Neuroanatomy - Spinal cord Flashcards
_____, _____, ____ and _____ account for >75% of the entire CNS
sensorimotor, reflex, and autonomic function pathways and nuclei
Ascending pathways discriminate what 5 things?
1 touch
- vibration
- pain and temperature
- conscious and non-conscious proprioception
descending pathways control what 2 things
voluntary and non-voluntary reactions
- what is the primary neuron in ascending tracts?
- secondary neuron?
- tertiary neuron?
- termination?
- dorsal root ganglion
- brain stem or spinal cord
- thalamus (ventrobasal nuclear complex)
- cerebral or cerebellar cortex, or brain stem
three types of receptors for ascending pathways
- Exteroceptor
- interoceptor
- proprioceptor
Posterior (dorsal) column - medial lemniscus pathway:
modalities (4)
receptors?
- discriminative touch sensation
- vibration
- conscious proprioception
Most receptors except free nerve endings
Medial Lemniscus
1st, 2nd, 3rd neurons and termination
1st Dorsal root ganglion - posteriorcolumn
2nd dorsal column nuclei (gracilis/cuneatus) - in caudal medula
[deccusates as internal arcuate fibers to medial lemniscus]
3rd Thalamus (VPL) - [posterior limb of internal capsule via central thalamic radiations]
Termination: primary somatosensory cortical area (post-central gyrus)
What comprises the dorsal column?
Fasiculus Gracilis:
Cuneatus:
lumbosacral to T6
T6 and above
lesion to medial lemniscus pathway would show:
ipsalateral loss of discriminative touch, sensation/vibration and conscious proprioception below the level of the lesion.
Spinothalamic tract - anterolateral system
Modality (3):
Receptors
M: pain, temperature, light touch (non-disc)
R: free nerve ending
Spinothalamic tract - anterolateral system: 1st neuron 2nd neuron 3rd neuron Termination
1st: Dorsal Root Ganglion
2nd: Dorsal horn (substantia gelatinosa)
anterior white commissure
—-spinothalamic tract—
3rd: Thalamus (VPL)
—- Internal capsule, corona radiata —
Term: primary somatosensory area (SI) & diffuse widespread cortical region
decussation for spinothalamic tract
anterior white commissure
What is unique about the substantia gelatinosa?
tract it is assosiciated with?
Some dorsal root ganglion axon branches ascend or descend 1-2 levels.
spinothalamic tract
describe a lesion to spinothalamic tract
contralateral loss of pain and temperature sensation below the level of the lesion.
Spinoreticular tract:
Modalities:
positioned closely to the lateral spinothalamic tract; relays automatic responses to pain such as in the case of injry
Spinoreticular tract: 1st neuron 2nd neuron 3rd neuron Termination
1st: Dorsal Root Ganglion
2nd: Dorsal horn (substantia gelatinosa)
anterior white commissure
3rd: brainstem (medullary-pontine reticular formation)
4: intramedian nucleus of thalamus
5. Diffuse widespread cortical region
Spinocerebellar tract:
Modalities:
Receptor:
M: non-conscious proprioception
R: Muscle spindle, golgi tendon apparatus
Three forms of spinocerebellar tract
(a) dorsal horn (nucleus proprius) - anterior spinocerebellar tract.
(b) Clarkes column - posterior spinocerebellar tract.
(c) Accessory Cuneate Nucleus - cuneocerebellar tract
Term: Cerebellar vermis and cortex
- all end up ipsilateral
Anterior spinocerebellar tract encompasses what receptor region of the body
sacral and lower lumbar trunk, lower extremity
Anterior spinocerebellar tract pathway: 1st neuron 2nd neuron 3rd neuron Termination
1st dorsal root - nucleus proprious
anterior white commissure
anterior spino cerebellar tract
superior cerebellar peduncle
Posterior spinocerebellar tract encompasses which receptor region of the body
upper lumbar and thoracic
Posterior spinocerebellar tract pathway: 1st neuron 2nd neuron 3rd neuron Termination
1st dorsal root - clarke’s nucleus
posterior spinocerebellar tract
inferior cerebellar peduncle
Lesions of the spinocerebellar tracts?
rough uncoordinated movements ipsilateral to the lesion.
(isolated lesion of spinocerebellar tract rarely occurs and may be masked by weakness or hemiplegia due ot loss of descending motor influences)
Cuneocerebellar tract encompasses what body region?
Cervical C1-7
Cuneocerebellar tract: 1st neuron 2nd neuron 3rd neuron Termination
DRG axons ascend in ipsilateral
fasiculus gracillis
synapse in accessory cuneate nucleus
inferior cerebellar peduncle
Name the 7 originating areas of the corticospinal tract
- cortex (Brodman areas)
- Corona radiata
- Internal capsule posterior portion
- Crus Cerebri, middle portion
- Longitudinal pontine fiber
- Pyramid - pyramidal decussation
- corticospinal tract - lateral and anterior
Where does the corticospinal tract terminate
spinal gray matter (rexed IV-IX)
Name the 6 Brodmann areas associated with the corticospinal tract
BA 4 (Primary motor area, MI)
BA 6 (Premotor area, PM)
BA 3, 1, 2 (Primary somesthetic area, SI)
VA5 (Anterior portion of superior parietal lobule)
Differentiate the anterior and lateral corticospinal tracts
- anterior corticospinal tract to proximal muscles and interneurons (postural adjustment)
- lateral corticospinal tract to distal muscles (skilled movement of the extremities)
modalities of corticospinal tract
conveys voluntary motor information to lower motor neurons
Lateral corticospinal tract crosses in the _______ and innervates ______ motor neurons which control _____
- caudal medulla
- LMN
- distal muscles at all spinal cord levels
Anterior corticospinal tract descends until _____ then synapses with _____
ipsilateral unit level of LMN innervation.
