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PHASE ONE > Spinal tracts > Flashcards

Spinal tracts Flashcards

1
Q

Ascending pathway vs Descending pathway

A

Ascending = sensory pathway to brain

Descending = motor pathway to periphery

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2
Q

The specific ascending pathways that transmit information from somatic receptors (Skin, skeletal muscle, tendons and joints) go to where in the brain?

A

somatosensory cortex

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3
Q

Ascending pathways

A

DCML
Spinothalamic
Spinocerebellar

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4
Q

Descending tracts

A

Corticospinal (pyramidal)
Corticobulbar (pyramidal)
Extra pyramidal tracts

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5
Q

What is the DCML for?

A

Fine touch, vibration, proprioception

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6
Q

DCML: Information travels …

A

via dorsal columns in the spinal cord then is transmitted through medial lemniscus in brainstem

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7
Q

DCML

A

First order neurons carry sensory information from peripheral nerves to the medulla. (FG + FC)

Second order neurons carry information from gracilis nuclei to 3rd order neurons and decussate in the medulla and travel to CONTRALATERAL THALAMUS.

Third order neurons transmit information to thalamus and ipsilateral sensory cortex.

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8
Q

DCML: Signals from upper limbs (T6 and above)

A

Fasciculus cuneatus

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9
Q

DCML: Signals from lower limbs

A

Fasciculus gracilis

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10
Q

Spinothalamic/Anterolateral Tracts consists of …

A

Anterior spinothalamic tract (MEDIAL)
= crude touch, pressure

Lateral spinothalamic tract
= pain, temperature

Pathways are the same for both tracts and they run alongisde each other

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11
Q

Spinothalamic

A

First order neurons arise from sensory receptors in the periphery. They enter the spinal cord and synapse at the tip of dorsal horn.
Second order neurons carry info from dorsal horn to thalamus.
The fibres DECUSSATE in spinal cord.
From thalamus -> ipsilateral primary sensory cortex.

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12
Q

Spinocerebellar tracts

A

Posterior spinocerebellar
Cuneocerebellar
Anterior spinocerebellar
Rostral spinocerebellar

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13
Q

Posterior spinocerebellar tract:

A

From lower limbs to ipsilateral cerebellum

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14
Q

Cuneocerebellar tract:

A

From upper limbs to ipsilateral cerebellum

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15
Q

Anterior spinocerebellar tract:

A

From lower limbs to ipsilateral cerebellum

Fibres in this tract decussate twice

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16
Q

Rostral spinocerebellar tract

A

From upper limbs to ipsilateral cerebellum

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17
Q

Clinical relevance

Injury to DCML

A
  • A lesion of the dorsal column medial lemniscus pathway causes a loss of proprioception and fine touch
  • However, a small number of tactile fibres travel within the anterolateral system, and so the patient is still able to perform tasks requiring tactile information processing
  • If the lesion occurs in the spinal cord, the sensory loss will be ipsilateral because decussation occurs in the medulla oblongata
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18
Q

Clinical relevance

Injury to spinothalamic tract

A
  • Injury to the anterolateral system will produce an impairment of pain and temperature sensation.
  • In contrast to DCML lesions, this sensory loss will be contralateral because the spinothalamic tracts decussate within the spinal cord
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19
Q

Brown-Sequard Syndrome

A
  • A hemisection (one sided lesion) of the spinal cord
  • This is most often due to traumatic injury, and involves both the anterolateral system and DCML pathway
  • DCML - Ipsilateral loss of touch, vibration and proprioception
  • Spinothalamic - contralateral loss of pain and temperature sensation
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20
Q

Clinical relevance

Injury to spinocerebellar tracts

A
  • Lesions of the spinocerebellar tracts present with an ipsilateral loss of muscle co-ordination
  • However, the spinocerebellar pathways are unlikely to be damaged in ‘isolation’ - there is likely to be additional injury to the descending motor tracts
  • This will cause muscle weakness or paralysis, and usually masks the loss of muscle co-ordination
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21
Q

Descending tracts

A

Pyramidal

  • corticospinal
  • corticobulbar

Extrapyramidal

  • Vestibulospinal
  • Reticulospinal
  • Rubrospinal
  • Tectospinal
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22
Q

Pyramidal tracts

A

Originate in the cerebral cortex and carru motor fibres to spinal cord and brainstem.

Responsible for voluntary control of musculature.

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23
Q

Extrapyramidal tracts

A

Originate in brainstem and carry motor fibres to spinal cord.
Responsible for involuntary and autonomic control of musculature.

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24
Q

Where does corticospinal tract begin?

A

Cerebral cortex

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25
Q

Corticospinal tracts inputs

A

Primary motor cortex
Premotor cortex
Supplementary cortex

26
Q

Pathway of corticospinal tract

A

Cortex -> Descends through internal capsule -> Crus cerebri -> Pons -> Medulla

inputs -> internal capsule -> synapse in medulla -> decussation of 85% of fibres -> down spinal cord -> synapses at ventral horn

27
Q

In the caudal part of the medulla, the tract divides into 2:

A
  1. Lateral corticospinal tract
    - > Decussates at medulla and then descends, terminating in the ventral horn.
  2. Anterior corticospinal tract
    - > Remains ipsilateral to the spinal cord, then decussates at ventral horn and terminates in the ventral horn of the upper thoracic levels and synapses there.
28
Q

Clinical relevance of corticospinal tract

A

The internal capsule is particularly susceptible to compression from haemorrhagic bleeds, known as ‘capsular stroke’. This could cause a lesion in the descending tracts.

29
Q

Where does corticobulbar tract begin?

