Pyramidal neurons: functions and location in the brain

Neurons are the main type of cells that make up each of the elements of the nervous system. These structures are well known to most people today.

But although in the collective imagination we have a typical image or representation of what a neuron is, and many people imagine that all or almost all of them have the same structure and shape, the truth is that not all neurons are the same: there are very different types depending on their shape, where they send information to or even their relationship with other neurons. neurons. In this article we will focus on pyramidal neurons and their functions.

• Related article: "Types of neurons: characteristics and functions

pyramidal neurons

pyramidal neurons are one of the different types of neurons present in our nervous system. It is one of the most common types of multipolar neuron, accounting for around 80% of the neurons in the cortex (not surprisingly, two of the layers of the cortex are called internal and external pyramidal) and are among some of the most relevant in the organism. They are generally considered projection neurons. That is, they act by sending the message to cells that are far and away from the area where they are born.

Discovered by Santiago Ramón y Cajal, the name of this type of neuron refers to the shape of its soma, triangular or pyramidal in appearance. They are mostly glutamatergic neurons, glutamate being the neurotransmitter that activates them, and they usually act as excitatory type neurons. They can be of different sizes, the largest being the giant pyramidal or Betz cells.

Like other neurons, the structure of this type of neuron consists of a soma, which, as we have said, has a pyramidal shape, a axon and dendrites. However, they have a particularity: in regards to the dendrites, they have a fairly long length compared to the rest, called apical dendrite, and numerous basal and shorter dendrites that are going to branch.

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Location of these nerve cells

Pyramidal neurons can be found at different points in the nervous system, but they are much more prevalent in some specific areas. Among them are the following.

1. Cerebral cortex

Pyramidal neurons are found to a large extent in the cerebral cortex, forming part of most of it and being found in five of the six layers that make up this brain region. Specifically, they can be observed in the granulosa and pyramidal layers, both external and internal.

They stand out especially in the third and fifth layers (which are actually called external pyramidal and internal pyramidal), being larger the deeper they are in the crust. Within the cortex, likewise, there are areas where its existence has been detected more often.

2. motor cortex

In the motor cortex we can find a large number of pyramidal type neurons, being especially linked to motor control. In this area of ​​the cortex those known as Betz cells abound, giant pyramidal neurons that carry motor information from the brain to areas of the spinal cord where they synapse with motoneurons that activate movement.

3. prefrontal cortex

Pyramidal neurons can also be found in the prefrontal cortex, influencing higher mental processes. These cells are considered are the main primary excitation neurons of the prefrontal, participating in numerous functions and being considered essential for the existence of behavior control.

4. corticospinal tract

Pyramidal neurons are especially visible along the corticospinal tract, which sends motor information from the different brain nuclei. responsible for motor skills to motor neurons which will generate muscle contraction, passing through the spinal cord.

4. Hippocampus

Not only in the cortex can we find pyramidal neurons, but also can be found in subcortical structures. One of them is the hippocampus, linked to aspects such as memory and orientation.

• Related article: "Hippocampus: functions and structure of the memory organ"

5. Amygdala

Another of the structures in which these neurons are found is in the cerebral amygdala, an area of ​​the limbic system linked to the emotional memory.

Functions of pyramidal neurons

Like the rest of neurons, those of the pyramidal type are structures that transmit information in the form of electrochemical pulses that will be captured by other neurons until they reach their final destination. Being such a prevalent type of neuron in the cortex, pyramidal neurons are activated and linked to a large part of the functions and processes carried out by the human being. Examples of such functions are as follows.

1. Motion

Motor control is one of the functions that has been most traditionally associated with pyramidal neurons. Specifically, these neurons are deeply associated with voluntary motor control of muscles.

2. Cognition and executive functions

The excitatory role of pyramidal neurons in the prefrontal cortex means that their activation can be linked to highly relevant cognitive processes, such as executive functions or cognition.

3. Emotion

The activity of pyramidal neurons in the prefrontal cortex is linked to the connection of these areas with different subcortical regions, including the limbic. In this sense, the amygdala and the hippocampus play a fundamental role.

4. memory and orientation

Memory and special orientation are other functions in which great activation occurs in pyramidal neurons, in this case those of the hippocampus.

Bibliographic references

• Kandel, E.R.; Schwartz, J.H. & Jessell, T.M. (2001). Principles of neuroscience. Fourth edition. McGraw-Hill Interamericana. Madrid.
• McDonald, A.J. (1992). Cell types and intrinsic connections of amygdala. Program Neurobiol. 55: 257-332.