Week 2 Flashcards by Jihan Haji

What occurs during condition of injury?

Convergent signalling

Sometimes what would normally be innocuous stimuli feels painful

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What is Allodynia?

Innocuous stimuli is felt as painful

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What is Hyperalgesia?

Painful stimulus appears more painful

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How can convergent processing be identified?

Knock on head

Rubbing head

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What is the gate control theory?

Non-painful input closes the nerve “gates” to painful input

Prevent pain sensation from travelling to the CNS

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What are the physiological mechanisms of sensation?

Transduction
Transmission
Perception
Modulation

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What is transmission?

AP going from periphery to CNS and then upward through the system to our perception

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Where does opioid receptors modulate in?

Brain and spinal cord

Central

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What receptors are related to noxious heat?

TRPV1/2 or TREK channels

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What is TRPA1 opened by?

Number of chemical mediators

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What are cold stimuli mediated by?

TRPM8

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What is TRPV1 ?

Capsaicin receptor (hot pepper)

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Where does Bipolar neuron stay?

In visual system

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Where does Pseudo-unipolar stay?

Somatosensory system or motor system

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What is the function of contact projection neurons?

Send information more centrally

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What can contact projection neurons induce?

Cognitive response
Behavioural response
Integration of other information

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What is the major neurotransmitter of sensory afferent?

Glutamate

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What is the function of AMPAR receptors?

Induce a fast polarising current

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What is the function of Cl-?

Act as intracellular messenger altering metabolism of cells binding to EKC

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Metabotropic receptors

Have links to GPCR to CAMP

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What does Glutamate on the second neuron allow?

Plasticity

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What can induce central sensitisation?

Metabotropic receptors

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What can AP fired be?

Different sequence and intensity

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What are examples of cutaneous?

Pricking
Stabbing
Burning
Well localised

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What are examples of muscle?

Aching | Cramping

What are examples of Visceral?

Fullness Dullness Vague

In the muscle what is innocuous stimuli brought by?

Ad fibre and A fibre

What doesn’t the free nerve ending detect?

Innocuous stimuli

What are the characteristics of larger neurons?

Large diameter axons | Myelinated

What is C-fibre?

Slow conduction velocity

Myelinated fibres

Fast conduction velocity

What are C fibres?

Polymodal

A fibre

Low threshold mechanosensation

C fibres

High threshold | Mechano, thermo, chemonociception

What are itch fibres conveyed by?

C-fibres

What are C fibres important for?

Crude touch

What are properties of A fibres ?

Ad fibres can be innocuous Fast conduction velocity Low threshold mechanoreceptors Innervate specific peripheral receptors

What are properties of C fibres?

``` Unmyelinated fibres Slow conduction velocity Innervate free nerve endings Predominantly polymodal nociceptors 2 subgroups: Peptide rich Peptide poor ```

Define polymodal nociceptors

Nociceptors respond to more than one of these modalities

What are the 2 different types of axon that nociceptors have?

A delta fibre axon | C fibre axon

A delta fibre axon

Myelinated and can allow action potential to travel at a rate of about 20 meters/second towards the CNS Unconscious circuitry

C fibre axons

More slowly conducting Only conduct at speeds of around 2 meters/second Light or non-myelination of the axon

What are the two phases pain comes in?

1. Fast-conducting A delta fibres | 2. Polymodal C fibres

What can the pain associated with A-delta fibre be associated with?

Initial extremely sharp pain

What are peptidergic fibres?

Largest group of nociceptors and contain one or both of the neuropeptides substance P and CGRP

What are TrkA?

High affinity receptor for NFG

What are critical for the development of nociceptors ?

TrkA and NGF

What allows the release into periphery?

Terminal region of C-fibre

What can peptides cause?

Leakiness Invasion of inflammatory cells Release of inflammatory mediators Neurogenic inflammation

What can sensitize c-fibres even further?

Blood circulation Protection of injury site Sensitisation of that inflammation site

What are the nonpeptidergic nociceptors defined by?

Expression of Ret

Myelinated fibres

Have neurofilaments: heavy and light chain | Phosphorylated

What are all C fibres dependent on?

Nerve growth factor

What is the function of growth factor?

Responsible for the development of tissues in adults

What are Neurotrophins?

Family of proteins that include the survival, development and function of neurons

What are examples of neurotrophins?

Neurotrophin 3 (NT3) BDNF GDNF ligands

What does tract-tracing reveal?

Correlation between neurochemistry and peripheral target type

What does each class of axon have?

Specific lamina distribution of its central terminal

Where does nociceptors stretch?

Upper more superficial laminae and at a laminae 1-2

Where does pain fibres have input in?

Laminae 5

What projects to different parts of Lamina II?

CGRP + IB4 C fibres

What is found in the innermost of Lamina II?

Substantia gelatinosa

What doesn’t Lamina 2 Contain and what are most cells in that region?

Doesn’t have much myelinated axons | Region: interneurons

Where are peptidergic found?

Lower part of epidermis and associated with blood vessels in the dermis

Where is CGRP found?

Stratium spinosum

Where is IB4 found?

Stratium Granulosum

What are examples of thermoreceptor molecule?

TRPV1 | TRPA1

What is an example of sensitive ion channel?

Piezo2

What are examples of other receptors?

``` Cytokines Cannabinoid Bradykinin Prostanoid Serotonin Trophic factors Histamine Adrenergic Potassium Calcium Opioids Glutamate/transporters ```

What is the Merkel cell-neutrite?

Gentle touch receptor in the skin that mediated slowly-adapting responses of AB sensory fibres to encode find details of objects

What is Piezo2?

Mechanically activated cation channel | Expressed in Merkel cells

What physiological role does Piezo play?

Mechanosensation in mammals

What does merkel cell display?

Touch-sensitive currents

What does fibres have?

Mechanosensation abilities

Cold sensation

TRPM8

What is TRPA1?

Channel that opens when there is tissue damage and it is due to chemicals released

What is TRPM8?

Open by menthol/cooling/mint

TRPV1

Threshold is 47 | Inflammatory pain

TRPV2

Higher threshold stimulus which opens

What happens if you knock out TRPV1 In inflamed tissue?

There is no hyperalgesia

Damage to tissue

Increase in acidification of the tissue

What can lipids do?

Sensitise the receptor to open more easily

Where is TRPV1 found in rats?

CJP IB4

What is Mrgd?

Largest population of the non-peptidergic cells

What does Mrgd have?

P2X3/ VR1 receptors

What is Mrgd involved in?

Noxious mechanosensation

What is associated with itch?

Mrga

What is Mrgb4?

Involved in C fibres that are not nociceptors | Involved in innocuous pleasurable touch

What are 2 different fibres of C fibres?

1. Non-peptidergic: goes into the higher peripheral parts of skin 2. Peptide: found in lower level associated with blood vessels

What is the protein encoded by Vglut?

Vesicle bound | Sodium-dependent phosphate transporter

What is Vglut associated with?

Membranes of synaptic vesicles | Functions in Glutamate transport

What expresses Vglut1?

Myelinated fibres

What is Vglut1?

Myelinated fibres

What is Vglut 2?

nociceptors (& CNS interneurons)

What is Vglut3?

Subpopulation of C LTMs

What detects innocuous mechanoreceptors?

C fibre - low threshold mechanoreceptors

What is C-LTMRs?

Low threshold mechanoreceptors

Week 2 Flashcards

(97 cards)