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

One of the types of neurons that inhabit our brain are the Purkinje neurons or 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’s neurons?

Purkinje’s cells or neurons are named after the Czech anatomist, physiologist and botanist Jan Evangelista Purkyne, who discovered these elements. These large cells are found in all invertebrate animals , 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 studying these cells . Thanks to this research, we now have almost absolute knowledge of the anatomy and structure of Purkinje’s neurons, as well as the specific details and 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

In the cerebellum alone, there are approximately 30 million such neurons, each of which is attached to about one million nerve endings from a different type of cell. These cells to which Purkinje’s neurons are attached are classified into two types:

Spongy cells

They come from the brain stem and the spinal cord. As they are closer to Purkinje’s neurons, they branch out into fibers that are located parallel to each other.

Climbing cells

They ascend from the medulla oblongata and the brain stem . However, these types of climbing cells only bind to a single Purkinje neuron.

What is the structure of these nerve cells?

As mentioned above, Purkinje’s neurons are some 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 placed in front of each other, like dominoes, forming layers between which parallel fibers from the deeper layers pass.

Through the synapses, parallel fibres transmit weak potential excitatory impulses to the dendritic spines of Purkinje’s neurons . However, the impulses of those ascending fibres coming from the lower olive core of the medulla emit excitatory impulses of high intensity. In addition, these parallel fibres circulate at right angles through the dendritic axis of the Purkinje cell. These fibres, which can be counted in hundreds of thousands, form synapses with a single neuron of this type.

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

What are their functions?

Purkinje’s 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. Single ear activity

The electrophysiological activity rate of single spikes ranges from 17 to 150 Hz . This activity may appear spontaneously or at times when Purkinje neurons are activated by parallel fibres.

2. Complex spike activity

In the case of complex spikes, the intensity slows down considerably, ranging from 1 to 3 hz of power.

Complex spikes are distinguished by a long, high-amplitude initial spike, which follows in a high-frequency shot but with a lower amplitude. These bursts of electrical activity originate from the activation of the climbing fibres , named above.

What is known about them through research

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

However, the results of these investigations have been widely discussed. The reason is that data from 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’s neurons always function in a fully active state.

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

Pathologies and associated diseases

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

For individuals, there are a number of causes that can lead to the deterioration or injury of Purkinje’s neurons. Genetic alterations, autoimmune or neurodegenerative diseases and toxic elements present in certain substances such as lithium, can cause serious damage to these types 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 the atrophy and malfunctioning of these neurons long after birth. This disease known as cerebellar abiotrophy is distinguished by a large number of symptoms, among which are

  • Hyperactivity.
  • Lack of reflexes .
  • Lack of ability to perceive space and distance.
  • Ataxia.
  • Shivering.

In the case of cerebellar hypoplasia , Purkinje’s neurons have not finished developing or they die when the child is still in the mother’s womb.