Part 22 (1/2)

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What has the largest brain in comparison to its size?

a) Elephants b) Dolphins c) Ants d) Humans The ant.

An ant's brain is about 6 per cent of its total body weight if we were to apply the same percentage to humans, our heads would have to be nearly three times as large, making us all look rather like the Mekon or Morrissey.

An average human brain weighs 1.6 kg (3.5 lb), which is a little over 2 per cent of body weight. An ant's brain weighs approximately 0.3 mg.

Although an ant's brain has only a fraction of the neurons of a human brain, a colony of ants is a super-organism. An average-sized nest of 40,000 ants has about the same number of brain cells as a person.

Ants have been around for 130 million years and there are about 10,000 trillion of them at large as we speak. The total ma.s.s of ants on the planet is slightly heavier than the total ma.s.s of human beings.

There are about 8,000 known species of ant. Ants account for about 1 per cent of all the insects on earth. The total number of insects in the world has been calculated at one quintillion (or 1,000,000,000,000,000,000.

Ants sleep for only a few minutes a day and can survive for nineteen days under water. A wood ant can manage for twenty-four days without its head. A single ant cannot live alone outside the colony, head on or not.

Ants appear to have photographic memories to help them navigate. They seem to take a series of snapshots of landmarks. Scientists do not understand how ants' tiny brains can store so much information.

Ants are not stronger than people. Though ants can lift many times their own weight, this is only because they are small. The smaller an animal is, the stronger its muscles are in relation to its body ma.s.s. If people were the same size as ants, they would be equally strong.

ALAN I had an ant's nest in my flat, once. I had an ant's nest in my flat, once.

STEPHEN Did you? What did you do? Did you? What did you do?

ALAN Well, I was fairly stupid about it because I saw an ant. I thought, 'There's an ant in the flat!' Well, I was fairly stupid about it because I saw an ant. I thought, 'There's an ant in the flat!'

STEPHEN Ah. Ah.

ALAN And the next day, I saw an ant and thought, 'Oh ... there he is.' And the next day, I saw an ant and thought, 'Oh ... there he is.'

How much of our brains do we use?

One hundred per cent.

Or 3 per cent.

It's commonly said we only use 10 per cent of our brain. This usually leads to discussions of what we might do if only we could harness the other 90 per cent.

In fact, all of the human brain is used at one time or another. On the other hand, a recent paper by Peter Lennie of the New York University Center for Neural Science indicates that the brain should ideally have no more than 3 per cent of neurons firing at any one time, otherwise the energy needed to 'reset' each neuron after it fires becomes too much for the brain to handle.

The central nervous system consists of the brain and the spinal cord and is made of two kinds of cells: neurons and glia.

Neurons are the basic information processors, receiving input and sending output between each other. Input arrives through the neuron's branch-like dendrites; output leaves through the cable-like axons.

Each neuron may have as many as 10,000 dendrites but only has one axon. The axon may be thousands of times longer than the tiny cell body of the neuron itself. The largest axon in a giraffe is 4.5 metres (15 feet) long.

Synapses are the junctions between axons and dendrites, where electrical impulses are turned into chemical signals. The synapses are like switches, linking neurons to one another and making the brain into a network.

Glia cells provide the structural framework of the brain, they manage the neurons and provide a housekeeping function, removing debris after neurons die. There are fifty times more glia than neurons in the brain.

There are nearly five million km (about three million miles) of axons, one quadrillion (1,000,000,000,000,000) synapses, and up to 200 billion neurons in a single human brain. If the neurons were spread out side by side they would cover 25,000 square metres (nearly 30,000 square yards): the size of four football fields.

The number of ways information is exchangeable in the brain is greater than the number of atoms in the universe. With such astonis.h.i.+ng potential, whatever percentage of our brains we use, we could all, clearly, do a little better.

What colour is your brain?

So long as you're alive, it's pink. The colour comes from the blood vessels. Without fresh oxygenated blood (as when it's removed from the body) the human brain appears grey.

To confuse things, about 40 per cent of the living brain is made of so-called 'grey matter' and 60 per cent of 'white matter'. These terms are not accurate descriptions of the colours you see, but thinly sliced, and in section, they are clearly two different kinds of brain tissue.

Using brain scans, we have begun to understand what functions they each perform. Grey matter contains the cells where the actual 'processing' of information is done. It consumes about 94 per cent of the oxygen used by the brain.

The white matter is a fatty protein called myelin myelin which sheathes and insulates the dendrites and axons that extend out from the cells. It is the brain's communication network, linking different parts of the grey matter together and linking the grey matter to the rest of the body. which sheathes and insulates the dendrites and axons that extend out from the cells. It is the brain's communication network, linking different parts of the grey matter together and linking the grey matter to the rest of the body.

A good a.n.a.logy is the computer. The grey matter is a processor, the white matter is the wiring. What we call intelligence requires both to work together at high speed.

Now it gets even more interesting. Recent studies at the Universities of California and New Mexico scanned the brains of men and women with identical IQs. The results were surprising: the men had six and a half times more grey matter than women, and women had nearly ten times more white matter than men.

The women's white matter was found in a high concentration in the frontal lobes, whereas the men had none. This is significant, as the frontal lobes are believed to play a key role in emotional control, personality and judgement.

So, all the various 'Mars and Venus' theories of gender difference might find soon find a physiological justification. Men's and women's brains do seem to be differently wired and configured. The output (intelligence) is the same, but the way it is produced is very different.

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What effect does alcohol have on brain cells?

Good news. Alcohol doesn't 'kill' brain cells. It just makes new cells grow less quickly.

The idea that alcohol destroys brain cells dates back at least as far as the temperance campaigners of the early nineteenth century, who wanted all alcoholic drinks banned. It has no basis in scientific fact.

Samples from alcoholics and non-alcoholics show no significant difference in either the overall number or the density of neurons between the two groups. Many other studies have shown that moderate drinking can in fact help cognition. A study in Sweden showed that more more brain cells are grown in mice that are given alcohol. brain cells are grown in mice that are given alcohol.

Alcohol abuse does causes serious damage, not least to the brain, but there is no evidence that these problems are to do with the death of cells it's more likely that alcohol interferes with the working processes of the brain.

A hangover comes from the brain shrinking due to dehydration, causing the brain to tug on its covering membrane. It's the membrane which is sore. The brain itself feels nothing, even if you stick a knife in it.

The philtrum is the vertical groove on your upper lip that n.o.body knows the word for. It allows you to drink beer from the bottle by letting the air in.

If you were to open a beer can in zero gravity all the beer would come out at once and float around in spherical droplets.