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term 2 control yr 2 > Ascending Sensory Pathways I + II > Flashcards

Ascending Sensory Pathways I + II Flashcards

1
Q

What is Somaesthetic pathways?

A

Involves perception of bodily senses – pain,

temperature, touch and position

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2
Q

What is Proprioception? What structures are invovled?

A

the positon of where you are in space
Involves the DCP
Golgi tendons or muscle spindles in the muscles that detect the positon of the muscles and what they are doing without you having to see

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3
Q

What does Somaesthetic pathways carry?

A

Carry information of different types or modalities from:

Skin, mucus membranes, joints and muscles to the brain

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4
Q

What detects each modality involved in Somaesthetic pathways?

A

Each modality is detected by specific sensory receptors/specialised nerve endings

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5
Q

What are the two Somaesthetic pathways?

A

Spinothalamic Pathway

Dorsal column pathway

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6
Q

Which somaesthetic modality is essential for survival?

A

Somaesthetic pathways

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7
Q

Which somaesthetic modality increases detail?

A

dorsal column pathway

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8
Q

What type of reception modality does Spinothalamic Pathway

A
  • Pain, temperature, some touch and pressure
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9
Q

What type of reception modality does Dorsal Column Pathway carry?

A

Discriminative touch: 2-point discrimination and vibration

Proprioception

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10
Q

What type of fibers are involved in Spinothalamic Pathway? Is the conduction fast or slow?

A

Carried via thin, poorly mylinated or
unmylinated fibres

Conduction relatively slow

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11
Q

What type of fibers are involved in Dorsal column pathway? Is the conduction fast or slow?

A

Carried via large diameter, heavily mylinated fibres

Fast conduction

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12
Q

How many neurones are invovled in the general sensory pathway?

A

3

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13
Q

When talking about sensory sensation of the body where specifically in the thalamus is the neurone going to?

A

VPL of the thalamus

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14
Q

What part of the brain is involved in general sensation?

A

Post central gyrus

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15
Q

What is the role of each of the 3 neurones in the general sensory pathway?

A

1st neurone: Is a Pseudounipolar that synpase on the same side of the spinal cord that is entered in.

2nd neurone: Axon crosses midline –> Ascends to ventral posterior thalamus

3rd neurone: Axon projects to post central
Gyrus (parietal lobe)

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16
Q

What is a Pseudounipolar?

A

. A neuron with a single stalk, that splits to give of two process –> one branch runs to he periphery and the other to the spinal cord.

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17
Q

What is a dorsal root ganglion?

A

Collection of cell bodies of the dorsal root neurones.
Specifically Pseudounipolar
Afferent nerves as they carry information towards the brain

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18
Q

How many neurones does the general sensory pathway compromise and where do these neuroens reside and move?

A

1)Comprise 3 neurons: first order, second order and third order
2)Cell bodies of 1st order neurons reside in dorsal root ganglia (PNS)
3)Cell bodies of 2nd order neurons reside in CNS ipsilateral grey matter
4)Axons of 2nd order neurons cross midline and ascend to thalamus
5)Cell bodies of 3rd order neurons reside in thalamus and axons project to somato-
sensory cortex
.

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19
Q

What is the blood supply of the medial surface of the post central gyrus?

A

anterior cerebral artery

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20
Q

What is the blood supply of the lateral surface of the post central gyrus?

A

Medial cerebral artery

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21
Q

How can imput from the 1st to 2nd and then 3rd neuroens be modified?

A

It is not simple relay. Can be modified by other inputs: eg. Convergence/divergence or descending pathways.
Can make the message more widespread or specific

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22
Q

Describe the crossing over of the Spinothalamic

tract and Dorsal column.

A

The spinothalamic tract crossess over the midline as soon as it enters the spinal tract

The dorsal column does not cross the midline at the level it enters the cord. It will ascend right up to the medulla then it will cross over

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23
Q

Describe the route of the Spinothalamic

tract?

A

1) 1st neurone originates from the DRG and ascends towards the spinal cord
2) The 1st neurone fibre ascends 1-2 segments then
contacts 2 neurone in dorsal grey horn
3) The 2nd neurone crosses midline in ventral white commisure
4) Then the 2 neurone fibres ascend in Spinothalamic tract to thalamus

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24
Q

What is the position where the 2nd neurone in spinothalamic tract crosses over the midline?

A

anterior ventral to the ventral white commissure

Close association between VWC and central canal

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25
Q

What structures in the CNS are somatotopically tract?

A

Medulla, thalamus and spinal cord

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26
Q

Once the spinothalamic tract has passed the medula what does it become?

A

Spinal lemniscus

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27
Q

What part of the medulla does the spinothalamic tract go to?

A

Lateral lemniscus

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28
Q

What is the route of the dosral column pathway at the level of the spinal cord?

