Somatosensation 2 Flashcards by Misha Gandhi

Congenital insentivity to pain - ex

No nociceptors
= bad, get injured, do not know when to stop,
Extremities more susceptible
Die young,missing limbs

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Congenital insentivity to pain - gene

Hsn2 gene
Genes associated with congenital insensivity to pain = affect all small diameter unmyelinated fibres = which are important for controlling autonomic activities too = heart rate, skin temp so autonomic deficits then

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Describe limbic touch

Caress, feather, pleasnet
Small unmyelinated fibres, - C fibres, sensitive to low intensity mechanical stimulation
Sensation associated with emotional response, like opposite of pain tho
Intact in ppl who cannot feel pain

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Describe loss of tactile sensitivity

Cannot perceive pain = only at chance level

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Describe thermoalgesic sensivity preserved

Similar to control
Smaller diameter fibres for pain and temp intact

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Describe limbic touch preserved

Tactile receptors encodes - unmyelinated fibres
Sensation and another receptor separate = encode pleasantness
Rates as pleasure

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Describe 1st relay

Dorsal horn spinal cord
Tactile fibres —> mostly to lamina 1 and 2

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Describe where info goes

Touch= crosses over at level fo brain stem temp and pain = info crosses over in spinal cord then ascends to brain

Lateral spinothalamic tract = neuron connects spine to thalamus
Ventral posterior nucleus of thalamus —>
Cerebral cortex

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Name spinal projection neurons

2nd neuron in spinal cord where nociception relayed =
Specific to nociception
Wide dynamic range

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Describe spinal projections neurons specific to nociception

Only respond to nociception
If noxious stimulus

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Describe spinal projections neurons Wide dynamic range

Encodes intensity of stimulus from non noxious to noxious = gradually increases firing as a function of intensity of stimulus

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Where is pain intensity theory most correct

In spinal cord =
Mix specificity and intensity

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Where is pain specificty theory most correct

In periphery

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Describe pattern theory

Pattern of activity across large population neurons
Not specific celll but pattern across large pop

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Describe gate control theory - gen

Melzack
Stroke pain in. Body = reduces it
Tactile A fibres and nociceptive C fibres —> inhibitory interneuron in dorsal horn layer 2
Then all synapse on spinal transmission neuron in dorsal horn spinal cord —> brain
Like when hammer bangs thumb

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Gate control theory = only C fibres activated

T neuron activated
At baseline = substancia gelatinosa (sg) neuron always inhibits t neruon
But sg inhibited by c = t neruon activation
End result = more activation = + -

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Gate control theory = only a fibres activated

T neruon activated
At baseline, sg neruon always inhibits t neruon
But sg neuron activated by a fibre = increases inhibition coming from sg neuron = more initiation (+ - -)

Describe transmission neurons and relationship to nociceptive c and tactile a fibres

Transmission neuron more activated by C fibres nociceptive
Than by a fibres - tactile

Describe when fibres c and a activated at Same time = gate control theory

C and a fibres activate t neruon
Sg inihibtor interneuron = activated and deactivated by a and C fibres = remains at baseline
At baseline sg neuron inhibits t neyron
T transmission neyron = less activated when a and C fibres activated at sametime than when just c
T neuron more activated than when just A alone = ++ - -
Brain can control circuit

What type of spinal projection neurons associated with gate control Theory

Wide dynamic range neurons
In between sensation - need to receive info from both c and a fibres
= activity combo across fibres

Describe tens unit

Transcutaneous electrical nerve stimulation = tens
Low electrical intensity current to body part that hurts = a fibers can habituate

Mechanism of action of opioids = pre synaptic neuron

Activation of mu opioid receptors prevents calcium from entering synaptic terminal = Prevent release nt

Mechanism of action of opioids = post synaptic neuron

Activation of mu opioid receptors results in more potassium leaving neuron = hyperpolarizes membrane and makes it difficult to depoalrize

Mechanism of action of opioids = result

Nocicpetive signal blocked in spinal cord - affects cns

Describe placebo Analgesia exp

In part associated with endogenous opioids Block blood until hurts too much Give treatments - placebo Used naloxone = antagonist to opioids, blocks mu receptors = reverse placebo analgesia Note = no effect of naloxone alone = placebo analgesia mediated by rerelease of endogenous opioids = if block opioids= blocks effects

Describe referred pain

To skin Ex = heart attack = overactive visceral - heart = can also activate skin receptor Nocicpetive info from heart and arm dermatome enter at same place Nociceptive system bad at detecting location of pain if inside body/organ = bc useless to know viscera pain = bc cannot fix on own, not as clear as sensory info typically

Describe spinotahalmic vs dorsal column pathway

Spinothalamic = crosses over immediately Dorsal Column= crosses over in brain stem - like touch

Describe brown sequard syndrome

Lesion t4 right side = tactile loss on same side,- touch But loss of temp and pain on contra lateral side - bc crosses over

Describe descending pain modulation

Brain modulates transmission of nocicpetive info to brain Helps so pain will stop eventually Brain —> dorsal horn spinal cord, brain stem modulates

Describe conditioned pain modulation exp - ice bucket

Test pain threshold on right hand - before and after put left hand in cold water = Pain inhibits pain, pain activates descending mdoaultion - then body affected so reduces pain = increases pain trheshold in body, person less sensitive to pain after other hand in ice water

Describe conditioned pain modulation exp - describe fibromyalgia

Chronic pain disorder Widespread musculoskeletal pain - fatigue, cognitive issue sleep issues Conditions involves icnreasesd sensitivity to pain, wide spread tenderness, heightened resposivness of nervous system Cayuse unknown, thought to be about abnormal pain processing within cns = descending modulatory system bad

Describe conditioned pain modulation exp - describe submerge arm in cold water healthy ppl

2 conditions = submerged in cold water gradually Or = take out hand from water (should activated many receptors = lots of descending modulation so by time get to fibers = more inhibition of pain) Results = less pain when start with full arm

Describe conditioned pain modulation exp - describe submerge arm in cold water fibromyalgia ppl

Phenomenon reversed = Lacking descending inhibition

Describe nociceptive flexion reflex = effects of emotions on pain

Withdrawal reflex = involuntary spinal reflex triggered by nocicpcetive stimuli - heat, mechanical pressure Involves rapid contraction of flexor muscle= withdraw limbs and extension in contralteral limb = to maintain balance and stability (cross extension reflex) Widely used in pain rescreach - as objective measuer of spinal nocicpetive processing and pain sensitivity Spirally mediated reflex - so anything affected transmission could affect transmission of nociception

Describe effects of emotions on pain = exp set up

Diff pics And measure reflex/pain

Describe effects of emotions on pain = types of images

Neutral pics, happy, erotic (works very well), unpleasnet pics

Describe effects of emotions on pain = exp results of types of images

Less pain if pleasant More pain if unpelsaemnt And also for reflex = amplitude nociceptive recpetor = reflex stronger when looking at unpelsment pic

Describe effects of emotions on pain = exp set up Music

Listen to music while mesureing reflex and pain

Describe effects of emotions on pain = exp results of music

Music can influence pain at spinal level Most pain = unpleasnet music, then less pain for pleasant stimulating, least pain for pleasant relaxing Same effect for reflex strength

Pain sensitivity

Pain sensitivity = could be associated with absence of inhibition of pain= why ppl sensitive