Pain and analgesics first half of 1 Flashcards
What is pain?
The subjective conscious appreciation of a stimulus that is causing, or threatening to cause, tissue damage
What is nociception?
The physical process of detection and transmission of damaging or potentially damaging (noxious) stimuli
What are nociceptors?
Structures that detect noxious stimulus
What is algesia?
The induction of a condition leading to nociception and pain
What is analgesia?
Reduction or prevention of either nociception or pain without loss of consciousness
What is the detection of touch?
Mecanoception
Which specific structures are involved in the perception of touch?
Merkel’s Disc, Pacinian Corpuscle, Meissners Corpuscle
What are the two main types of nociceptor?
Polymodal, mechanical
What level of mechanical stimuli do both types of nociceptor respond to?
High intensity
What level of thermal input can stimulate polymodal nociceptors?
> 45 degrees, <10 degrees
What level of thermal stimuli can stimulate mechanical nociceptors?
> 60 degrees
What is the order of structures for detecting a noxious stimulus?
Skin/viscera–> Sensory receptor–> primary afferent axon–> spinal cord
What are the types of receptor in nociceptors?
ASIC (acid sensing ion channel), Purinergic receptors (P2x3), Voltage gated Na+ channels, VR-1/TRPV-1
What is the main agonist of ASICs?
Protons
What is the main agonist of Purinergic receptors?
ATP
What type of stimulation do purinergic receptors respond to?
High intensity mechanical stimulation
What type of stimulation do voltage gated sodium channels respond to?
Mechanical stimulation
What are the main agonists of VR-1/TRPV-1?
H+, high levels of heat and capsaicin
Speed of nociceptive APs compared to touch APs?
Slower
Why are nociceptive APs slower than touch ones?
The C fibres are very thin and unmyelinated
Which types of fibre are used for nociception?
C and a delta
Which type of nociceptor is linked to c fibres?
Polymodal
Which type of nociceptor is linked to A delta fibres?
Mechanical
Why do APs flow down Adelta fibres quicker than C fibres?
The Adelta fibres are myelinated
Why is there an initial pain felt, then a throbbing?
Different fibres transmit at different speeds so one transmits slower after the other
Which fibres are responsible for the initial pain?
A delta
Which pain fibres are responsible for the second pain?
C fibres
Which receptors detect reasonable temperatures (10-40 degrees)?
Thermoreceptors
Which receptors detect extreme temperatures?
Cold/heat pain receptors
Why do thicker fibres transmit APs quicker?
There is less resistance
Where does sensory input enter the spinal cord?
Through the dorsal root
Where is the first synapse (in the spinal cord) that is responsible for nociceptive input into the brain?
The most dorsal part of the spinal cord
