Lecture 25 - Pleasure and Pain I

Question 1

Aspects of the pain experience
1)
2)
3)

Answer 1

1) Pain is always subjective
2) It is an experience
3) Relationship between pain and tissue damage is variable

Question 2

Way that touch and joint sense are projected to the brain
1)
2)

Answer 2

1) Receptors in skin project to dorsal column nuclei.

2) Dorsal column nuclei project to the thalamus via the Medial lemniscus

Question 3

Way that nociceptive signals project to the brain
1)
2)

Answer 3

1) Receptors in the skin project to neurons in the dorsal horn
2) Receptors in the dorsal horn project to thalamus, via the spinothalamic tract

Question 4

Example of nociceptors that project to the dorsal column

Answer 4

GIT nociceptors

Question 5

Cutaneous mechanoreceptors
1)
2)
3)
4)
5)

Answer 5

1) Hair follicles
2) Meissner corpuscle
3) Pacinian corpuscle
4) Merkel cell-neurite complex
5) Ruffini corpuscle

Question 6

Skin stimulus detected by Meissner corpuscle

Answer 6

Dynamic deformation. Objects slipping over skin.

Question 7

Skin stimulus detected by Pacinian corpuscle

Answer 7

Vibration

Question 8

Skin stimulus detected by Merkel cell-neurite complex

Answer 8

Indentation depth. For fine tactile discrimination.

Question 9

Skin stimulus detected by Ruffini corpuscle

Answer 9

Stretch.

Question 10

Two types of C-fibre mechanoreceptors

Answer 10

1) LTM, responsible for pleasant contact.

2) Polymodal nociceptor (with Adelta fibres)

Question 11

Example of a transducer in polymodal nociceptors

Answer 11

TRPV1

Question 12

TRPV1

Answer 12

A cation channel (Ca2+, Na+) in Adelta and C-fibres (nociceptors)

Question 13

Four functional types of nociceptors

Answer 13

1) Thermal (Adelta fibre)
2) Mechanical (Adelta fibre)
3) Polymodal (C-fibre)
4) Silent (C-fibre)

Question 14

Things that polymodal C-type fibres can detect
1)
2)
3)
4)

Answer 14

1) Noxious heat
2) Noxious cold
3) Peptidergic receptors (noxious peptides)
4) Nonpeptidergic

Question 15

Ion channel types in nociceptive neurons 
1)
2)
3)
4)
5)

Answer 15

1) Transient Receptor Potential channels (EG: TRPV1)
2) Voltage-gated Na+ channels
3) Hyperpolarisation-activated cation channels
4) K+ channels
5) Voltage-gated Ca2+ channels

Question 16

Functional difference between Adelta and C fibres

Answer 16

Adelta are larger, myelinated, faster conducting.

C-fibres are smaller, unmyelinated, slower conducting

Question 17

Silent nociceptors

Answer 17

C-fibres.

Not active in normal tissues. Activated when a tissue is damaged.

Question 18

Nociceptors in hairy skin

Answer 18

Adelta, C

Question 19

Nociceptors in glabrous skin

Answer 19

Only C-fibres

Question 20

Pain that Adelta are responsible for

Answer 20

Sharp pain

Question 21

Pain that C-fibres are responsible for

Answer 21

Slow, burning pain

Question 22

Differential projection of Adelta and C-fibres into the spinothalamic tract
1)
2)

Answer 22

1) C-fibres project to superficial layers (layers I and II)

2) Adelta project to deeper layers (IV, V)

Question 23

Proportion of neurons in the dorsal horn that project to the brain

Answer 23

5-10%

Question 24

Evidence that nociceptor activation doesn’t have to result in emotional response to pain

Answer 24

Reflex pathways of the dorsal horn

Question 25

What can lead to referred pain?

Answer 25

Two nociceptive inputs converging on the one spinal circuit

Question 26

Primary hyperalgesia

Answer 26

Tissue is damaged, leading to release of factors (EG: prostaglandin, bradykinin from mast cells).
This leads to nociceptors being easier to depolarise.

Question 27

Allodynia

Answer 27

Sensation of pain from light touch

Question 28

Difference between primary and secondary hyperalgesia

Answer 28

Primary occurs in the tissues that were damaged.

Secondary occurs in undamaged tissues surrounding damaged tissues

Question 29

Area responsible for sensory aspect of pain

Answer 29

Projections to primary somatosensory cortex

Question 30

What correlates with phantom limb pain?

Answer 30

Functional remodelling in brain of somatosensory cortex (detected with fMRI)

Question 31

Non-somatosensory parts of brain that are activated in nociception

Answer 31

Prefrontal cortex, anterior cortex, singulate cortex.

Question 32

Example of pain not correlating with tissue damage

Answer 32

Hot/cold grill results in sensation of burning heat

Question 33

Affective-motivational pain pathway

Answer 33

1) Anterolateral system
2) Middle thalamic nuclei
3) Insular cortex and anterior singulate gyrus

Question 34

Sensory-discriminative pain pathway
1)
2)
3)

Answer 34

1) Anterolateral system
2) Ventral posterior nucleus
3) Somatosensory cortex (S1, S2)

Question 35

Outcome of the complex network of centres stimulated by nociception in the brain.

Answer 35

Experience of pain is modulated by emotional factors
Positive emotion reduces unpleasantness of pain
Lack of attention to pain reduces intensity of pain