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Neuro first semester 23-24 > Spinal cord tracts I > Flashcards

Spinal cord tracts I Flashcards

1
Q

WHere do descending tracts decussate?

A

usually before reaching the final destination

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2
Q

which are the descending tracts?

A

lateral:
-laterak corticospinal (pyramidal)
-rubrospinal

ventral:
ventral corticospinal
reticulospinal
vestibulospinal
tectospinal

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3
Q

Where does the lateral corticospinal tract decussate?

A

pyramidal decussation, at cervicomedullary junction

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4
Q

Where does the rubrospinal tract decussate?

A

Ventral tegmental decussation, in the midbrain

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5
Q

Where does the tectospinal tract decussate?

A

dorsal tegmental decussation, in the midbrain

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6
Q

What is the function of the lateral corticospinal tract?

A

control of fine
movements of the limbs, particularly the
digits of the hand

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7
Q

What is the function of the ventral corticospinal tract?

A

control of axial muscles

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8
Q

Explain the corticospinal tract

A

-Descending fibers converge in the
corona radiata and then pass
through internal capsule.

  • Tract continues through the basis
    pedunculi of the midbrain (fibers
    of cervical part of body are medial
    to fibers of lower limbs).
  • On entering pons, tract is broken
    into bundles by the transverse
    pontocerebellar fibers.
  • In medulla oblongata, bundles
    group to form a swelling known as
    the pyramid.

-At the junction of the medulla
oblongata and the spinal cord,
most fibers cross the midline at
the pyramidal decussation and
enter the lateral white column of
spinal cord as the lateral
corticospinal tract.

  • The remaining fibers do not cross
    in the decussation but descend in
    the ventral white column as the
    anterior corticospinal tract.
  • Some fibers of anterior
    corticospinal tract eventually cross
    the midline and terminate in ventral
    horn where they synapse on motor
    neurons
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9
Q

What are some deficits due to lesions in corticospinal system?

A

-Clasp-knofe spasticy: resistance to stretching by muscle due to abnormally increased tension with heightened deep tendon reflex
-hyperreflexia: exaggeration reflexes (si corta upper motor neuron)
-spastic hemiparesis: muscle weakness
-babinski signv(positive)

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10
Q

What deficits will there be if there is an injury ABOVE the pyramidal decussation in corticospinal tract?

A

Contralateral deficits (opposite side to injury)

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11
Q

What deficits will there be if there is an injury BELOW the pyramidal decussation in corticospinal tract?

A

Ipsilateral deficits (same side as decussation/injury)

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12
Q

What is superior alternating hemiplegia?

A

weber’s syndrome (midbrain)
1. caused by hemorrhage of branches of posterior cerebral artery supplying
the midbrain.
b. results in contralateral hemiparesis (weakness) and deviation of the ipsilateral eye (down and lateral/abducted) [occulomotor nerve affected]

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13
Q

What is middle alternating hemiplegia?

A

Pons
a. caused by hemorrhage of paramedian branches of basilar artery
b. results in contralateral hemiparesis (weakness) and deviation of the ipsilateral eye (inward). ojo va a aDD [abducens nucleus affected]

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14
Q

What is inferior alternating hemiplegia?

A

medulla oblongata
a. caused by occlusion of penetrating branches of anterior spinal artery
b. results in contralateral hemiparesis (weakness) and ipsilateral flaccid paralysis of tongue (deviates toward side of lesion) [hypoglossal muscle]
c. tongue will stick out to the side of the lesion

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15
Q

What is the function of the rubrospinal tract?

A

Provides control of fine movements of primarily upper limbs and excitatory influence to flexor motor neurons

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16
Q

where does rubrospinal tract originate?

A

Originates in neurons of the red nucleus
(“núcleo rubro”) of midbrain tegmentum

LMNs Cervical SC: receive fibers from dorsal part of Red Nucleus

LMNs Lumbosacral SC: receive fibers from ventral part of Red Nucleus

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17
Q

Where do fibers of the rubrospinla tracts decussate, descend and terminate?

