The Human Brain
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98 free The Human Brain trivia questions with answers — science & nature quiz, new questions added Oct 2026.
The human brain weighs about as much as a bag of sugar, has the consistency of soft tofu, burns a fifth of the body's energy and floats in fluid so that 1,400 grams of tissue effectively weighs less than 50. It holds around 86 billion neurons, most of them packed into the little cerebellum at the back, and it has taught scientists most of what they know through accidents and operations: a railroad foreman with an iron rod through his skull, an epileptic patient who could never form a new memory again, and a dye that stained every organ except one. These 98 questions cover the anatomy and the stories: the cerebrum, brainstem and cerebellum, the four lobes and the skull bones they are named for, the corpus callosum's 200 million fibres, the six layers of the neocortex and Brodmann's fifty areas, the hippocampus, amygdala, hypothalamus and pineal gland, the three meninges and four ventricles, the carotid and vertebral arteries, Broca's area and left-brain language, glia and myelin, action potentials and synapses, Ramón y Cajal, Sherrington and Hans Berger's first EEG, Phineas Gage, H.M., Egas Moniz's lobotomy, phrenology, Neanderthal brain size, the sperm whale's 8-kilogram brain, concussion and neuroplasticity. Easy questions stick to lobes and neuron counts; the hardest ask about oligodendrocytes, alpha-wave frequencies and the default mode network. Every answer is cited to a page we checked, with a short explanation so you learn something even when you miss. Play it solo or print it for a biology class or a pub science round.
30 of 98 questions with answers and explanations. Play the quiz
Q 01Roughly how many neurons does the human brain contain?
86 billion
86 billion. Textbooks long quoted a round 100 billion, plus ten times as many support cells, until a 2009 count found about 86 billion neurons and roughly the same number of other cells.
Q 02About what share of the body's energy does the brain consume?
20%
20%, more than any other organ uses. Aristotle had it backwards: he placed thought in the heart and took the brain for a device to cool the blood.
Q 03About how much does an adult human brain weigh?
1.4 kilograms
1.4 kilograms, or about three pounds. Weight says little about ability: Albert Einstein's brain, weighed after his death in 1955, was on the small side at 1,230 grams.
Q 04A neurosurgeon's well-known comparison likens the feel of a living brain to which food?
Soft tofu
Soft tofu, the choice of neurosurgeon Katrina Firlik. Some of her colleagues say toothpaste, but she finds that too runny: a cube cut from a living brain more or less holds its shape.
Q 05Which three main parts make up the human brain?
Cerebrum, brainstem and cerebellum
Cerebrum, brainstem and cerebellum. The wrinkled cerebrum does the thinking, the brainstem keeps breathing and heartbeat going, and the cerebellum is what you lean on to play the piano or hit a tennis ball.
Q 06The four lobes of each hemisphere are named after what?
The skull bones above them
The skull bones above them. So the names record where each lobe sits, not what it does: nothing in the word 'frontal' tells you that this is the lobe that plans and weighs up choices.
Q 07Which lobe of the brain is dedicated to vision?
Occipital
Occipital. It is the smallest lobe and sits at the very back of the head, about as far from the eyes as it could be, yet damage there can leave a person blind even with healthy eyes.
Q 08A stroke in the brain's left hemisphere typically paralyses which part of the body?
The right side
The right side. Nearly all the signals between brain and body cross over on the way, so each hemisphere mainly controls the opposite side of the body.
Q 09What is the name of the largest bundle of fibres connecting the two hemispheres?
Corpus callosum
Corpus callosum. When surgeons cut it, the two halves stop sharing what they know: such patients can name an object that one half of the brain has seen, but not one shown only to the other.
Q 10Why can surgeons operate on the brain while the patient is awake and talking?
The brain has no pain receptors
The brain has no pain receptors. Only the scalp and skull need numbing, so surgeons can keep the patient naming objects aloud to check that they are steering clear of the areas needed for speech.
Q 11Why is the brain's outer layer of grey matter so deeply folded?
To pack more surface into the skull
To pack more surface into the skull. The layer is only about as thick as a stack of two or three dimes, so folding is the way to fit in more of it, and more nerve cells with it.
Q 12Which brain chemical, depleted in Parkinson's disease, also drives the brain's reward system?
Dopamine
Dopamine. In Parkinson's the cells that make it die off in a small region called the substantia nigra, and by the time symptoms show most of them are already gone.
