Pain lecture 2 Flashcards
What are pain tranducers known as?
-Nociceptors
What are the different types of nociceptors?
- Mechanical
- Thermal
- Polymodal
- Chemical
What are mechanical subtypes of nociceptors?
- Force
- Trauma
What are the receptor types for nociceptors?
- Transient receptor potential
- Prostaglandin/purino and pyrimidine receptors
What are the chemical subtype of nociceptors?
-H+ ions
What are the thermal subtypes of nociceptors?
- Cold
- Heat
What receptor type is found in thermal nociceptors?
-TRP
What are polymodal subtypes of nociceptors?
- Mechanical
- Thermal
- Chemical
What does Capsaicin activate?
-Polymodal nociceptors TRPV1
What is the transmitter for Capsaicin?
-Substance P
What is the positive feedback that causes secondary activation of nociceptor nerves?
-Chemical messengers released from activated nociceptor nerve endings act locally to release messengers that further activate the nociceptors
Action potentials propagate toward the cell body in the ______ and then enters the ______?
- Dorsal root ganglion
- Spinal cord
What is sensitization?
-Increased sensitivity and response to stimuli in and near the injured area caused by chemical messengers that make the nociceptors more excitable
What is Hyperalgesia?
-Increased perception of pain in response to painful stimuli
What is Allodynia?
-Pain evoked by normally nonpainful stimuli
What are the major candidates for sensitization?
- Substance P from nerve endings
- Prostaglandins from damaged cells
Prostaglandin receptor stimulation results in activation of what?
-Specific Na+ channels
What do you the activation of specific Na+ channels by PG receptor stimulations do?
-Makes the nociceptive nerve endings more excitable
Do we have selective COX-1 inhibitors?
-No
What is COX-1?
-Is constitutive (always present) in many tissues
What does COX-1 do?
- GI cytoprotection
- Platelet aggregation
- Renal electrolyte homeostasis
- Renal blood flow maintenance
What are COX -1 inhibited by?
-NSAIDS
What are some adverse effects of classic NSAIDS?
- Bleeding
- stomach irritation
- GI side effects
What does COX-2 do?
- Pain (inducible)
- Fever (inducible)
- Inflammation (inducible)
- Cardiovascular protection (constitutive)
What is COX-2 inhibited by?
- NSAIDS
- Selective COX-2 inhibitors (Celebrex)
What stimulated COX-2?
- Hormones
- Growth Factors
- Inflammatory mediators
What do NSAIDS inhibit?
-Synthesis of prostaglandins that are involved in sensitizing the nociceptor nerve ending
How are nociceptors in the viscera normally activated?
-Mechanical stimulation such and distention or contractions (visceral pain can be referred to outside areas)
Do you take NSAIDS for visceral or somatic pain?
-Somatic
Which pain pathways are small, myelinated, and fast conducting?
-A -delta
What are A-delta fibers associated with?
-Mechanical and thermal nociceptors
Are A-beta fibers pain associated?
-No they are proprioception fibers
What pain fibers are small, unmyelinated, and slow conducting?
-C axons
What are C- axons associated with?
-Polymodal nociceptors
What are plexus of nerves in the tooth called?
- Sub-odontoblastic plexus
- Plexus of Raschkow
Which fiber gives you sharp pain?
-A-delta
Which fiber gives you dull diffuse pain?
-Dull diffuse
Nociceptive fibers synapse with “projection” neurons in what area?
-Dorsal horn
What are important pain neurotransmitters in modulation?
- Glutamate
- Substance P
T/F Projection neurons send axons across midline
True
Where do the ascending pathways ascend contralaterally?
- Spinothalamic tract
- Thalamus
- Somatosensory relay
Where does the trigeminal nucleus input to?
-Thalamus
Where is nociceptive input heavily modulated at?
-=Dorsal horn with both facilitatory and inhibitory influences
What is Central sensitization?
-Dorsal horn projection neurons also become sensitized and hyper-responsive to nociceptive input.
T/F Prostaglandins can sensitize at the nociceptive level and at the spinal cord level (central sensitization)
True
T/F The dorsal horn is a major site of action for analgesic drugs
True
What is a second mechanism for the anti-nociceptive action of NSAIDS for central analgesia?
-Inhibits the synthesis of prostaglandins in the dorsal horn that participate in central sensitization
T/F The dorsal horn is a major site of action of opioids
True
Sometimes strong touch stimulation can inhibit what?
-Nociception
T/F A Beta and A delta fibers never converge together
False
-They do converge
Visceral afferent nociceptors ________ on the same pain projection neurons as the afferents from the somatic structures in which the pain is perceived?
-Converge
What is a type of referred pain that can be thought of a possible dental problem?
-Sinusitis feels like tooth pain sometimes
