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RR Y2 NEURO > Somatosensory System FINAL > Flashcards

Somatosensory System FINAL Flashcards

1
Q

Mechanoreceptors function

A

Detect touch and proprioception

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2
Q

Sensory neuron types fastest to slowest and uses of each

A

ABeta- Innoucuous mechanical stimulation
ADelta- Noxious mechanical and thermal stimulation
C fibres- Noxious mechanical, thermal and chemical stimulation

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3
Q

Features of ABeta,ADelta and Cfibres that affect its speed

A

ABeta- Largest diameter +myelinated
ADelta- smaller diameter +myelinated
C fibres - smallest diamater and not myelinated

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4
Q

Sensory Receptor:

A

Transducer that converts energy from environment into neuronal action potential

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5
Q

Receptors with Free endings

A

Nocioceptor and thermoceptors

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6
Q

Receptors with enclosed endings

A

Mechanoreceptors

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7
Q

Thermoreceptors are what type of fibres

Express what on their neurons

A

Adelta and C fibres

Express TRP -Transient Receptor Potential ion channels

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8
Q

Heat activated TRP

Cold activated TRP

A

TRP1,2,3,4

TRPM8, TRPA1

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9
Q

Mechanoreceptors are what sort of fibres

A

AB fibres

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10
Q

5 types of mechanoreceptors and functions

A

1) Meissner’s corpuscle
2) Merkel Cells
3) Pacinian Corpuscle
4) Ruffini endings
5) Hair follicle receptors

1) Meissner’s-Discrimnative touch
2) Merkel Cells-light and superficial pressure
3) Pacinian corpuscle-High frequency vibration
4) Ruffini endings-continous pressure/touch and stretch
5) Hair follicle receptors: light touch

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11
Q

Nociceptors are what fibres

A

Adelta and C fibres like thermoceptors

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12
Q

Stimulus threshold:

A

Point of intensity at which person can JUST detect the presence of a stimulus 50% of the time– absolute threshold

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13
Q

Stimulus Intensity

A

Increased stimulus strength and duration=increased neurotransmitter release=greater intensity
> encoded by how quickly neurons fire

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14
Q

Adaption: what are the 2 types

What is sensory adaption

A

1) Tonic receptors
2) Phasic Receptors

Change with time in responsiveness of a sensory receptor to a stimulus

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15
Q

Mechanism of tonic receptors

E.g of tonic receptor

A

1) Detect continuous stimulus strength
2) Fire quickly at point of stimulation and slow down after
3) Continue to transmit impulses to brain as long as stimulus is present
4) Keeps brain constantly informed

Merkel cell
–>Slowly adapt, allowing for superficial pressure and fine touch to be percieved

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16
Q

Mechanism of phasic receptors

E.g

A

1) Detect change in stimulus strength
2) Transmit impulse at start and end of stimulus

Pacinian Corpuscle

  • Sudden pressure excites receptor
  • Transmits signal again when pressure is released
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17
Q

Receptive fields

A

Region of skin which causes activation of a SINGLE sensory neuron when activated

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18
Q

Small receptive fields

A

Precise perception- allow for detection of fine detail over small area

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19
Q

Large receptive fields

A

Less precise, allow cell to detect changes over a wider area

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20
Q

Two point discrimnation

A

min distance at which 2 points are perceived as separate

->related to size of receptive fields

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21
Q

Where are the dermatomes C5, T4

A

c5- Clavicle, t4= nipple

22
Q

Where are cell bodies found in body and in the face

A

In body–dorsal root ganglia

In face- Trigeminal ganglia

23
Q

Info from upper and lower bodies received at what level of spine

A

Upper= Cervical

Lower=Lumbar

24
Q

Where are gracilis and cuneatus fasciulus located

A

In spinal cord

25
Q

Where are secondary (internal arcuate fibres) from and reach where

A

From gracilis and cuneatus in spinal cord to thalamus

26
Q

Secondary neurons cross over where and form

A

Cross over at medulla

Medial leminiscus tract

27
Q

Secondary neurons axons synapse on neurons in

A

Ventral nuclear group

28
Q

Tertiary neurons from where to where

A

Thalamus to primary motor cortex

29
Q

Somatosensory function from face: Enters brain at

Where do primary neurons synapse

A

Pons

Trigeminal nucleus

30
Q

2 main types of dorsal horn neurons

A

1) Projection neurons-Neurons with axons that project to brain
2) Interneurons- Neurons with axons that remain in spinal cord

