Pain Quiz 2 Flashcards
What are the four major somatosensory modalities?
Sensory receptor cells located on which organs?
Stimuli encoded as?
- Discriminative touch
- Proprioceptive - awareness of own body position
- Temperature
- Nociception - pain
Sensory receptor cells located on sense organs
Stimuli encoded as action potentials
Dorsal Root Ganglion (DRG) - primary receptor cell
What type of cells?
Neuron cell body is located in the what and adjacent to the what?
The axon of the DRG neuron has what kind of transmission line? With one polarity between what? Has two branches?
For which organs in the body?
Anatomy of the DRG
Dorsal root vs Ventral root?
Pseudounipolar cells: a type of sensory neuron that appears to have only one process extending from its cell body
Neuron cell body is located in the DRG adjacent to the spinal cord
The axon of the DRG neuron single transmission line
- With one polarity between receptor terminal and CNS
- Has two branches(one branch to spinal cord or to brain and other branch is like a dendrite it receives on the receptor), one projects to the periphery and one to the CNS
For skin, muscle and viscera
Anatomy of the DRG
Dorsal root: sends sensory info revised from periphery to brain
Ventral root: motor info send from brain and spinal cord out to periphery
Which correctly ranks the diameter of afferent sensory axons from smallest to largest?
C, A-delta, A-beta, A-alpha
C smallest
A-alpha largest
How do we sense a number of different sensations in the periphery?
What are Primary Afferents?
Fiber are?
Non-Noxious(painful or damaging)(another word for non-noxious is innocuous), Touch
Primary Afferents = periphery to spinal cord or brain stem
Primary afferents are sensory neurons (axons or nerve fibers) in the peripheral nervous system that transduce information about mechanical, thermal, and chemical states of the body and transmit it to sites in the central nervous system.
Fiber are axons
What are the 3 myelinated afferent sensory axons/fibers and for what body?
What is the 1 unmyelinated afferent sensory axons/fibers and for what body?
Myelinated:
Aα(alpha) - proprioception - fast mainly skeletal muscle
Aβ(beta) - mechanoreception - little smaller for skin
Aδ(delta) – pain and temperature - smaller diameter
Unmyelinated:
C – pain, temperature, itch - more than 90% and slow
Merkel (non painful superficial layer):
what adapting?
receptive field/resolution?
responds to?
slowly adapting(constant rate of firing like holding heavy object - activate for entire length of stimulus,
small receptive field/high spatial resolution (dark and smaller area - the smaller the field the higher resolution so able to pinpoint where stimulated)
responds to edges, corners, and points
Mechanoreceptors so not painful
Meissner (non painful superficial layer):
what adapting?
receptive field/resolution?
responds to?
rapidly adapting
small receptive field/high spatial resolution
responds to stroking, fluttering, and low frequency vibration, example wind or feather or shirt fluttering on skin
Mechanoreceptors so not painful
Pacinian (glabrous, deep layers subcutaneous):
what adapting?
receptive field/resolution?
responds to?
high frequency vibration,
rapidly adapting (abrupt - changing throughout stimulus like wind)
large receptive field/low spatial resolution, example standing near bus and feel vibration or like earthquakes
Mechanoreceptors so not painful
Mechanoreceptors
Glabrous, superficial layers includes which two?
Glabrous, deep layers (subcutaneous) have more receptive fields includes which two?
Hairy skin is which layer?
Hair receptors innervate how many hairs in same what cm and feel?
Fingertips higher density of?
Palm lower amounts of what but more or equal of?
Forearm have them inches apart bc of?
Reading braille is best for which area?
