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Pathophysiology 1 > Pain > Flashcards

Pain Flashcards

1
Q

define pain

A

Unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.

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2
Q

Journey of pain

A

Sensory neurones called nociceptors stimulated

Impulse transmitted through peripheral nerve into spinal cord

Continues up to thalamus and then sensory cortex

Sensory cortex perceives it as pain

Pain is physical response to injury

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3
Q

Females vs males

A

Males suffer worse pain treated by female practitioners

Women more likely to be chronic pain sufferers than men

Pain is physical and emotional experience and can be linked to social values and past experiences of pain.

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4
Q

Pain can be inconsistent

A

Sometimes pain can be inconsistent with amount of structural damage present

Pain perceived differently in people as brain makes sense of pain related to memories, fears and emotions

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5
Q

Types of sensory receptors

A

Sensory receptors relay info to our brain to sensory cortex

They can be:

SPECIAL SENSES= Vision, hearing, balance, taste and smell
SOMATORY SENSORS= Detect touch, pressure, vibration, thermal stimuli, proprioception and pain (nociceptors).

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6
Q

3 important nerve fibres for pain

A 
DELTA FIBRES (nociceptors)- small diameter and myelinated. Respond to mechanical and thermal stimuli 
Rapid and sharp pain signals sent up delta fibres 
Produce initial reflex response to acute pain

C- fibres (nociceptors)- unmyelinated and smallest type of nerve fibre. Slowest conduction and respond to chemical, mechanical and thermal stimuli.
Slow burning pain.

A-beta fibres (mechanoreceptors)- highly myelinated and large diameter. Rapid signal conduction and low activation threshold.
Respond to light touch + transmit non painful info, mechanical stimuli and thermal stimuli.

Summary=
Delta and C fibres carry pain signals to brain and a-beta fibres carry non-painful signals

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7
Q

Classes

A

A fibres (alpha, beta, gamma and delta)
4-20 micrometers
Highly myelinated
Conduction is 150 m/s

B fibres
2-4 micrometers
Moderately myelinated
18 m/s

C fibres
Less than 2 micrometers
Unmyelinated
1 m/s

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8
Q

General rule about thickness

A

Thicker a fibre, more myelination it has, and faster conduction speed of the fibre

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9
Q

ALPHA nerve

A

Information about proprioception

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10
Q

A- beta nerve

A

Carries info relating to touch

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11
Q

A delta fibres

A

Carries info related to sharp, fast pain

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12
Q

C fibres

A

Carry info related to slow burning pain

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13
Q

What is substantia gelatinosa?

A

Neurones that Cary info to brain about pain and temperature in the right side of posterior norm

Corresponds to lamina rex on other posterior horn

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14
Q

What neurotransmitters enable pain to transfer from neurone one to two ?

A

Glutamate

Substance P

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15
Q

Signals of pain from PNS to CNS

A

Nociceptors stimulated

Signal sent along afferent neurone - first order neurone

The a-delta or c fibres transmit info to specific neurones in spinal cord dorsal horn called Rex lamina

The info crosses from first to second neurone via glutamate and substance P to carry sensory info over junction in posterior horn of spinal cord

PNS part was nociceptors stimulating and first order neurone
CNS part is spinal cord, second order neurone and the brain to sensory cortex where third neurone goes

Second order neurone transmits the sensory info up to thalamus and synapses with 3rd order neurone to sensory cortex

Junction between first and second neurone is where we can modulate pain

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16
Q

The two main ascending pain pathway are:

A

Lateral spinothalamic tract

Spinoreticular tract

17
Q

Spinothalamic tract

A

Carries main pain signals

From dorsal horn via second order neurone with a projection to PAG grey matter- ends at thalamus to connect to third order neurone

18
Q

Spinoreticular tract

A

Laterally to the spinothalamic tract

Ascends to the reticular formation in brainstem then onto thalamus to connect with third order neurone

The spinoreticular tract plays a role in MEMORY and EMOTIONAL aspects of pain

19
Q

Descending pathways ?

A

We have some descending pathways to try and control and inhibit the pain ascending pathways

20
Q

How do descending pathways work ?

