Physiology of Muscles & Pain Flashcards
What are the 4 components of pain physiology?
transduction. transmission, modulation, perception
What is transduction of pain?
translation of harmful stimulus into electrical activity at the peripheral nociceptor
What is transmission of pain?
the propagation of a pain signal as nerve impulses through the nervous system
What is pain modulation?
modification/hindering of pain transmission in the nervous system, e.g. inhibitory neurotransmitters like endogenous opioids
What is pain perception?
the conscious experience of pain - causes psychological and behavioural responses.
Which component of pain physiology describes how the body conveys a noxious signal to the brain?
transduction
What is a nociceptor?
specific primary afferent neurones normally activated (depolarised) by intense noxious stimuli
Describe the nociceptive pathway form a peripheral site to the spinal cord.
- Noxious stimulation at free nerve ending
- AP travels along nociceptor (1st order) axon
- Neurotransmitters released at dorsal horn of spinal cord
- Stimulation of projection (2nd order) neurone, travels up axon, terminates at thalamus
- Sensory information relayed to primary sensor from thalamus
What are the neurotransmitters released in a nociceptive pathway?
glutamate and the peptides substance P & neurokinin A
What is the spinothalamic tract (STT) involved in?
pain perception (location, intensity)
What is the spinothalamic tract (SRT) involved in?
autonomic responses to pain, emotional responses, fear of pain.
What are the stimulants of nociceptors?
noxious mechanical, thermal or chemical stimuli
What are the fibre types comprising nociceptors?
A-gamma-fibres
C-fibres
Which fibre type senses mechanical/thermal stimulation?
A-gamma-fibres
Which fibre type is polymodal?
C-fibres
Which fibre type responds to ‘first’ or fast pain? Why is this?
A-gamma-fibres since they are thinly myelinated - faster conduction
What type of sensations do C-fibres respond to? What do they feel like?
collectively respond to all noxious stimuli - slower conduction rate.
burning, throbbing, cramping, aching sensations
What is nociceptive pain? What is its function?
normal response to injury by noxious stimuli.
= early warning physiological protective system to detect & avoid noxious stimuli
What is inflammatory pain?
caused by activation of immune system by tissue injury or infection
What does inflammatory pain promote and how does it do so?
Promotes repair until healing occurs.
Heightened pain sensitivity to noxious stimuli & innocuous stimuli; discourages physical contact.
What is allodynia?
stimuli that doesn’t normally cause pain but does at this time (inflammatory pain feature)
What are the types of pathological pain?
neuropathic and dysfunctional
Describe neuropathic pathological pain.
caused by damage to neural tissue, can be perceived as burning, shooting, numbness, pins & needles; may be less localised.
What can cause neuropathic pain?
compression neuropathies peripheral neuropathies central pain (post-stroke or spinal injury) postherpetic neuralgia trigeminal neuralgia phantom limb
Describe dysfunctional pathological pain.
No identifiable damage or inflammation.
Simple analgesics not very effective
What are some causes of dysfunctional pathological pain?
fibromyalgia IBS tension headache TMJ disease interstitial cystitis
Which types of pain are adaptive and maladaptive?
Adaptive -> nociceptive, inflammatory
maladaptive -> dysfunctional
Why is adaptive pain protective?
discourages movement, contact with affected area, inflammation encourages rest of limbs etc.
enables and speeds up healing
What does hyperalgesia mean?
hypersensitivity to pain from noxious stimuli
What causes referred pain?
convergence of nociceptive visceral and skin afferents upon the same spinothalamic neurones at the same spinal level
- leads to feeling pain in an area of skin distant from internal organ where pain originates.
What are the main physiological functions of skeletal muscle?
maintenance of posture purposeful movement respiratory movements heat production contribution to whole body metabolism
