7.1 Pain Flashcards
Recall the purposes of pain
- Avoid harm
- Promote immobility and healing
List three types of pain
- Nociceptive
- Inflammatory
- Pathological
Physiological vs pathological pain
Physiological: normal and adaptive
Pathological: nonprotective, maladaptive
What are the three classifications of nociceptive pain?
- Somatic (deep/superficial)
- Visceral
(Think of sensory modalities, like in cranial nerves)
What are the three types of pathological pain? What characterises them?
- Neuropathic
- Phantom
- Psychogenic
Threshold of inflammatory vs nociceptive pain?
Inflammatory: low
Nociceptive: high
Which types of pain are pathological/physiological?
Patho: Pathological (wow!)
Physio: inflammatory and nociceptive
What is nociceptive pain?
Pain in response to noxious stimulus (i.e., damage/potential damage to the body)
Describe the tissues involved in the three different types of nociceptive pain
Sup. Somatic: Skin, superficial tissues
Deep somatic: bone, tendon, ligament, muscle
Visceral: internal organs
Describe the stimuli that can cause the three different types of nociceptive pain
Sup. somatic: burns, shallow cuts, chemicals
Deep somatic: sprains, fractures
Visceral: stretching, hypoxia
Describe the character of the three different kinds of nociceptive pain
Sup somatic: sharp
Deep somatic: dull, aching
Visceral: dull, deep & squeezing
Which types of nociceptive pain are easy/difficult to locate?
Sup Somatic: Easy
Deep Somatic/Visceral: Difficult
Two things happen before a nociceptive signal reaches the brain. What are they?
- Motor pathway activation (e.g. withdrawal reflex)
- Modulation
Inflammatory pain is associated with…
Peripheral inflammation and tissue injury
Inflammatory pain causes two phenomena related to pain hypersensitivity. What are they?
- Hyperalgesia: increased pain from a stimulus that is normally painful
- Allodynia: pain from a stimulus that isn’t normally painful
Describe neuropathic pain
- Pain from nerve damage after initial insult, e.g.:
Postsurgical, diabetic neuropathy, cancer pain
Describe the character of neuropathic pain
- Shooting/electric shock (like trigeminal neuralgia)
- Tingling, burning, aching
In what kind of nerve endings are nociceptors located?
Free nerve endings
What are the five kinds of nociceptors?
- Mechano
- Chemical
- Mechano-thermal
- Polymodal (all three)
- Silent nociceptors (respond to inflammation)
Outline the full sensory pathway of pain from the face/head/mouth.
- Primary afferents from CN V head trigeminal spinal nucleus
- Decussate, and head to thalamus
- A delta head to 1° somatosensory cortex
- C fibres head to 2° somatosensory cortex
Describe the role of the primary vs secondary somatosensory cortices in pain.
Primary: precise location of pain, assessing intensity
Secondary: Recognising pain, remembering past pain
Define chronic pain
Pain that lasts beyond normal healing time of injury/illness.
Describe how peripheral nerve sensitisation can cause chronic pain
- Chronic inflammation/nerve injury
- Concentration of voltage-gated sodium channels
- Lowered nociceptive threshold
- Chronic firing of silent nociceptors
Describe two mechanisms of central sensitisation
- “Wind up” from repetitive stimulation
- Abnormal sprouting of axons causing unusual connections, meaning non painful stimuli become painful
Describe 3 broad effects of microglial activation on pain synapses. What is the overarching consequence of this?
- Increased pre/postsynaptic firing
- Decreased inhibition
- Decreased glutamate recycling by astrocytes
Result: nociceptive hypersensitivity
