Pain Quiz 2

Question 1

What are the four major somatosensory modalities?

Sensory receptor cells located on which organs?

Stimuli encoded as?

Answer 1

1. Discriminative touch
2. Proprioceptive - awareness of own body position
3. Temperature
4. Nociception - pain

Sensory receptor cells located on sense organs

Stimuli encoded as action potentials

Question 2

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?

Answer 2

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

Question 3

Which correctly ranks the diameter of afferent sensory axons from smallest to largest?

Answer 3

C, A-delta, A-beta, A-alpha
C smallest
A-alpha largest

Question 4

How do we sense a number of different sensations in the periphery?

What are Primary Afferents?

Fiber are?

Answer 4

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

Question 5

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?

Answer 5

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

Question 6

Merkel (non painful superficial layer):

what adapting?

receptive field/resolution?

responds to?

Answer 6

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

Question 7

Meissner (non painful superficial layer):

what adapting?

receptive field/resolution?

responds to?

Answer 7

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

Question 8

Pacinian (glabrous, deep layers subcutaneous):

what adapting?

receptive field/resolution?

responds to?

Answer 8

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

Question 9

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?

Answer 9

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

Question 10

Which two adaptation types?

Receptive Fields and Adaptation of Mechanoreceptors reflects?

Answer 10

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

Question 11

Receptive Field Plasticity

Newly discovered mechanoreceptors for innocuous mechanical stimuli? What does it mediate? What happens if knockout?

Answer 11

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

Question 12

Proprioceptive Receptors

Which fibers?

Muscle spindles?

Golgi tendon organs?

Golgi Tendon Reflex?

Answer 12

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

Question 13

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?

Answer 13

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

Question 14

Where are TRP receptors expressed?

Answer 14

At peripheral nerve terminals by skin - TRP determines reception

Question 15

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?

Answer 15

> 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

Question 16

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?

Answer 16

~ 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

Question 17

Mediators released during tissue damage and inflammation:

Answer 17

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

Question 18

Merkel cell afferent fibers convey information about which variable(s)?

Answer 18

Shape and texture

Question 19

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

Answer 19

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

Question 20

Nociception (nociceptors located in skin muscles joints and viscera)

Primary afferent preferentially sensitive to a?

Mechanical?

Thermal?

Polymodal?

First pain is?

Second pain is?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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?

Answer 22

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

Question 23

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?

Answer 23

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

Question 24

Sensation Pathway – Touch Discrimination
Medial Leminiscal Pathway(dorsal column) – BODY

Answer 24

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

Question 25

Ascending Nociceptive Pathways - don't split until get to brain - palo neo Anterolateral Pathway – 2 Parts: pain, itch, temp, visceral

Answer 25

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!

Question 26

Medial Lemniscal System:? Trigeminal Sensory System:? Anterolateral system:? Caudal to rostral rostral to Caudal

Answer 26

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

Question 27

Which fibers conduct the sensation of first pain?

Answer 27

Myelinated A delta

Question 28

Example Touch: from left foot

Answer 28

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

Question 29

Example Pain: from left foot

Answer 29

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

Question 30

Primary Somatosensory cortex Location? Organization?

Answer 30

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

Question 31

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.

Answer 31

A-beta, medulla, A-delta and C, dorsal horn of spinal cord

Question 32

Which deficit would a lesion restricted to the right side of the spinal cord produce?

Answer 32

Pain deficit on the left side and mechanosensory deficit on the right side of the body

Question 33

Primary somatosensory cortex true or false: The amount of cortex dedicated to each body part is proportional to the density of the body part

Answer 33

True

Question 34

What change could improve the two-point discrimination of a region of skin?

Answer 34

An increase in the density of innervation of Merkel cells

Question 35

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.

Answer 35

A-beta, medulla, A-delta/C, Dorsal horn of spinal cord

Question 36

Dermatomes

Answer 36

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

Question 37

In the early 1900s, Sherrington defined nociceptive behavior: Nociception include all events following damage or threat of damage to tissue: which three?

Answer 37

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

Question 38

Peripheral Terminations of Nociceptors Peripheral Axonal Terminal START? Central Axonal Terminal? Cell Body (soma) DRG?

Answer 38

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

Question 39

Classification of Nociceptors Morphology? Somatic and axonal? Neurochemical profile? Functional properties:?

Answer 39

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)

Question 40

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

Answer 40

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

Question 41

Organization of the Spinal Cord Dorsal Horn Nociception input to spinal cord?

Answer 41

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

Question 42

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)

Answer 42

Small, 1 or 2

Question 43

Cutaneous and Subcutaneous Somatic Nociceptors (skin, fascia, etc) Myelinated nociceptors (mostly Aδ - Adelta) Which three? Unmyelinated nociceptors (C fibers) which?

Answer 43

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

Question 44

Myelinated Nociceptors: Conduction velocity? Receptive field? Most sensitive to? Poor response to? Many become sensitized to?

Answer 44

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

Question 45

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?

Answer 45

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

Question 46

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 - ?

Answer 46

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

Question 47

Which cutaneous nociceptor is less likely to be activated by a stubbed toe but more likely to be activated by stepping on a nail?

Answer 47

HTM

Question 48

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?

Answer 48

Accelerating linear function - more AP sent with greater temp

Question 49

Deep Somatic Nociceptors (muscle, bones, teeth, cornea, joints, etc) Muscle Nociceptors? Two types: ? How can you experimentally excite muscle sensory neurons?

Answer 49

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

Question 50

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?

Answer 50

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

Question 51

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)

Answer 51

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

Question 52

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?

Answer 52

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

Question 53

Correlation of Human Pain Sensation with Nociceptor Activity

Answer 53

Human Psychophysics: Good correlation with activity of C-fiber nociceptors Microneurography: Simultaneous human description of sensation associated with response of individual nociceptor

Question 54

Functional properties and neurochemical expression NT? slow fast Receptors

Answer 54

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

Question 55

How do you figure out what neurotransmitters and receptors that DRG neurons and dorsal horn neurons express?

Answer 55

Immunohistochemistry!

Question 56

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

Answer 56

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

Question 57

Research problem afferent toward brain from periphery:

Answer 57

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

Question 58

HTM

Answer 58

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)

Question 59

AMH I

Answer 59

Myelinated A-delta mid mechanical threshold sensitive to very high temps sensitizes to noxious heat fast conduction velocity

Question 60

AMH II

Answer 60

Myelinated A-delta, low mech threshold, sensitive to borderline noxious temperatures, desensitizes to strong thermal stimuli, slower conduction velocity (faster than CMH)

Question 61

CMH

Answer 61

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

Question 62

Group 3

Answer 62

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

Question 63

Group 4

Answer 63

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