A well protected jelly like mass at the top of a network of fibres extending to all parts of the body.
About the brain; almost 80% of the it is made of water (mainly in the cytoplasm of its cells) with a further 10-12% being fatty lipids and 8% protein.
Glial cells, in a roughly 10:1 proportion to neurons, form a firm jelly like support system for neurons. They create the insulating myelin, provide structure to the neuronal network, manage waste, and clean up neurotransmitters.
The human brain is made up of 100 billion nerve cells or neurons – about the same as the number of trees in the Amazon rainforest. Each cell is connected to thousands of others. So the total number of connections in your brain is the same as the number of leaves in the rainforest – about 1000 trillion or the equivalent to the world’s telephone system, which is the biggest machine on the planet.
Grey matter, in the cortex, is the outer part of the brain containing neural cell bodies, in contrast to the inner white matter which does not and mostly contains myelinated axon tracts, over 170,000 km of them. These route the millions of nerve fibres from all parts of the body into and around the central nervous system. Scientists now believe that repeated activity / practice leads to greater myelination, improved nerve fiber insulation, which increases the efficiency of neuronal pathways.
The brain is protected by the thick bones of the skull, suspended in cerebrospinal fluid, and isolated from the bloodstream by the blood-brain barrier.
For the average human adult, the brain weighs 1.35 kilograms (just under 3 lbs). Although it accounts for just 2% of body weight, it uses 20% of the body’s glucose as fuel, supplied by constant blood flow.
The creature with the largest brain on the planet is the Sperm whale at 7.8 kilograms.
Average adult human brain width = 140 mm, length = 167 mm and height = 93 mm.
There is still some doubt at this stage that size correlates directly with intelligence. For example, Einstein had an average sized brain.
The nervous system is the network of neurons which transmit information in the form of electrical signals. Neurons communicate with each other at special junctions called synapses, where chemicals help to bridge the gap between one neuron and the next.
The chemical changes that occur in these areas of the brain are the basis of our ability to retrieve memories.