Week 6 Flashcards by Jihan Haji

Primary sensory cortex

Sensory discrimination

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Anterior cingulate cortex

Emotions/Attention

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Prefrontal cortex

Cognition

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Insula

Sensory motor integration

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Amygdala

Emotional affect

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What is Angular cingulate involved in?

Perception of pain

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Where does ACC have a connection between?

Emotional limbic system

Cognitive prefrontal cortex

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What is the role of ACC?

Affect regulation: ability to control and manage uncomfortable emotions

Decision making
Emotional regulation
Regulation of physiological process such as BP and HR

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Where is most of the information for pain found?

Red 1-2

Lamina 5

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What is Lamina 10 associated with?

Visceral afferent input

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What is found throughout the dorsal horn?

Interconnections

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What does innocuous stimulus to Lamina 3,4,5 contact?

Projection neurons into the pain system

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What is found in outer Lamina 1 and outer part of Lamina 2 in the cord?

CGRP

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What do you label skin afferent with?

tracer CTB

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What is the organisation of afferents?

On entry from spinal root - bifurcate
Contact neurons - reflex motor activity 
A fibre - quite far 
A fibre - dorsal column nuclei 
C fibres don’t go fat 
C fibre - Lissauer’s tract

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where does A fibre ascend to and do?

Dorsal column nuclei

Collaterals contact spinal cord neurons

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Where does C fibre run in and do?

Lissauer’s tract
Ascend and travel 1-2 segments within cord where they synapse
Project neurons transmit ascending afferent information to opposite side
Contra laterally to spinothalamic tract

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What is found within glabrous skin?

Different receptors

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What does glabrous skin contain?

Encapsulated A fibres

Meissner’s and Merkel disc - transduce touch, sensitivity across skin

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Where does Ad-type pain stimuli come from?

Free nerve endings

High threshold mechanoreceptors - mechanical pain

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What do hairs detect ?

Vibration and movement

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What is Innocuous touch information processed by?

Glabrous and hairy skin

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In glabrous skin, what 4 types of mechanorceptors is innocuous touch mediated by?

Merkel cells
Meissners corpuscles
Ruffini endings
Pacinian corpuscles

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Hairy skin

Tactile stimuli are transducer through 3 types of hair follicles

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What is noxious touch detected by?

Free nerve endings found in epidermis of both glabrous and hairy skin Characterised by both A delta and C HTMR responses

What is organisation in spinal cord of distinct input ?

Somatotopy with different afferents showing characteristic termination pattern

What does myelinated fibres relate to?

Reflex arcs

What do we modify movements based on?

Innocuous sensory inputs

Why are Many of the afferents myelinated?

Reflexes and integration and modification of nociceptive input

In the context of inflammation what do we get?

Allodynia

What does afferents do?

Modulate the particular region of the cord

What is spinal cord?

Somatotopically organised

Somatotopy

All different modalities of sensation are organised in dorsal horn together

What is spinal cord

Sensory organisation integration area

What does innocuous and noxious input show?

Distinct but overlapping distribution pattern in the spinal cord

What did early studies look at?

Recording and filling an individual neuron to see where it is projection within cord They have different projection

Where does noxious heat project to?

Lamina 1 and 5

Where does Ab project to?

Lamina 5

Where does C fibres project to?

Lamina 1

What does afferents cells contact?

Dorsal horn interneurons | Projection neurons

What are 99% of cells?

Interneurons | Short projection neuron with local circuit in region of dorsal horn

What are 1% of cells?

Projection neurons

What can interneurons be divided into?

Excitatory or inhibitory or neuromodulators

What do interneurons have?

Particular input | They can be wide-dynamic range from noxious stimulus to innocuous stimuli

High threshold

Noxious stimuli only

Low threshold

Innocuous stimuli only

Wide dynamic range

Both noxious and innocuous stimuli

Where does LTMR afferents project into?

