How many neurons does the human brain have?

If the human brain is the set of organs that houses thought, it can be thought that all our mental processes are actually the consequence of many nerve cells functioning in our head. However... How many neurons are there in the average human brain?

Knowing this is not easy, since on a microscopic scale the variation in the number of cells is always very large and making mistakes in measurements is very easy. However, it is currently estimated that the brain of an adult person usually has almost one hundred billion neurons. Or, expressed in numbers, between 86,000,000,000 and 100.000.000.000 (10 to the 11th power).

But these figures are not as important as one might first suppose ...

• Recommended article: "Parts of the human brain (and functions)"

Massive numbers of neurons and synapses

This figure may seem overwhelming, but it is worth remembering that what really makes the human brain such a complex system is not the number of neurons a person has, but the way in which these neurons interact with each other.

The variability of things that can happen in our brain does not depend so much on the number of neurons as on what they do, the way in which they communicate. And to know this we have to take into account what happens at the points where these nerve cells connect to each other. These places are called synaptic spaces, and the same neuron can be associated with several of them, through which it receives and sends information.

How many synaptic spaces are there in the adult human brain? 10 to the 14th power. Namely: 100.000.000.000.000. In addition, each of these synaptic spaces hosts a lot of events at the same time: thousands of particles called neurotransmitters are emitted and taken up by the neurons that share the synaptic space, and depending on the type of neurotransmitters and their quantity, the neurons will be activated following one or another pattern of frequencies.

Age also counts

Another aspect that must be taken into account when considering how many neurons the human brain has is that this figure varies depending on the age of the person. The brain of newborns is not much smaller than that of an adult person, and it has a much larger number of neurons. However, they are nerve cells that are not closely connected to each other, and that is why many of them are not yet fully functional.

During the first two decades of life, the maturation process of mental processes has to do with encourage the neurons that are used to connect with each other, not by increasing the number of cells nervous What makes our ability to think in abstract terms enhanced during puberty and adolescence It is not that new parts of the brain are born or that the number of neurons grows, but that there are more efficient. This is reflected in a process called myelination, whereby large regions of the brain turn white.

This color is a sign that axons, the parts of the neuron that "stretch" to reach neurons that are far away, are beginning to spread to many parts, since this part of the anatomy of the nerve cells is covered by a whitish substance call myelin.

Regarding the number of neurons in the brain, just after the first months of life, when large numbers of neurons are already beginning to connect massively, the human body causes many of them to die. In this way, the material from which these unused nerve cells are made can be reused for other things.

How many neurons do other animals have in their brains?

As an example, or as a curiosity, we can compare those 100,000,000,000 neurons in the human brain with the number of nerve cells estimated to have on average other animal species.

• Bee: 960.000
• Frog: 16.000.000
• Cat: 300.000.000
• Raccoon: 453.000.000
• Rhesus Macaque: 480.000.000
• Chimpanzee: 6.200.000.000
• African elephant: 11.000.000.000

What are neurons like?

If after reading all this you have realized that you don't even know very well what a neuron is, You can read this article to see what its structure is like and what are the main types of neurons:

• It may interest you: "Types of neurons: characteristics and functions"

Bibliographic references:

• Saladin, Kenneth (2011). Human anatomy (3rd ed.). McGraw-Hill.
• Shepherd, GM (1994). Neurobiology. Oxford University Press.
• Triglia, Adrián; Regader, Bertrand; García-Allen, Jonathan (2016). Psychologically speaking. Paidos.