Purkinje neurons: their functions and characteristics.

They are one of the largest types of neurons, and are found in the Heart and cerebellum.

It is estimated that, at the moment 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 the Purkin cells. neurons or Purkinje cells. Throughout this article we will explain what these neurons consist of, how they work and what they are used for, as well as the pathologies associated with them.

What are Purkinje neurons?

Purkinje cells or neurons are named after the anatomist, physiologist and botanist of Czech origin Jan Evangelista Purkyne, 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.They 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 now have almost complete knowledge of the anatomy and structure of Purkinje neurons, as well as the details and specific functions of these cells.

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, i.e. in the muscular part of the heart..

Purkinje cell connections

In the cerebellum alone there are about 30 million of these neurons, each of which is linked to about one million nerve endings of other different cell types. neurons of this type alone, each of which is linked to about one million nerve endings of other different cell types. These cells to which Purkinje neurons are attached are classified into two types:

Mossy cells.

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

Climbing cells

Ascend from the medulla oblongata and the brainstem.. However, this type of climbing cell only attaches to a single Purkinje neuron.

What is the structure of these nerve cells?

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

These cells are arranged one in front of the other, like dominoes, forming layers between which parallel fibers from deeper layers pass.

Through synapses, the parallel fibers transmit excitatory impulses from the deeper layers. transmit weak potential excitatory impulses to the dendritic spines of the Purkinje neurons.. However, impulses from those ascending fibers originating from the inferior olivary nucleus of the medulla emit excitatory impulses of high intensity. In addition, these parallel fibers run at right angles through the dendritic axis of the Purkinje cell. These fibers, which may number in the hundreds of thousands, form synapses with a single neuron of this type.

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

What are their functions?

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.

Activity in simple spikes

The rate of electrophysiological activity in simple spikes ranges between ranges from 17 to 150 Hz.. This activity may occur spontaneously or at times when Purkinje neurons are activated by parallel fibers.

2. Activity in complex spikes

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 initial spike of high amplitude, which follows in a high-frequency firing but with a lower amplitude. These bursts of electrical activity originate from the activation of the climbing fibersnamed above.

What is known about them from research

Sodium and calcium play a fundamental role in the electrophysiological activity of Purkinje neurons and thus in the proper function of the cerebellum. In addition, in recent years it has been revealed that stimulation of the climbing fibers triggers an alteration in the activity of the cell, going from a resting to an active state and vice versa) as if it were a kind of button or push 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, Purkinje neurons always function in a state of full activity.

Finally, the results drawn from recent research suggest that Purkinje neurons have the capacity to discharge endocannabinoid substances that can impair the potential of both excitatory and inhibitory synapses.

Associated pathologies and diseases

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

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

In addition, in Alzheimer's 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 some time 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.
• Shivering.

In the case of cerebellar hypoplasiaThe Purkinje neurons have not finished developing or die when the child is still in the mother's uterus.