detection of noxious stimuli through the activatino of nociceptors
Stimulus for nociception
mechanical, thermal or chemical
The path of nociception for superficial and deep pain are the same. T/F
F. Superficial and Deep pain have completely different pathways
What are the two main two nerve fiber types:
A delta fibers and C fibers
Delta fibers sense
sharp and pricking pain
fast conducting, myelinated
C fibers sense
dull, ahcing, burning, throbbing pain
slow conducting, unmyelinated
What makes the refelx arc more exaggerated?
Is pain a reflex?
No, it is a voluntary behavior
arises from trauma or inflammation
persists beyond the expected time fram for the given disease/injury (present longer than 3-6
decreased perception of pain
complete absence of pain perception
absense of all senesory perception
hypalgesia, algesia and anesthesia all refer to changes in
ARAS stands for
ascending reticular activating system
What is clinically relevent about ARAS?
link between sensory stimulation and conscious awareness of stimuli (alertness)
Noxious stimuli increases:
alertness and autonomic functions (heart and respiratory rate)
spinocervicothalamic tract transmits
superficial pain and tactile sensation
How to test spinocervicothalamic tract?
lightly and briefly pinch the skin
Both proprioception and nociception decussate where?
to the contralateral cortex
The spinoreticular tract transmits
deep pain and visceral sensation
Spinoreticular tract is characteristically
indiscriminate- animal experiences pain/arousal, but cannot identify the source (diffuse nature)
How to test spinoreticular tract?
apply hemostats to the base of the toenail, dont include skin
(stimulates nociceptors in the periosteum)
What is the goal of deep pain sensation?
To notify as much CNS as possible
What kind of image does the deep pain pathway create?
2D impression of a massive recruitment of signaling, 3D to vast areas of the CNS
Which tract is more susceptible to compressive injury: spinocervico thalamic or spinoreticular?
GVA generally respond to
stretch, ischemia, dilation or spasm (colic, GDV)
What is the affective component of pain?
pain notifies the CNS of knowing the body is in trouble
What does connecting pain pathways to the limbic system ensure?
that the individual will have a negative emotional reaction to pain
How can a stimulus modify the perception of pain?
periphery, spinal cord, brainstem and higher centers
Where are inflammatory mediates released at?
What are examples of inflammatory mediators
Inflammatory mediators modulate pain by
- lowering the threshold of nociceptors
2. directly stimulate nociceptors
minimal noxious stimuli produces greater than normal nociceptive activity
non-noxious stimuli activates nociceptors
Wide- dynamic range (WDR) neurons respond to
noxious and non-noxious simuli
What are WDR neurons associated with?
referred pain of visceral organs and cell associated “wind up”
What are examples of referred pain?
- kidney –> back pain
* heart attack–> left arm pain
What is cell “wind-up”?
rapid, continuous firing of primary nociceptive afferents
ie. chronic or intense pain
In cell wind up, how does activation of the 1st neuron effect the second neuron?
1st neuron activation can result in sustained, amplified depolarization of the 2nd neuron
How do NMDA receptors function?
allow Ca and NA into the cell
What are the effects of wind-up?
long term changes in the postsynaptic cell that decreases its threshold for excitement
Does anesthesia prevent wind up?
How do you prevent wind-up?
nerve blocks and aggressive pain management
What are Pre-med options to treat wind-up?
local nerve blocks, anti-inflammatories, opioids, NMDA reecptor inhibitors
The gate control theory states that
pain perception is achieved, but decreased by:
- simultaneous tactile info traveling up the WDR neurons with the nociceptive info.
- inhibitory neurons directly affecting the C fiber
What are examples of therapy that utilize the gat control theory
What are examples of neuotransmitters at the level of the spinal cord that have anti-nociceptive properties?
multimodal pain control
- modulate or prevent transduction at the nociceptor
- interfere with conduction to the CNS
- gate control therapy
- inhibit spinal cord sensitization
- augment descending modulatory mechanisms
What stimuli provokes an itch?
- thermal stimuli
- chemicals (histamine)
results from injury to the nervous system, causing inappropriate pain signal
What is an example of TRAUMA that can cause neuropathic pain?
amputation, crushing injury
declaw –> neuroma
What is an example of vASCULAR INJURY that can cause neuropathic pain?
What is an example of ENDOCRINOPATHY that can cause neuropathic pain?
What is an example of INFECTION that can cause neuropathic pain?
post- herpetic neuralgia
unpleasant sensation associated with neuropathic pain (tingling or electric)