Pain is a simple word but with multiple complex meanings and emotions attached to it.
Even a simple Google image search on google produced a wide range of pictures.
However, today I will be talking to you about physical pain.
Nociceptors are the receptors in your skin that allow you to feel pain.
There are 4 types;
Mechanical that respond to excess pressure and tearing,
Thermal that respond to temperature,
Chemical that respond to chemical concentrations and
Sleeping receptors that respond to inflamed tissues.
Here is the simple structure of a neuron.
The main section i shall be talking about for a bit will be the axon.
A neuron has a resting potential and an action potential.
When there is no stimulus the axon is said to be polarised at -65mV.
Then when the stimulus exceeds the threshold value, the action potential is propagated.
You can see on the graph the change in membrane potential when the electrical current passes through the axon.
The change in charge is due to the concentration of sodium ions and potassium ions in the axon compared to the surrounding cell.
Sodium rushing in, potassium rushes out. The Potassium out (-90mV). Na-K pump.
Thresholds different between receptors but similar between individuals.
This is just a close up picture of a sodium channel on an axon membrane.
So this is what facilitates the sodium ions into and out of the axon during the propagation of an impluse.
Sodium channels will also be relevant later on.
Myelinated axons have a quicker conduction speed.
Unmyelinated takes longer due to all the axon becoming depolarised.
Nothing physical moves.
(maybe audience participation)
A synapse is the junction between two membranes.
So using all these methods the impulse is passed into the brain where it is processed.
Different areas of the brain means the sensation of pain can be:
Memorised so learning can be done
And recognised, if the injury has occurred previously.
A-delta, first pain myelinated, sharp and localised. prevents further damage
C-fibres, second pain, unmyelinated, duller and less localised. allows healing.
Long term pain, maybe from a bad back or cancer, or psychological.
Not advantageous, however one of the most common complaints.
Local anaesthetics prevent impulse in tissues. blocks channels.
Regional numbness when injected into spinal cord.
General anaesthetics not known. maybe similar to local but works on central nervous system.
Pain pathways develop in babies by touch as well as pain.
University College London hospital. compared healthy and premature babies.
Premature babies undergo painful procedures and have a lower threshold for pain in later life.
Well established connections.
However the adult brain is still seen as plastic.
Neuromas occur due to neurones trying to reconnect. sump pain.
Phantom limb pain
However phantom limb essential to successfully use prosthetics.
Your body's a mechanism to moderate pain.
Jonathan Metz. 31 years old, American, arm stuck between heating filaments when cleaning boiler.
2006 Cambridge Institute for Medical Research.
Dr Woods discovered gene. solely involved in pain and no other bodily function.
10 known mutations cause excess pain.
Other mutations cause as complete insensitivity to physical pain
Case study; Pakistani, 3 families, 6 people, inbreeding allowed gene mapping.
Individual mutations effecting sodium channels.
10 year old boy street performer died at 14.
Ethics however future of painkillers? -no unwanted side effects.