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Neurology > Structure and function of the somatosensory system > Flashcards

Structure and function of the somatosensory system Flashcards

1
Q

What is the function of the ascending tracts

A

Carry information from pain, thermal, tactile, muscle and joint receptors to the cerebral cortex (conscious centres) or the cerebellum and brain stem (unconscious centres)

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2
Q

What are the main tracts that conscious level information travels? (2)

A

Dorsal( posterior column

Anterolateral system tracts

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3
Q

What are the types of specialised endings of peripheral receptors

A

Unencapsulated/Free nerve endings
Modified/encapsulated endings
Proprioceptors

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4
Q

Give examples of peripheral receptors that have Unencapsulated/Free nerve endings

A

Merkels disk
Hair follicles
Nociceptors

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5
Q

Give examples of peripheral receptors that have Modified/encapsulated endings

A

Meisners corpuscles Pacinian corpuscles

Ruffini ending

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6
Q

Give examples of peripheral receptors that are Proprioceptors

A

Muscle spindles
Golgi tendon organs
Joint kinaesthetic receptors

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7
Q

What senses are detected by Proprioceptors

A

Stretch
pressure
pain

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8
Q

What senses are detected by peripheral receptors with Unencapsulated/Free nerve endings

A

Pain
Temperature
Pressure

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9
Q

What senses are detected by peripheral receptors with Modified/encapsulated endings

A 
pressure
touch
vibration
stretch
pain
proprioception
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10
Q

Name the main ascending tracts (4)

A

Dorsal column
Dorsal spinocerebellar
Ventral spinocerebellar
Spinothalamic/ anterolateral tract

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11
Q

Label the ascending tracks on a cross section of the spinal cord

A

https://i.pinimg.com/originals/52/a4/df/52a4df6ce9c0d681fe3fa728270a85ef.jpg

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12
Q

What is the Dorsal column split into

A

Gracile fasculus

Cuneate fasiculus

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13
Q

What are ascending tracks structurally

A

White matter axons or projections going out from the periphery up through the spinal cord to the brain stem cerebellum and thalamus

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14
Q

What sense information does the Dorsal column carry

A

Touch

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15
Q

What sense information does the Dorsal spinocerebellar carry

A

Proprioception

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16
Q

What sense information does the Ventral spinocerebellar carry

A

Proprioception

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17
Q

What sense information does the Spinothalamic/anterolateral tract carry?

A

Pain

Temperature

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18
Q

How is touch information travelled to the brain stem

A

Primary afferent neuron
Detects sensation from receptor (fine touch, vibration and proprioception)

Enters the spinal cord through the dorsal root
Cell bodies are in Dorsal Root Ganglion
ASCENDING TRACT
The main fibre remains ipsilateral (same side of the cord)
First order neurons Synapses to become second order neurons in the medulla oblongata of the brain stem

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19
Q

Where do axons come from in the cuneate fasciculus

A

Upper thoracic and cervical level

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20
Q

Where do axons come from in the gracile fasciculus

A

Sacral lumbar and lower thoracic

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21
Q

What happens to neurons at the brain stem

A

Second-order neurons form tracts that decussate in medulla as the internal arcuate fibres and ascend through brainstem as the medial lemniscus

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22
Q

How is touch information travelled to the brain stem

A

Primary afferent neuron
Detects sensation from receptor (fine touch, vibration and proprioception)

Enters the spinal cord through the dorsal root
Cell bodies are in Dorsal Root Ganglion
ASCENDING TRACT
The main fibre remains ipsilateral (same side of the cord)
Synapses on second order neuron in the medulla oblongata of the brain stem

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23
Q

Where do axons come from in the cuneate fasciculus

A

Upper thoracic and cervical level

24
Q

Where do axons come from in the gracile fasciculus

A

Sacral lumbar and lower thoracic

25
Q

What happens to neurons at the brain stem

A

Second-order neurons form tracts that decussate in medulla as the internal arcuate fibres and ascend through brainstem as the medial lemniscus

26
Q

Where do the first order neurons synapse into the medulla?

A

Gracile fasciculus in the gracile nucleus

Cuneate fasciculus in the cuneate nucleus

27
Q

What does the thalamus do?

A

Receive information via second-Order neurons
Integrates, modulates and relays information
Thalamic radiation projects to the Sensory cortex via
the internal capsule

28
Q

What happens to information that reaches the thalamus?

A

From the medial lemniscus synapses into the ventral posterior lateral nucleus. Third order neurons project to the primary/ somatosensory cortex( also known as ssensory motor cortex
Thalamic radiation projects to the Sensory cortex via
the internal capsule

29
Q

What is sensory decussation

A

Neurons cross over to the other side and become contralateral

30
Q

Where is the thalamus located ?

