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How do headaches happen?

Medicine & HealthLesson on requestFree to readयह पेज हिंदी में पढ़ें

Quick answer

Headaches occur when pain-sensitive structures around the brain—blood vessels, muscles, and nerves—are irritated or activated. These structures release chemicals that stimulate nerve endings, sending signals through the trigeminal nerve to the brain, which interprets them as pain. The brain tissue itself cannot feel pain.

A headache happens when pain-sensitive structures around the brain—such as blood vessels, muscles, and nerves—are irritated or activated, not from the brain tissue itself, which lacks pain receptors. Chemical signals then travel to the brain, which interprets them as head pain.

Step by step

  1. Pain-sensitive structures in the head, such as blood vessels, meninges, and muscles, are stretched, inflamed, or compressed.
  2. Irritated tissues release chemicals like prostaglandins that sensitize nearby nerve endings.
  3. These nerve endings send electrical signals along the trigeminal nerve toward the brainstem.
  4. The brainstem relays the signals to the thalamus and then to the cerebral cortex.
  5. The cortex interprets the signals as pain, producing the experience of a headache.

Key things to understand

  1. The brain itself has no pain receptors, so headaches arise from surrounding tissues like blood vessels, meninges, and muscles.
  2. When these structures are stretched, inflamed, or compressed, they release chemicals such as prostaglandins that sensitize nerve endings.
  3. These signals travel along the trigeminal nerve to the brainstem and then to the cortex, where pain is perceived.
  4. Tension-type headaches involve sustained contraction of neck and scalp muscles, often from stress or poor posture.
  5. Migraines involve abnormal brain activity that activates the trigeminal nerve, which releases inflammatory signals such as CGRP around blood vessels and the meninges.

Labelled diagram

  1. Trigger

    Stress, dehydration, or inflammation irritates blood vessels and muscles around the brain.

  2. Chemical release

    Irritated tissues release prostaglandins and other chemicals that sensitize nerve endings.

  3. Nerve signal

    The trigeminal nerve carries electrical impulses from the head to the brainstem.

  4. Brain relay

    The brainstem passes signals to the thalamus, which forwards them to the cortex.

  5. Pain perception

    The cortex interprets the signals as head pain, completing the headache experience.

How a headache signal travels

Real-world examples

  • Tension headaches often follow hours of hunching over a laptop, when neck and scalp muscles stay contracted and release pain chemicals.
  • A migraine can begin with visual zigzags called an aura, then progress to throbbing pain as activated trigeminal nerves sensitise the meninges.
  • Sinus headaches occur when inflamed sinuses press on the trigeminal nerve branches around the cheeks and forehead.
  • A hangover headache after drinking alcohol involves dehydration and widened blood vessels, which stretch pain-sensitive nerves.

Common mistake

✗ Myth: Headaches come from the brain itself hurting.

✓ Fact: Brain tissue has no pain receptors, so it cannot feel pain. Headaches arise from pain-sensitive structures around the brain, such as blood vessels, meninges, and muscles.

People also ask

What causes headaches?
Headaches are caused by irritation or activation of pain-sensitive structures around the brain, including blood vessels, meninges, and muscles. Common triggers are stress, dehydration, lack of sleep, eye strain, and certain foods. These factors release chemicals that stimulate nerve endings, which send pain signals to the brain.
Why do I get headaches every day?
Daily headaches often result from ongoing triggers like muscle tension from poor posture, chronic stress, disrupted sleep, or medication overuse. Keeping a headache diary can help identify patterns. If daily headaches persist, see a doctor to rule out underlying conditions.
How do migraines differ from regular headaches?
Migraines involve abnormal brain activity that activates the trigeminal nerve and releases inflammatory chemicals around the meninges, leading to throbbing pain, often on one side. They may include nausea and sensitivity to light or sound. Tension headaches usually cause a dull, steady ache without these extra symptoms.
Why do some headaches cause nausea?
Migraines and other severe headaches can activate the brainstem area that controls nausea and vomiting. The same trigeminal nerve pathways that carry pain signals also connect to the vomiting center in the brain, so strong headache signals can trigger queasiness.
What is a headache behind the eye?
Pain behind the eye often comes from the trigeminal nerve, which supplies sensation to the eye and forehead. It can occur in migraines, cluster headaches, or sinus problems, where inflammation presses on nerve endings around the eye socket.
Can dehydration cause headaches?
Yes. When the body loses water, the brain can shrink slightly and tug on pain-sensitive membranes, and reduced blood volume may add to the irritation. The exact mechanism is not fully settled.
Why do headaches get worse when you bend over?
Bending over briefly raises pressure inside the head, which stretches pain-sensitive blood vessels and meninges. If those structures are already irritated, the extra pressure makes the pain sharper. Persistent worsening with position changes should be checked by a doctor.

Part of the guide: How Your Body Works →