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anatomy - head, neck & spine > L17 spinal chord nerves, tracts > Flashcards

L17 spinal chord nerves, tracts Flashcards

1
Q

what are the 5 regions of paired nerves of the spinal chord & how many are there?

A
  • cervical nerves - 8 pairs
  • thoracic nerves - 12 pairs
  • lumbar nerves - 5 pairs
  • sacral nerves - 5 pairs
  • coccygeal nerve - 1 pair
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2
Q

what can neurons / nerves within the spinal chord be classified as?

A
  • somatic afferent / efferent
  • visceral afferent/ efferent
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3
Q

what do the anterior roots vs the posterior roots of the spinal chord contain?

A
  • anterior root -they contain motor/efferent nerve fibers to skeletal muscle etc
  • posterior root - they contain sensory/afferent nerve fibers from skin, subcutanous tissues
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4
Q

what is the vertebral column?

A
  • the spine
  • extending from the cranium (skull) to the coccyx - forms the skeleton of the back and neck
  • functions to protect the spinal chord and spinal nerves
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5
Q

what are the rootlets of the spinal chord - what do they form?

A

multiple rootlets attach to the posterior and anterior surfaces of the spinal chord and converge to form posterior and anterior roots of the spinal nerves

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6
Q

what is a segment of the spinal chord?

A

the part of the spinal chord to which the rootlets of one bilateral pair of roots attach

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7
Q

what does the central grey matter of the spinal chord contain?

A
  • nerve cell bodies and fibres
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8
Q

what does the white matter of the spinal chord contain?

A

myelinated fibres that may be ascending or descending

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9
Q

compare the dorsal vs ventral horns of the spinal chord

ie what type of nerve are associated with them etc

A
  • dorsal/ posterior horns - receive axons of sensory afferent neurons
  • ventral/anterior horns send out axons of motor / efferent neurons
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10
Q

what is the acronym for remembering dorsal vs ventral horns and what nerves are associated with them?

A

SAME DAVE
* Sensory Afferent Motor Efferent
* Dorsal Afferent Ventral Efferent

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11
Q

how do the spinal nerves exit the vertebral column?

A

through the intervertebral foramina

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12
Q

what is the white matter of the spinal chord divided into?

A
  • divided into the posterior, anterior and lateral funiculi
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13
Q

what is a funiculus or column?

A

a bundle of one or more nerve fascicles or tracts

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14
Q

what is descussation?

A

the crossing of patheays from one side of the CNS to the other

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15
Q

what is somatotopy?

A

a precise spatial relationship between tract fibres which reflect orderly mapping of the body

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16
Q

what are the 3 main types of tracts & what is their function?

divided by their direction & functiom

A
  • ascending - transmit sensory information
  • descending - transmit motor information
  • intersegmental - transmit information between spinal segments
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17
Q

Describe ascending (somatic sensory) pathways

A
  • these pathways conduct sensory afferent impulses upward - typically through a chain of 3 neurons to various areas of the brain
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18
Q

what are the first order neurons of the ascending pathway?

also describe function

A
  • first order - **cell bodies residing in a ganglion **
  • they conduct impulses from cutaneous receptors of skin & proprioreceptors to the spinal cord or brainstem to synapse with 2nd order neurons
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19
Q

what are the 2nd order neurons and what is their function?

A
  • 2nd order neurons are** cell bodies residing in the dorsal horn of the cord** or medullary nuclei
  • they transmit** impulses to the thalamus or cerebellum where they synapse**
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20
Q

what are 3rd order neurons and what is their function?

A
  • cell bodies in the thalamus
  • they project axons to a speciic area of the cerebral cortex (primary somatosensory cortex)
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21
Q

what are the 3 pathways that carry somatosensory information on each side of the spinal cord?

