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Neurology > Ascending and Descending Pathways > Flashcards

Ascending and Descending Pathways Flashcards

1
Q

What occurs at each segment of the spinal cord?

A

A series of rootlets emerge from the dorsal and ventral aspects of each segment = coalesce to form posterior and anterior rami respectively

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2
Q

Where do roots of the spinal cord travel through before they enter the appropriate intervertebral formaina?

A

The subarachnoid space

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3
Q

What happens to the posterior root once it passes through the foramina?

A

It is enlarged by the dorsal root ganglion

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4
Q

What does the spinal cord terminate as?

A

Conus medullaris = tapered cone shape

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5
Q

What does the conus medullaris continue as?

A

Filum terminale = thin connective tissue cord anchored to the dorsum of the coccyx

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6
Q

What is the denticulate ligament?

A

Suspends spinal cord laterally in the spinal canal = attaches to dura at points along length of the cord

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7
Q

What is the denticulate ligament formed from?

A

Pial and arachnoid tissue

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8
Q

What does the spinal cord consist of?

A

An outer layer of white matter and an inner H shaped core of grey matter

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9
Q

What does white matter consist of?

A

Longitudinally oriented axons, glial cells and blood vessels

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10
Q

What does grey matter contain?

A

Neuronal soma, cell processes, synapses, glia and blood vessels

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11
Q

Where is the central canal of the spinal cord located?

A

Along the length of the cord = opens rostrally into 4th ventricle, caudally has blind end

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12
Q

What are the components of the white matter?

A

Posterior, lateral and anterior fasciculi

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13
Q

What does each fasciculi contain?

A

A variety of fibre sizes from small unmyelinated to large myelinated fibres

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14
Q

What is grey matter divided into?

A

4 parts = left and right posterior and anterior horns which correspond to 4 vertical segments that make the H shape

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15
Q

What does the horizontal part of the H shape of grey matter represent?

A

Dorsal and ventral commisures, which surround the central canal

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16
Q

What is the arterial supply of the spinal cord?

A

Three major longitudinal arteries
Segmental arteries
Radicular arteries

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17
Q

Where is the extra lateral horn in the spinal cord located?

A

At the T1-L2 level = contains preganglionic sympathetic neurons

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18
Q

What are some features of the three major longitudinal arteries that supply the spinal cord?

A

One anterior and two posterior that originate from the vertebral arteries
Run length of cord

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19
Q

Where do the segmental arteries that supply the spinal cord originate from?

A

Vertebral, intercostal and lumbar arteries

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20
Q

Where do the radicular arteries that supply the spinal cord run?

A

Travel along dorsal and ventral roots

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21
Q

What can embolic occlusion of any of the arteries that supply the spinal cord cause?

A

Areas of spinal cord occlusion

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22
Q

How is the venous drainage of the spinal cord organised?

A

In a similar way to the arterial supply, with both longitudinal and segmental veins

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23
Q

Where is the epidural space located?

A

In the spinal canal between the dura and bone = contains adipose tissue, anterior venous plexus and posterior venous plexus

24
Q

What is the epidural space used for in medicine?

A

Giving epidural anaesthesia

25
Q

How is the primary somatosensory cortex organised?

A

Somatotrophic organisation of neurons = body mapped onto cortex

26
Q

Why are sensory fibres from the left side of the body represented on the right cortex?

A

Sensory fibres cross the midline

27
Q

What is different about sensory info from the scalp and face?

A

It doesn’t travel in the spinal cord

28
Q

In what areas is the spinal cord larger?

A

The cervical and lumbar regions

29
Q

What happens to white matter as you descend down the spinal cord?

A

It occupies a smaller portion of the cord

30
Q

What are some components of the ascending tract?

A

Dorsal funiculus, dorsal column/medial lemniscus system, spinothalamic tract

31
Q

What makes up the dorsal funiculus?

A

The fasciculus gracilis and fasciculus cuneatus

32
Q

What are some features of the dorsal column?

A

Carries fine touch and conscious proprioception

Fibres cross in the medulla

33
Q

Where do the fibres of the ascending tract synapse?

A

In the thalamus

34
Q

What are some features of the spinothalamic tract?

A

Carries pain, temperature and deep pain

Fibres cross segmentally

35
Q

How is the primary motor cortex organised?

A

In the same way as the primary somatosensory cortex

36
Q

What is the cortical motor homunculus?

A

Reflects the relative space occupied on the primary motor cortex by each part of the body

37
Q

What is the corticospinal tract responsible for?

A

Fine, precise movement = especially of the distal limb muscles

38
Q

What forms the pyramidal tract?

A

Corticospinal tract = forms visible ridges called pyramids on the anterior surface of the medulla

39
Q

What happens to most of the fibres in the corticospinal tract in the medulla?

A

About 85% of fibres cross in the caudal medulla at the decussation of the pyramids

40
Q

Where do the fibres of the corticospinal tract originate from?

A

Crossed fibres come from lateral CST

Uncrossed fibres come from ventral CST which cross segmentally

41
Q

What is decorticate posturing?

A

Spastic paralysis with hyperflexion of upper limbs = due to CVA of internal capsule

42
Q

Why does a CVA of the internal capsule cause decorticate posturing?

A

CST intermingles with other fibres = results in lack of descending control

43
Q

What does the extrapyramidal system refer to?

A

Collective name for a number of motor systems outside of the pyramidal tract

44
Q

What are the components of the extra-pyramidal system?

A

Tectospinal tract, reticulospinal tract and the vestibulospinal tract

45
Q

What are some features of the tectospinal tract?

A

Input mostly to cervical segments

Thought to mediate reflex head and neck movements due to visual stimuli

46
Q

What does the reticular formation form?

A

Central core of the brainstem = has many nuclei and receives input from virtually all parts of CNS

47
Q

Where do the fibres of the reticulospinal tract originate?

A

Areas of the reticular formation in the pons and medulla

48
Q

What do the fibres of the reticuospinal tract that originate in the pons allow?

A

Facilitate extensor movement and inhibit flexor movement (opposite applies to medullary fibres)

49
Q

What is one of the functions of the reticulospinal tract?

A

Influences voluntary movement

50
Q

What are some features of the vestibulospinal tract?

A

Excitatory input to antigravity extensor muscles

Fibres originate in vestibular nuclei of pons and medulla

51
Q

Where do the vestibular nuclei of the pons and medulla receive input from?

A

The vestibular apparatus and cerebellum

52
Q

In what group of patients is the vestibulospinal tract thought to play an important role in?

A

Those with decerebrate rigidity and paraplegia in extension

53
Q

What can lesions in the brainstem at the level of the midbrain cause?

A

Lack of descending control in the vestibulospinal tract = leads to domination of extensor muscle tone and hyperextended spastic paralysis

54
Q

What occurs in Brown-Sequard syndrome?

A

Ipsilateral paralysis with hyper-reflexia and extensor plantar reflex
Ipsilateral loss of vibratory sense and proprioception
Contralateral loss of pain and temperature sense

55
Q

What are some causes of Brown-Sequard syndrome?

A

Spinal cord lesion, trauma, ischaemia, TB, multiple sclerosis

Neurology (48 decks)

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