PAIN ANATOMY - BIO&PHYSILOGY Flashcards
What are nociceptors
Sensory receptors that detect signals and respond to chemicals released. They are nerve endings in the skin, muscle, joints and bone
Define nociception
Neural process of encoding noxious stimuli
What is congenital analgesia
Rare genetic condition where the person feels no pain even when stimuli are introduced
What ion channels are key in encoding pain?
- voltage gates sodium channels
- voltage gated calcium channels
Describe the structure of a voltage gated sodium channel
There are 4 domains which form a pore. Upon activation the pore can open allowing sodium ions to flow through it. The pore is made up of four protein domains and has helices that surround the pore opening
The loop sticks on the inner side of the pore make it very selective to Na+ ions
Describe the basic nociceptive pathway
Noxious stimulus>detected at nociceptor>signal travels down afferent nerve fibre to dorsal horn (spine)>(central terminal)SYAPSE>signal travels down secondary neuron>left side of brain
What detects noxious stimuli in the nociceptor nerve endings
Cation channels
What is TRPV1 a receptor for and how does it work?
Receptor for capsaicin, protons and detects noxious heat
Sodium and calcium ion permeable
Ion influx leads to depolarisation which can lead to generation of action potential
What is TACAN a receptor for and how does it work
Ion channel that opens in response to pressure stimulation
Can be open or closed and causes a small change in membrane potential when there is an influx of ions
What is cation gating
Ion gating channels vary between being open and closed based on the presence of stimuli
Eg TACAN receptors on nociceptors
What fibres are involved in nociception
A gamma
C
How does glutamate work
Main excitatory NT
Voltage gated ca channels facilitate NT release
What are the different neurotransmitters that interact with interneurons (modulate pain present in the spinal cord)
GABA (inhibitory)
Glutamate (excitory)
opioid peptides (inhibitory)
how do opioid pepties work
localised presynaptically
inhibit adenylyl cyclase = less cAMP
reduced synaptic transmission
how does GABA work
inhibitory
synthesised from glutamate (excitatory)
binds to ligand gated ion channels - opening of pored leads to cl- ion influx = hyperpolarisation
causes hyperpolarisation
