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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
What happens to neurons at the brain stem
Second-order neurons form tracts that decussate in medulla as the internal arcuate fibres and ascend through brainstem as the medial lemniscus
26
Where do the first order neurons synapse into the medulla?
Gracile fasciculus in the gracile nucleus Cuneate fasciculus in the cuneate nucleus
27
What does the thalamus do?
Receive information via second-Order neurons Integrates, modulates and relays information Thalamic radiation projects to the Sensory cortex via the internal capsule
28
What happens to information that reaches the thalamus?
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
What is sensory decussation
Neurons cross over to the other side and become contralateral
30
Where is the thalamus located ?
Located either side of the third ventricle
31
What does the thalamus do?
Receive information via second-Order neurons Integrates, modulates and relays information Thalamic radiation projects to the Sensory cortex via the internal capsule
32
What is the Posterior Limb of Internal Capsule (Somato-Sensory Radiation)?
White matter tract that let the axons travel from the thalamus to the cortex
33
What happens to information within the internal capsule
Differentiate into the right pathways so they travel to the right parts of the cerebral cortex
34
What sense information do A delta fibres carry
fast sharp well- localised pain Nociceptive specific Thermal or mechanical
35
What sense information do C- fibres carry
Dull Aching burning pain Nociceptive specific Polymodal
36
Structure of C- fibres
Non-myelinated
37
What sense information do A delta fibres carry
fast sharp well- localised pain
38
What sense information do C- fibres carry
Dull Aching burning pain
39
What are the anterolateral tracts/ spinothalamic tracts?
Lateral spinothalamic tract Anterior spinothalamic tract Spinoreticular tract — reticular formation — cortex Spinocerebellar tract — cerebellar peduncles cerebellum Spinotectal tract
40
What sense information does Lateral spinothalamic tract carry?
Pain and temperature
41
What sense information does anterior spinothalamic tract carry?
crude touch and pressure
42
What does the spinotectal tract do?
orientates eyes and head towards stimulus
43
Which of the anterolateral system are direct?
Lateral spinothalamic tract | Anterior spinothalamic tract
44
Which of the anterolateral system are indirect?
Spinoreticular tract Spinocerebellar tract Spinotectal tract
45
What happens to sensory information travelling in the anterolateral system
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
How is sensory information from the face taken to the brain
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
What happens to sensory information going along the spinoreticular tract?
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
What nerves supply the somatic sensation of the face?
Trigeminal nerves-mainly Facial Vagus Gasopharyngeal
49
How is sensory information from the face taken to the brain
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
What makes up the trigeminal nerve nuclei
Principal sensory nucleus Spinal nucleus Mesencephalic nucleus Motor nucleus
51
What sense information does Principal sensory nucleus carry
Touch pressure conscious Proprioception
52
How is modulating pain regulated? (ascending)
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
What sense information does Mesencephalic nucleus carry
Non-conscious proprioceptive information
54
What sense information does Motor nucleus carry
Innervates muscles of mastication
55
How is modulating pain regulated?
Touch or proprioceptive afferents in the vicinity of the pain afferents Activating touch receptors
56
How is modulating pain regulated? (descending)
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
What does reticular formation do?
More alert of pain

Neurology (14 decks)

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