Glabrous, superficial layers:
Meissner’s corpuscles → storking, fluttering - decet initial contact
Merkel disks → edges, corners, points
Glabrous, deep layers (subcutaneous) have more receptive fields:
Pacinian corpuscle → vibration
Ruffini ending → skin stretch and feel large objects
Hairy skin is superficial layer
Hair receptors - innervate 10-30 hairs in same 2-3 cm and feel stroking and fluttering
Fingertips higher density of superficial
Palm lower amounts of superficial but more or equal of subcutaneous
Forearm have them inches apart bc of density of mechanoreceptors and respective fields so density is different
reading braille so superficial will have smaller areas therefore will have accurate signals sent for merkel vs Pacinian/Ruffini will have larger area and can’t sense braille
Which two adaptation types?
Receptive Fields and Adaptation of Mechanoreceptors reflects?
Rapidly adapting (Mesinner RA1 and Pacinian RA2)
Slowly adapting SA1 Merkel and SA2 Ruffini - burst at the start and then constant
Receptive Fields and Adaptation of Mechanoreceptors - reflects location and distribution
Receptive Field Plasticity
Newly discovered mechanoreceptors for innocuous mechanical stimuli? What does it mediate? What happens if knockout?
Piezo-2: mediates mechanosensitive currents in sensory neurons; enhanced activity associated with mechanical hypersensitivity (non-painful stimuli is now painful so knockout Piezo-2 decreases allodynia
Proprioceptive Receptors
Which fibers?
Muscle spindles?
Golgi tendon organs?
Golgi Tendon Reflex?
Mostly Aα- myelinated fast condition, some Aβ
Muscle spindles: Stretch sensitive ion channels in muscle spindle so depo is proportional to velocity and amp - fast or large muscle stretch is proportional
Golgi tendon organs: between muscle and tendons that measures forces generated by muscle contraction
joint capsule receptors
Golgi Tendon Reflex: Curial reflex arc that operates as a feedback mechanism
Temperature (Noxious and NonNoxious) - TRP channels
Thermal Receptors?
Senses temperature changes: 4 classes, have preferred range?
Thermal sensitivity of neuron is determined by?
TRPA1?
TRP4 and TRPV3?
TRPV1?
Thermal Receptors: A-Delta and C fibers
Senses temperature changes: 4 classes, have preferred range - cold, cool, warm, hot
Cold and hot are painful
Cool and warm are innocuous
Thermal sensitivity of neuron is determined by TRP receptors expressed
TRPA1(allium like garlic and radish) and 8(mint) are for cooling and cold stimuli
TRP4 and TRPV3 at skin temp resting are stimulated
TRPV1 spicy
TRP are channels that respond to different channels of temp - pain and no pain - located at A-delta and C fibers which include both noxious and non noxious
Pain - is TRPV1(heat and chemicals like peppers) and TRPV2 damage hat
TRPA1 cold damage - dry ice
TRPM8 cool not damage
TRPV4, TRPV3 not pian temp
Where are TRP receptors expressed?
At peripheral nerve terminals by skin - TRP determines reception
Transduction of noxious heat
What is the most painful temp?
Multiple TRP receptors sensitive to these temperature ranges?
Knockout lines of TRP receptors sensitive to noxious temperatures have deficits in?
> 42 degrees Celsius (108 F)
Multiple TRP receptors sensitive to these temperature ranges TRPV1 and TRPV2
Knockout lines of TRP receptors sensitive to noxious temperatures have deficits in heat sensitivity
TRPV1 - Phenotype of TRPV1 KO mice
Transduction mechanisms for low pH - TRP temp and low PH
Which fibers with TRP express low PH?
pH activated currents in sensory neurons are?
TRPV1 most likely mediates?
heteromeric Acid sensing channels (ASIC) channels may underlie?
~ 30% of C-fibers with TRP receptors expressed on them respond to low pH
pH activated currents in sensory neurons are sustained or transient
TRPV1 most likely mediates sustained pH responses
heteromeric Acid sensing channels (ASIC) channels may underlie transient pH responses
ASIC3: role in cardiac ischemia
Mediators released during tissue damage and inflammation:
ATP, bradykinin
ATP released from damaged cells can signal through P2X and P2Y receptors (P2X3 and P2Y2)
bradykinin-induced thermal hyperalgesia requires both TRPV1 and TRPA1
Merkel cell afferent fibers convey information about which variable(s)?
