Fast pain transmission by Aβ nociceptors Flashcards
What is the name of the pathway used for fast pain transmission?
Spinothalamic pathway
How many neurons are involved in transmission of fast pain through the spinothalamic pathway?
3 neurons in total:
First-order nociceptor (neuron)
Second-order neuron
Third-order neuron
What structure of the nociceptor detects the noxious stimulus, and what order neuron is this nociceptor?
Free nerve endings of the first-order nociceptor detect noxious stimulus
After the first-order nociceptor has detected the noxious stimulus, how is the signal transmitted to the spinal cord?
Signal transmitted down peripheral axon of the nociceptor to sensory ganglion, then down central axon which soon enters dorsal horn of the spinal nerve in the spinal cord
What are the laminae I-VI of the dorsal horn, and why are they labelled in that order?
Neuronal cell layers that receive different primary afferent sensory fibres
labelled I-VI in dorsal-ventral root direction
In which 2 laminae of the dorsal horn are A-delta nociceptors received for fast pain transmission?
Lamina I and V
In which 2 laminae of the dorsal horn are C fibre nociceptors received for slow pain transmission?
Lamina I and II
What occurs at the first relay site of fast pain transmission, and where does it happen?
In dorsal horn, the proximal/central axon of first-order nociceptor terminates and nociceptive signal is transmitted to laminae I and V second-order neurons via synaptic transmission
How do second-order neurons reach the anterolateral aspect of the spinal cord, in fast pain transmission?
Second-order neuron crosses spinal cord midline at same segmental level then comes to anterolateral aspect
After second-order neurons have reached the anterolateral aspect of the spinal cord, what structure do they form that projects to brain, in fast pain transmission?
Multiple second-order neurons form group of axons in white matter called spinothalamic tract
Where is the second relay site of fast pain transmission?
Nociceptive signal transmitted through second-order neurons up spinothalamic tract then synapse with third-order neurons in thalamus (in brain), which is the second relay site
Which 2 brain regions do third-order neurons project to from the thalamus, in fast pain transmission?
Primary and secondary somatosensory cortices
What does a specific activated area within the somatosensory cortex indicate, and what does the frequency of activating signals indicate, in fast pain transmission?
Somatosensory cortex is a topological map of body regions, so activated area indicated that noxious stimulus was detected in that body part
More frequent the signals the more intense the pain in that body region