A

Lateral aspect of primary motor cortex

30
Q

Inputs corticobulbar

A

lateral aspect of primary motor cortex
premotor cortex
supplementary cortex

31
Q

Pathway of corticobulbar

A

Cortex → Descend through internal capsule → Crus cerebri → Brainstem → Terminate and synapse on motor nuclei of cranial nerves (acting on facial and neck muscles)

32
Q

Most fibres innervate motor neurones bilaterally. What are the exceptions?

A

facial nerve

hypoglossal nerve

33
Q

Clinical relevance

corticobulbar

A

It is important to understand the organisation of the corticobulbar fibres. Many of these fibres innervate the motor neurones bilaterally. For example, fibres from the left primary cortex act as upper motor neurones for the right and left trochlear nerves.

Exceptions
Facial nerve

⇒ Upper motor neurones for CN VII have a contralateral innervation

⇒ Only affects muscles in lower quadrant of the face (below eyes)

Hypoglossal nerve

⇒ Only provides contralateral innervation

34
Q

Where do extrapyramidal tracts originate?

A

brainstem

35
Q

Vestibulospinal tract

A
  • Arise from vestibular nuclei
  • Medial and lateral tracts
  • Supply ipsilateral information
  • Controls balance and posture
36
Q

Reticulospinal tract

A

Medial tract

  • Arises from the pons
  • Facilitates voluntary movement
  • Increases muscle tone

Lateral tract

  • Arises from the medulla
  • Inhibits voluntary movement
  • Decreases muscle tone
37
Q

Rubrospinal tract

A
  • Arises from red nucleus
  • Fibres decussate and then descend
  • Plays a role in the fine control of hand movement
38
Q

Tectospinal tract

A
  • Arises from superior colliculus
  • Decussate and then enters spinal cord
  • Co-ordinates movements of the head in relation to vision stimuli
39
Q

Damage to Corticospinal tracts

A

The pyramidal tracts are susceptible to damage because they extend almost the whole length of the central nervous system. They are particularly vulnerable as they pass through the internal capsule, a common site of cerebrovascular accidents.

  • If there is only UNILATERAL lesion of the left or right corticospinal tract, symptoms will appear on the contralateral side of the body.
40
Q

Signs of a UMN lesion

A
  • Hypertonia - increased muscle tone
  • Hyperreflexia - increased muscle reflexes
  • Clonus - involuntary, rhythmic muscle contractions
  • Babinski sign - extension of the hallux in response to blunt stimulation of the sole of the foot
  • Muscle weakness
41
Q

Damage to corticobulbar tracts

A

Due to bilateral nature of majority of corticobulbar tracts, a unilateral lesion usually results in mild muscle weakness.
However, not all cranial nerves receive bilateral input, and so there are a few exceptions:

Hypoglossal
- A lesion to the upper motor neurons for hypoglossal will result in SPASTIC PARALYSIS of the contralateral genioglossus.

= CONTRALATERAL TONGUE DEVIATION

contrast to LMN lesion; IPSILATERAL tongue deviation (to damaged side)

Facial :
A lesion to upper motor neurons for facial nerve will result in spastic paralysis of the muscles in the CONTRALATERAL LOWER QUADRANT OF FACE.

42
Q

Damage to extrapyramidal tract

A

Extrapyramidal tract lesions are commonly seen in:

  • Degenerative diseases
  • Encephalitis
  • Tumours

They result in various types of dyskinesia or disorders of involuntary movement

43
Q

White matter tracts

A

Commissural tracts
Association tracts
Projection tracts

44
Q

Commissural tracts

A

Travel from one cerebral hemisphere to another via commissures.
Most of these tracts travel through the CORPUS CALLOSUM.

45
Q

Association tracts

A

Connect different areas of the same brain hemisphere.

46
Q

Projection tracts

A

Extend from high brain regions to areas deep within the brain and spinal cord, relaying information from the cerebrum to the rest of the body.

47
Q

White matter injuries

A

When you suffer an injury to ONLY white matter, you will retain movement and sensation, but your brain may have difficulty coordinating and sending signals.

  1. Challenges with ‘executive’ function (ability to co-ordinate, plan and monitor your thought process)
  2. Difficulty co-ordinating muscle movements; shaky or uncoordinated.
  3. Problems with memory, spatial reasoning and planning.
  4. Difficulty controlling your emotions, or changes in psychological health.
48
Q

Multiple sclerosis

A

MS occurs when the brain’s white matter steadily breaks down, and interferes with movement and muscle co-ordination.

49
Q

Dorsal horn of spinal cord

A

POSTERIOR

Somatosensory

Ascending pathways TO brain

50
Q

Ventral horn of spinal cord

A

ANTERIOR

Motor

Exit spinal cord to innervate skeletal muscle

51
Q

Intermediate column and lateral horn

A

innervate visceral and pelvic organs

52
Q

Substantia gelatinosa

A

Located at top of dorsal horn

Pain, temperature and light touch sensation TO brain

53
Q

Nucleus proprius

A

Neck of dorsal horn

Mechanical and temperature sensation TO brain

54
Q

Dorsal nucleus of Clarke

A

Most dorso-medial nuclei

Unconscious proprioceptive information to the brain

C8-L3 spinal segments

55
Q

Front of arm spinal

A

C5

C6

56
Q

Back of arm spinal

A

C7

C8

57
Q

Diaphragm spinal

A

C3
C4
C5

58
Q

Erection of penis spinal

A

S2
S3
S4

59
Q

Ankle jerk reflex

A

S1
S2

1, 2 buckle my shoe

60
Q

Knee jerk reflex

A

S3
S4

3, 4 kick down the door

61
Q

Wrists and biceps reflex

A

C5
C6

5, 6 pick up sticks

62
Q

Triceps reflex

A

C7
C8

7,8 push open the gate

PHASE ONE (19 decks)

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