As a doctor, I’ve learnt that everyone is fascinated by their body: what comes out of it, what can go wrong with it and why people have the symptoms they do. But unless you go to medical school, you are never really taught about how your body works, or how it can fail.
The best bit of my job as a hospital doctor (I work in neurology) is giving patients explanations and seeing them understand exactly what is wrong with them — what’s going on inside their body that’s making them feel unwell. Here are some of my more surprising favourites:
Headaches: It's not the brain that hurtsYour brain can’t feel pain. It receives all the information that leads to headaches from pain sensors around your body, but it has none of its own (which is why brain surgeons can operate while you are awake).
This means the pain of a headache doesn’t come from your brain. Instead, the muscles in your scalp, neck and face, your sinuses (spaces behind your cheekbones and forehead), eyes, teeth, ear canals, blood vessels throughout your head and the inner bony surface of your skull are all pain-sensitive.
Medically known as sphenopalatine ganglioneuralgia, the intense pain known as brain freeze is caused by eating or drinking something cold, such as ice cream. The icy food or drink rapidly cools the blood in the vessels in the roof of your mouth
Anything irritating, stretching, pulling on, pushing on, infecting or otherwise damaging these structures can give you a headache.
That’s not the only trigger, though. Since your brain is 75 per cent water, it’s exquisitely sensitive to dehydration. Inadequate fluid intake can temporarily cause your brain to shrivel slightly.
As your brain contracts from your skull, it tugs on the meninges (the membranes that cover the brain), yanking on the pain-sensitive outer layer which is anchored to your skull. You experience this internal tug of war as a headache.
How to ease agony of brain freezeMedically known as sphenopalatine ganglioneuralgia, the intense pain known as brain freeze is caused by eating or drinking something cold, such as ice cream.
The icy food or drink rapidly cools the blood in the vessels in the roof of your mouth.
This sudden drop in temperature causes the vessels to squeeze tight, then rapidly reopen to restore blood flow.
This triggers pain receptors in your head. Pressing your tongue to the roof of your mouth will usually provide enough heat to relieve the pain.
Fever fires up your immunityYour body temperature is around 37c — the temperature at which all the chemical reactions that keep you alive function optimally.
Body temperature is controlled by a region in the brain called the hypothalamus. Think of it like your body’s thermostat.
Whenever your immune system is fighting an infection, it pumps out chemicals called pyrogens, which travel through your bloodstream and, eventually, flow past your hypothalamus.
When your hypothalamus sees a pyrogen, it turns up the thermostat, resetting your target temperature higher, perhaps at 39c.
Because this means your current temperature of 37c is now considered too cold, you might start to shiver. (Nerve impulses cause rapid contractions of muscles, which raise body temperature.)
Successful infection requires a bug to breed and disperse quicker than your immune system kills it.
A fever offers a level of protection because it speeds up your immune system and renders invading bugs weak in the heat. Even if your fever only stymies the invasion rate by a few per cent, that might be enough to stop infection taking hold.
The immune system is a complex series of chemical reactions. Heat it and it works faster. Warmed white blood cells are deployed faster, travel faster, devour micro-organisms and multiply faster.
When your immune system detects the battle is over, it stops releasing pyrogens. Your hypothalamus’ set point will drop back to 37c and your body will go into ‘cool down’ mode (perhaps with plenty of perspiration and flushed skin to speed the heat loss process).
Is it bad to try and reduce a fever?Paracetamol is a modern ‘chill pill’ that can help reset your hypothalamus back to 37c when you’ve got a fever.
Although it would be logical to assume this would negate the beneficial effects of the fever, real-world studies have found this not to be the case.
In 2015, a study of 700 patients in intensive care with fevers of at least 38c showed that paracetamol lowered temperatures without impacting death rates or time spent in intensive care.
Fever probably offers only a small benefit: enough to offer a survival advantage on an evolutionary timescale but not enough to make a difference when you’re critically ill.
Paracetamol is a modern ‘chill pill’ that can help reset your hypothalamus back to 37c when you’ve got a fever
To ENABLE you to hear, sound waves hit your eardrum, causing it and the bones behind it to vibrate.
This sends a wave of fluid rippling through the microscopic hairs that line your cochlea (a curled 3cm long tube), causing the hairs to bend. These hairs are ‘tuned’ to respond to differently pitched sounds, firing off an electrical impulse to the brain as they bend.
You’re born with a quota of hair cells; you don’t sprout new ones and dead ones can’t be replaced. They have to endure substantial buffeting over your lifetime with years of exposure to music, traffic noise and conversations.
As hair cells age, they become brittle, less responsive to stimulation, and generate poorer-quality signals for your brain to decipher.
The hairs that respond to high-pitched sounds are the first to deteriorate with age (which is why people who are losing their hearing might notice women and children’s voices are the first to seem indistinct, since their voices are naturally higher-pitched than men’s).
Next, consonant sounds such as ‘f’, ‘s’ and ‘th’ will drop off their hearing radar because they’re higher pitched than vowel sounds.
