Pain Flashcards
Two subtypes of Aδ fibers
Two subtypes of Aδ fibers
Type I Aδ- respond to dangerously intense mechanical and chemical stimuli, but have relatively high heat thresholds
Type II Aδ- more sensitive to noxious heat than mechanical and chemical stimuli
T/F the TRP channels are always selective
FALSE
Not Always Selective
T/F smelling mint can be painful
TRUE
Szalassi
TRPV1:
TRPA1:
1 and V3 by___
Szalassi
TRPV1: capsacin
TRPA1: cinnamon, horseradish, garlic
1 and V3 by menthol (mint)
which fibers tell if there is a threat
C fibers
i think
• Two different kinds of nociceptor fibers
• Aδ fibers and C fibers
*first pain fibers
sharp, Aδ fibers
which is faster Aδ fibers or C fibers
Aδ fibers are slightly faster I think
anterolateral system can be divided into
(i think): first pain and second pain
pain matrix
Pain is complex
Not singled layered
Our perception of pain is complex
Example: knowing something is going to hurt before it starts vs unexpected pain
Emotions, learning/memory, cognition, motor response… all of that has be integrated into our experience of pain
Honestly, there is a whole lot more to it
All of the brain structures involved in pain are collectively referred to as the pain matrix
• Once in the dorsal horn: the nociceptive axons synapse on second order neurons in laminae _____
• Once in the dorsal horn: the nociceptive axons synapse on second order neurons in laminae I, II, and V
• Once in the dorsal horn, C fibers (slow) synapse in second order neurons in laminae ____ and Aδ (faster) fibers synapse in ____
• Once in the dorsal horn, C fibers synapse in second order neurons in laminae I and II and Aδ fibers synapse in I and V
marginal zone
layer I of the laminae
Non-painful somatosensory stimuli synpase in second order neurons in laminae_____
Non-painful somatosensory stimuli synpase in second order neurons in laminae III, IV, and V
What is pain***
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of tissue damage
T/F Nociceptors only discharge once the stimulus reaches a certain threshold
TRUE
• Nociceptors only discharge once the stimulus reaches a certain threshold
TRP receptors
allow cation flux into a nerve ending that leads to depolarization
-the channels in free nerve endings
second pain fibers **
• C fibers for delayed, diffuse, and longer-lasting pain
First vs second pain *
- First pain: sensory-discriminative
- Second pain: affective-motivational
- The sensory-discriminative dimension, often referred to simply as ‘intensity’ or given the label ‘sensory’, includes the spatial, and temporal characteristics and quality of pain.
- The pain experience includes motivational and affective aspects/components, such as negative emotions and arousal.
type of info for first vs second pain*
- First pain: Information about location, quality, intensity of the pain
- second pain: Fear and anxiety, the unpleasant feeling, and autonomic relationships happen through this pathway
first pain pathway
–> VPL of thalamus –> primary and secondary somatosensory cortices
Anterolateral System Vs Dorsal column-medial lemniscus
Dorsal column-medial lemniscus: no axons cross the midline until after they synapse in the medulla
Axons of the second-order neurons in the brainstem nuclei cross midline
Body somatosenosry system
Anterolateral: axons cross the midline when they are leaving the spinal cord
Axons of the second-order neurons in the spinal cord cross midline
For pain
second pain pathway - first targets
Reticular formation, Periaqueductal gray, Superior Colliculus: Parabrachial nucleus (in the pons), Medial thalamic nuclei
what are the types of pain info?
- mechanical: strong pressure
- thermal: extreme temperature
- chemical: histamines (itch) and other chemicals
- polymodal
how do opioids work
• Opioid receptors on terminals of primary afferent Bind to presynaptic terminal to inhibit glutamate/Substance P release
neurotransmitter for primary afferents (for pain)
• All primary afferents use glutamate as transmitter
second order projection neurons in _____ of the laminae cross the midline and then ascend towards the brainstem and thalamus
Axons from the second order projection neurons in I and V CROSS THE MIDLINE and then ascend towards the brainstem and thalamus
anterolateral system
Anterolateral system also transmits non-painful temperature information
Anterolateral system
(aka spinothalamic tract)
Fiber size: small
Function: carry pain, temperature, and itch sensation
Course: ascends the spinal cord contralateral to their side of origin
Inner fibers: arms
Outer fibers: leg
Generally, the lateral regions of the anterolateral system subserve pain and temperature and the anterior regions subserve tactile and pressure sensation.
T/F the somatosensory system for pain and the noiceceptive of pain use the same system
FALSE
pretty sure
C-fibers
2 functions
- also transmit non-discriminative touch information: Goes through anterior spinothalamic tract (subdivision of anterolateral system) and not the DC-ML like other somatosensory information
- Some C-fibers also mediate the transmission of “itch
what are the channels in free nerve endings?
TRP channels – transient receptor potential
• Sensitization:
When a painful stimulus leads to non-painful stimuli being perceived as painful or more painful than they should be
• Example: poking a bruise
• Making you super sensitive to additional pain because there is healing going on there (after was injured)
• Example: increased sensitivity after a sunburn
• Allodynia **
pain caused by a normally innocuous stimulus
(the result of central sensitization)
(innocuous: not harmful or offensive.
what does the inflammatory response do?
enhances nociception
what type of sensitization is the result of the “inflammatory soup” of substances released after injury interacting with nociceptors
• Peripheral sensitization
what is the difference between A delta and C fibers?
