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ascending pathways Flashcards

1
Q

what are somatoesthetic pathways?

A

they are general sensory pathways

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2
Q

what do somatoesthetic pathways carry?

A

they carry information of different types or modalities from the skin, mucus membranes, joints or muscles to the brain

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3
Q

how is each modality detected?

A

through a specific sensory receptor or specialised nerve endings

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4
Q

what types of sensory modality are there?

A

pain temperature touch pressure vibration and proprioception

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5
Q

where does information about what we feel go to?

A

the dorsal spinal cord and then via the brainstem to the cerebrum

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6
Q

where is the primary somatosensory cortex?

A

it is behind the central sulcus - the post central gyrus and is for pain temperature and touch

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7
Q

where are other senses?

A

auditory is lateral and vision is posterior

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8
Q

how many spinal nerves are there and what are they for?

A

there are 31 - sensory modalities are transmitted by specific ones or cranial nerves in the head and neck

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9
Q

what innervates the legs and arms?

A

legs is the lumbar / sacral nerves and arms is C8-T1

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10
Q

what forms small fibres in the lateral division?

A

pain and temperature information

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11
Q

what forms the large fibres in the medial division?

A

vibration, proprioception of tendons and muscles and light touch

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12
Q

what is a dermatome?

A

it is a specific region of skin that is innervated by sensory fibres of a single segmental spinal nerve/segment

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13
Q

what is comparable to dermatomes?

A

specific regions of the face that are supplied by single cranial nerves can be identified and mapped

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14
Q

how would you identify where a lesion is in the dermatome?

A

you would test sensation in specific area to find localised area of injury

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15
Q

what is T4 and T10?

A

T4 - nipple

T10 - umbilical

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16
Q

what is hsv?

A

herpes zoster virus - infection of the sensory nerve roots of specific spinal nerves

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17
Q

what is the result of chicken pox?

A

you develop resistance or memory as develop antibodies however it does remain dormant in the spinal nerve roots and can re-establish as shingles in the immunosupressed

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18
Q

why are blisters in shingles localised?

A

they are localised to the area of skin that correspond to the nerve where the virus is latent

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19
Q

what is in the lateral horn and specifically in which areas?

A

there are preganglionic visceral neurons from T1-L2 and S2-S4

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20
Q

what is in the dorsal and ventral grey matters and what is this for?

A

dorsal is synapses for sensory information and ventral is cell bodies for sensory neurones
somatic motor

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21
Q

what is the DCML?

A

it is the dorsal column medial lemniscus pathway that is a sensory pathway for the CNS carrying ipsilateral fine touch, joint position sense, pressure and vibration

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22
Q

what are the two groups of somatesthetic pathways?

A

modalities that are essential to survival and modalities that increase detail

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23
Q

what are the differences between the two gorups of somatesthetic pathways?

A

essential:
pain temperature and some touch and pressure
conduction is relatively slow as it is carried via thin, unmyelinated or poorly myelinated fibres
detail:
discriminative touch: 2 point discrimination and pressure, proprioception and vibtation
carried via large diameter heavily myelinated fibres and has fast conduction

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24
Q

what is the general sensory pathway?

A

it is a three neuron chain
from a sensory receptor the first neuron is pseudouniploar with a cell body in a sensory ganglion. This connects with the secondary axon which crosses the midline and ascends to the ventral posterior VPL of the thalamus. This then synapses with the tertiary neuron which has an axon projecting to the post central gyrus in the parietal lobe

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25
Q

what is the function of synapses?

A

they allow information processing to occur

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26
Q

how can synapse response be modified?

A

via convergence (when many neurons influence a single neuron), divergence (where one neuron influences many) and by descending pathways

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27
Q

where are cell bodies of first order neurons?

A

they are in the peripheral ganglia

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28
Q

where are cell bodies for second order neurons?

A

in the CNS - ipsilateral grey matter

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29
Q

where do cell bodies of this order neurons resides?

A

in the thalamus

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30
Q

where are the spinothalamic tracts and what are they for?

A

they are in the anterolateral white columns - they span both on both sides and they are for pain temperature and pressure

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31
Q

how is the spinothalamic tract used?

A

first order neuron arrives and central process uses the dorsal root of spinal nerve to enter the dorsal horn of grey matter of cord. They enter Lissauer’s tract and contact cell body of second order which immediately has an axon crossing midline via ventral white commissure and uses the spinal tract to the cortex

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32
Q

how is the STT organised?

