Pain Flashcards
What are pain receptors called?
Nociceptors
Nociceptors are usually ______ _____ __________.
Free Nerve Endings
Nociception constitutes an _________ ________ _______ from discriminative perception and thermoception.
anatomically distinct modality
Where do the nerve cell bodies of nociceptors reside?
Dorsal Root Ganglion (like mechanosensors)
What are the two classifications of nociceptors?
Conduction velocity of AP’s
Conduction velocity and modality
What are the two types of fibers for classifying conduction velocity?
A-Delta fibers
C fibers
Conduct at about 20 m/s
Associated with sharp, first pain
A-Delta fibers
Conduct at about 2 m/s
Associated with dull, slow pain
C fibers
What are the three types bases on conduction velocity and modality?
A-Delta mechanosensitive
A-Delta Mehcanothermal
C polymodal
Sensitive to chemicals
Low sensitivity to temperature
A-delta mechanosensitive
Wide variety of stimuli
C polymodal
Sensitive to mechanical stimuli and temperature.
A-Delta mechanothermal
What is the major central pain pathway?
Spinothalamic Tract
Pain fibers are associated with ____________ _____________ of pain.
discriminative aspect
What is discriminative aspect?
Location, intensity, and quality from body
Overview of Major Central Pain Pathway
Enter via dorsal tract of Lissauer
Ascend a couple of spinal segments
Penetrate gray matter and synapse with targets in several of Rexed’s laminae.
Axons ascend via anterolateral tract (continuing into the brain) via the spinothalamic tract to the thalamus
Synapse on 3rd order neurons in thalamus, which project to post-central gyrus (somatosensory cortex)
Describe the location of the termini A-delta and C fibers in the Rexed’s laminae.
Where C fibers are located is different than where A-Delta fibers are located in talking about the location of the termini.
How many layers are in the Rexed’s laminae?
Six
The affective motivational pathway is the parts of the pain system that convey? (2)
Unpleasantness of Pain
Fear and anxiety associated with pain
Affective, motivational pathway can activate what kind of response?
Fight or Flight
The affective, motivational pathway is characterized by branches to __________
Reticular Formation (not effective) Amgydala and hypothalamus
What is the reticular formation associated with?
Attention
What does TRP stand for?
Transient Receptor Potential Channels
What are two different types of TRP channels?
Vannilloid Receptors and Vannilloid-Like Receptors
What receptor is activated by heat (45 C) and capasaicin?
Vanilloid Receptors
What receptor is activated by higher heat (52 C) but NOT capasaicin?
Vanilloid Like Receptors
What receptors are found both in A-Delta and C fibers?
Vanilloid Receptors
What receptors are found in A-Delta fibers?
Vanilloid-Like Receptors
What does TRP channels involve in?
Signal Transduction
TRP Channels
6 TM Domains
Pore forming domain b/w 5 & 6
Conduct Na+ and Ca2+
TRP Channels are similar to?
cNMP-gated channels or v-g K+ channels
Capsaicin
Lipid soluble interacts with intercellular domain
Heat
Activates TRP channel
Proteins, Capsaicin, Heat
Activates channel. Hot and burning sensation.
What happens when nociceptor is activated?
Depolarized. If sufficient depolarization then will have an action potential(s)
Increased sensitivity to stimulation in an area of damaged tissue
Hyperalgesia
Hyperalgesia is resulting from ?
Sensitization
Increased responsiveness of nociceptors caused by various chemical substances released by injured tissue
Sensitization
What are the two kinds of sensitization?
Central and Peripheral
Example of hyperalgesia?
Bruise
Increased responsiveness –> increased activity of nociceptors stimulates the release of substances –> Release of histamine –> Histamine increases responsiveness of nociceptive receptor endings.
Peripheral Sensitization
What type of feedback loop is peripheral sensitization?
Positive Feedback Loop