A
  1. the posterior column -medial lemniscus pathway (PCML)
  2. the anterolateral (spinothalamic) pathway
  3. the** trigeminothalamic **pathway
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22
Q

Describe the posterior column medial lemniscus (PCML) pathway

A
  • carries information about** fine touch, vibration and proprioception** from the limbs, trunk, neck and posterior head
  • sensory information travels through the dorsal (posterior) column - cuneate fasciculus and gracile fasciculus
  • the 2nd order neurons** decussate in the medulla** and** travel through the medial lemniscus in the brain stem **to the thalamus
  • impulses are then projected into specific areas of the somatosensory cortex
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23
Q

Describe the anterolateral (spinothalamic) pathway

function and 3 neurons

A
  • transmits impulses for pain, temperature, itch, tickle, crude touch from limbs, trunk, neck and posterior head
  • 1st order neurons synapse in the dorsal horn
  • second order neurons decussate almost immediately in the spinal chord and continue as lateral or anterior spinothalamic tracts
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24
Q

what information does the anterior-spinothalamic tract carry?

A

carries sensation for crude touch and pressure

25
Q

what information does the lateral spinothalamic tract carry?

A

carries sensation for pain & temperature

26
Q

what information does the lateral spinothalamic tract carry?

A

carries sensation for pain & temperature

27
Q

Describe the** trigeminothalamic pathway**

what info does it carry? 1st order, 2nd order neurons etc

A
  • nerve impulses from most somatic sensations -** touch, thermal and pain from the face, nasal cavity, oral cavity and teeth**
  • first order neurons extend from somatic sensory receptors through the trigeminal nerve
  • synapse with 2nd order neurons** in the pons or medulla**
  • ascend as trigeminothalamic tract to the ventral posterior nucleus of the thalamus where they synapse with the 3rd order neurons
28
Q

how do somatic sensory impulses reach the cerebellum?

A

via spinocerebellar tracts - anterior and posterior

29
Q

what occurs as a result of a lesion to the PCML pathway?

A
  • loss of proprioception and fine touch
  • patient will still be able to perform tasks requiring tactile information pricessing
  • if lesion is in spinal cord = sensory loss will be ipsilateral (on same side of body)
30
Q

what can occur if there is a lesion to the spinothalamic tract?

A
  • impairment of pain and temperature sensation
  • sensory loss will be** contralateral **(loss will be on opposite site of the body where the lesion occured)
31
Q

what is brown-sequard syndrome?

causes and symptoms

A
  • may be caused by traumatic spinal cord injury, tumour, MS, stabbing etc
  • symptoms include ipsilateral vibration and proprioception loss & contralateral pain and temp loss
32
Q

what are lower motor neurons & what structures do they innervate ?

A
  • they are neurons that extend out of the brain stem and spinal cord
  • they innervate skeletal muscles of the face and head through cranial nerves
  • innervate skeletal muscles of the limb through spinal nerves
33
Q

what are the 2 groups of descending somatic motor pathways?

& function

A

* pyramidal tracts - originate in cortex and carry motor fibres to brain stem and spinal cord- voluntary control of body and face muscles
* **extrapyramidal tracts **- originate in brain stem and carry motor fibres to spinal cord - involuntary and autonomic control of all muscularture - tone , balance etc

34
Q

In what 2 types of pathways (descending) do the upper motor neurons (UMNs) extend to lower motor neurons (LMNs)?

A
  1. direct motor pathways deliver siganls to LMN’s from cerebral cortex via pyramidal tracts
  2. indirect motor pathways delover signals to LMNs from motor centers in the basal nuclei, cerebellum and cerebral cortex via extrapyramidal tracts
35
Q

what 2 pathways is the pyramidal tract composed of & what do they supply?

A
  • corticospinal pathway - supply the musculature of the body
  • corticobullar pathway - supply muscles of head anc neck
36
Q

Describe the corticospinal tract

ie where the neurons descend etc

A
  • the corticospinal tract begins in the cerebral cortex
  • form the cortex, the neurons descend through the internal capsule
  • they then pass through the crus cerebri, pons and into the medulla oblongata
  • in the medulla, the tract divides into the lateral and anterior corticospinal tract
37
Q

what are corticospinal tract neurons referred to as and why?