Shape and texture
The Uniqueness of Itch
Itch is different from pain bc pain causes a withdraw from stimulus while itch?
Pruritic itch inducing agents at which afferents in skin - information sent from periphery travels through which located in to what?
Two agents that cause itch?
Neuron firing rate decreases with scratch?
When tissue damage or inflammation skin cells like keratin ascites and fibroblasts addition to infiltrating resident immune cells can release what? that active which receptors in which fibers like what? so can bind to which protein and recruit in increase intracellular what through what
Itch is different from pain bc pain causes a withdraw from stimulus while itch causes scratch
Pruritic itch inducing agents at primary afferents in skin - information sent from periphery travels through primary afferents C fibers(no myelin) located in DRG to brain
Cause itch:
Histamine
Chloroquine
Neuron firing rate decreases with scratch - so itchy stimuli cause AP — neurons responding to histamine sending const AP saying itchy so when scratch no more AP - dont feel itchy anymore bc inhibiting neurons sending itch
When tissue damage or inflammation skin cells like keratin ascites and fibroblasts addition to infiltrating resident immune cells can release Pruritogens that active pruritic receptors in C fibers like Histamine and other RNAS and can bind to G protein and recruit in increase intracellular Ca through TRPV1
Nociception (nociceptors located in skin muscles joints and viscera)
Primary afferent preferentially sensitive to a?
Mechanical?
Thermal?
Polymodal?
First pain is?
Second pain is?
Primary afferent preferentially sensitive to a noxious stimulus that damage tissue
Mechanical – high threshold, mostly Aδ - (delta as short latency which is sharp and prickly)
Thermal - Aδ and C fibers(dull diffuse)
Directly mechanical and thermal but indirectly chemical
Polymodal – C fibers - medicinal, thermal, chemical
Propagation in nociceptors - cross sectional diameter:
– First pain is sharp and fast mediated by A-delta
– Second pain is throbbing and aching and lingers mediated by C-fibers
Tissue injury damages cells, attracts inflammatory cells - release chemokines that attract immune cells like mast cells, macrophages, and dendritic
Damaged/Inflammatory cells release several substances:?
Stimulated nociceptors release: ?
Substance P VS Glutamate
Damaged/Inflammatory cells release several substances:
Histamine
Arachadonic acid → prostaglandins
Stimulated nociceptors release:
Substance P
Increases vasodilation so more can be recruited by circulation, inflammation makes redness, release of histamine
Excites interneurons(2* afferents) in spinal cord
Glutamate
Excites interneurons(2* afferents) in spinal cord - send pain to brain
Which processes contribute to sensitization (increasing pain) following tissue damage?
How are signals sent from the periphery to the brain?
Which fibers conduct the sensation of first pain?
Which processes contribute to sensitization (increasing pain) following tissue damage? Release of peptides and NT from nociceptors, migration of immune cells to the site of damage, release of proinflammatory substances by the non-neuronal cells, damage skin cells releasing cytokines to recruit immune cells
How are signals sent from the periphery to the brain? Somatosensory Pathways
Which fibers conduct the sensation of first pain? Myelinated A-delta
Projections of Sensory Neurons - pseudounipolar
Neurons carry APs from skin to spinal cord
Spinal nerves: ? Divisions VS “Mixed” nerves
Central Somatosensory Pathways: The 3 neuron rule - For touch, temperature and pain: It takes 3 neurons for a sensory signal to be relayed from the body to the sensory cortex
Pain/Temp VS Touch?
