If the brain has no pain receptors, why do I get headaches?

We tend to experience pain when unpleasant stimuli activate sensory nerve fibres called nociceptors. Although it may feel like a deep pain in your brain, it might surprise you to know that headaches don’t originate from the brain itself. We can find nociceptors in the skin, in the joints and in some internal organs, but curiously not in the brain. So the brain itself doesn’t feel pain. This has been demonstrated in neurosurgical procedures, in which stimulation of the brain tissue itself in patients who are awake did not cause pain.

Even though the brain cannot perceive pain, its surroundings, such as the meninges (the covering of the brain), nerve tissues, blood vessels, and neck muscles, can.

Once stimulated, a nociceptor sends a signal through nerve fibres to the nerve cells in the brain, indicating that part of the body hurts.

There are different types of headaches, thought to arise for different reasons.

For example, tension headaches may be caused by tightening of the muscles in the neck and scalp. There are also pain receptors in the face, mouth and throat, which is why problems in these areas might trigger a headache.

Migraines are different: we don’t know the exact cause, but they’re thought to be the result of abnormal brain activity temporarily affecting nerve signals, chemicals and blood vessels in the brain. Some people think that migraines are caused by the activation of sensory nerves which release peptides or serotonin, causing inflammation in arteries and the coverings of the brains, and also causing blood vessels to dilate.

Oestrogen may also play a part, which is why some women get migraines during their menstrual cycle. Triptans, medications which treat migraines, work by blocking serotonin receptors and constricting blood vessels.

Read more:

• What is pain?
• Why do I have such a low pain threshold compared to my sister?
• Why do we wince when others are in pain?
• Why can emotional pain feel physical?

Asked by: Charlie Simpson

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