Purkinje neurons: their functions and characteristics

It is estimated that, at the time of our birth, we possess approximately 80 million neurons or brain cells. Thanks to their activity, our nervous system is able to function at full power.

One of the types of neurons that inhabit our brain are neurons or Purkinje cells. Throughout this article we will explain what these neurons consist of, how they work and what they are for, as well as the pathologies associated with them.

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

What are Purkinje neurons?

Purkinje cells or neurons are named after the Czech anatomist, physiologist and botanist Jan Evangelista Purkyne, who discoverer of these elements. These large cells are found in all invertebrate animals, are a type of GABAergic neuron and constitute the functional units of the cerebellum.

After its discovery, many researchers have tried to decipher the enigmas of this neuron. The well-known scientists Camillo Golgi and Santiago Ramón y Cajal, dedicated years of their lives to study these cells

. Thanks to this research, we currently have practically absolute knowledge about the anatomy and structure of the Purkinje neuron, as well as the details and specific functions of these.

Although they are mainly found in the cerebellar cortex, forming the Purkinje layer between the molecular layer and the granular layer, They can also be found in the myocardium, that is, in the muscular part of the heart.

Purkinje cell connections

Only in the cerebellum are approximately 30 million of neurons of this type, each one of them being united to around a million nerve endings of another type of different cells. These cells to which Purkinje neurons are attached are classified into two types:

Mossy cells

They come from brainstem and of the spinal cord. As they are closer to the Purkinje neurons, they branch into fibers that are located in parallel.

Climbing cells

Ascend from the brainstem and brainstem. However, these types of climbing cells only bind to a single Purkinje neuron.

What is the structure of these nerve cells?

As discussed above, Purkinje neurons are one of the largest cells found in our brain. Its dendritic axis is extremely complex and it is distinguished by presenting a large number of tangled dendritic spines.

These cells are placed opposite each other, as if they were dominoes, forming layers between which the parallel fibers that come from the deeper layers pass.

Across the synapses, the parallel fibers transmit excitatory impulses of weak potential to the dendritic spines of Purkinje neurons. However, the impulses of those ascending fibers that come from the inferior olivary nucleus of the medulla emit excitatory impulses of great intensity. Furthermore, these parallel fibers circulate at right angles through the dendritic axis of the Purkinje cell. These fibers, which can number in the hundreds of thousands, form synapses with a single neuron of this type.

Finally, Purkinje neurons transmit inhibitory fiber projections to the cerebellar nuclei deep, becoming the only escape route from the cerebellar cortex with effects on coordination motorboat.

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

What functions do they have?

Purkinje neurons exert their effects through the use of electrophysiological activity. This type of activity can occur in two different ways, depending on whether the spikes of the neuron are simple or complex.

1. Simple spike activity

The rate of electrophysiological activity of simple spikes ranges between 17 and 150 Hz. This activity can appear spontaneously or at times when Purkinje neurons are activated by parallel fibers.

2. Complex spike activity

In the case of complex spikes, the intensity slows down considerably, oscillating between 1 and 3 hz of power.

Complex spikes are distinguished by having a long, high-amplitude initial spike, which follows a high-frequency shot but with a smaller amplitude. These bursts of electrical activity are caused by the activation of climbing fibers, named above.

What is known about them through research

Sodium and calcium play a fundamental role in the electrophysiological activity of Purkinje neurons and, therefore, in the correct function of the cerebellum. Furthermore, in recent years it has been revealed that stimulation of climbing fibers triggers an alteration in the activity of the cell, going from a state of rest to an active one and vice versa) as if it were a kind of button or button.

However, the results of these investigations have been widely debated. The reason is that the data obtained in other studies point to the idea that these alterations in activity only occur when the person or animal is anesthetized; Whereas if they are awake, the Purkinje neurons always function in a full state of activity.

Finally, results from recent research suggest that Purkinje neurons have the ability to discharge endocannabinoid substances that can undermine the potential of synapse, both excitatory and inhibitory.

Associated pathologies and diseases

Since Purkinje neurons are found in both animals and humans, there are a wide variety of factors that can cause species-specific and specific abnormalities.

In the case of people, there are a large number of causes that can cause the deterioration or injury of the Purkinje neurons. Genetic alterations, autoimmune or neurodegenerative diseases and toxic elements present in certain substances such as lithium, can cause serious damage to this type of cells.

Also, in the Alzheimer disease, a decrease in the dendritic branches of these neurons has been described.

On the other hand, in the animal world there is a strange condition that causes atrophy and malfunction of these neurons long after birth. This disease known as cerebellar abiotrophy is distinguished by presenting a large number of symptoms, among which are:

• Hyperactivity
• Lack of reflexes.
• Lack of ability to perceive space and distances.
• Ataxia.
• Shudder.

In the case of cerebellar hypoplasia, Purkinje neurons have not yet fully developed or die while the baby is still in the womb.