A

They come from the PAG, down to the nucleus raphe magnus and synapse withsecond and first neurones

Junction between first and second neurones = descending Pathway communicates with interneurones and stops messages being sent from first to second neurone

21
Q

Pain transmission + descend tracts

A

Normally ;
Pain stimulus from receptors
Alon first order neurone to junction to second
Pain transmits over the gap via substance P and glutamate
Second neurone crosses over at spinal cord
Ascends to thalamus
Synapses with third at thalamus and goes to sensory cortex

NEURONE FROM DESCENDING PATHWAY
Comes from PAG
Connects with junction
Inhibits substance P so pain signal does not cross
Also stimulates interneurone in substantia gelatinosa to release opioid
Stops signals being transmitted along second order neurone

22
Q

Nociceptors

A

Free nerve endings
Detect thermal, mechanical and chemical, stimuli
Found in muscles, skin, joint capsule and internal organs

23
Q

PAIN PATHWAY

A

Nociceptors stimulated by painful stimulus

Action potential formed + a delta and c fibres send pain signal along first neurone to dorsal horn

Info transmitted across junction to second order neurone via neurotransmitters glutamate and substance P

Second neurone crosses spinal cord up to thalamus

Synapses and third order neurone up to sensory cortex

Descending pain pathway comes from PAG of midbrain and nucleus raphe magnus of medulla

They inhibit substance P

Stimulate interneurone in substantia gelatinosa so opioid released

24
Q

Registering pain in brain

A

Dull ache pain is slow

Sharp pain travels fast

Pain messages at thalamus - transferred to limbic system and sensory cortex

Located : source of injury, assess damage and course of action

Sensory cortex activates automatic response systems
Eg, increase blood flow to tissue damage
Release pain suppressing chemicals to stop pain messages transmitting over junction in spinal cord

25
Q

Limbic system and pain

A

Associated emotions of pain like sadness, frustration, anxiety and fear. That can make pain more or less intense

26
Q

Reflex

A

Rapid automatic response , no conscious thought

Immediate response to harmful scenarios

Spinal reflex occurs in grey matter of spinal cord and initiated reflex arc

27
Q

How does reflex work?

A

Sensory neurones in tissue stimulated

Info passed down first neurone

Goes through interneurone from post to ant horn

Motor info directly sends the info to effect organ

Automatic response initiated at the effectors eg, moving limb out of fire

28
Q

Pain gate

A

Rub it better - means activating a beta fibres to inhibit pain signals to brain (BETA makes it BETTER)

C fibres would slowly transmit pain across junction to second neurone, but if we rub it better we activate a beta fibres that travel faster.

They arrive faster and close the pain gate

If no stimulus = pain gate closed

If we activate a beta fibres by pressure, inhibitory inyerneuron inhibits substance P (stops pain signal transmission).
Substantia gelatinosa excited and closes pain gate, no passage of pain up to brain

If we activate a delta and C fibres, pain transmits from first to second neurone and up to brain
Inhibitory interneuron is inhibited so pain gate is open

29
Q

Unmodulated pain

A

C fibres transmit slow dull pain to junction between first and second neurones, crosses due to neurotransmitters and then goes up to brain perceived as pain in CNS

30
Q

Modulated pain.

A

C fibres send signals to junction BUT we have activated a beta fibres too

A beta fibres travel faster

Cross at junction UP TO BRAIN

reduces transmission of c fibres, causing modulation of pain

31
Q

TREATMENTS TO CLOSE PAIN GATE

A

SEC

State of mind = anxiety opens pain gate, more pain to brain
If we relax, we can activate substantia gelatinosa and close the pain gate

Encephalins and endorphins - opioid release closes pain gate (from interneuron in SG)
Levels of this increased in exercise

Central control- brain can affect pain gate as it controls memories, past experiences and response strategies to the pain,

32
Q

Types of pain

A

Always call neighbours nosy please

ACUTE pain- lasts less than 3 months

CHRONIC PAIN- persistent pain lasting more than 3 months

NOCICEPTORS PAIN- pain caused by stimulating nociceptors in soft tissue, eg bump your elbow

NEUROPATHIC PAIN- damage to nervous system by burning pain or altered sensations. Disorders of peripheral neuropathic or central neuropathic pain

PSYCHOGENIC PAIN- pain brought by psychological factors

33
Q

CHRONIC PAIN

A

10% of patients have chronic persistent pain

Beyond time of healing

Unknown

Maybe pathology , eg cancer damaging tissues or arthritis

Also DYSFUNCTIONAL NOCICEPTIVE SYSTEM.
Modifies CNS so patient more sensitive and more pain

Peripheral sensitisation - increased sensitivity to afferent nerve stimulation

Also may spread to other parts of body with no pathology - central sensitisation , constant state of high reactivity

34
Q

Can cause

A

Central sensitisation can cause

Widespread hyperalgesia= enhanced sensitivity to pain
Allodynia= pain from stimuli that aren’t usually painful
Chronic pain state

A healthy person can have descending inhibition but in central sensitisation, malfunction to descending pathways so they experience more pain in painful stimuli and pain in non-painful stimuli

35
Q

Example

A

Patient with knee osteoarthritis pain

Peripheral sensitisation

Changes to CNS

Central sensitisation

Widespread pain, hyperalgesia and allodynia

36
Q

Nociceptors pain

A

Visceral pain - activates receptors in abdominal, pelvic and thoracic organs

Somatic pain- receptors in skin, joints and muscles activated

Pathophysiology 1 (22 decks)

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