-functions
delta fibers are myelinated, while C fibers are not – different speeds, so that first pain response comes from the delta fibers, with duller pain from the C fibers
where do delta and C fibers travel? where are their cell bodies?
in the spinal nerve; cell bodies at dorsal root ganglia
where do delta and C fibers enter? where do they synapse?
at the dorsal horn of the spinal column; at the dorsal horn
what pathway do the delta and C fibers travel in?
anterolateral/spinothalamic
how is the dorsal horn of the spinal cord divided?
six layers – C fibers synapse in layers 1 and 2, delta fibers in layers 1 and 5
What is in layer II of the dorsal horn?
substantia gelatinosa; uses substance P
• Lots of interneurons in II
what synapses in layers III and IV of the dorsal horn?
non-noxious stimuli
anterolateral system pathway
- synapses in the dorsal horn, cross and travel up the spinal cord ventrally
- travels through the medulla, up through the pons, and then through the midbrain to synapse in the ventral posterolateral nucleus of the thalamus and on to the cortex
Reticular formation
: alerting and threat area
Triggering threat responses
-some fibers synapse here; also called the paleo thalamic system; synapses at some of the intralaminar nuclei, important for alerting stimuli that are related to painful stimuli
Periaqueductal gray
: contains enkephalin-producing cells which can help suppress pain
Superior Colliculus:
avoidance and defensive behaviors??
face pain terminates where in the trigeminal nucleus
Terminate in two subdivisions of trigeminal nucleus: pars interpolaris and pars caudalis
therapeutically, what nuclei have been targeted for treatment of chronic pain?
centromedian and parafascicular
how does pain come in for the face
trigeminal tract – crosses and then goes to the ventral posteromedial nucleus and then on to the cortex
T/F just like ike in body pain systems, in regards to face pain systems, first pain/sensory discriminative pain and second pain/affective-motivational are pain kept separate
TRUE
First pain/sensory discriminative pain and second pain/affective-motivational pain kept separate like in body pain systems
how does pain info from different areas of the body travel?
sacral and lower parts of the body arrive laterally?; within the anterolateral system, cervical is more medial, sacral is more lateral;
what cranial nerves are associated with the face pain?
• Cell bodies of sensory afferents are located in the trigeminal ganglion and ganglia associated with cranial nerves VII, IX, and X (facial, glossopharyngeal, and vagus)
where do the dorsal columns cross?
in the medulla
for somatosensory I think
what receptors are in the periaqueductal gray?
lots of opioid receptors
noiciception vs pain
activation of the receptors and info coming up the spinal cord; pain is the larger concept, which can be modulated by central processes
Voltage-Gated Sodium Channels
Nav1.7 dysfunction related to many pain disorders
Loss of function inability to detect painful stimuli
Gain of function disorders leading to intense burning sensations
If over works = more sensitive
Upregulated in inflammatory pain models
Inhibitors reduce pain
Can be targeted
V stands for voltage
Na = sodium
Nav1.8 highly expressed by C nociceptors
No Nav1.8 no transmission of cold stimuli
Does not inactivate under cold temperatures
what is the gate theory of pain?
rub an area, activating A-beta fibers; this inhibits the inflammation coming from the C fiber and lessens pain
(dont think you need to know)
Which of the following might be associated with loss of taste from the anterior 2/3 of tongue, accompanied by paralysis of ipsilateral facial muscles, and impaired secretion of nasal and lacrimal and salivary glands?
a. Acoustic neuroma (CN VII tumor within the auditory meatus)
b. Destruction of the Vagus Nerve
c. Lesion of the Facial Nerve
d. Glioblastoma multiforme
e. A severe upper respiratory infection
Which of the following might be associated with loss of taste from the anterior 2/3 of tongue, accompanied by paralysis of ipsilateral facial muscles, and impaired secretion of nasal and lacrimal and salivary glands?
Lesion of the Facial Nerve
The only neurons that are in direct contact with the external environment are
a. Touch receptors in the skin
b. Photoreceptors
c. Vestibular hair cells
d. Olfactory receptors
e. Taste cells
The only neurons that are in direct contact with the external environment are
Olfactory receptors
Which substance enhances the sensitivity of pain receptors but does not directly excite them?
a. Bradykinin
b. Serotonin
c. Potassium ions
d. Prostaglandins
Which substance enhances the sensitivity of pain receptors but does not directly excite them?
Prostaglandins
Interneurons that utilize the neurotransmitter enkephalin to inhibit afferent pain signals are most likely to be found in which region of the central nervous system?
a. Dorsal horn of spinal cord
b. Postcentral gyrus
c. Precentral gyrus
d. d-type A
e. Type C fiber
f. Ventral horn of spinal cord
Dorsal horn of spinal cord
neuropathic pain
Pain caused by a lesion or disease of the somatosensory nervous system; implies an abnormal processing of the pain message from an injury to the nerve fibers. This type of pain is the most difficult to assess and treat. Pain is often perceived long after the site of injury heals, and it evolves into a chronic condition.
Referred pain
Referred pain
- Pain that is felt at a particular site but originates from another location
- Both sites are innervated by the same spinal nerve, and it is difficult for the brain to differentiate the point of origin
Peripheral Sensitization vs Central Sensitization- why, differences in pain treatment outcomes**
Allodynia
what fibers can transmit transmit non-discriminative touch information?
C-fibers
Goes through anterior spinothalamic tract (subdivision of anterolateral system) and not the DC-ML like other somatosensory information
(the result of central sensitization)
Allodynia
Hyperalgesia
Hyperalgesia is a condition in which you experience an enhanced sensitivity to pain. This is caused by specific nerve receptors in your body becoming more sensitive. Hyperalgesia can develop due to tissue or nerve injury as part of a surgery or procedure. It can also occur in people who are taking opioids.
