neurons: VPL nucleus -> primary somatosensory cortex (post central gyrus)
What is the function of the dorsal medial lemniscus tract?
Function: pressure, vibration, touch, proprioception to lower extremities
Describe the pathway of the dorsal medial lemniscus tract?
Ascending tract
- First order neuron: sensory nerve ending -> enters via dorsal horn -> ascends ipsilaterally in dorsal column -> medulla (gracile and cuneate nuclei)
- Second order neuron: fibers decussate in medulla -> form medial lemniscus -> thalamus (ventral posteromedial or posterolateral nucleus)
- Third order neuron: ascend posterior limb of internal capsule -> primary sensory cortex (post-central gyrus)
Differentiate between thoracic and cervical vertebrae?
Cervical vertebrae
- Small size
- One vertebral foramen, two transverse foramina
- Spinous process is slender, often bifid (C2-6)
- Small transverse process
- Not articular facets for ribs
- Articular facet directions- posterosuperior and anterosuperior
- Thick intervertebral discs relative to size of vertebral bodies
Thoracic vertebrae
- Larger size
- One vertebral foramen
- Spinous process is long, thick (most project inferiorly)
- Large transverse process
- Articular facets for ribs present
- Articular facet directions- posterolateral, anteromedial
- Intervertebral discs thin relative to size of vertebral bodies
Describe the myotomes of the hip?
- Hip Flexion: L2 (femoral)
- Hip Extension: L5 (inferior gluteal)
Describe the myotomes of the knee?
- Knee Extension: L3-4 (femoral)
- Knee Flexion: S1 (sciatic)
Describe the myotomes of the foot?
- Ankle Dorsiflexion: L4 (deep peroneal)
- Ankle Plantarflexion: S1 (tibial)
- Great toe flexor: L5 (deep peroneal)