31
Q

Lateral inhibition is

what is the purpose

How is it mediated

A

Difference between adjacent inputs is enhanced by lateral inhibtion

Prevents overlap of receptive field
Facilitates
-pinpoint accuracy in localisation
-enhanced sensory perecption

inhibitory interneurons with dorsal horn of of spinal cord

32
Q

Describe the ascending pathway of touch proprioception

A

1) Innocuous mechanical stimuli: -fine discriminatory touch or vibration
2) ABeta fibres enter via dorsal horn and enter ascending dorsal column pathways
3) Info from limbs travel ipsilaterally long respective dorsal column tracts (gracilis/cuneatus)
4) Fibres in gracile tract have their first synapse in the gracile nucleus –same for cuneatus
5) 1st order neurons terminate in medulla
6) 2nd order axons decussate in medulla at caudal medulla and form contralateral medial lemniscus tract
7) 2nd order neurons terminate in thalamus at ventral posterior lateral nucleus (VPL)
8) 3rd order neurons from VPL project to somatosensory cortex of post central gyrus of parietal cortex

33
Q

Describe the ascending pathway of pain, temperature and crude touch

A

1)Pain and temperature sensations ascend within Lateral spinothalamic tract

Crude touch ascends within the anterior spinothalamic tract

2)Primary afferent axons terminate upon entering spinal cord
Secondary neurons decussate immediately in spinal cord and form spinothalamic tract

3) Secondary neurons terminate in VPL of thalamus

34
Q

Dorsal column Vs Spinothalamic tracts

A

Dorsal column:

  • Light touch
  • Vibration
  • 2 point discriminiation

Spinothalamic tracts:

  • Pain
  • Temp
  • Crude/Coarse touch
35
Q

Meissner’s corpuscle type of fibre

A

Abeta

36
Q

Crude touch uses what fibre

A

Adelta

37
Q

Nociceptors

Are what types of fibres and each mediate

A

ADelta and Cfibres

ADelta
Sharp, Intense first pain

CFibres
Dull, aching or second pain

38
Q

Describe the 2 types of Adelta fibres of nociceptors

A

Type 1
-Noxious mechanical
Type 2
-Noxious heat

39
Q

Cfibres

A

Noxious thermal, mechanical and chemical stimulus

40
Q

Type of neurotransmitter released from sensory afferents in response to noxious stimuli

A

Glutamate –> Excitatory

41
Q

Pain pathway:

Sensory component through which tract?

A

Lateral spinothalamic tract

42
Q

Pain pathway:

Emotional component through which tract?

A

Spinoreticular tract

43
Q

What is the gate control theory

Common behaviour that shows this

A

Inhibition of primary afferent inputs before transmitted to brain through ascending pathways

Instinctive rubbing– stimulates ABeta which blocks C fibres of pain to brain

44
Q

Descending control pathways for pain can be inhibited by? potential

A

Strong emotions can inhibit pain
-Electrical analgesia Descend from somatosensory cortex
P

45
Q

Key area in descending control pathway

A

PAG- periaqueductal grey

46
Q

Nociceptive processing in dorsal horn can be affected by

A

Facilitation and inhibition

47
Q

Monoamines that inhibit activity in spinothalamic tract and function of efferent C fibres

A

Serotonin–facilitate pain

Noradrenaline –inhibit pain

48
Q

Nociceptive pain
e.g
Neuropathic pain:
e.g

Mixed

A

Noxious stimulation of a nociceptor (somatic or viscera)
e.g
Lesion/ disease or somatosensory system
e.g sciatica, diabetic, trauma

Ostearthritis

49
Q

Tissue damage results in release of

Result of release

A 
Neurotransmitters 
Peptides
Lipids
Protease
Cytokines
Chemines

Produce inflammation, initiate healing, make nociceptors more sensitive by modulating their excitability

50
Q

Peripheral sensitisation

Central Sensitisation

A

Reduce threshold to peripheral stimuli at site of injury

Reduce threshold to peripheral stimuli at an adjacent site to injury

  • Expansion of receptive field
  • Spontaneous pain
51
Q

Allodynia

A

Pain due to a stimulus that does not normally provoke pain

52
Q

Hyperalgesia

Primary
Secondary

A

Increased pain from stimulus that normally provokes pain
Primary- at site of stimulus
Secondary- around site of stimulus

RR Y2 NEURO (24 decks)

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