05b: Somatosensation and Pain Flashcards
List various sensory receptor types, from deep to superficial
- Pacinian corpuscles
- Ruffini’s corpuscles
- Merkel’s disks
- Meissner’s corpuscles
- Free nerve endings
T/F: All classes of cutaneous sensation are represented among the free nerve endings.
True
Two-point discrimination smaller on (fingertips/back)
Fingertips
Central neurons, (like/unlike) receptors, use (X) mechanism for transmitting info about a stimulus intensity.
Like;
X = frequency coding
(Primary afferent fibers/central neurons) have complex receptive fields. Explain.
Central neurons;
Lateral inhibition (sharpens transmission of sensory messages)
Detailed topographical representation of (ipsi/contra)-lateral body forms within thalamus.
Contralateral
Cutaneous afferents are found within (X) regions of thalamus.
X = posterior
T/F: Pain is always subjective.
True
T/F: Pain is always unpleasant.
True
T/F:Pain is activity induced in nociceptor/nociceptive pathway by noxious stimulus.
False - pain is psych state
T/F: Noxious stimulus is defined as one that produces tissue damage.
True
List 3 classes of nociceptors.
- Mechanical
- Thermal
- Polymodal
Mechanical nociceptors respond to (X) stimuli and have (small/large) receptive fields.
X = crushing P
Large
Thermal nociceptors respond to (X) stimuli and have (small/large) receptive fields.
X = temperatures above 45C or below 15C
Large
Polymodal nociceptors respond to (X) stimuli and have (small/large) receptive fields.
X = both high threshold mechanical and thermal stimulation;
Large
(X) caused by (Y) provide(s) the principal stimulus for nociceptor activation.
X = chemicals; Y = release from damaged tissue (into extracellular fluid)
List some “pain related molecules”. Star those that sensitize all classes of nociceptors.
- Bradykinin
- Substance P
- Histamine
- K+
- Prostaglandins*
A noxious stimulus evokes release of (X) from (Y). Be specific.
X = Bradykinin Y = damaged tissue
List effect(s) of bradykinin.
- Excites nociceptor
- Increases prostaglandin production
- Dilates blood vessels
You step on a nail. In response to (excitatory/inhibitory) actions of (Y), the nociceptor terminal releases (X).
Excitatory;
X = bradykinin and prostaglandins;
Y = substance P
You step on a nail. Effect of Substance P, when released from (X).
X = nociceptor terminal
- Further sensitizes nerve terminal
- Increases blood vessel dilation
- Increases inflammatory response
T/F: Similar to other receptors, nociceptors adapt with frequent stimulation.
False - sensitize with frequent stimulation
Pain is subserved primarily by which peripheral nerve fiber types?
- A-delta
2. C
In terms of conduction velocity, A-delta are the most rapid of (X) fibers, but the slowest of the (Y) fibers.
X = pain; Y = A
A-delta fibers are distributed in (X) parts of body and carry information about (Y) stimuli.
X = skin and mucous membranes Y = mechanical and thermal
C fibers are distributed in (X) parts of body and carry information about (Y) stimuli.
X = deep tissues and skin Y = polymodal
T/F: C fibers outnumber A-delta fibers in the skin.
True
Sharp, stinging painful sensation carried by which type of pain fibers?
A-delta
Burning, unpleasant painful sensation carried by which type of pain fibers?
C fibers
A-delta fibers synapse in (X), on the dendrites of neurons with somata in Rexed’s Laminae (Y). This gives rise to (Z) tract.
X = substantia gelatinosa Y = 1 and 5 Z = neospinothalamic
Neospinothalamic tract terminates in (X). Then signal goes to (Y) cortex.
X = VPL thalamus; Y = somatosensory cortex
C fibers synapse in (X), on the dendrites of (Y), which send info to cells in Rexed’s Laminae (Z).
X = substantia gelatinosa Y = small, excitatory interneurons Z = 5-8
C-fibers use (X) as the NT at their synapse in substantia gelatinosa.
X = Substance P
Rexed Laminae (X) give rise to paleospinothalamic tract.
X = 6-8
Rexed Lamina 5 neurons, receiving input from (A-delta/C) pain fibers, contribute primarily to (X) tract.
C-fibers;
X = spinomesencephalic
T/F: Both neo and paleospinoathalmic tracts are somatotopically organized.
False - paleo is not
Paleospinothalamic tract terminates in (X). Then signal goes to (Y) cortex.
X = intralaminal nucleus of thalamus; Y = cingulate
Collaterals from (neo/paleo)spinothalamic tracts contribute to which ascending brainstem tracts?
Both;
- Spinomesencephalic
- Spinoreticular tract
Spinomesencephalic tract arises from neurons in lamina (X) and projects to (Y).
X = 1 and 5 Y = PAG
Spinoreticular tract arises from neurons in lamina (X) and projects to (Y) via (Z).
X = 6-8 Y = thalamus Z = reticular formation
WDR, aka (X), neurons are in lamina (Y). They’re termed this because of which characteristic?
X = wide dynamic range; Y = 5
Excited by multimodal/diverse inputs from A-beta, A-gamma, and C fibers
WDR neurons activate (X) via (Y) tract.
X = PAG; Y = spinomesencephalic
In addition to receiving pain info from WDR neurons, the (X) receives input from (Y), conveying info on emotional/physio responses to pain.
X = PAG Y = amygdala, hypothalamus, neocortical areas
PAG neurons normally (stimulate/inhibit) nucleus raphe magnus (NRM).
Inhibit
Enkephalin, released by (X), has (stimulatory/inhibitory) effect on (Y), thus activating (Z).
X = PAG neurons
Inhibitory;
Y = other PAG neurons
Z = NRM cells
Descending serotonergic (PAG/NRM) inputs (excite/inhibit) (X) interneurons in (brainstem/SC).
NRM;
Excite;
X = enkephalinergic
SC
Release of enkephalin in SC has which effect(s)?
Inhibits:
- Afferent pain fiber activity
- WDR activity
Ideal way to alleviate pain is to:
Treat underlying disease
Pharmacological treatment of pain is possible via:
- NSAIDS
2. Opioids
NSAIDS mechanism
Inhibit cyclooxygenase
Cyclooxygenase involved in which reaction?
Conversion of arachidonic acid to prostaglandin
Give examples of commonly used NSAIDS
- Ibuprofin
- Aspirin
- Acetaminophen