Spinal nerves:
Divisions: 8 Cervical, 12 Thoracic, 5 Lumbar, 5 Sacral, 1 Coccygeal
“Mixed” nerves
Contain both motor and sensory neurons in periphery – contains information sent from mechanoreceptors and nociceptors - for touch, pain, temp, and pain
Pain/Temp: 1 ipsilateral Sensory Neuron, 2(second order neuron) Spinal Neuron (crosses), 3 Thalamic Neuron
Touch: 1 ipsilateral Sensory Neuron, 2 Medulla Neuron Brain Stem (crosses), 3 Thalamic Neuron
Sensation Pathway – Touch Discrimination
Medial Leminiscal Pathway(dorsal column) – BODY
Carries information about discriminative touch
1* afferents terminate in medulla (ipsilateral – same side):
2* afferents from dorsal column nuclei to dorsal thalamic nuclei
Decussate – cross over to contralateral (opposite) side
3* afferents from VPN(dorsal thalamus) to primary somatosensory cortex parietal lobe
Ascending Nociceptive Pathways - don’t split until get to brain - palo neo
Anterolateral Pathway – 2 Parts: pain, itch, temp, visceral
Paleospinothalamic tract – SLOW
To thalamus and parietal cortex: From C fiber nociceptor axons
To the reticular activating system: Affects arousal, mood, attention response
Neospinothalamic tract - FASTER
To the thalamus and parietal cortex:
From Aδdelta fiber nociceptor axons
Both decussate (cross-over) to the contralateral side in the spinal cord!
Medial Lemniscal System:?
Trigeminal Sensory System:?
Anterolateral system:?
Caudal to rostral
rostral to Caudal
Medial Lemniscal System:
- Touch for BODY
- Doesn’t cross over until the medulla
Trigeminal Sensory System:
- Touch for Face
- Crosses over in pons
Anterolateral system:
- Pain, itch, visera(internal organs) and temperature information
- Crosses over immediately in the spinal cord
Organized Caudal to rostral - feet to head for touch
Anterolateral system rostral to Caudal
Which fibers conduct the sensation of first pain?
Myelinated A delta
Example Touch: from left foot
Example Touch: from left foot TO cell body for sensory neuron DRG first order neuron (dorsal column area of spinal cord for white matter tract) TO spinal cord TO synapse in medulla same side which is second order neuron TO dorsal column for synapse in thalamus third order neuron cross over TO cortex. Lower body axons travel closer to midline sacral and synapse on gracile nucleus and upper body cuneate nucleus - dorsal column nuclei are both gracile and cuneate
Example Pain: from left foot
Example Pain: from left foot TO first order neuron is sensory DRG same side synapse TO cross over in spinal cord dorsal horn TO pass through medulla TO synapse thalamus 3rd TO cortex
1 Sensory Neuron DRG, 2 Spinal Neuron (crosses) spinal cord dorsal horn, 3 Thalamic Neuron
Primary Somatosensory cortex
Location?
Organization?
Located in parietal lobe
Somatotopic Organization:
Regions of body represented like a map in cortex based on sensitivity so more in lips and fingertips than thigh seen by homunculus
Discriminative touch is sent by BLANK fibers. The second order neuron is located in the BLANK, where its axons then cross over. Pain and temperature are sent by BLANK fibers. The second order neuron is located in the BLANK, where its axons then cross over.
A-beta, medulla, A-delta and C, dorsal horn of spinal cord
Which deficit would a lesion restricted to the right side of the spinal cord produce?
Pain deficit on the left side and mechanosensory deficit on the right side of the body
Primary somatosensory cortex true or false: The amount of cortex dedicated to each body part is proportional to the density of the body part
True
What change could improve the two-point discrimination of a region of skin?
An increase in the density of innervation of Merkel cells
Discriminative touch is sent by BLANK fiber. The second order neuron is located in the BLANK, where the axons then crossover. Pain and temp are sent by BLANK fibers. The second order neuron is located in the BLANK, where its axons then cross over.
A-beta, medulla, A-delta/C, Dorsal horn of spinal cord
Dermatomes
The area of skin and tissue innervated by a single dorsal root
31 pairs of dorsal root nerves are projected onto the surface of the body
The ability to localize touches to the skin varies across the body - two point threshold
Location discrimination is best on the hand and face
In the early 1900s, Sherrington defined nociceptive behavior:
Nociception include all events following damage or threat of damage to tissue: which three?