A

-Fibers cross/decussate in ventral tegmental of midbrain
-Descends in the lateral funiculus (column) of the spinal cord.
-Terminate in ventral horn

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18
Q

Explain the medial vestibulospinal tract

A
  1. Originates in ipsilateral and contralateral
    medial vestibular nuclei.
  2. Descends bilaterally in medial
    longitudinal fasciculus (MLF). [una decusa la otra no]
  3. Terminates on interneurons that then project and synapse with ventral horn motor neurons in the cervical spinal cord.
  4. Adjust the position of the head in response to changes in posture.
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19
Q

explain the lateral vestibulospinal tract

A
  1. Originates in lateral vestibular nucleus
  2. Descends ipsilaterally in ventral funiculus.
  3. Projects to all levels of the spinal cord
    synapsing to ipsilateral interneurons that
    then project and synapse with ventral horn
    motor neurons of extensor muscles of the
    trunk and ipsilateral limbs.
  4. Controls muscles that maintain upright
    posture & balance (facilitates activation of
    ipsilateral extensor muscles)
20
Q

What is the tectum?

A

roof of cerebral aqueduct

21
Q

Explain the tectospinal tract

A

-Fibers concerned with reflex postural
(head, neck & eye) movements in
response to visual stimuli.
* Fibers arise from neurons in tectum:
superior colliculus (visual) and
inferior colliculus (auditory) of midbrain
* Most fibers cross midline soon after
origin and descend through brainstem
close to medial longitudinal fasciculus
and then through ventral white column of
spinal cord close to anterior median
fissure.
* Fibers synapse onto interneurons and
motor neurons of the upper cervical
spinal segments.

22
Q

Where does the pontine medial reticlospinla tract originate, descent and terminate?

A
  1. Originates in the caudal and
    rostral pontine nuclei.
  2. Descends mostly ipsilaterally in
    the medial reticulospinal tract to
    all levels of spinal cord
  3. Terminates by synapsing onto
    ipsilateral ventral horn
    interneurons & motor neurons
23
Q

Where does the medullary lateral reticlospinla tract originate, descent and terminate?

A
  1. Originates in gigantocellular
    nucleus in the medullary reticular
    formation.
  2. Descends mostly ipsilaterally in
    the lateral reticulospinal tract to
    all levels of the spinal cord.
  3. Terminates by synapsing onto
    ipsilateral (and contralateral)
    ventral horn interneurons &
    motor neurons
24
Q

WHat neurons does the reticulospinal tracts facilitate or inhibit?

A

Both sets of fibers enter the
ventral gray columns of the spinal
cord and may facilitate or inhibit
the activity of the alpha and
gamma motor neurons.

25
Q

What kind of activity does the reticulospinaltracts influence?

A

Thus, the reticulospinal tracts
influence voluntary movements
and reflex activity.

26
Q

More specifically, the medial
(pontine) tract facilitates

A

extensor Spinal reflex activity

27
Q

lateral (medullary) tract
suppresses

A

extensor spinal reflex activity

28
Q

What is th efunction of the dorsal column medial lemniscus pathway

A

FineP daistcrhimwinaatiyve touch,
vibratory sense, & conscious
proprioception, 3-D shape
(stereognosis), and motion

29
Q

Where are the neurons of the DCML?

A

1º neuron – Dorsal root ganglion (DRG) [1a, 1b, II]
* 2º neuron – gracile nucleus and cuneatus nucleus in caudal medulla
* 3º neuron - ventral posterolateral (VPL)
nucleus of thalamus

30
Q

What information processes fascucuus gracilis?

A

lower limb

31
Q

What information processes fascucuus cuneatus?

A

upper limb

32
Q

how are axons of 2nd order neurons called in DCML?

A

Internal arcuate fibers

33
Q

What deficits can we encounter due to lesions of the DCML?

A

Loss of sense of fine touch, vibration and conscious proprioception

34
Q

Lesion ABOVE level of IAF?

A

Deficits are below and on contralateral side of lesion

35
Q

Lesion BELOW level of IAF?

A

Deficits are below and on ipsilateral side of the lesion

36
Q

WHat is the function of the spinothalamic tract?

A

Pain, temperature, crude touch[non discriminative] & pressure

37
Q

Where are theneurons of the spinothaalamicpathway located?

