Nervous · Encephalon
Brain
Three pounds of tissue that generated the sentence you are reading and the one you just thought about it.
- Mass
- ~1.3 to 1.4 kg
- Power draw
- ~20 W, about 20% of intake
- Neurons
- ~86 billion
- Blood supply
- ~15% of cardiac output
What it does
The control surface for everything: movement, breath, memory, language, mood, and the running model of the world you mistake for the world itself.
The marvel
It runs on about 20 watts, roughly a dim light bulb, while consuming a fifth of your entire energy budget. No computer has come close to that ratio. It also has no pain receptors of its own: brain surgery can be performed on a conscious patient who feels nothing.
How to serve it well
Sleep is not optional maintenance
Clearance of metabolic waste from brain tissue increases substantially during sleep. Short sleep is not a neutral lifestyle choice for this organ.
Aerobic exercise
Currently the best-evidenced intervention for preserving cognitive function with age. Nothing in a bottle matches it.
Protect your hearing and your head
Untreated mid-life hearing loss is one of the larger modifiable dementia risk factors identified so far. Helmets and hearing protection are brain care.
Stay in company
Social connection and continued learning are consistently associated with better late-life cognitive outcomes.
Book an appointment
- Memory changes that people close to you notice, not just you
- Persistent changes in mood, personality, or word-finding
- New headaches that are different from your usual pattern
- Recurring dizziness, or a new tremor
Emergency, go now
- Face drooping, arm weakness, or slurred speech: call emergency services immediately, note the time symptoms began
- Sudden severe headache described as the worst of your life
- Sudden loss of vision, balance, or consciousness
- A seizure in someone with no seizure history
What you may have been told
“You only use 10% of your brain.”
Imaging shows essentially all of it active across a day. The myth persists because it sells courses. There is no dormant 90% waiting to be unlocked.
Where this comes from
- The Lancet Commission · Dementia prevention, intervention and care
- National Institute of Neurological Disorders and Stroke · Stroke signs and symptoms
- NHS · Stroke, act FAST
LUMEN is education, not medical advice, and it cannot know anything about you. It does not diagnose. If something here matches what you are experiencing, take it to a clinician who can examine you.