Defined noxious stimulus as having a certain intensity and quality sufficient to trigger nociceptive reaction in an animal
Responses mediated by nociceptors, nocicipients
Nociception include all events following damage or threat of damage to tissue:
- Activity in nociceptors
- Activity in non-neuronal cell types
- Subsequent activity in CNS neurons and pathways
Peripheral Terminations of Nociceptors
Peripheral Axonal Terminal START?
Central Axonal Terminal?
Cell Body (soma) DRG?
Peripheral Axonal Terminal START:
- Transduction, generator potential
- Interact with surroundings
Central Axonal Terminal:
- Neurotransmitter release
- Neuromodulator release
Cell Body (soma) DRG:
- Maintenance of entire neuron
- Protein synthesis and trafficking
- Phenotypic change
- Pathologic generation of action potentials
Classification of Nociceptors
Morphology?
Somatic and axonal?
Neurochemical profile?
Functional properties:?
Morphology - soma size or afferent type
Somatic and axonal electrophysiological properties
Neurochemical profile - NT and receptors
Functional properties: Modality(mechanical,thermal,chemical), Threshold(forcer or temp required), Receptive field characteristics(size disruption), Stimulus-response relations and dynamics(how do they respond is excitation linear)
Cell Bodies (somata) of nociceptors
Correlations of functional and morphological properties
What three factors?
Cells with largely myelinated VS small myelinated VS unmyelinated axons
Larger axons have
Somal size, axonal diameter, and axonal CV (conduction velocity)
Cells with largely myelinated axons usually have large stomata
Cells with small myelinated axons can have large or small somata
Cells with unmyelinated axons usually have small somata
Larger axons have higher conduction velocity and smaller axons had lower/slower conduction velocity
Organization of the Spinal Cord Dorsal Horn
Nociception input to spinal cord?
Somatosensory input to spinal cord
Nociception input to spinal cord
- C - lamina 1 and 2
- Small A-delta lamina 1+ 4
- Abeta mecho - lamina 4 + 5
- Interneurons that connect layers after injury signal gets mixed so touch is pain
You are a researcher trying to determine which of the cells in the DRG is a C-fiber nociceptor. You use an antibody that is able to stain the cell body and the two axonal branches. Answer the following questions:
What size will the cell body be? fill in blank (large or small)
Where will you find the central terminals in the dorsal horn (which can be more than one). fill in blank (1, 2, 3, 4)
Small, 1 or 2
Cutaneous and Subcutaneous Somatic Nociceptors (skin, fascia, etc)
Myelinated nociceptors (mostly Aδ - Adelta)
Which three?
Unmyelinated nociceptors (C fibers) which?
Myelinated nociceptors (mostly Aδ - Adelta)
- High Threshold Mechanical nociceptors (HTM or AδHT)
- A-Mechanoheat Type I (or AMH I)
- A-Mechanoheat Type II (or AMH II)
HTM - A delta and need higher amount of input to be activated so not just pinch more like hit or burn
Unmyelinated nociceptors (C fibers)
- CMH and C Polymodal Nociceptors
Myelinated Nociceptors:
Conduction velocity?
Receptive field?
Most sensitive to?
Poor response to?
Many become sensitized to?
Conduction velocity: 15-25 m/sec
Receptive field: discrete spots, up to 20
Most sensitive to sharp objects placed on RF spot
Poor response to heat or cold
Many become sensitized to mechanical and thermal stimuli after intense thermal stimulus - hyper sensitivity following injury
A-Mechanoheat Type I and II (AMH I and II)
Conduction velocity?
Mechanical threshold?
Thermal threshold?
Responds quickly pr slow?
sensitizes or de-sensitizes to heat?
