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Sem 4 - Nervous System > Somatosensory System > Flashcards

Somatosensory System Flashcards

1
Q

What are the different types of sensation?

A

General sensation

Special sensation

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2
Q

What is general sensation?

A

Sensory information from all over the body

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3
Q

What is special sensation? What are some examples of special sensation?

A

Sensory information from special sense organs e.g. vision from eyes, hearing from ears, smell from nose

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4
Q

What are the types of general sensation?

A

Somatic

Visceral

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5
Q

What is somatic sensation?

A

Refers to sensory information from skin, muscles, bones and joints that a person is conscious of

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6
Q

What is visceral sensation?

A

Refers to sensory information from internal organs, glands and blood vessels that a person is unaware of

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7
Q

What are modalities?

A

Refers to the different types of sensation that a person can experience

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8
Q

What are some examples of modalities?

A

Temperature

Pain

Pressure

Vibration

Proprioception

Light touch

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9
Q

How are different modalities detected?

A

By different types of receptors

One type of receptor for each modality

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10
Q

How are receptors in the somatosensory system classified?

A

Based on the modality they detect

Based on how they adapt to stimuli

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11
Q

What are the different types of receptors based on how they adapt to stimuli?

A

Rapidly adapting

Slowly adapting

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12
Q

What are rapidly adapting receptors?

A

Initially generate high frequency action potentials

But then the frequency decreases

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13
Q

What are rapidly adapting receptors good at detecting?

A

Changes in stimuli rather than absolute levels

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14
Q

What is an example of a rapidly adapting receptor?

A

Cutaneous mechanoreceptors detecting pressure

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15
Q

What are slowly adapting receptors?

A

Generate action potentials with the same frequency

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16
Q

What is an example of a slowly adapting receptor?

A

Pain receptors

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17
Q

What is a primary sensory neurone?

A

Cell body located in the dorsal root ganglion

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18
Q

What do the axons of primary sensory neurones do?

A

One axon enters the dorsal horn of the grey matter of the spinal cord

One axon travels through the spinal nerve into the PNS

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19
Q

What is located at the end of the primary sensory neurone’s axon in the PNS?

A

Receptors

All of same type, detect same modality

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20
Q

What is a receptive field?

A

Refers to the region of body surface that a sensory neurone supplies

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21
Q

What carries sensory information from a receptive field?

A

The primary sensory neurone that supplies that receptive field

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22
Q

How do different receptive fields relate to each other?

A

There is often overlap between the receptive fields of different sensory neurones

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23
Q

What is an autonomous region?

A

Regions where there is no overlap between receptive fields

24
Q

What is acuity?

A

Refers to how precise sensation is

25
Q

How are receptive fields and acuity related to each other?

A

Acuity is inversely proportional to the size of the receptive field

26
Q

If a sensory neurone has a large receptive field, what is its relative acuity?

A

Low acuity

27
Q

If a sensory neurone has a small receptive field, what is its acuity?

A

High acuity

28
Q

What is a secondary sensory neurone?

A

Its cell body is located in the dorsal horn or the medulla

It decussates, meaning it crosses the midline to the contralateral side of the body

29
Q

What is a tertiary sensory neurone?

A

Its cell body is located in the thalamus

Projects to primary somatosensory cortex in the post-central gyrus of the parietal lobe

30
Q

What is somatotopy?

A

Refers to how adjacent parts of the body correspond to adjacent parts of the cortex

31
Q

How are sensory neurones organised in the spinal cord?

A

By dermatomes

32
Q

How are sensory neurones organised in the cortex?

A

Sensory homuncular pattern

By dermatomes converging together

33
Q

What are the two main sensory pathways?

A

Dorsal column-medial lemniscus pathway

Spinothalamic pathway

34
Q

Where is the dorsal column-medial lemniscus pathway located?

A

Dorsal funiculus

35
Q

What modalities does the dorsal column-medial lemniscus pathway carry?

A

Vibration

Proprioception

Light touch

36
Q

What forms the dorsal column part of dorsal column-medial lemniscus pathway?

A

Primary sensory neurone axons ascending up to the medulla

37
Q

How are primary sensory neurones in the dorsal column organised?

A

Primary sensory neurones from lower half of body are medial

Primary sensory neurones from upper half of body are lateral

38
Q

Where do primary sensory neurones synapse with secondary sensory neurones in the dorsal column-medial lemniscus pathway?

A

In the medulla

Primary sensory neurones from the lower half of the body in the gracile nucleus

Primary sensory neurones from the upper half of the body in the cuneate nucleus

39
Q

What forms the medial lemniscus part of the dorsal column-medial lemniscus pathway?

A

Secondary sensory neurones decussating and ascending up to the thalamus

40
Q

Where do secondary sensory neurones synapse with tertiary sensory neurones in the dorsal column-medial lemniscus pathway?

A

Thalamus

41
Q

How are tertiary sensory neurones organised in the dorsal column-medial lemniscus pathway?

A

Tertiary sensory neurones for the lower half of the body project medially

Tertiary sensory neurones for the upper half of the body project laterally

42
Q

Where is the spinothalamic pathway located?

A

In the lateral ventral funiculus

This overlies the ventral horn of the grey matter of the spinal cord

43
Q

What modalities does the spinothalamic pathway carry?

A

Temperature

Pain

Pressure

44
Q

Where does the primary sensory neurone synapse with the secondary sensory neurone in the spinothalamic pathway?

A

Dorsal horn of grey matter of spinal cord

45
Q

What does the secondary sensory neurone do in the spinothalamic pathway?

A

Decussates through ventral white commissure

Ascends up spinal cord to thalamus

46
Q

How are secondary sensory neurones organised in the spinothalamic pathway?

A

Secondary sensory neurones for the upper half of the body are medial

Secondary sensory neurones for the lower half of the body are lateral

47
Q

Where do secondary sensory neurones synapse with tertiary sensory neurones in the spinothalamic pathway?

A

Thalamus

48
Q

How are tertiary sensory neurones organised in the spinothalamic pathway?

A

Tertiary sensory neurones for upper half of body project laterally

Tertiary sensory neurones for lower half of body project medially

Cross over each other as they do so

49
Q

What is Brown-Sequard syndrome?

A

Destruction of one half of spinal cord segment

50
Q

What causes Brown-Sequard syndrome?

A

Trauma

Ischaemia

51
Q

What are the sensory abnormalities in Brown-Sequard syndrome? E.g. T10 level

A

Loss of all sensory modalities in ipsilateral T10 dermatome

Loss of vibration, proprioception and light touch in ipsilateral T11-S5 dermatomes

Loss of temperature, pain, pressure in contralateral T11-S5 dermatomes

52
Q

What are primary sensory neurones carrying pain stimuli called?

A

C fibres

53
Q

What are primary sensory neurones carrying pressure stimuli called?

A

A fibres

54
Q

How are A fibres and C fibres related to each other?

A

A fibres activate interneurones in the grey matter of the spinal cord

These interneurones inhibit secondary sensory neurones that synapse with C fibres

55
Q

What else can activate inhibitory interneurones in the grey matter of the spinal cord apart from A fibres?

A

Descending nerve fibres from the brain

56
Q

What can inhibit a painful sensation?

A

Pressure on the painful site, activates mechanoreceptors and A fibres supplying that site

Psychological inhibition

Sem 4 - Nervous System (25 decks)

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