Ok sure. You asked how I knew how many neurons are in the human brain:
Here you have a number of sources:
Herculano-Houzel S (2009). The human brain in numbers: A linearly scaled-up primate brain. Frontiers in Human Neuroscience, 3(31). doi:10.3389/neuro.09.031.2009
Orca, S. (2009, Nov 30). The race to reverse engineer the human brain. H + Magazine. Retrieved from
The Race to Reverse Engineer the Human Brain
Randerson, J. (2012, Feb 28). How many neurons make a human brain? Billions fewer than we thought. The Guardian. Retrieved from
How many neurons make a human brain? Billions fewer than we thought | James Randerson | Science | theguardian.com
Williams, Robert W. (2000). "Mapping Genes that Modulate Mouse Brain Development: A Quantitative Genetic Approach". In: Mouse brain development (Goffinet AF, Rakic P, eds), Springer Verlag, New York, pp 21–49.
Or you could just google it. The answer is between 80 and 100 billion.
Then you asked how I knew those neurons had to be arranged a certain way. Well, think about if they weren't, you would just have a gooey blurb of neurons. But, as we know, the brain is made up of neurons, and the brain has defined structures, with each structure having a defined function. Source:
Brain Structures and Their Functions
Therefore, the specific arrangement of neurons is critical to having a working brain.