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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
Corticospinal tracts inputs
Primary motor cortex Premotor cortex Supplementary cortex
26
Pathway of corticospinal tract
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
In the caudal part of the medulla, the tract divides into 2:
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
Clinical relevance of corticospinal tract
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
Where does corticobulbar tract begin?
Lateral aspect of primary motor cortex
30
Inputs corticobulbar
lateral aspect of primary motor cortex premotor cortex supplementary cortex
31
Pathway of corticobulbar
Cortex → Descend through internal capsule → Crus cerebri → Brainstem → Terminate and synapse on motor nuclei of cranial nerves (acting on facial and neck muscles)
32
Most fibres innervate motor neurones bilaterally. What are the exceptions?
facial nerve | hypoglossal nerve
33
Clinical relevance | corticobulbar
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
Where do extrapyramidal tracts originate?
brainstem
35
Vestibulospinal tract
- Arise from vestibular nuclei - Medial and lateral tracts - Supply ipsilateral information - Controls balance and posture
36
Reticulospinal tract
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
Rubrospinal tract
- Arises from red nucleus - Fibres decussate and then descend - Plays a role in the fine control of hand movement
38
Tectospinal tract
- Arises from superior colliculus - Decussate and then enters spinal cord - Co-ordinates movements of the head in relation to vision stimuli
39
Damage to Corticospinal tracts
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
Signs of a UMN lesion
- 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
Damage to corticobulbar tracts
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
Damage to extrapyramidal tract
Extrapyramidal tract lesions are commonly seen in: - Degenerative diseases - Encephalitis - Tumours They result in various types of dyskinesia or disorders of involuntary movement
43
White matter tracts
Commissural tracts Association tracts Projection tracts
44
Commissural tracts
Travel from one cerebral hemisphere to another via commissures. Most of these tracts travel through the CORPUS CALLOSUM.
45
Association tracts
Connect different areas of the same brain hemisphere.
46
Projection tracts
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
White matter injuries
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
Multiple sclerosis
MS occurs when the brain's white matter steadily breaks down, and interferes with movement and muscle co-ordination.
49
Dorsal horn of spinal cord
POSTERIOR Somatosensory Ascending pathways TO brain
50
Ventral horn of spinal cord
ANTERIOR Motor Exit spinal cord to innervate skeletal muscle
51
Intermediate column and lateral horn
innervate visceral and pelvic organs
52
Substantia gelatinosa
Located at top of dorsal horn Pain, temperature and light touch sensation TO brain
53
Nucleus proprius
Neck of dorsal horn Mechanical and temperature sensation TO brain
54
Dorsal nucleus of Clarke
Most dorso-medial nuclei Unconscious proprioceptive information to the brain C8-L3 spinal segments
55
Front of arm spinal
C5 | C6
56
Back of arm spinal
C7 | C8
57
Diaphragm spinal
C3 C4 C5
58
Erection of penis spinal
S2 S3 S4
59
Ankle jerk reflex
S1 S2 1, 2 buckle my shoe
60
Knee jerk reflex
S3 S4 3, 4 kick down the door
61
Wrists and biceps reflex
C5 C6 5, 6 pick up sticks
62
Triceps reflex
C7 C8 7,8 push open the gate

PHASE ONE (19 decks)

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