AMH Type I
- Conduction velocity: 25-30 m/s - fast
- Mechanical thresholds: higher than type II, lower than HTM
- Thermal threshold: fairly high (>50 C)
- Delayed/prolonged response to noxious heat
- Usually sensitizes to noxious heat
AMH Type II
- Conduction velocity: ~ 15 m/s
- Mechanical threshold: lower than type 1
- Thermal threshold (43-44 C) < AMH I
- Responds quickly to heat, then adapts
- Often de-sensitizes to heat
AMH 1: myelinated A-delta fibers, medium mechanical threshold, sensitive to high noxious stimulus, fast conduction velocity
AMH 2: myelinated A-delta fibers, low mechanical threshold, sensitive to borderline temp, desensitized after noxious temp, fast condition velocity but slower than AMH 1
C-Mechanical/Heat Nociceptors (CMH)
Receptive field?
Mechanical thresholds?
Thermal thresholds?
Sensitized by heat: to ?
Many CMH’s also respond to ?
CMH Response to Stimuli - ?
Receptive field: fewer spots: 1-2 mm squared
Mechanical thresholds, variable: mid to high
Thermal thresholds: low 38-45 deg C – codes well 45-53 deg C, fast utilization time
Sensitized by heat: to subsequent heat stimuli, but not mechanical stimuli
Many CMH’s also respond to chemical stimulation, called C Polymodal Nociceptors– eg acid, bases, algesic agents
CMH Response to Stimuli - Accelerating linear function
CMH: slower conduction velocity, mid/high mechanical threshold(poking), unmyelinated c-fiber, sensitized to boldrine noxious temp, sensitive to very high/noxious temps, sensitized following strong thermal stimuli, slower conduction velocity, active during inflammation, sensitive to algesic substances
Which cutaneous nociceptor is less likely to be activated by a stubbed toe but more likely to be activated by stepping on a nail?
HTM
If you graphed the pattern of activation compared to stimulus intensity of a CMH nociceptor during gradual temperature increases, what line would you expect to see?
Accelerating linear function - more AP sent with greater temp
Deep Somatic Nociceptors (muscle, bones, teeth, cornea, joints, etc)
Muscle Nociceptors?
Two types: ?
How can you experimentally excite muscle sensory neurons?
Nociceptors in muscles aimed at detecting stretch outside the normal range and analgesic agents released following strenuous activity – movement outside normal
Two types:
Group III - A-delta
Group IV - C-fiber - chemical
How can you experimentally excite muscle sensory neurons?
Injection combination of muscle metabolites like pH, ATP, and Lactate
Low concentration? Fatigue
High concentration? Pain
Deep Somatic Nociceptors (muscle, bones, teeth, cornea, joints, etc)
Joint Nociceptors?
Two types:?
Is there activity in a healthy joint?
What happens when the joint becomes inflamed?
Nociceptors in joints aimed at detecting movement past normal range and agents that produce inflammation
Two types: both sensitive to algesic agents and agents that produce inflammation, both play a likely role in arthritis
Group III (3) - A-delta myelinated
Group IV (4) - C-fiber unmyelinated
Is there activity in a healthy joint?
There is some activity of group III and group IV afferents during innocuous movement in the normal range
What happens when the joint becomes inflamed?
Number of axons with ongoing activity doubles
Number of non-nociceptive neurons doubles - silent nocireceptors only on for inflammation
Ie – respond to movement in normal range
Describe the activation of Group III and IV nociceptors (NOT silent nociceptors) in the joints before and after inflammation.
Active during normal movement? fill in blank (yes or no)
Active after inflammation? More, less or the same as normal? fill in blank (yes or no) fill in blank (more, less, same)
Plays a role in arthritis? fill in blank (yes or no)
Active during normal movement? fill in blank (yes or no) YES
Active after inflammation? More, less or the same as normal? fill in blank (yes or no) fill in blank (more, less, same) YES, MORE
Plays a role in arthritis? fill in blank (yes or no) YES
Visceral Nociceptors (internal organs like heart, intense etc)
Many challenges in study of visceral nociceptors?
