Purkinje Neurons: Their Functions And Characteristics
It is estimated that, at the time of our birth, we have 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.
Purkinje cells or neurons receive their name from the Czech anatomist, physiologist and botanist 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.
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 currently have practically absolute knowledge about the anatomy and structure of Purkinje neurons, as well as their specific details and functions.
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
Approximately 30 million are found in the cerebellum alone of neurons of this type, each of them being linked to around a million nerve endings of other types of different cells. These cells to which the Purkinje neurons are attached are classified into two types:
Mossy cells
They come from the brain stem and spinal cord. As they are closer to the Purkinje neurons, they branch into fibers that are located in parallel.
Climbing cells
They ascend from the medulla oblongata and brainstem However, these types of climbing cells only attach to a single Purkinje neuron.
What is the structure of these nerve cells?
As mentioned above, Purkinje neurons are some of the largest cells found in our brain. Its dendritic axis is extremely complex and is distinguished by having a large number of tangled dendritic spines.
These cells are placed in front of each other, as if they were dominoes, forming layers between which the parallel fibers that come from the deeper layers pass.
Through the synapses, the parallel fibers transmit excitatory impulses of weak potential to the dendritic spines of Purkinje neurons However, the impulses from 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 deep cerebellar nuclei, constituting the only escape route from the cerebellar cortex with effects on motor coordination.
Purkinje neurons They exert their effects through the use of electrophysiological activity This type of activity can occur in two different ways, depending on whether the neuron spikes are simple or complex.
1. Activity in simple spikes
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. Activity in complex spikes
In the case of complex spikes the intensity slows down considerably, ranging between 1 and 3 Hz power.
Complex spikes are distinguished by having 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 climbing fibers mentioned 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 the stimulation of climbing fibers triggers an alteration in the activity of the cell, going 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 debated. The reason is that the data obtained in other studies point towards the idea that these alterations in activity only occur when the person or animal is anesthetized; while if they are awake, the Purkinje neurons always function in a complete state of activity.
Finally, the results obtained from recent research suggest that Purkinje neurons They have the ability to release endocannabinoid substances that can reduce the potential of synapses, 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 specific and specific abnormalities for each species.
In the case of people, there are a large number of causes that can cause the deterioration or injury of 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.
Furthermore, 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 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:
In the case of cerebellar hypoplasia the Purkinje neurons have not finished developing or they die while the child is still in the mother’s womb.
