Anatomy & Physiology of Pain I Flashcards
What are the four physiological mechanisms of pain? [4]
TRANSDUCTION
Noxious (potentially harmful) stimuli translated into electrical activity at sensory nerve endings
TRANSMISSION
Propagation of impulses along pain pathways
PERCEPTION
Discrimination/ affect / motivation
MODULATION
Positive and negative modulation occurs
Which receptors detect pain? [1]
Nociceptors
Name 3 nociceptive channels and what they are activated by [6]
Acid-sensing ion channel (ASIC) channel:
* cation channel activated by pH changes and other stimuli - important in inflammatory response
(TRPM8)channel (cold and menthol receptor 1):
* ion channel activated by cold temperature and cooling agents (menthol).
Transient receptor potential cation channel subfamily V member 1 (TRPV1) channel (capsaicin receptor/vanilloid receptors 1):
* Non-selective cation channel that is activated by temperature, acid, capsaicin, and mustard/wasabi.
What type of nociceptive channel would be activated by temperature & pain? [1]
TRPV1
What type of nociceptive channel would be cold? [1]
TRPM8
What type of nociceptive channel would be activated acidity? [1]
ASIC
What are TRP channels activated by? [2]
TRPs activated by temperature AND chemical agonists
What are the three main subgroups of primary afferent sensory neurons and what are they stimulated by? [6]
ABeta fibre: non noxious; mechanical stimulus - cutaneous mechanoreceptors non-painful, mechanical stimuli (stroking, vibration)
Adelta fibres: noxious chemical stimulus - sharp, stinging, pricking (e.g. hit by hammer)
C fibres: activated by noxious chemicals & noxious heat / temp
Which fibres cause ‘1st pain’ and ‘2nd pain’?
State if they are myelinated or not
Myelinated Ad fibres carry ‘1st pain’ (i.e. sharp, stinging, pricking), then
Unmyelinated C fibres carry ‘2nd pain’ (i.e. diffuse and persistent burning pain)
Which arrow would be responsible for slow and fast pain? [2]
Which fibres would be resonsible for each? [2]
Voltage-gated [] channel found on sensory neurones and is important to perceive pain sensation by generation and conduction of action potential.
Voltage-gated sodium channel found on sensory neurones and is important to perceive pain sensation by generation and conduction of action potential.
Which type of Na channel is particularly important for nociceptive function [1]
State the gene that codes this channel [1]
Loss of NaV1.7 (sodium channel subunit).
SCN9A gene (encode sodium channel NaV1.7).
Loss of NaV1.7 can lead to which disease? [1]
Congenital insensitivity to pain (CIP): Rare condition in which individual cannot feel pain so often have wounds, broken bones, health issues not detected.
Name a disease if NaV1.7 is overexpressed / gain of function occurs [1]
Inherited erythromelalgia (IE): A painful neuropathy involving severe chronic burning pain sensations in hands and feet.
Neuropathy pain (loss of sensory fibres)
Name a disease that is caused by insensitivty to pain [1]
Which gene mutates to create this disease? [1]
Congenital insensitivity to pain with anhidrosis (CIPA)
- TRKA gene codes for TrKA receptor to create nerve growth factor (NGF)
- NGF is crucial for development of Adelta and C-fibres
Name an acquired neuropathy [1]
Diabetic neuropathy:
High blood glucose can damage nerve fibres, esp. legs and feet - loss of pain in peripheries
Different sensory neurons have distinct projections in the dorsal horn. State what they are
Lamina found within dorsal horn:
Lamina I to V
- Aβ: project deepest - lamina IV & V
- Aδ project middle: lamina I
- C fibres project into lamina I & II
What are TRP channels activated by? [2]
TRPs activated by temperature AND chemical agonists
What are TRP channels activated by? [2]
TRPs activated by temperature AND chemical agonists
Transmission
Describe the Aδ nociceptor pathway onto the dorsal horn [2]
Aδ nociceptor axon projects on to Lamina I via excitatory glutamate synapse on to either NMDA or AMPA receptors
Transmission
Describe the C-fibre nociceptor pathway [2]
C fibres activate lamina I cells via gluatmata onto excitatory interneurons in lamina II, which then excites lamina I dendrite with glutamate
