If the human brain is the set of organs that houses thought, it can be thought that all our mental processes are, in fact, the consequence of the fact that there are many nerve cells functioning in our head. Now… how many neurons are there in the brain of an average human being?

Knowing this is not easy, since on a microscopic scale the variation in cell number 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 raised to 11).

But these figures are not as important as one might initially assume…

Massive amounts 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, how 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 may be associated with several of them, through which it receives and sends information.

How many synaptic spaces are there in the human adult brain? 10 to 14. That is: 100,000,000,000,000 . Furthermore, each of these synaptic spaces hosts a lot of events at once: thousands of particles called neurotransmitters are emitted and captured 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 frequency pattern.

Age also counts

Another aspect to take into account when considering how many neurons the human brain has is that this figure varies depending on the person’s age . The brain of a newborn is not much smaller than that of an adult, and has a much larger number of neurons. However, they are nerve cells that are not very connected to each other, and therefore 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 encouraging the neurons that are used to connect with each other, not with increasing the number of nerve cells. What makes our ability to think in abstract terms stronger during puberty and adolescence is not that new parts of the brain are born or that the number of neurons grows, but that those that exist are more efficient. This is reflected in a process called myelinization, by which large regions of the brain become white.

This color is a sign that axons, the parts of the neuron that “stretch” to reach distant neurons, are beginning to spread in many places, since this part of the nerve cell anatomy is covered by a whitish substance called myelin.

As for the number of neurons in the brain, just after the first months of life, when large numbers of neurons are already beginning to be connected massively, the human body causes many of them to die . In this way, the material that these unused nerve cells are made of 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 be present on average in 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

How are the neurons?

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 looks like and what the main types of neurons are :

  • You may be interested in: “Types of neurons: characteristics and functions”

Bibliographic references:

  • Saladin, Kenneth (2011). Human anatomy (3rd ed.). McGraw-Hill.

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  • Shepherd, GM (1994). Neurobiology . Oxford University Press.

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  • Triglia, Adrián; Regader, Bertrand; García-Allen, Jonathan (2016). Psychologically speaking. Paidós.