A

upper motor neurons - since they do not innervate the muscle directly - CLINICALLY RELEVANT

38
Q

Describe the lateral corticospinal tract

A
  • fibres decussate in the medulla and descend in the cord to terminate in the ventral horn
  • lower motor neurons supply limb muscles
39
Q

Describe the anterior corticospinal tract

A
  • fibres remain ipsilateral (same side) and descend in cord
  • eventually ducussate in cord just before terminating in ventral horn
  • lower motor neurons supply proximal muscles (muscls closest to the core of the body) - upper legs, arms shoulders etc
40
Q

what is the function of the corticobulbar pathway?

A
  • controls skeletal muscles in the head
41
Q

in the corticobulbar pathway, where do the upper motor neurons terminate?

A

in the motor nuclei of 9 pairs of cranial nerves - oculomotor to hypoglossal

42
Q

what are examples of indirect pathway? (extrapyramidal pathway)?

A
  • rubrospinal tract
  • tectospinal tract
  • vestibulospinal tract
43
Q

what does a lesion in the primary motor cortex lead to?

A

motor function on the contralateral side being affected

44
Q

compare damage to corticospinal fibres above and below decussation

A
  • above - contralateral motor deficits
  • below - ipsilateral deficits
45
Q

what is hemiplegia?

A
  • paralysis of one side of the body
  • can happen due to damage to corticospinal tract
46
Q

what division of the corticospinal tract is also involved in brown sequard syndrome?

A

the lateral corticospinal tract

47
Q

where do upper motor neuron lesions occur?

A

they occur above the ventral horn of the spinal cord (or the motor nuclei of the cranial nerves) - they can occur in the spinal cprd, brain stem or motor cortex

48
Q

what are potential causes of upper motor neuron lesions?

A
  • cerebral palsy
  • spinal cord injury
  • traumatic brain injury
  • stroke
49
Q

what are signs/symptoms of upper motor neuron lesions?

A
  • hypertonia - high level of muscle tone/tension
  • hyperreflexia - overative body reflexes eg twitching
  • clonus - involuntary muscle contractions
  • positive response to babinski reflex - extension of big toe
50
Q

what are lower motor lesions?

A

damage to neurons which supply muscles

51
Q

what are signs of lower motor neuron lesions?

A
  • muscle atrophy - muscle weakness / wasting
  • hypotonia - too little tension/tone
  • relfex loss or hyporeflexia
  • negative response to the babinski reflex 9pin on foot)
52
Q

what are examples of causes of lower motor neuron lesions?

A
  • autoimmune diseases eg myasthenia gravis
  • pollo virus
53
Q

what is a quadriplegia?

A
  • injury to the cervical region of spinal cord
  • all four extremeties affected - arms, trunk, legs, pelvic organs
54
Q

what is paraplegia?

A
  • injury to thoracic, lumbar or sacral segments
  • two extremeties affected - impairment in trunk, legs and pelvic organs depending on the level of injury
55
Q

what is complete injury or ASIA?

A

total loss of sensory and motor function below the injury level

56
Q

what is incomplete injury?

A

some sensory and motor function remains present below injury level

57
Q

what are different types of incomplete spinal cord injuries?

A
  1. brown sequard syndrome
  2. posterior cord syndrome
  3. central cord syndrome
  4. anterior cord syndrome
58
Q

what do A, B, C, D & E stand for the in the ASIA impairment scale?

A
  • A= complete injury - no sensory or motor function presevered in sacral segments
  • B= sensory incomplete - sensory but not motor function preserved below level
  • C=** motor incomplete** - motor function is presevrved in the most caudal (posterior part of body )sacral segments for voluntary anal contraction
  • D - **motor incomplete **
  • E = **normal **

anatomy - head, neck & spine (21 decks)

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