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Brain and behaviour > Somatosensory cortex > Flashcards

Somatosensory cortex Flashcards

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1
Q

Where do sensory nerve fibres entering dorsal root synapse?

A

One of 6 layers (rexed laminae) or dorsal horn

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2
Q

Where do touch afferents synapse?

A

lamina III and IV`

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3
Q

Where do proprioceptors synapse?

A

lamina V and VI

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4
Q

Where do nociceptors synapse

A

lamina I and II

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5
Q

What do you call the cells in the dorsal horn

A

Second order afferents

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6
Q

Where do axons of second order afferents travel?

A

Cross spinal cord within 1 segment of cell body and project up contralateral spinal cord in spinothalamic tract

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7
Q

What are the 2 components of spinothalamic tract?

A

Older lateral (paleo) part and newer medial (neo) part

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8
Q

What forms of cutaneous sensation does spinothalamic tract transmit

A

Heavy pressure, crude touch, temp and pain

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9
Q

What 2 places do touch and proprioceptive nerve fibres synapse/ branch to?

A

Cells in dorsal horn

Dorsal funiculi

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10
Q

What are the dorsal funiculi

A

Large tracts of white matter in dorsal spinal cord

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11
Q

What side of the spinal cord do fibres of dorsal columns ascend?

A

Same side they enter

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12
Q

Are fibres in dorsal columns post synaptic

A

No- they are actual extensions of afferent fibres in peripheral nerves with cell bodies in dorsal root ganglia

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13
Q

Where does dorsal fasciculi project to

A

The dorsal column nuclei in the lower medulla

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14
Q

What are the fibres leaving the base of the cuneate and gracile nuclei called

A

The start of the medial lemniscus

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15
Q

Where do medial lemniscal fibres leaving dorsal column nuclei send their axons?

A

Across the midline as internal arcuate fibres, and ascend to the VPL nucleus of contralateral thalamus. VPL cells project to somatosensory cortex

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16
Q

Where are medial lemniscal fibres known as internal arcuate fibres

A

At the region they cross the midline- the lower closed medulla

17
Q

Where do cutaneous afferents from the face come from?

A

Contralateral trigeminal nucleus

18
Q

Where do fibres from the trigeminal nucleus terminate

A

In the ventro-postero-medial nucleus

19
Q

Where is the somatosensory cortex?

A

Runs medio-laterally just posterior to central sulcus

20
Q

In the sensory homunculus, where are legs and face relativelly?

A

Legs- medial

Face- lateral

21
Q

Why are the legs medial on the sensory homunculus?

A

Because the nerve fibres from the thalamus to the somatosensory cortex rotate 180 degrees

22
Q

What does the somatosensory cortex tell us?

A

Where something is on your body, its touch and temperature

23
Q

What types of areas occupy largest areas of map?

A

Areas with highest density of touch and proprioceptive receptors

24
Q

Why do we have 2 pathways to the somatosensory cortex?

A

Spinothalamic tract conveys crude touch

Dorsal columns conveys discriminate touch

25
Q

What does Rombergs test check?

A

Proprioception from muscles and joints

26
Q

What is sensory ataxia?

A

Inability to balance with eyes closed

27
Q

What are nocicepors and where are they found?

A

Receptors specific to tissue damage

Found at end of A delta and C nerve fibres

28
Q

What is the function of nociceptor activity

A

Protective- minimises injury

29
Q

How does inflammation promote pain?

A

Free nerve endings have TTX resistant sodium channels

Inflammation opens these channels leading to tonic depolarisation and nerve activity

30
Q

Where do nociceptor afferents end

A

Lamina I and II

31
Q

Where do cells from lamina I and II send their axons

A

across contralateral spinothalamic tract to form lateral part of spinothalamic tract

32
Q

What receptors does a painful stimulus stimulate?

A

Touch receptors and nociceptors

33
Q

Where do touch receptors project to?

A

Neospinothalamic which ends in VPL nuclei of thalamus

34
Q

Why is the paleospinothalamic tract poor at localising pain?

A

Receptive fields of fibres are very large

35
Q

What does paleospinothalamic tract register in terms of pain

A

Degree and chaacter

36
Q

What mediates paleospinothalamic detection of pain

A

Cingulate and insula cortex of the limbic system

Brain and behaviour (22 decks)

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