A

somatotopically - fibres bring specific information from specific part of body - upper limbs medial, trunk central and lower limbs are dorsolateral

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33
Q

what variation can there be in STT?

A

the first order neuron may ascend one or two segments before synapsing with second order

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34
Q

what are lissauer’s tract and subgelatinosa for?

A

the dispersal and relaying of information - entry point of many sensory fibres

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35
Q

what is the grey matter of the spinal cord divided into?

A

rexxed lamina

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36
Q

what rexxed lamina are present in the whole spinal cord?

A

I-IV

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37
Q

where are first order neurons received?

A

in rexxed lamina I-IV cells

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38
Q

`what happens after receiving the first order neurons?

A

there are second order cell bodies for crude touch, pain and temperature

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39
Q

what happens for pain and temperature?

A

the sensory fibres make a stop at the substantia gelatinosa and cross the midline immediately and enter the tract to ascend in the lateral spinothalamic tract

40
Q

what happens for crude touch?

A

they enter and ascend a few segments and then make a stop at I, III or IV to synapse, then ascend medially in the tract

41
Q

what is a characteristic of using the lamina?

A

can differentiate between the senses

42
Q

what are the function of lamina I-IV?

A

I and III-IV are spinothalamic tract cells and II is pain and temperature

43
Q

what are the nuclei of lamina I-IV?

A

I is the marginal zone
II is substantia gelatinosa
III-IV is the nucleus proprius

44
Q

where are the tertiary fibres found for the spinothalamic tract?

A

in the thalamus - VPL

45
Q

where is the primary somatosensory cortex?

A

the post central gyrus

46
Q

how does the spinothalamic tract reach the VPL from the medulla?

A

via the spinal lemniscus

47
Q

what is the function of the dorsal column medial lemniscus pathway?

A

to bring information about conscious proprioception, pressure, vibration and discrimative touch

48
Q

How many dorsal white columns are there?

A

2

49
Q

what are the fascicles in the DWCs?

A

the cuneate (T6 and above for the upper limb) and the gracile (whole spinal cord for the lower limb)

50
Q

how are the DWCs organised?

A

somatotopically

51
Q

how does the DWC run?

A

the first order neuron will enter the spinal cord and uses the tract - it then leaves and uses the DWCs to go all the way up the spinal cord on the same side as when it enters

52
Q

what are the characteristics of the fibres entering the DWC?

A

they are from thick, fast receptors

53
Q

where do the primary fibres ascend?

A

in one of the ipsilateral dorsal columns

54
Q

what are the bumps in the dorsal brainstem?

A

the fascicles and then the tubercles at the top of the medulla which is where the nuclei are - where the first order and second order neurons synapse

55
Q

what is on the ventral medulla?

A

the pyramids

56
Q

what happens in the dorsal columns after the first and second order synapse?

A

the second order neurons cross the midline, crossing over the internal arcuate fibres that are curved, and enter the medial lemniscus to go to the thalamus

57
Q

how is the medial lemniscus organised?

A

somatotopically - the cuneate / arm information will go to the top laterally

58
Q

both pathways (STT and DWC) will project to opposite hemisphere but how do they differ?

A

fibres are pain, temperature and crude touch for STT and they cross midline in the SC immediately or almost so travel contralaterally
in the DCMLP they travel ipsilaterally in the cord as do not cross until the level of the closed medulla

59
Q

what happens at the level of the closed medulla?

A

the secondary order neurons of the DCML cross the midline - arm at the top of the medial lemniscus and then trunk and then leg to ascend to thalamus

60
Q

what happens at the VPL?

A

secondary and tertiary neurons of the DCML pathways synapse and tertiary project to the SCC in post central gyrus

61
Q

how are regions of the spinal cord defined?

A

by spinal nerves

62
Q

what are the names of the segments in the spinal cord?

A

cervical, thoracic, lumbar, sacral and coccygeal

63
Q

where is the coccygeal segment found?

A

behind L1 and L2 levels

64
Q

where does the coccygeal nerve leave?

A

it begins in the coccygeal level of the cord and travels down to leave through the coccyx

65
Q

what happens with nerves from the sacral segments?

A

they travel using the cauda equina to leave the intervertebral foramina at the level of the sacrum

66
Q

what is the trigeminal sensory pathway used for?

A

there are tracts which are used to bring information to the cortex from all four nerves - V, VII, IX, X

67
Q

what is the general sensation of the head from?