A

Located either side of the third ventricle

31
Q

What does the thalamus do?

A

Receive information via second-Order neurons
Integrates, modulates and relays information
Thalamic radiation projects to the Sensory cortex via
the internal capsule

32
Q

What is the Posterior Limb of Internal Capsule (Somato-Sensory Radiation)?

A

White matter tract that let the axons travel from the thalamus to the cortex

33
Q

What happens to information within the internal capsule

A

Differentiate into the right pathways so they travel to the right parts of the cerebral cortex

34
Q

What sense information do A delta fibres carry

A

fast sharp well- localised pain
Nociceptive specific
Thermal or mechanical

35
Q

What sense information do C- fibres carry

A

Dull Aching burning pain
Nociceptive specific
Polymodal

36
Q

Structure of C- fibres

A

Non-myelinated

37
Q

What sense information do A delta fibres carry

A

fast sharp well- localised pain

38
Q

What sense information do C- fibres carry

A

Dull Aching burning pain

39
Q

What are the anterolateral tracts/ spinothalamic tracts?

A

Lateral spinothalamic tract
Anterior spinothalamic tract
Spinoreticular tract — reticular formation — cortex

Spinocerebellar tract — cerebellar peduncles cerebellum
Spinotectal tract

40
Q

What sense information does Lateral spinothalamic tract carry?

A

Pain and temperature

41
Q

What sense information does anterior spinothalamic tract carry?

A

crude touch and pressure

42
Q

What does the spinotectal tract do?

A

orientates eyes and head towards stimulus

43
Q

Which of the anterolateral system are direct?

A

Lateral spinothalamic tract

Anterior spinothalamic tract

44
Q

Which of the anterolateral system are indirect?

A

Spinoreticular tract
Spinocerebellar tract
Spinotectal tract

45
Q

What happens to sensory information travelling in the anterolateral system

A

Axons from DRG enter and ascend/descend a few spinal cord levels before
synapsing in the substantia gelatinosa or at the same level
Second-order neurons can form the reflex arc OR immediately decussate at the anterolateral tract
Ascend in spinothalamic tract
Distinct tract alongside medial lemniscus
Synapses chiefly in the VPL of the thalamus
Directly from the spinal cord to the thalamus without synapsing at the brainstem

46
Q

How is sensory information from the face taken to the brain

A

Trigeminal nerve synapses onto second order neurons in the ipsilateral principal/sensory trigeminal nucleus
Axons decussate and project in the trigeminal lemniscus to the ventral posterior medial nucleus of the thalamus
Fibres project to the sensory cortex through the somatosensory radiation

47
Q

What happens to sensory information going along the spinoreticular tract?

A

Neurons from the dorsal horn
Decussate and pass up the spinal thalamic tract
Then send projection also into the reticular formation of the brain stem then projections tot he inta- median nucleus of thalamus

48
Q

What nerves supply the somatic sensation of the face?

A

Trigeminal nerves-mainly
Facial
Vagus
Gasopharyngeal

49
Q

How is sensory information from the face taken to the brain

A

Trigeminal nerve synapses onto second order neurons in the ipsilateral principal trigeminal nucleus
Axons decussate and project in the trigeminal lemniscus to the ventral posterior medial nucleus of the thalamus
Fibres project to the sensory cortex

50
Q

What makes up the trigeminal nerve nuclei

A

Principal sensory nucleus
Spinal nucleus
Mesencephalic nucleus
Motor nucleus

51
Q

What sense information does Principal sensory nucleus carry

A

Touch
pressure
conscious
Proprioception

52
Q

How is modulating pain regulated? (ascending)

A

Touch or proprioceptive afferents in the vicinity of the pain afferents
Activating touch receptors give off another branch which has a inhibitory neuron which inhibit transmission of that pain information up through the spinal thalamic pathway

53
Q

What sense information does Mesencephalic nucleus carry

A

Non-conscious proprioceptive information

54
Q

What sense information does Motor nucleus carry

A

Innervates muscles of mastication

55
Q

How is modulating pain regulated?

A

Touch or proprioceptive afferents in the vicinity of the pain afferents
Activating touch receptors

56
Q

How is modulating pain regulated? (descending)

A

Neurons from periventricular and periaqueductal grey matter project to the Raphe Nuclei reticular formation
Medullary neurons project to dorsal horns
Inhibition of pain
Depress activity of nociceptive neurons

57
Q

What does reticular formation do?

A

More alert of pain

Neurology (14 decks)

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