A

1) the 1st neurone is at the dorsal root ganglion and then goes into the same side of the spinal cord
2) Synapse and the second neurone ascend in one of
ipsilateral dorsal columns
There is no crossing over

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29
Q

What is the distribution of the gracile and cuneate fasciles?

A

Gracile fascicle runs the whole length of the spinal cord –> information from the legs and lower part of the body
Cuneate fascicle runs above T6 only –> information from the upper body

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30
Q

What within the gracile and cuenate tubercles?

A

Gracile and Cuneate nucleus respectively where 1st neurone synpases

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31
Q

What type of sensation is involved in dorsal column pathway?

A

discriminative touch and

proprioception (plus some simple touch and pressure)

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32
Q

What type of sensation is involved in Spinothalamic pathway?

A

Pain, temperature, touch and pressure

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33
Q

At what point does the 1st neurone synapse with the second neurone in the dorsal column pathway?

A

At the closed medulla. At the gracile and/or cuneate fascicles

34
Q

What occurs at the closed medulla in the dorsal column pathway?

A

1˚ sensory neurons contact 2 neurone fibres which

cross midline and enter medial lemniscus

35
Q

What part of the medulla does the neurones of the dorsal column pathway run through?

A

Medial lemniscus

36
Q

What is a lemniscus?

A

A collection of fibers

37
Q

What is the name of the position where the 2nd neurones in dorsal column pathway cross the midline?

A

internal arcuate fibers –> going towards a specific part of the medial lemniscus
Medial lemniscus is somatotopically organized

38
Q

What happens once the 2nd neurone reaches the medial lemniscus in the dorsal column pathway?

A

The secondary neurones project towards the VPL thalamus where they synapse.
The 3rd neurones are projected towards the somatosensory cortex

39
Q

What direction does the fibers in the spinothalamic pathway travel in the spinal cord

A

Travel contralaterally in the cord

40
Q

What direction does the fibers in the dorsal column pathway?

A

Travel ipsilaterally in the cord

41
Q

What level does the fibers cross in the Spinothalamic pathway and DCP?

A

STP–> cross at level of spinal cord entry

DCP–> cross at level of closed medulla

42
Q

What are the 3 branches of the trigeminal nerve?

A

V1 –> Opthalmic
V2 –> Maxillary
V3 –> Mandibular

43
Q

What foramen do each of the trigeminal nerves pass?

A

V1 –> SOF
V2 –> foramen Rotundum
V3 –> forame ovale

44
Q

What supplies the sensory information to the upper and lower teeth?

A

V2 supplies the upper teeth ( maxillary teeth) via the superior alveolar nerve.

V3 –> Supplies the mandibular teeth via the lower alveolar nerve

45
Q

What cranial nerve does the herpes zoster virus infect?

A

It infects the sensory roots of trigeminal nerve .

46
Q

Once the chicken pox has passed where does it reside?

A

The virus resides in the sensory roots of specific spinal nerves.

47
Q

What does reactivation of the herpes zoster virus cause?

A

Reactivation causes shingles but the virus is restricted to a specific segmental spinal nerve, the vesicles blister and are distrubuted only in the dermatome of the affected spinal nerve

48
Q

What are the somaethetic modalitis that are essenital to survival?

A

Pain, temperature, some touch and pressure

49
Q

What are the somaethetic modalitis that increase detail?

A

Discriminative touch: 2-point discrimination and vibration

Proprioception

50
Q

How many neurones are there in a neurone chain from receptor to sensroy cortex?

A

3
First order neurons
From PNS to CNS. Cell bodies in peripheral ganglia.

Second order neurons
Axons cross midline. Extend to thalamus

Third order neurons
Extend from thalamus to post-central gyrus

51
Q

Where a cranial nerve nuclei located?

A

Within the brain stem

52
Q

What do sensory and motor cranial nerve nuclei give rise to?

A

Sensory: receive information from fibres entering brainstem in cranial nerves

Motor: give rise to motor fibres that leave the brainstem in cranial nerves

53
Q

What is equivelant to the dorsal grey horn of the spinal cord in the brain stem?

A

Sensory cranial nerve nuclei

54
Q

Do the cranial nerves like the spinal nerves have the same cranial nerve nuclei?

A

No they don’t. The cranial nerve supplies different things so have specific sensory and motor cranial nerve nuclei.

55
Q

General sensation from the head/face is carried in which 4 cranial nerves?

A

Trigeminal 5

Facial nerve 7

Glossopharyngeal 9

Vagus 10

56
Q

The trigeminal nerve is a major carrier of general sensory from what areas of the head?

A

Major carrier of sensation from the face, nose, scalp and dura.

57
Q

The facial nerve is a major carrier of general sensory from what areas of the head?

A

External ear

58
Q

The glossopharyngeal nerve is a major carrier of general sensory from what areas of the head?

A

Posterior 1/3rd of tongue
Pharynx
Middle ear

59
Q

The vagus nerve is a major carrier of general sensory from what areas of the head?

