Presynaptic Inhibtion II Flashcards
What is the first relay centre for the peripheral nociceptive signals
Spinal cord dorsal horn
Which laminae of the dorsal horns receive most of the nociceptive fibres
Superficial laminae
Where do low threshold mechanoreceptors terminate
Deeper laminae
What type of neurons are in LI-III
GABAergic (25-40%)
Gate control theory
Large diameter fibres send excitatory signals
GABA vs Glycine release
GABA acts superficially on presynaptic sites
Glycine acts deeper on postsynaptic sites
2 types of PAD (primary afferent depolarisation)
Trisynaptic
Disynaptic
2 proposed mechanisms for PAD
Dendroaxonic circuit
Heterosynaptic spillover
Evidence is limited*
How is the Action potential generated in the dorsal root reflex (pain)
2nd afferent activated via GABAergic interneuron
Causes high enough depolarisation in the first neuron
Passes threshold for AP
How does the AP propagate in the dorsal root reflex in pain
Orthodromically (central) - reinforce pain sensation
Antidromically (peripheral) - drives neurogenic inflammation
What does the motor output of the spinal cord rely on
Local inhibitory inter neurons to fine tune motor unit responses
What does presynaptic inhibition regulate
Sensory motor drive
Role of renshaw cell
Inhibitory
Gives feedback
What is activated due to movement
Peripheral receptors become activated and give input of cutaneous and proprioceptive receptors
Info fed into spinal cord
Role of presynaptic inhibition
Decreases ability of afferent potentials to affect postsynaptic neurons
Slow prolonged response