A

carried in cranial nerves V, VII, IX and X

68
Q

what information does the trigeminal carry?

A

major carrier of general sensory information from the face, nose, scalp and dura

69
Q

what information does the facial nerve carry?

A

external ear

70
Q

what information does the glossopharyngeal nerve carry?

A

posterior 1/3 tongue, pharynx and middle ear

71
Q

what information does the vagus nerve carry?

A

the auditory canal, larynx, pharynx and the oesophagus

72
Q

where are the cranial nerve nuclei located?

A

within the brainstem - specific fibre types are associated with specific nuclei in the brainstem

73
Q

what happens for motor nuclei?

A

they give rise to motor fibres that leave the brainstem in the cranial nerves - nucleus for V3

74
Q

what happens for sensory nuclei?

A

the receive information from fibres entering the brainstem in cranial nerves, V, VII, IX and X - they all run within the trigeminal sensory nucleus

75
Q

where does the trigeminal sensory nucleus go?

A

it runs to the thalamus and spans the length of the brainstem

76
Q

where does the motor nuclei of the V lie?

A

medial to the sensory nuclei and the chief nuclei which is above the sensory - the motor is then above this and mesencephalic above this

77
Q

where is the trigeminal nerve and ganlion?

A

in the ventral aspect of the pons

78
Q

what are the divisions of the trigeminal nerve and what regions do they cover?

A

V1-3
V1 is the ophthalmic which is above the eye lid
V2 is the maxillary from the lower eyelid to the upper lip and the V3 is the mandibular which is the upper lip down

79
Q

where (with one exception) are the primary neuron cell bodies?

A

in the trigeminal ganglion

80
Q

which foramina do the trigeminal nerves pass through?

A

ophthalmic - superior orbital fissure
maxillary - foramen rotundum
mandibular - foramen ovale

81
Q

where is the motor nucleus with regards to the mesencephalic?

A

it is medial

82
Q

where is the mesencephalic located?

A

in the midbrain

83
Q

where is the pontine nucleus located?

A

in the pons

84
Q

what is the sensory trigeminal nucleus divided into and what do these receive?

A

it is divided into three - the pontine, spinal and the mesencephalic nucleus - difference parts receive different sensory modalities

85
Q

what sensory information goes to the mesencephalic nucleus?

A

proprioception

86
Q

which cell bodies are not in the trigeminal ganglion/peripheral ganglion?

A

the mesencephalic primary neuron cell bodies

87
Q

what sensory information goes to the pontine nucleus?

A

the pontine or chief sensory will receive discriminative touch

88
Q

what does the spinal nucleus receive?

A

rostral - simple touch and pressure

caudal - pain and temperature

89
Q

what is the pain and temperature pathway from the face?

A

there is a three neuron chain. The first order neuron is in the periphery, the central processes then extend to the spinal nucleus of CN V caudally and synapse with a second order which crosses midline. It travels via the trigeminothalamic tract to the VPM which is more medial in the thalamus

90
Q

what are the characteristics of the fibres carrying pain and temperature in the trigeminothalamic pathway?

A

thin and slow fibres

91
Q

how do fibres in the pain and temperature pathway for face descend to the spinal nucleus?

A

through the spinal tract of the trigeminal

92
Q

the crude touch and pressure pathway for the face is identical to the pain and temperature pathway except for one thing. what is this?

A

the spinal tract descends the primary order neurons to the rostral spinal nucleus for crude touch and not the caudal (caudal is for pain and temperature)

93
Q

how does discriminative information travel?

A

through fat fast fibres for the primary neurones, that synapse with the secondary order in the pontine chief nucleus. This then crosses the midline and travels to the VPM in the thalamus via the trigeminothalamic tract

94
Q

what trigeminal division is involved in the jaw jerk reflex?

A

V3 with the mesencephalic nucleus using proprioception receptors

95
Q

where are cell bodies for proprioception found?

A

in the mesencephalic nucleus

96
Q

how does proprioception information travel?

A

first order neurons to the mesencephalic nucleus, then synapse with second order along side the nucleus, cross midline and go to VMP through the trigeminothalamic tract

97
Q

how does the jaw jerk reflex work?

A

afferent first order axons travel in the mandibular divisions of V. These have cell bodies in the mesencephalic nucleus. Fibres will contact motor neurons in the trigeminal motor nucleus and synpase with motor fibres to the muscles of mastication

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