Lecture 2 Flashcards
What is a bottom up driver?
Peripheral driver
What is a top down driver?
Supraspinal driver
In acute injury, what is the main driver?
Peripheral driver - experience of pain is driven predominantly from nociception in peripheral tissue
In chronic injury, what is the main driver?
Most likely supraspinal (central) driver - link between pain and tissue damage is weaker
Any pain experienced less likely to have nociception as dominant driver. Pain mostly upregulated by central sensitisation
Describe the peripheral driver mechanisms
(Location, quality, intensity, behaviour, duration, clinical signs)
Location: Precise
Quality: sharp, aching
Intensity: worse with movement
Behaviour: does not spread
Duration: eased quickly with rest
Clinical signs: associated with an injury
Describe the central driver mechanisms
(Location, quality, intensity, behaviour, duration, clinical signs)
Location: shifting and spreading
Quality: unusual
Intensity: severe or not affecting by movement
Behaviour: unpredictable
Duration: does not ease quickly with rest
Clinical signs: pain that is not associated with an obvious mechanical driver
What are the 3 different sensory afferents?
A-beta fibres
A-delta fibres
C fibres
Describe A-beta fibres
(Diameter, myelination, conduction velocity, receptor activation thresholds, sensation on stimulation)
Diameter: large
Myelination: highly
Conduction Velocity: >40ms-1
Receptor Activation
Thresholds: Low
Sensation on stimulation: Light touch, non-noxious, rapid
Describe A-delta fibres
(Diameter, myelination, conduction velocity, receptor activation thresholds, sensation on stimulation)
Diameter: Small 2-5um
Myelination: Thinly
Conduction Velocity: 5-15ms-1
Receptor Activation
Thresholds: High and Low
Sensation on stimulation: Localised nociception
Describe C fibres
(Diameter, myelination, conduction velocity, receptor activation thresholds, sensation on stimulation)
Diameter: Smallest <2um
Myelination: Unmyelinated
Conduction Velocity:< 2ms-1
Receptor Activation
Thresholds: High
Sensation on stimulation: Slow, diffuse, dull nociception
HTMR
Free nerve ending
Epidermis/dermis
Noxious mechanical stimuli
LTMR
Pacinian corpuscle
Deep dermis
Vibration
Which Lamina do Alpha-Beta fibres synapse on?
Lamina 3, 4, 5
Which Lamina do Alpha-Delta fibres synapse on?
Lamina 1, 2 and 5
(1 through 5)
Which lamina do C fibres synapse on?
Lamina 1, 2 and 5
Where do nociceptors go?
I and II dorsal horn
Where do mechanoreceptors go?
III and IV
Where do proprioceptors go
V
What is nociception?
detection, transmission and processing of noxious stimuli
3 forms of energy for nociception
thermal, chemical or mechanical
Where is dorsal horn?
back of spinal cord
What neurotransmitters are released at the 2nd order neuron
Glutamate, Substance P, Calcitonin
2nd order neuron goes to brain via which tract
spinothalamic (thalamus)
What is the somatosensory cortex
area in outer part of brain which is associated with touch
Bigger areas in somatosensory cortex feel…
more sensation
What is the third order neuron in the thalamus responsible for
location and discrimination of pain. locates pain to be within certain area of somatosensory cortex
What happens at the dorsal horn?
area of spinal cord where primary afferent fibres synapse with second order neurons
What does the premotor/motor cortex do?
organise and prepare movements
What does the cingulate cortex do?
concentration
What does the prefrontal cortex do?
problem solving, memory
What does the amygdala do?
fear, fear conditioning, addiction
What does the sensory cortex do?
sensory discrimination
What does the hypothalamus/thalamus do?
stress response, autonomic regulation, motivation
What does the cerebellum do?
movement and cognition
What does the hippocampus do?
memory, spatial cognition, fear conditioning
What does the spinal cord do?
gating from periphery
What is the Amygdala’s relationship for descending pain modulation
modulates pain perception through direct connections with the descending pain inhibitory system
Describe Descending pain modulation
Periaqueductal Gray in midbrain –> rostral ventral medulla –> endogenous opiate system –> pain suppressed
What is the homunculus
a map along the cerebral cortex of where each part of the body is processed
Explain the process of nociception simply?
- Noxious stimuli occurs
- chemicals released by immune cells stimulate nociceptors
- nociceptors propagate information to dorsal horn (back of spine)
- nociceptors release neurotransmitters (glutamate, substance P, calcitonin) to second order neuron at dorsal horn
- information travels to thalamus via spinothalamic tract.
- 3rd order neuron locates pain to be within certain area of somatosensory cortex
