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Brain and Behaviour > 6 - Somatosensory Pathways > Flashcards

6 - Somatosensory Pathways Flashcards

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1
Q

Where do the sensory nerve fibres enter?

A

The dorsal roots

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2
Q

How many layers are there in the dorsal horn?

A

6

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3
Q

Where do the touch afferents synapse?

A

Lamina III and IV

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4
Q

Where do the proprioceptors synapse?

A

Lamina V and VI

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5
Q

Where do the nociceptors synapse?

A

Lamina I and II

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6
Q

What are the two compartments of the spinothalamic tract?

A

Paleo - lateral - older - crude touch - localises the pain stimulus to a part of the body
Neo - medial - new - pain and temperature - produces a sensation of pain

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7
Q

What does the spinothalamic tract do?

A

Transmits modalities of cutaneous sensation

  • Heavy Pressure
  • Crude Touch
  • Temperature
  • Pain
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8
Q

What fibres send a branch to the dorsal funiculi?

A

Touch and proprioceptive fibres (Aa & Ab)

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9
Q

What is the dorsal funiculi also known as?

A

Posterior or Dorsal columns

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10
Q

What are the two divisions of the dorsal columns?

A

Fasciculus gracilis and fasciculus cuneatus

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11
Q

What afferents do the two divisions of the dorsal columns contain?

A

Fasciculus gracilis - afferents from the lower limb and genitalia
Fasciculus cuneatus - afferents from the upper limb

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12
Q

What are the dorsal column nuclei?

A

Where the dorsal fasciculi project into - cuneate and gracile nuclei in the medulla

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13
Q

Where is the VPL nucleus?

A

In the contralateral thalamus

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14
Q

Which pathway is crossed - spinothalamic or dorsal column pathway?

A

Spinothalamic - crossed

Dorsal column pathway - uncrossed

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15
Q

What is the difference between VPL and VPM?

A

VPL is thalamic relay sensation from the body

VPM is thalamic relay sensation from face

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16
Q

Where is the somatosensory cortex?

A

Medio-lateral just posterior to the central sulcus

17
Q

Where is the face represented in the homunculus of the somatosensory cortex?

A

Lateral

18
Q

What does the somatosensory cortex tell you?

A

Where something is on your body and its touch and texture

Not temperature and whether it is painful

19
Q

Which areas on the body have the highest density of touch receptors?

A

Fingertips, lips and tongue

20
Q

Why do we have two pathways to the somatosensory cortex? What are they?

A

Both the spinothalamic and dorsal column medial lemniscus go to the somatosensory cortex
However they convey different kinds of somatosensory information
Spinothalamic tract = sense of pressure and heavy touch
Dorsal columns = discriminative touch and recognising objects by handling them

21
Q

What is Romberg’s test?

A

Assesses proprioception (ability to sense the position of our limbs)
Patient stands upright with eyes closed, instability is positive
a. What are 3 other tests for dorsal column function?
- Two-point discrimination
- Vibration Sense
- Joint position sense
- Graphesthesia (recognise shapes of objects drawn on the skin)

22
Q

Where does the DCML cross over?

A

Closed Medulla

23
Q

What are tissue damage receptors called?

A

Nociceptors

24
Q

What is the difference between Ad and C nerve fibres?

A

Ad - small myelinated - fast pain

C - unmyelinated - slow pain

25
Q

What is neuropathic pain?

A

Pain not due to a tissue injury but due to spontaneous activity in nerves or CNS

26
Q

What causes normal pain?

A

Nociceptor activity

27
Q

What are the 3 features of normal pain?

A
  • Requires noxious stimulus
  • Has protective function
  • Has acute and chronic components
28
Q

How do you treat nociceptive pain?

A

Conventional analgesics e.g NSAID

29
Q

How does inflammation promote pain?

A

Inflammation opens up Na channels at free nerve endings leading to tonic depolarisation

30
Q

Where do cells in lamina I and II decussate and project to?

A

Decussate in the spinal cord

Project through the brainstem to the thalamus (NOT synapsing at the dorsal column nuclei)

31
Q

Where do touch receptors project to?

A

Neospinothalamic tract which ends in the VPL nuclei of the thalamus

32
Q

What does the paleospinothalamic tract do?

A

Register the degree of pain and its character

33
Q

What is the paleospinothalamic mediated by?

A

Cingulate and insula cortex of the limbic system

34
Q

Where is liver and gallbladder pain felt?

A

Shoulder

35
Q

Where are the lesions for brown-sequard, a stroke and diabetic neuropathy?

A

Brown-sequard - Spinal lesion
Stroke - Cortical lesion
Diabetic neuropathy - PNS lesion

36
Q

What do the posterior and anterior spinocerebellar pathways do?

A

Convey proprioceptive information to the cerebellum to regulate balance
a. what are the tests for the spinocerebellar tract?
- Motor coordination
Heel to shin
Pigeon step
Supination/Pronation
Finger to nose test

37
Q

Does the spinocerebellar tract cross?

A

NO

38
Q

What is the input for the spinocerebellar tract?

A

Joint receptors and muscle spindles

Brain and Behaviour (20 decks)

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