Q 13The cortex is mapped into about fifty functional regions named after which anatomist?
Brodmann
Q 21Which structure links the nervous system to the endocrine system via the pituitary gland?
The hypothalamus
The hypothalamus. Tiny as it is, it works as the body's thermostat and alarm clock: it sets temperature, hunger and thirst, and it is what wakes you up in the morning.
Q 22Which small organ produces melatonin and was called 'the principal seat of the soul' by Descartes?
The pineal gland
The pineal gland, named for its pine-cone shape. It steps up its output of melatonin once the light fades, which is what helps the body wind down for sleep.
Q 23What are the three membranes covering the brain and spinal cord collectively called?
Meninges
Brodmann. In 1909 Korbinian Brodmann published a map of 52 numbered areas, told apart purely by how their layers of cells looked under the microscope.
Q 14What is the brain's white matter mostly made of?
Insulated nerve fibres
Insulated nerve fibres, which fill about half the brain's volume. Their fatty coating, myelin, is what looks white; grey matter is grey because its nerve cells lack that insulation.
Q 15Which structure deep in the brain is the relay station for nearly all incoming sensory signals?
The thalamus
The thalamus. Only smell bypasses it, and it does more than pass messages along: it helps keep you awake and alert, so severe damage to it can leave a person in a coma.
Q 16Which part of the brainstem contains the centres controlling heart rate, breathing and blood pressure?
The medulla
The medulla, the lowest part of the brainstem. It also fires off the reflexes you never have to think about, such as swallowing, coughing, sneezing and vomiting.
Q 17Most vivid dreams happen in which stage of sleep, when the body's limb muscles are switched off?
REM sleep
REM sleep. The brain is almost as busy as when it is awake, so the brainstem switches off the muscles of the arms and legs to stop you acting out your dreams.
Q 18Which part of the brain holds most of its neurons while taking up only about 10% of its volume?
The cerebellum
The cerebellum, Latin for 'little brain'. About four in five of the brain's neurons are packed into it as tiny granule cells, and damage shows up as clumsy, unsteady movement.
Q 19Which structure consolidates short-term memories into long-term ones and supports spatial navigation?
The hippocampus
The hippocampus. Its role became clear in 1953, when surgeons removed most of it from a patient known as H.M.: he could still learn new skills but never again formed a lasting memory of events.
Q 20Which almond-shaped structure in the temporal lobe is central to processing fear?
Amygdala
Amygdala, from the Greek for almond. A patient known as S.M., whose amygdalae were destroyed by a rare disease, is left almost unable to feel fear at all.
Meninges. An infection of them is meningitis, which can come on suddenly and progress fast enough to kill, so doctors treat a suspected case as an emergency.
Q 24Which of the three membranes around the brain is the tough outermost layer?
Dura mater
Dura mater, Latin for 'hard mother'. The phrase was translated word for word from Arabic, where 'mother' and 'father' were used for things that stand in a relation to other things.
Q 25Which disease, the most common cause of dementia, leaves plaques and tangles of protein in the brain?
Alzheimer's disease
Alzheimer's disease. It is named after Alois Alzheimer, the German doctor who in 1906 found the clumps and tangled fibres in the brain of a woman who had died after years of memory loss.
Q 26What makes the living brain effectively weigh just a few percent of its true weight?
Cerebrospinal fluid
Cerebrospinal fluid. The brain floats in it, so it bears only a sliver of its own weight, and the same fluid cushions it against knocks.
Q 27The temporal lobes hold the brain's primary centre for which sense?
Hearing
Hearing. The same lobes help turn sound into meaning: damage to one patch of them can leave a person speaking fluently in sentences that make no sense.
Q 28The blood–brain barrier remains permeable to which of these?
Alcohol
Alcohol. Small, fat-soluble molecules slip straight through the barrier, which first showed itself when Paul Ehrlich injected dyes that coloured every organ of his animals except the brain.
Q 29Which vessels supply blood to the front of the brain?
The internal carotids
The internal carotids. At the base of the brain they join the arteries feeding the back in a ring, so if one vessel is blocked, blood can often still get round by another route.
Q 30In the great majority of right-handed people, which ability is housed mainly in the brain's left hemisphere?
Language
Language. When surgeons separated the two halves of patients' brains, the isolated right hemisphere proved mute: it could recognise an object but had no way to say its name.