- Pain via direct nerve damage - Crush injury, amputation --> damages nerve

Week 4 - Pathophysiology of pain Flashcards by Lydia Rose

Is pain always from actual tissue damage?

No, can be potential damage or described in terms of damage

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List structures from most to least sensitive to a noxious

Periosteum and joint capsule
Subchondral bone, tendons, ligaments
Muscle and cortical bone
Synovium and articular cartilage

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“____” fractures produce little to no pain, while ____ fractures (tear away periosteum) are very painful

silent, aulvsions

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Nociceptive pain is…?

Pain via stimulation of nociceptors (pain sensors)

- Something causing the pain (burn, bruise, fracture)

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Neuropathic pain…?

Pain via direct nerve damage

- Crush injury, amputation –> damages nerve

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A nerve ending is the termination of a …?

nerve fibre in a peripheral structure

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Receptor nerve ending Meissners corpuscles ….?

skin, light touch

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Receptor nerve ending Pacinian corpuscles…?

skin, deep pressure

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Receptor nerve ending Merkels corpuscles…?

skin, deep pressure, hair follicle deflection

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Receptor nerve ending Ruffini corpuscles…?

in skin, sensitive to touch, tension: in joint capsule, sensitive to position

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Receptor nerve ending pain receptors…?

sensitive to extreme mechanical, thermal, or chemical energy. Respond to noxious stimuli

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Meissners corpuscles, Pacinian corpuscles, Merkels corpuscles are all _______

mechanoreceptors (different responses to different stimuli)

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Ruffini corpuscle’s are …?

mechanoreceptor/proprioceptor

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Krause end bulbs are…?

Thermoreceptor (cold)

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Pain receptor are…?

Nociceptors

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Afferent/sensory nerve fibres transmit impulses ____ the brain

towards

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Efferent/motor nerve fibres transmit impulses ____ the brain

(away) from

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Type Ia receptors are in the …?

muscle spindle (therefore, detect change)

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Type Ib fibres are…

golgi tendon organ (detect tension/force in muscle)

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Type A-beta (II) fibres are…

all cutaneous mechanoreceptors

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Type A-delta (III) fibres are…

Free nerve endings of touch and pressure. Cold thermoreceptors, nociceptors of neospinothalamic tract (—–sharp pain & primary pathway)

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Type C (IV) fibres are…

Nociceptors of paleospinothalamic tract, warmth receptors

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What are the primary nerve fibres associated with pain?

A-delta (III) & type C (IV)

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A sharp pain is likely through what pathway?

A-delta (III)

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A dull pain is likely through what pathway?

C (IV) fibres

A-delta fibres are fast or slow?

Fast

C-fibres fibres are fast or slow?

slow

Are A-delta fibres myelinated or unmyelinated?

myelinated

Are C-fibres myelinated or unmyelinated?

unmyelinated

Second order afferent fibres carry messages from the _______ to the _____

dorsal horn to thalamus

Third order afferents: Carry information to various _____ centers for _____/_____

brain, integration/interpretation

_________ specific neurons receive input from A-delta and C-fibres only

Nociceptive

Cortical processing of pain is very complex, there are lots of structures involved, and it is at the level of...?

The cortex in the brain

The contact point between different neurons is called a _____

synapse

A neuron only synapse with one neuron (T/F)

False, it may synapse with many more neurons

Synaptic transmission is...

The movement of electrical signals between different neurons

To pass information, a transmitter substance must be released from one neuron terminal (______________) and attach to the receptor site on the next neuron (______________)

pre-synaptic membrane, post-synaptic membrane

Are neurotransmitters excitatory or inhibitory?

Can be both (turn it on or turn it off)

Neurotransmitters are chemicals which....?

relay, amplify, and modulate signals between neurons

Substance P is a...?

peptide believed to be the neurotransmitter of small-diameter primary afferents - the pain neurons

Serotonin is ...?

- a neurotransmitter found in descending neurons | - Increased levels are associated with analgesia (pain relief)

Glutamate Enkephalin is...?

Neurotransmitter proteins that block the passage of noxious stimuli from first to second order afferents, they also inhibit the release of substance P

Norepinephrine is...?

