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Fundamentals of neuroscience > Nociceptions & somatosensation (systems) > Flashcards

Nociceptions & somatosensation (systems) Flashcards

1
Q

What is pain?

A

An unpleasant sensroy & emotional experience associated with actual or potential tissue damage

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2
Q

What are the 3 branches of pain?

A
  • Acute
  • Subchronic
  • Chronic or clincal
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3
Q

Acute pain:

  • Duration
  • Characteristics
  • Adaptive?
A
  • Duration = seconds
  • Characteristics = e.g. contact w a hot surface
  • Adaptive? = high - prevents or reduces damage
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4
Q

Subchronic pain

  • Duration
  • Characteristics
  • Adaptive?
A
  • Duration = hours to days
  • Characteristics = resolves on recovery e.g. inflamed wound
  • Adaptive? = protective
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5
Q

Chronic or clinical:

  • Duration
  • Characteristics
  • Adaptive?
A
  • Duration = months to years
  • Characteristics = exceeds resolution of damage - oftern profound psychological components
  • Adaptive? = none - maladaptive
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6
Q

What are the 4 types of pain?

A
  • Hyperalgesia
  • Causalgia
  • Allodynia
  • Dysaesthesia
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7
Q

What is hyperalgesia?

A

An enhanced perception of pain in response to noxious stimuli

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8
Q

What is causalgia?

A

A chronic burning pain that persists in the absence of an obvious noxious stimulus

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9
Q

What is allodynia?

A

Abnormal painful responses to innocuous or tactile stimuli that do not usually cause pain

(e.g. touching sunburned skin)

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10
Q

What is dysaethesia?

A

Unpleasant abnormal sensations

(e.g. pins and needles)

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11
Q

Why is it important that we feel pain?

A

Important to protect ourselves from stimuli that will harm us

People who suffer from genetic pain disorders can end up with serious injuries as their body does not know when to stop

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12
Q

What gene mutation causes genetic pain disorders & why?

A

The gene SCN9A (sodium channel protein type 9 subunit alpha)

It codes for the alpha subunit of NaV1.7 channels = associated w a spectrum of pain disorders

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13
Q

How can genetic pain disorders differ from one another?

A

Slightly different mutation of the same alpha subunit can cause a different pain disorder:

  • PEPD effects the Na+ channels but causes the opposite effect to other disorders = heightenes pain response in the eyes and rectum
  • Other ones affect feet & hands
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14
Q

What sort of receptors do primary afferent fibres have?

A
  • Mechanosensitive = low threshold
  • Also have nociceptors = high threshold reponse
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15
Q

What are DCRASIC channels & ASIC activated by?

A

Can be activated by blunt force trauma

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16
Q

What is TRPM8 activated by?

A

By cold

17
Q

What response do ion channels have to burning?

A

Allow an influx of sodium ions into the channel as a response to burning

18
Q

What can nociceptors detect?

A

Changes in pH

The channels are not very specific to one type of stimulus

19
Q

Where do pain reflexes miss out?

A

They don’t travel to the brain

Makes the response much faster

20
Q

What are the 3 types of primary afferent fibres?

A
  • Abeta fibres
  • Adelta fibres
  • C fibres

(These are classified by axon diameter)

21
Q

What are Abeta fibres like?

A

They are larger & usually myelinated so transmit APs very fast

30-70m/s

22
Q

What are Adelta fibres like?

A

Can be involved in touch perception & sometimes in pain too

Smaller but also myelinated, will send APs quickly to the spinal cord

2-10 m/s

23
Q

What are C fibres like?

A

Are nociceptors

Very small & unmyelinated - much slower response

1 m/s

24
Q

Where do sensory afferent nerve fibres project to?

A

The spinal cord

25
Q

What theory did Melzak & Wall, 1965 come up with?

A

The Substantia Gelatinosa & the Gate Theory of Pain

26
Q

What does the substantia gelatinosa contain?

A

Inhibitory interneurones - these have a gate keeper function

27
Q

Why do we rub an area when we hurt it?

A

Rub the area to modulate the amt of pain signals reaching the brain by doing this

Dampens the signal

28
Q

Why does rubbing an area when we hurt it help to reduce the pain we feel?

A
  • Pain signals are sent to sc, glutamate etc are relased on the secondary neurone to trigger a response
  • When rubbing the area - touch receptors around this are activated –> touch receptors are mainly Abeta = signals are sent faster than C fibres
  • So touch receptors synapse w an area close to C fibres & activate the inter neurons which the C fibres try to inhibit so the pain signal can be sent to the brain –> by rubbing around the area we dampen the signal that goes to the brain
29
Q

Where do most signals we recieve synapse at first and where do they move onto?

A

The thalamus

They move on from there to the primary somatosensory cortex

30
Q

What is the role of the somatosensory cortex?

A

This is the area that maps our body in the brain based on the size & sensisivity of the body area

More sensitive = larger area

31
Q

What do ascending fibres do?

A

Connect brainstem & midbrain

32
Q

What does the anterior cingulate cortex do?

A

Very important in concious perception

e.g. we can pretend not to feel the pain, this is shutting this area off

33
Q

What are the descending pain pathways for?

A

Send signals from the brain to the SC & other parts of the body to control movement & regulate sensory input

34
Q

Where do ascending nociceptice nerves transmit signals to?

A

Not only to the higher centres in the brain, but also make connections to the brainstem & midbrain

e.g. the periaqueductal grey matter (PAG) & nucleus raphe magnus (NRM)

35
Q

Where do the PAG & NRM return efferent signals to?

A

Return them downwards to various levels of the spinal cord, where, with help of inhibitory interneurones they produce a diffuse inhibition

36
Q

Summarise the Central Gate Control of Pain:

A
  • PAG & NRM = important areas
  • Primary afferent fibres innovate skin, sent up the spinal cord, switches to the other side & then ascends up the spinal cord
  • Some of these synapse in NRM or PAG but most synapse in the thalamus
37
Q

Finish from descending inhibitory controls

A

:)

Fundamentals of neuroscience (38 decks)

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