A

1st order neuron – dorsal root ganglion (DRG)

2nd order neuron – Dorsal horn

3rd order neuron – Ventral Posterolateral (VPL) of thalamus (and other nuclei of thalamus), Reticular formation, superior colliculi & periaqueductal gray

38
Q

explain Neospinothalamic tract

A

1st order neurons (soma in DRG) enter Lissauer tract and synapse with 2º neurons in dorsal horn (i.e. substantia Gelatinosa, nucleus Proprius)

Axons of 2nd order neurons from dorsal horn decussate via anterior/ventral white commissure to contralateral side to enter anterolateral pathway.

Axons in Anterolateral pathway project to 3rd order neurons in VPL of thalamus

Axons from VPL pass through posterior limb of internal capsule and corona radiata to reach somatosensory cortex.

39
Q

Explain paleospinothalamic trcat

A

1st order neurons (soma in DRG) synapse on 2º neurons in deeper laminae (V-VIII)

Axons of 2nd order neurons project to reticular formation (RetIF;spinoreticular tract) for arousal, mesencephalic nuclei including the superior colliculus (SC) for visual reflex, periaqueductal gray (PG;spinomesencephalic tract) for pain modulation, which project to 3º neurons in intralaminar (IL) and midline nuclei of thalamus

3º order neurons from thalamus terminate in multiple sites throughout the cerebral cortex.

40
Q

what deficits can we see in spinothalamic trcats

A

Loss of pain and temperature sensation on contralateral side of the body, beginning one to two levels below the lesion

Bilateral loss of pain & temperature sensation only on a few dermatomes can occur when anterior/ventral white commisure is damaged (syringomyelia)

41
Q

functions of dorsal spinocerebellar tract?

A

unconscious propioception from lower limb and lower trunk

42
Q

explain the dorsal spinocerebellar tract?

A

Axons from 1st order neurons enter the spinal cord from the DRG (T1-S3) and terminate by synapsing on 2nd order neurons at base of the dorsal gray horn.

2º neurons are located in the nucleus dorsalis of Clarke’s (extends from T1 to L3).

The tract then joins inferior cerebellar peduncle and terminates in cerebellar cortex.

Axons entering spinal cord from lower lumbar and sacral segments ascend in the dorsal white column until they reach L3-L4 where they enter the nucleus dorsalis.

The dorsal spinocerebellar fibers receive muscle joint information from the muscle spindles, tendon organs, and joint receptors of trunk & lower limbs (coordination of limb movements and maintenance of posture).

43
Q

explain ventral/anterioe spinocerebe;;ar tract

A

Axons from 1st order neurons enter spinal cord from DRG (T1-S3) and terminate by synapsing on 2nd order neurons in nucleus dorsalis of Clarke at base of dorsal horn.

Majority of axons of these 2nd order neurons cross to opposite side and ascend as ventral spinocerebellar tract in contralateral white column.

These axons of 2nd order neurons ascend through medulla oblongata and pons, enter cerebellum through the superior cerebellar peduncle and terminate in the cerebellar cortex.

Fibers then decussate again to opposite side in spinal to cerebellum.

Conveys muscle joint information from muscle spindles, tendon organs, and joint receptors of lower limbs.

44
Q

explain cuneocerebellar tract

A

Axons from 1st order neurons enter spinal cord from DRG (C2-T7) and ascend along fasciculus cuneatus to synapse on 2nd order neurons in Accessory Cuneate Nucleus (lateral to nucleus cuneatus in medulla)

2nd order neurons ascend ipsilaterally & enter cerebellum through inferior cerebellar peduncle.

Convey information of muscle joint sense (propioception) to the cerebellum from upper limb and trunk.

45
Q

What are some deficits due to lesions of the spinocerebellar tracts or cuneocerebellar

A

dystaxia or ataxia - difficulties in coordination and/or control of voluntary movements

Dorsal spinocerebellar tract:
ipsilateral leg dystaxia

Ventral spinocerebellar tract
contralateral leg dystaxia

Cuneocerebellar tract
ipsilateral arm dystaxia

46
Q
A

Neuro first semester 23-24 (9 decks)

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