Sensations from some organs restricted mostly to pain – eg blood vessels, respiratory tree, biliary system, pancreas, ovaries, testis?
Many challenges in study of visceral nociceptors:
Nature of “adequate” noxious stimulus
What is a noxious stimulus?
Nociceptors have been identified in some visceral organs:
- Some organs give rise to non-painful and painful sensations – eg esophagus, bladder, urethra, and much of GI tract
- Sensations from some organs restricted mostly to pain – eg blood vessels, respiratory tree, biliary system, pancreas, ovaries, testis
Example: Bladder
Crosstalk of Visceral Nociceptors - heartache not just chest pain so referred pain the internal organs manifest body surface pain
Correlation of Human Pain Sensation with Nociceptor Activity
Human Psychophysics:
Good correlation with activity of C-fiber nociceptors
Microneurography:
Simultaneous human description of sensation associated with response of individual nociceptor
Functional properties and neurochemical expression
NT? slow fast
Receptors
Neurotransmitters:
Peptides slower - Substance P and CGRP
Glutamate faster
ATP faster
Receptors:
Glutamatergic receptors - NMDA, mGluRs
Opioid receptors - mu-opioid
Peptide receptors - NK-1 for Substance P, CLR for CGRP
Purinergic receptors
TRP receptors
How do you figure out what neurotransmitters and receptors that DRG neurons and dorsal horn neurons express?
Immunohistochemistry!
Sensory transduction and activation of nociceptors
Convert mechanical, thermal, chemical energy into electrical signal?
Challenges to study of transduction mechanisms
Possible direct vs indirect mechanisms
Convert mechanical, thermal, chemical energy into electrical signal
Graded generator potential AP
Challenges to study of transduction mechanisms
- Multiple modalities possible in same neuron
Wide range of intensities
Direct mechanisms: transduction molecule in axonal membrane. Mechanical or thermal gated ion channel
Possible indirect mechanisms: chemical signals from neighboring cells
Research problem afferent toward brain from periphery:
sensitivity of merkel disks to different depths - greater amount of AP/response sent with greatest indentation right on the center or on top of merkel receptive field and distance from center of simulation the lower the response. The deeper the indication the greater the response and greater at the center of the respective field.
Adaptation types of merkel dicks have slowly adapting - change detectors and releases NT serotonin (primary afferent innervation merkel cell will have receptor NT serotonin)
Another way to confirm serotonin is the NT merkel dicks release this could record from afferents in presence of different antagonist, block postsynaptic receptor, measuring NT released, stain for NT or presence of receptor, knockout model in mouse
HTM
Myelinated A-delta
High mechanical threshold
Poor response to heat or cold
Sensitizes following intense thermal stimuli
fast conduction velocity
HTM: high mechanical thresholds, myelinated A-delta, fast conduction velocity, sensitized following strong thermal stimuli (like when pook), poor response to heat/cold temp, this is a mechanical nociceptors, (where you have burn you take a strong pook)
AMH I
Myelinated A-delta
mid mechanical threshold
sensitive to very high temps
sensitizes to noxious heat
fast conduction velocity
AMH II
Myelinated A-delta, low mech threshold, sensitive to borderline noxious
temperatures, desensitizes to strong thermal stimuli, slower conduction
velocity (faster than CMH)
CMH
Unmyelinated C-fibers, mid mechanical threshold, sensitive wide range
of temps – both borderline noxious and very high, sensitized following
strong thermal stimuli, active during inflammation, sensitive to algesic
substances, slower conduction velocity
Group 3
Myelinated a-delta
active during normal movement in JOINTS but not muscles
sensitive to movement outside normal range in joints AND
muscles
sensitive to algesic agents in joints AND muscles
active during inflammation in joints AND muscles
fast conduction velocity
Group 4
Unmyelinated C-fibers
active during normal movement in JOINTS but not muscles
sensitive to movement outside normal range in joints AND
muscles
sensitive to algesic agents in joints AND muscles
active during inflammation in joints AND muscles
slow conduction velocity
