Week 1 Part 2 Flashcards
Noxious (harmful, unpleasant)
Mechanical pain
Innoxious (harmless)
Low threshold mechanoreceptors
What is TRKC receptors?
Wrap around hair
Found in merkel cells, Corpuscle
What is TRAP1?
Found in rats and not in humans
Meant to be cold receptors
What are the functional properties of peripheral afferent receptors?
High threshold - mechanical pain
Itching
What is Exteroceptors?
Cutaneous mechanoreceptors
Transduce physical stimuli from body wall
What is proprioceptors?
Deep mechanoreceptors
Transduce physical stimuli from within body
What is nociceptors?
Transduce noxious stimuli
What is thermoreceptors?
Transduce temperature stimuli
What is itch?
Transduce itch stimuli
What are the two types of primary afferent?
A fibres
C fibres
What is A fibre?
Myelinated
What is C fibres?
Unmyelinated
Found in bundles called remak bundles
Why is myelinated conduction faster?
Saltatory conduction
Where does first pain you feel come from?
Ad fibres
What gives second type of pain?
C fibres
What surrounds a single bundle of nerve axons?
Perineurium
What are interneurons?
Multipolar
What are DRG neurons classified by?
- Size
- Protein expression
- Myelination +/- peptidergic
What do you stain small DRG neurons with?
IB4
What do you stain medium DRG neurons?
CGRP
What do you stain large DRG neuron by?
NF200
If neurons don’t have peptides in them what will they be?
IB4+, P2X3 positive
What are two roots within DRG?
- Dorsal root
2. Ventral root
What comes together to form spinal nerve?
- Dorsal root
2. Ventral root
What is Orthodromic?
Normal direction of conduction
In case of injury what direction does Orthodromic follow?
Injury —> cell body —> spinal cord
What is antidromic conduction?
Opposite normal direction of conduction
Go from CNS —> skin
If the injury occurs at the cell body, what does it release?
Substance P
What does DRG run up and meet up with?
Run up the dorsal root
Meet at dorsal root entry root
What is DREZ?
Boundary between PNS and CNS for sensory axons
Where do Ad and C fibre enter?
Dorsal horn
Ascend and descend 1-2 spinal segments in Lissauer’s tract
Where does C fibre terminate ?
Predominantly in lamina I-V
Where does Ad fibre terminate ?
Lamina I, V & X
High threshold
Detect mechanical pain
What is within grey matter?
Dorsal horn
Intermediate column/lamina
Lamina rex
Where does large diameter myelinated afferent enter?
Medially through posterior funiculus
Where does small diameter unmyelinated afferent enter?
Literally near substantia gelatinosa
What does afferents form contacts with?
Interneurons
Directly onto motor neurons
Where are motor neuron pools generated?
Ventral horn
How are motor neuron pools for distal muscles located?
Laterally in the spinal cord
How are motor neuron pools for axial muscle located?
Medically in the spinal cord
How are motor neuron pools for flexor muscles located?
Dorsal in the spinal cord
What controls the muscles for arms and legs?
Cervical and lumbar
What is corticospinal tract?
Fine motor control of limbs and trunks
Where is the location of the corticospinal tract for human?
Lateral
Where is the location of the corticospinal tract for rat/mouse?
Base of dorsal funiculus/column
Corticospinal tract
Size: Humans > rodents
What is Rubrospinal tract?
Voluntary motor control
Gross motor and motor velocity
Rubrospinal tract
Size: Rodents > Humans
What is Raphe spinal tract?
Modulate pain transmission
Size: Rodents > Human
Which tract is depressed laterally and anteriorly within the spinal cord?
Corticospinal tract
What is organisation based on?
Action
How is the somatosensory topography imprinted onto spinal cord?
Active synaptic connections
What is topographical organisation of tactile input in spinal cord ?
Action-based and not body map-based
What are 2 types of dorsal horn interneurons?
Excitatory (e.g. glutamate)
Inhibitory (e.g. GABA, glycine, enkephalins)
What are 2 types of oligodendrocytes?
Interfascicular (between nerve fibres in white matter) Perineuronal satellite (close to neuronal cell bodies in grey matter)
What are 2 types of astrocytes?
Fibrous (long unbranched processes in white matter)
Protoplasmic (short and highly branched processes in grey matter)
Microglia
Innate immune surveillance
Endothelial cells
Lining of blood vessels