DCML Carries innocuous mechanical information i.e. discriminative touch Project into cord and activate a range of dorsal horn interneurons for reflexes/integration

What is the role of polysynaptic pathway?

Take input from second order neuron and send information to higher centres Medulla and dorsal column Postsynaptic dorsal column pathway (PSDC) + spinocervical tract

What does Lamina I and V projection neurons carry to the brain?

Nociceptive information

What are the pain fibres?

C and Ad fibres | Going to Lamina 1 and 2 outer mainly

What does C fibres Lamina I express?

CGRP

What does Ad fibres have?

Monosynaptic inputs

Where does Ab fibre innocuous go through?

Middle portion Lamina 3-5

What is the spinothalamic tract?

Main pathway up to the thalamus then to consciousness through input to cortices

What is the pathway of spinothalamic tract?

``` Brachial nucleus Reticular formation Periaqueductal grey Input to amygdala Cortices ```

What does nociceptors activate?

Projection neurons of the spinothalamic tract

What are projection cells?

Modality specific

What are Lamina I cells?

Morality specific | Via medial, posterior thalamus projections to cingulate and insular cortex

What are Lamina V cells?

Integrate inputs | Wide dynamic range I.e. noxious and innocuous

What are ilet cells?

Inhibitory cells involved in particular circuitries in central cells

1% of cells

Projection neurons Projecting into spinothalamic tract Projecting out of the spinal cord

What can lesions of dorsal column reduce?

Pain | E.g. cancer pain of the viscera

What is referred pain?

Converge with cutaneous input

What are projection neurons identified by?

NK1 receptors

What are 30-50% of cells in laminae I-II?

Inhibitory

What are NK1?

Substance P receptor Mostly projection neurons Mainly found in Lamina I

What is the function of NK1?

Taking burning pain/ information upwards

What are the neurochemistry of dorsal horn neurons?

GABA + = inhibitory markers of inter neurons | GABA - = excitatory markers of neurons

What is hypothesis 1 of labelled lines?

Afferents carry separate information to different neuronal population

What results in decreased pain sensation in chronic pain conditions?

Deletion of NK1 or PKC gamma

What is activated by acute noxious stimulus?

NK1

What do you see in noxious stimuli?

Increase of c-Fos activity within cord

What is trans neuronal transporter traces?

Transgenic nice | Localised go Nav1.8 cells [non-peptidergic]

Peptidergic ones

CGRP substance P cells synapse on Lamina I cells

Where does NK1 positive cells project up to and what does it do?

Project up thalamus via parabrachial nucleus | Project to amygdala - hot stimulus keep away from it

What does information relayed by Nav1.8 nociceptors contribute to?

Affective component of pain experience

What are PKC gamma innervated by?

A fibre and C low threshold mechanoreceptors

What is C fibres associated with?

High thermal temperatures | High mechanoreceptor ones (peptidergic)

What can TRPV1 have a lesion by?

High level of capsaicin

What can Lamina I and V get?

Convergence signalling

What are Lamina I and V ?

Mainly convergent | Lamina I C and Ad - nociceptors mainly

Lamina II

Segregation of inputs

What does Mrgprd population of cells innervate ?

Wide range of Lamina II interneurons

What happens if you knock out b5i inhibitory cells?

Neurons no longer respond to somatostatin

What reduces itch sensation?

Put cooling stimuli on same area

What is the consequence of putting cholorfilm on animal?

Cause it to itch

What’s reduced itch?

Menthol

What does Dynorphon act to do?

Reduce itch | Cells are contacted by menthol cells that have TRPM8

What is required for the survival o class of Lam I/II interneurons ?

Bhlhb5

What inhibits neuronal activity?

somatostatin

What is the only somatostatin receptor that is expressed by dorsal horn neurons?

sst2A

What does B5-I neurons do?

Inhibit itch

What is required for menthol modulation of itch?

Dynorphin cells

What does non painful input do?

Close the gate to painful input | Prevent pain sensation from travelling to the central nervous system

Week 6 Flashcards

(95 cards)