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Back to basics, continued

22/6/2015

The Withdrawal Reflex

In the last blog, I described what happens when you get a paper cut, how the pain signal is transmitted to your brain for you to feel the pain.

Here is a modified diagram from the last post, showing what happens even before the signal reaches your brain:

Before you were even aware of the pain from the paper cut, you probably reacted involuntarily, e.g., pulled the piece of paper away from your finger, or pulled your finger away from the paper, or both. This is a reflex response, called a withdrawal reflex, and happens at the spinal cord level (a spinal reflex) cord to sudden pain. Motor nerve fibres (motor neurons) are activated to bring about arm muscle contraction, to pull away.

This reflex helps to protect the body from damaging stimuli.

The same thing happens when you touch a hot stove. You immediately whip your hand away without even thinking, and before the pain sets in. Without this spinal reflex, you might leave your hand there until you feel the pain before you removed your hand, at which point you may have severely burnt your hand.

This is your amazing body.

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Back to basics (Why it hurts)

8/6/2015

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Over the next few entries, I will break down and explain the different types of pain and pain responses; why and how we hurt, what happens when things go wrong and healing does not go according to “schedule”.

Nociceptive (normal) pain

This is pain in response to a cut, a fracture, toe stubbing, the accidental touching of a hot element on a stove. Post-operative pain is another form of nociceptive pain. The intensity and quality of this pain response are appropriate to the applied stimulus.

Let’s use a paper cut as an example:

1)     This tissue damage is registered by nociceptors (pain receptors) in your skin which send a signal up to the spinal cord in your neck along an axon (this is a nerve fibre which connects a pain receptor to the spinal cord). Many axons form a peripheral nerve.

2)      Within the dorsal horn of the spinal cord, this signal is transmitted via a series of synapses, and then passed up into the brain. Chemical messengers (neurotransmitters) pass this signal across the synapses.

3)      On reaching the thalamus in the brain, this signal is streamed to different parts of the brain such as:

        a.       Somatosensory cortex, giving you the sensation of pain

        b.      Frontal cortex, making you think, “Ow! What did I do?”

        c.       Limbic system, resulting in annoyance or irritation on getting a paper cut.

Hopefully, the diagram below will help to simplify things for those of us who learn better this way:

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Back to basics, continued

Back to basics (Why it hurts)

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