Biogenic amine transmitter that inhibits synaptic transmission between first and second order nociceptive afferents

GABA is...?

Inhibitory transmitter found at the spinal and cortical levels of pain modulation

Nortriptyline is a tricyclic _______ that prevents the reuptake of...?

antidepressant, norepinephrine

Nortriptyline reduces pain by inhibiting....

synaptic transmission between first and second order nociceptive afferents

Nortriptyline increases ____ as it is a major catecholamine with epinephrine and dopamine

heart rate

On the early onset of pain, local inflammatory substances are released. These include... (3)?

histamine, prostaglandins (NSAIDS target), bradykinin

On the early onset of pain, there is a _____ depolarisation threshold of peripheral nociceptors

lower

Lowers depolarisation threshold of peripheral nociceptors from immediate pain causes...

- Primary hyperalgesia - nerves threshold to noxious stimuli is lowered - Increases the pain response

After several hours of pain... ___ ____ occurs?

Secondary hyperagesia

Secondary hyperagesia causes chemicals to spread...?

throughout surrounding tissue, increasing size of affected area and creating hypersensitivity of the receptors in the region.

silent nociceptors don't exhibit sensitivity to _____ stimuli

noxious

silent nociceptors develop sensitivity to ...?

the inflammatory response

Key inflammatory mediator: bradykinin is and causes..

- 9 amino acid peptide chain | - Causes blood vessels to dilate

Key inflammatory mediator: Prostaglandins is..

- Lipid compound derived from fatty acids | - Oxidation of various fatty acids by the COX-1 and -2 isoenzymes produces prostaglandin

Prostaglandin functions (4)?

- Constriction/dilation of smooth muscle - Aggregation or disaggregation of platelets - Sensitize spinal neurons - Regulate local inflammation

The overall effect of primary sensitisation and activation of "silent" afferents is to _____ the total nociceptive barrage to the spinal cord

increase

Remember silent nociceptors: - _____ exhibit sensitivity to noxious stimuli - Develop sensitivity to the inflammatory process

Don't

Increased afferent input (activity from the periphery) releases _____ ions and activates NMDA receptors (known as____)

magnesium, excito-toxin

Increased activation of NMDA receptors increase the responsiveness of the _________ neurons

second order

For single dorsal horn neurons, from ongoing activity, there is expansion of the receptive field and increased responsiveness by ....

lowering excitatory threshold (takes less stimuli to feel same pain)

Each neuron can synapse with thousands more ____ and ____ neurons

spinal, supraspinal

When there is an increase in cortical representation and activity in 'pain pathways', you can feel the 'pain' ______ actual pain receptors flaring (due to path already being so highly used)

without

Dextromethorphan is a specific NMDA receptor antagonist that....?

- is a cough suppressant | - When used in excessive dosages it can act as a psychedelic drug

Nitrous oxide is a specific NMDA receptor antagonist that....?

- commonly known as laughing gas - seems linked to endogenous opioid production - minimal metabolism -> retains potency when exhaled

Methodone is a specific NMDA receptor antagonist that....?

- also an opioid agonist

Tramadol is a specific NMDA receptor antagonist that....?

-mild role as an opioid agonist

Morphine is or is not NMDA antagonist

Is not

Morphine is considered the prototype of...

opioid agonist | - and has high level of addiction

Arthrogenic Muscle inhibition is the CNS response that leads to _______ voluntary activation (CNS drive to muscle) to a muscle that has been injured

decrease

Allodynia means...

Pain due to a stimulus that does not normally provoke pain

Hyperalgesia means...?

Increased response to s stimulus that is already painful

Dysaesthesia means...

An unpleasant abnormal sensation (allodynia and hyperalgesia are specific examples)

Hyperaesthesia means..

Increased sensitivity to stimulation

Ways to work with chronic pain patients...?

- Careful with wording (avoid harsh words) - Don't focus on pain symptom to guide improvement - Educate client about chronic pain and healing - Focus on balance whole body program - Don't keep asking for pain level or avoid things that cause any pain