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sensory systems > somatosensory pathway and cortex > Flashcards

somatosensory pathway and cortex Flashcards

1
Q

wat are the two basic ascending pathways from neurons to cortex?

A

-one is specialised for pain and temperature
-one is specialised for touch and joint sense

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2
Q

which receptors are responsible for touch and joint sense?

A

low threshold mechanoreceptors

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3
Q

what did vesalius do?

A

described the complete anatomy of the human body as far as the eye can see it

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4
Q

spinal nerves

A

axons that innervate each of your somatosensory receptors coalesce into large bundles called nerves
Where they exit or ender the spinal nerve

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5
Q

what does each spinal nerve do?

A

innervate a particular area of the body

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6
Q

how many spinal nerves do humans have??

A

31 pairs

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7
Q

the spinal nerve splits into two sections near teh spinal cord, what are these?

A

the dorsal root and the ventral root

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8
Q

ventral root contains

A

motor neuron efferents

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9
Q

dorsal root contains

A

sensory afferents

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10
Q

dorsal root ganglion

A

cell bodies of primary sensory fibres
swelling in the spinal nerve

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11
Q

grey matter

A

where the cells bodies are predominantly located

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12
Q

white matter

A

heavy concentration of myelinated axons

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13
Q

morphology of dorsal horn

A

granular- cell bodies are small

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14
Q

morphology of ventral horn

A

cell bodies are large

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15
Q

hypothesis for different cell bodies sizes in ventral and dorsal horn?

A

hypothesised that these differences are likely to have important functional correlates
so they divided the grey matter up into different local regions depending on cell morphology

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16
Q

two divisions of the grey matter

A

dorsal horn and ventral horn

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17
Q

rexed’s laminae

A

split grey matter into 9 regions based on cell morphology

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18
Q

rexed’s laminae dorsal horn divisions

A

lam 1-6

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19
Q

rexed’s laminae transition zone laminae

A

lam 7

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20
Q

rexed’s laminae ventral horn laminae

A

lam 8 and 9

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21
Q

rexed’s laminae temp/ nociception laminae

A

lam 1-2 (and 5)

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22
Q

rexed’s laminae skin-touch laminae

A

lam 3-5

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23
Q

rexed’s laminae joint position laminae

A

lam 6

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24
Q

what fibre types synapse in the spinal cord

A

all fibre types

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25
Q

touch/ proprioception fibres synapse in the spinal cord and…

A

send direct collaterals to the brain

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26
Q

what are tracts/ columns?

A

Neurons in the spinal cord send their axons towards the brain, and these axons coalesce into nerve bundles called tracts/columns

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27
Q

which column does touch and proprioception information go through?

A

dorsal column

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28
Q

what can the dorsal column be split into?

A

gracile facile and cuneate fasicle

29
Q

gracile fascicle receive information from

A

the legs and lower trunk

30
Q

cuneate fascicle receives information from

A

the upper trunk and arms

31
Q

which column does the nociceptive and touch information run through?

A

the anterolateral columns
e.g., spinothalamic tract

32
Q

what pathway is the anterolateral column a part of?

A

the anterolateral pathway

33
Q

what pathway is the dorsal column a part of?

A

teh dorsal column medial lemniscus pathway

34
Q

what is the dorsal column pathway?

A

axons in the dorsal column terminate in the medulla oblongata

35
Q

what are the two constituent parts of the brainstem

A

medulla oblongata and pons

36
Q

what is the trigeminal nuclei sensitive to?

A

touch on the face

37
Q

what three nuclei do we have a complete representation

A

trigeminal nuclei
cuneate nuclei
gracile nuclei

38
Q

where do the trigeminal, cuneate and gracile nuclei project their axons to?

A

ribbon like structure: medial lemniscus

39
Q

what does the medial lemniscus do?

A

takes tactile stimulus to the thalamus

40
Q

two divisions of the thalamus involved in somatosensation

A

ventroposterior lateral nucleus (VPL)
ventroposterior medial nucleus (VPM)

41
Q

where do thalamic neurons project to?

A

the somatosensory cortex

42
Q

where is the somatosensory cortex located?

A

on the post central gyrus

43
Q

summary of the dorsal column medial lemniscus pathway

A

mechanoreceptors
dorsal root ganglion
dorsal columns
medial lemniscus
Ventroposterior lateral nucleus (VPL- thalamus)
primary somatosensory cortex

44
Q

supragranular cortical layers

A

layers 1-3

45
Q

granular cortical layers

A

4

46
Q

infragranular cortical layers

A

5-6

47
Q

cortical layer 4 projects to

A

cortical layer 2/3

48
Q

cortical layer 2/3 projects to

A

cortical layer 5/6
cortex

49
Q

cortical layer 5/6 projects to

A

subcortex

50
Q

where do axons from the somatosensory thalamus terminate?

A

cortical layer 4

51
Q

what did Brodmann do?

A

Brodmann noticed the layered staining pattern was different in different parts of the cerebral cortex
Noted these anatomical differences are have functional differences
Made brodmann’s map, based on cytoarchitecture

52
Q

how many areas are there in Brodmann’s map?

A

around 40

53
Q

how many Brodmann areas do the VPL and VPN project to?

A

about 4 areas
Area 1, 2 , 3a, 3b located in the postcentral gyrus

54
Q

DR wilder penfield

A

Operating on people to treat epilepsy
Localised location in the brain from which the epiliectiform activity originates, aimed to treat by removing this focus
Electrically stimulated different parts of the surface in conscious patients, could see where the epilepsy was coming form, and also parts of the brain that controlled important functions, such as speech
He also made important discoveries about how the cortex is organised

55
Q

what feeling was reported when parts of teh postcentral gyrus were stimulated?

A

typically reported a tingling sensation in some part of their body

56
Q

what was the resolution of penfield’s data?

A

only 1mm

57
Q

what was the resolution of penfield’s data?

A

only 1mm

58
Q

what type of map is the homunculus?

A

topographic map
somatotopic map

59
Q

method of electrophysiological recording on anesthetised animals

A

put in microelectrodes into different parts of the post central gyrus

Gently stimulate different parts of the body as you record response from the neuron

Receptive field of the neuron is the part of the body that field represents

60
Q

how did body maps produced by animal experiments relate to penfield’s data?

A

on a coarse scale, penfields data seemed very accurate as the same sequence was observed

61
Q

what did high resolution somatotopy reveal in the finger? what is this consistent with?

A

there is a second representation of the body in the postcentral gyrus
which coincides with brodmanns areas 3b and 1

62
Q

what did fMRI bold responses show?

A

fMRI data is consistent with Brodmanns map
humans have 4 maps of the body in postcentral gyrus, corresponding to the 4 brodmanns areas

63
Q

what did monkey electrophysiology studies show?

A

different parts of the body represented at different spatial resolutions (homunculus)

64
Q

magnification factor

A

area of teh cortex devoted to given body part by its skin area

65
Q

what are different magnification factors caused by?

A

Large differences in the number of neurons devoted to different parts of the body

66
Q

magnification factor of vibrissae

A

high

67
Q

behaviourally important parts of the body

A

lips for language
hands for object manipulation

68
Q

relationship between magnification of body parts and receptive field size

A

inverse relationship
small receptive field = large magnification

69
Q

discrimination threshold

A

determined by 2 point discrimination task
threshold is low where magnification factor is high and receptive fields are small

sensory systems (17 decks)

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