A

Auditory canal
Larynx
Pharynx
Oesophagus

60
Q

What common site do all the sensory fibres from the cranial nerves V, 7,9 and 10 run through?

A

All run within the trigeminal nucleus to the thalamus

61
Q

What are the name of the 3 parts of the trigeminal nucleus and where in the brain stem are they situated?

A

Mesenphalic nucleus of trigeminal nerve –> found at the top of the pons bordering the mid brain

Prinicpal sensory nucleus of trigeminal nerve (chief) is found in the middle of the pons

Spinal tract and spinal nucleus of trigeminal nerve which is found in the brain stem/spinal tract

62
Q

What part of the trigeminal nerve does cranial nerve 7,9 and 10 enter?

A

Cranial nerve 7 Enters the bottom part of the chief region.

Cranial nerve 9 and 10 enter the spinal tract and spinal neurone of trigeminal nerve region

63
Q

What is the position of motor cranila nerve nuclei to the sensory of the trigeminal?

A

The motor nuclei of the trigeminal lies medially to the sensory nuclei

64
Q

What part of the trigeminal nucleus recieves pain and temperature modality?

A

Caudal part of the spinal nucleus

65
Q

What part of the trigeminal nucleus recieves simple touch and pressure modality?

A

Rostal part of the spinal nucleus

66
Q

Explain the pain and temperature pathway?

A

The fiber is thin and slow

The 1st neurone cell bodies starts in the trigeminal ganglion

The fibres run caudually in spinal tract of trigeminal lateral to the nucleus

Synapse with the 2nd fiber in the spinal nucleus on the same side

Cross the midline and ascends in trigeminothalamic tracts towards the thalamus (VPM)

67
Q

Are the descending fibers running towards the spinal trigeminal necleus in the brain stem superficial or deep?

A

They are superficial and therefore easily damaged

68
Q

Are the trigeminothalamic tract deep or supefecial?

A

They are deep, they run adjacent to the cerebal aqueduct.

69
Q

Explain the dscriminatory touch pathway?

A

Fat and Fast Fibres

1st neurone cell bodies found in trigeminal ganglion.

They do not descend but enter at the pontine chief nucleus.

Then synapse with the 2nd neurone at the chief nucleus

Cross the midline and ascend in the trigeminothalamic tract to the thalamus

70
Q

What part of the trigeminal nerve recieve disciminatory touch sensation?

A

The pontine chief nucleus

71
Q

Explain the touch and pressure pathway?

A

Thin and slow fibers

1st neurone cell bodies in the trigeminal ganglion

Fibres descend in spinal tract of trigeminal to the rostal part of the spinal nucleus.

Synapse with the 2nd neurone more rostarlly in the spinal nucleus

Cross the midline and ascends in trigeminothalamic tracts (VPM)

72
Q

What type of lesion would damage ascending spinothalamic tract and descending spinal tract? From what side of the body would they be coming from at the level of the medulla oblongata?

A

A superior lesion.

The spinothalamic tract would be coming from the contralateral side –> so damage to that nerve would cause sensory loss of the contralateral side of the body

The descending spinal tract would be coming from the ipsilateral side so the same side of the face would be affected.

73
Q

Where does discrimintive touch sensory pathway synapse in the trigeminal nerve?

A

At the pontine (chief) nucleus

74
Q

Where does proprioception pathway synapse in the trigeminal nerve?

A

Mesencephalic nucleus

75
Q

What is unique about the propriception pathway?

A

The 1st nucleus begins at the mesencephalic nucleus and not at a ganglion outside the brain stem

76
Q

What is the propioception pathway? Both sensroy and motor.

A

Most of these axons travel in the mandibular divsion of trigeminal as it involves understanding the position of your jaw.

1st neurone in the mesencephalic nucleus

Synapse along the mesencephalic nucleus

Cross the midline and ascend to the thalamus in trigeminothalamic tract

Other fibers from the Mesencephalic necleus contact motor neuroens in trigeminal motor nucleus.

Motor fibers go to muscles of mastication

77
Q

What are sensory pathways?

A

Somatotopic

78
Q

Is synaptic transmissioon of 1st ,2nd to 3rd neurone in the sensory pathway simply relay?

A

No it is not it can be modified by other inputs such as descending pathways

79
Q

How does convergence modification of synaptic transmission work?

A

Several inputs from a axon leads to the output of one neurone

80
Q

How does divergence modification of synaptic transmission work?

A

Is when the input of one neurone leads to the output of several

81
Q

Fibres travelling from the thalamus to the post central gyrus via what?

A

The posterior limb of the internal capsule

82
Q

Aneurysm in what artery would cause damage to the spinothalamic tract and spinal tract of the trigeminal?

A

Aneurysm in the anterior inferior cerebellar artery

term 2 control yr 2 (6 decks)

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