“The human brain has 86 billion neurons, give or take — on the same order as the number of stars in the Milky Way. If you look at the synapses, the connections between neurons, the numbers start to get beyond comprehension pretty quickly. The number of synapses in the human brain is estimated to be nearly a quadrillion, or 1,000,000,000,000,000. And each individual synapse contains different molecular switches. If you want to think about the brain in terms of an electrical system, a single synapse is not equivalent to a transistor — it would be more like a thousand transistors.
To make things more complicated, not all neurons are created equal. Scientists still don’t know how many different kinds of neurons we have, but it’s likely in the hundreds. Synapses themselves aren’t all the same either. And that’s not even taking into account all the other cells in our brain. Besides neurons, our brains contain lots of blood vessels and a third class of brain cells known collectively as glia — many of which are even more poorly understood than neurons.
Scientists are making progress breaking those numbers down into something more comprehensible. At the level of individual brain cells, research teams at the Allen Institute and elsewhere are making headway into sorting the cells into different categories, defined as “cell types,” as well as being able to record electrical activity from living human neurons using creative new techniques.
Many neuroscientists study the brain of the lab mouse, in part with the hopes of understanding basic principles of the mammalian brain that could apply to our brains too.
The mammal the octopus (cephalopods related to squid and cuttlefish-The octopus is classified as one branch of mollusks. — and its brain — are fascinating. For an animal with a brain, they’re about as different from humans as it gets. Octopuses have about half a billion neurons, more than five times as many as the lab mouse. But unlike in our nervous systems, more than half of those neurons are in the octopus’ arms. The animals have incredible autonomous control over their limbs — similar in some ways to our own spinal cords that send messages to out body to move. Understanding the octopus brain isn’t just interesting in its own right, it could also help us understand broad general principles of large brains and animals who can learn and remember complicated behaviors — like us.”
The human brain is probably one of the most, if not the most, complicated brains in any living species.”
Allen Institute (https://alleninstitute.org/news/why-is-the-human-brain-so-difficult-to-understand-we-asked-4-neuroscientists/)
QUOTE 2 – “The human brain can be subdivided according to various criteria. It can be explained in terms of evolution, as, like all vertebrates, it consists of an end brain, interbrain, midbrain, hindbrain and medullary brain. Anatomically, the areas known as the cerebrum, interbrain and cerebellum, as well as the brain stem, are particularly noticeable. Particularly striking is the cerebral cortex, which forms part of the end brain. During evolution, it has grown so strongly that it surrounds almost the entire brain. With its ridges and coils, the cortex gives the brain its walnut-like look.”
MAX-PLANCK-GESELLSCHAFT (https://www.mpg.de/brain)