LMN controlling truck muscles
Lesion signs of corticospinal tract
UMN signs include spastic paralysis, hyperreflexia, extensor plantar sign (babinski), limited muscle atrophy
Four descending tracts from Brain Stem
- rubrospinal tract
- Tectospinal tract
- Vestibulospinal tract
- Reticulospinal tract
Rubrospinal tract
- Originates:
- Decussate
- descend where:
- Terminate:
- Red Nucleus
- Midbrain
- contralateral side of the lateral column of the spinal cord
- LMNs that innervate flexors of the upper limb
With loss of corticospinal tract, rubrospinal tract influences may:
rubrospinal influence on upper limb flexors can become apparent (posturing in the decorticate comatose patient)
Tectospinal tract:
- Originates
- descends
- terminate:
- superior colliculus of the midbrain
- crossed fibers descend bilaterally in the anterior white columns of the spinal cord
- LMNs in cervical spinal cord where they nnervate motor neurons responsible for neck movements
Tectospinal tract is responsible for
innervating motor neurons in the cervical spinal cord for neck movements. responsible for orienting the head and neck during eye movements.
Medial vestibulospinal tract
originates
descends in
terminates:
- bilaterally through brainstem in anterior white columns.
- LMN circuit neurons of cervical and upper thoracic levels
Medial vestibulospinal tract is responsible for:
stabilizing the head as we move our bodies or as our head moves in space, and also plays a role in coordinating head movements with eye movements.
Lateral vestibulospinal tract
Descends:
Terminates:
descends in anteromedial area of the brainstem and travels in the anterior white column of the spinal cord.
Terminates at all levels of the ipsilateral spinal cord to facilitate the activity of the extensor muscles and inhibit the activity of the flexor muscles
Lateral vestibulospinal tract mediates:
postural adjustments to compensate for movements and changes in position of the body and to coordinate the orientation of the head and body in space.
Reticulospinal tract mediates
coordinates muscle group activation for primitive motor behaviors such as the orientation of the body toward or away from a stimulus, and motor behaviors that do not require dexterity.
Reticulospinal tract:
Descends:
Terminates:
D: mainly ipsilateral in the anteromedial area of the brainstem and the anterior white column of the spinal cord
T: bilaterally on LMN circuits throughout the length of the spinal cord
describe vascular supply to spinal cord
Posterior column vascular territory supplied by two posterior spinal arteries arise from the vertebral or posterior inferior cerebellar arteries.
Anterior column vascular territory is supplied by the single anterior spinal artery from the vertebral arteries.
Longitudinal pontine fiber- pontocerebellar fibers; describe feedback system
Longitudinal pontine fiber- pontocerebellar fiber… really cool feedback system where ponto cerebellar input provides descening info about motor action. This is compared to the actual movement (spinocerebellar tract) and adjustments are made accordingly.
Describe posterior cord syndrome
Loss of vibration and position sense due to loss of dorsal columns.
Describe anterior cord syndrome
Loss of motor, and pain/temp sensation due to loss of
1. anterolateral pathways (pain/temp)
2. Anterior horn cells (LMN)
3. Lateral corticospinal tract - most lateral, could be preserverd.
Ventral commissure
Describe central cord syndrome
Two types:
small (usually due to syrynx) - syringomyelia (loss of vibration and position sense, can get some motor of upper ext or pain/temp loss)
Large: due to contusion SCI: Loss of vibration/position, pain/temp, and motor
Describe a transverse cord lesion
Loss of pain/temp, motor, position/vibration below level of lesion.
Describe a hemicord lesion
contralateral pain and temperature loss (including a couple of levels above on ipsilateral side) and position/vibration loss with motor loss on ipsilateral side.
Differentiate function of lateral and anterior spinothalamic tract
Anterior (anterior column): itch, tickle, pressure, crude touch sensation
Lateral (lateral column): Pain and temperature
Tract: Lateral corticospinal.
Location
Function
lateral column
muscles of the limbs, hands and feet
Anterior corticospinal
location
function
anterior column
muscles of the axial skeleton
Corticobulbar
location
function
cerebral peduncle
skeletal muscles of the head and neck via CNs
Rubrospinal tract
location:
function:
lateral column
skeletal muscles of the limbs, hands, and feet
Tectospinal tract
location:
function:
anterior column
skeletal muscles of the head and eyes in response to visual stimuli
Vestibulospinal tract
location:
function:
anterior column
muscles for maintaining balance in response to head movements
Lateral reticulospinal tract
location:
function
anterior column
facilitates flexor reflexes, inhibits extensor reflexes
Medial reticulospinal tract
location:
function:
anterior column
facilitates extensor reflexes, inhibits flexor reflexes
