Nociception

Question 1

pain?

Answer 1

unpleasant sensory and emotional experience with actual or potential tissue damage

Question 2

nociception

Answer 2

neural process if encoding noxious stimuli

Question 3

noxious stimulus

Answer 3

potentially or actually damaging body tissue

Question 4

nociceptive pain

Answer 4

type of pain caused by damage to body tissue

Question 5

t/f

Noxious stimuli increases alertness and autonomic functions

Answer 5

true

Question 6

pain threshold

Answer 6

minimal intensity a stimulus is considered painful

Question 7

pain tolerance

Answer 7

the level of pain an individual is willing to tolerate or endure

Question 8

analgesia

Answer 8

absence of pain

Question 9

hypoalgesia

Answer 9

decrease sensitivity to painful stimuli or tolerance

Question 10

hyperesthesia

Answer 10

increase sensitivity to a normal stimulus

Question 11

T/F

pain threshold can vary greatly among individuals of a species

Answer 11

false

(pain tolerance varies tho)

Question 12

acute/adaptive pain?

Answer 12

from tissue damage for protective function

Question 13

acute/adaptive pain increases NS activity?

Answer 13

YES

Question 14

the more insulation and the thicker myelin lead to

Answer 14

better and faster transmission

Question 15

3 types of noxious stimuli?

Answer 15

1. mechanoreceptors
2. thermoreceptors
3. chemoreceptors

Question 16

two nocicepter nerve fibers

Answer 16

C fiber
A-delta fiber

Question 17

Which fiber type carries slow, dull pain?

Answer 17

C fibers

Question 18

Which fiber type carries fast, sharp pain?

Answer 18

A-delta fibers

Question 19

is c fiber myelinated?

Answer 19

No

Question 20

is a-delta myelinated?

Answer 20

Yes

Question 21

Which fiber is larger in diameter — A-delta or C?

Answer 21

A-delta fibers

Question 22

Which fibers have faster conduction velocity?

Answer 22

A-delta > C fibers

Question 23

Are nociceptors low or high threshold receptors?

Answer 23

High threshold / low sensitivity

Question 24

Which fiber is more selective for sharp, well-localized pain?

Answer 24

A-delta fibers

Question 25

Why are C fibers slower?

Answer 25

thin and unmyelinated

Question 26

Which fibers are less susceptible to electrical stimulation?

Answer 26

thin fibers - c fibers

Question 27

Where are A-delta and C fibers found?

Answer 27

Skin, muscle, joints, meninges, viscera (highest in skin → lowest in viscera)

Question 28

Which structures have the highest concentration of C fibers?

Answer 28

Visceral structures

Question 29

Which tissues have high concentrations of BOTH A-delta and C fibers?

Answer 29

skin

Question 30

Does the brain contain nociceptors?

Answer 30

No

Question 31

What fibers carry first pain?

Answer 31

a-delta fibers

Question 32

type of sensation is first pain?

Answer 32

Immediate, fast, sharp, well-localized pain

Question 33

What fibers carry second pain?

Answer 33

C fibers

Question 34

What type of sensation is second pain?

Answer 34

Delayed, slow, dull, aching pain

Question 35

Where are first-order pain neurons located?

Answer 35

peripheral nerves innervating body regions (dermatomes, viscera)

Question 36

first-order nociceptive neurons described as bidirectional?

Answer 36

Yes! conduct signals both centrally and peripherally

Question 37

Where do first-order pain neurons synapse with second-order neurons?

Answer 37

Dorsal horn of the spinal cord

Question 38

function of second-order sensory neurons?

Answer 38

cells of origin of ascending spinal sensory tracts

Question 39

Where are second-order neurons located?

Answer 39

Dorsal horn of the spinal cord

Question 40

What do second-order neurons do after receiving pain input?

Answer 40

cross (decussate) and ascend to higher centers like the thalamus

Question 41

5 steps of pain pathway

Answer 41

1. Transduction 2. Transmission 3. Primary/segmental modulation 4. Projection 5. Supra-segmental modulation

Question 42

transduction in the pain pathway?

Answer 42

noxious stimuli → electrical nociceptive impulses

Question 43

What receptor type detects mechanical pain

Answer 43

Mechanoreceptors

Question 44

How do mechanical nociceptors activate?

Answer 44

Stretch/bending opens mechanically-gated Na⁺/Ca²⁺ channels → depolarization

Question 45

What receptor type detects thermal pain (e.g., burn)?

Answer 45

Thermoreceptors

Question 46

What triggers thermal nociceptors?

Answer 46

Heat-sensitive ion channels open → depolarization → burning pain

Question 47

What detects chemical pain (e.g., during exercise)?

Answer 47

Chemoreceptors (acid-sensitive ion channels)

Question 48

Where does nociceptive transmission end up in the spinal cord?

Answer 48

dorsal horn

Question 49

What is the primary excitatory neurotransmitter released by nociceptors?

Answer 49

glutamate

Question 50

What receptor does glutamate bind for normal, protective pain transmission?

Answer 50

AMPA receptors on the dorsal horn neuron

Question 51

What produces central sensitization (increased spinal cord excitability)?

Answer 51

Glutamate binding NMDA receptors, and Substance P binding NK1 receptors.

Question 52

What is primary/segmental modulation?

Answer 52

Local spinal cord modulation of pain signals before projection (inhibitory or excitatory).

Question 53

What is projection in the pain pathway?

Answer 53

dorsal horn → ascending spinal tracts → brain

Question 54

Which neurons carry projected pain signals up the spinal cord?

Answer 54

Second-order neurons

Question 55

supra-segmental modulation?

Answer 55

Pain perception processed in the brain

Question 56

What does conscious pain perception involve?

Answer 56

Awareness linking pain with memory, emotions, and avoidance behaviors

Question 57

What does subconscious / autonomic perception involve?

Answer 57

Parasympathetic and sympathetic responses to pain

Question 58

Why don’t patients feel pain under general anesthesia?

Answer 58

conscious perception component is suppressed

Question 59

What natural analgesic substances does supra-segmental modulation produce?

Answer 59

endorphins

Question 60

What step of nociception is blocked by nerve blocks?

Answer 60

Action potential generation and propagation