Neuroscience

[il_bilge]

First of all, let's begin with the neurons, the beginning of everything...

A neuron is a nerve cell. The brain is made up of approximately 100 billion neurons.

Neurons are similar to other cells in the body in some ways such as:

• Neurons are surrounded by a membrane.
• Neurons have a nucleus that contains genes.
• Neurons contain cytoplasm, mitochondria and other "organelles".

However, there are differences, of course:

• Neurons have specialized projections called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body.
• Neurons communicate with each other through an electrochemical process.
• Neurons form specialized connections called "synapses" and produce special chemicals called "neurotransmitters" that are released at the synapse.

It has been estimated that there are 1 quadrillion synapses in the human brain. That's 1015 or 1,000,000,000,000,000 synapses! This is equal to about a half-billion synapses per cubic millimeter.*

The adult human brain weighs between 1300 g and 1400 g. A newborn human brain weighs between 350 and 400 g.

For comparison:
elephant brain = 6,000 g
chimpanzee brain = 420 g
rhesus monkey brain = 95 g
beagle dog brain = 72 g
cat brain = 30 g
rat brain = 2 g **

And let's talk about the length of neurons. Although research has shown that neurons may differ slightly in length, we can make a rough calculation.

1 neuron = 10 microns wide
10 neurons = 100 microns wide
100 neurons = 1000 microns wide = 1 mm wide
1,000 neurons = 10 mm wide = 1 cm wide
100,000 neurons = 100 cm wide = 1 m wide
100,000,000 neurons = 1000 m = 1 km
10,000,000,000 neurons = 100 km
100,000,000,000 neurons = 1000 km

Sources:

*/**Statistic from Changeux, J-P. and Ricoeur, P., What Makes Us Think?, Princeton: Princeton University Press, 2000, p. 78

Brain Facts, Society for Neuroscience, 1997 and other sources including The American Academy of Neurology


I will continue with the brain and interesting data about the boss of the body.