Locus coeruleus: its anatomy, functions and diseases
The whole of the human organism contains within it a whole series of internal structures and nuclei whose functions and tasks imply a level of complexity that still amazes the medical and scientific community. However, there is a system that stands out among the rest: the central nervous system.
Within this we can find a whole range of structures without which we could not perform practically anything, as well as respond to external stimuli or interact with the environment. One of these structures is the locus coeruleus , a nucleus located in the encephalic trunk and of which we will speak throughout this article.
- Related article: "Parts of the human brain (and functions)"
What is the locus coeruleus?
The locus coeruleus (LC), also known as cerulean locus or locus caeruleus, is a nucleus composed mainly of noradrenergic neurons that is located in the protuberance of the brainstem. This center is one of the parts belonging to the reticular activation system and its main functions are those related to the physiological responses of stress and fear .
In addition, the locus coeruleus provides the main source of noradrenaline (or norepinephrine, NE) for the entire brain, brainstem, cerebellum, and spinal cord. The neuronal activity of this plays an essential role in the integration of sensory information when it comes to regulating the activation, attention and certain functions of memory.
The connections and corresponding circuits between the locus coeruleus and the neocortex, the diencephalon, the limbic system and the spinal cord make its importance relevant to the functioning of the neural axis.
Due to the aging of the person or certain diseases, the locus coeruleus can suffer important losses in terms of the neuronal population, which contributes to the cognitive deterioration of the person and the appearance of a whole series of neurological disorders .
This center of the nervous system was discovered in the year 1784 by the French physician and anatomist Felix Vicq-d'Azyr, and later the German psychiatrist Christian Reil, redefined it in a more specific and specific way. However, it was not until 1812 that he received the name that remains to this day, which was granted to him by Brother Joseph Wenzel and Karl Wenzel.
Anatomy and connections of LC
The specific location of the locus coeruleus is located in the posterior area of the protuberance of the brainstem, more specifically in the lateral part of the fourth ventricle of the brain. This structure It is mainly composed of medium-sized neurons and it is distinguished by harboring melanin granules inside its neurons, which give it its characteristic blue coloration.
In an adult human, a healthy locus coeruleus can be made up of between 22.00 and 51.000 pigmented neurons of which it can vary in size to the point that the larger ones double in volume to the rest.
As for the connections of the locus coeruleus, this It has projections towards practically any area of the nervous system . Some of these connections include the conservative function performed in the spinal cord, brain stem, cerebellum and hypothalamus, or the thalamic transmission nuclei, amygdala, basal telencephalon and cortex.
We refer to the locus coeruleus as an innervating nucleus since the norepinephrine that exists in it has excitatory effects on most of the brain; mediating the excitement and driving the brain neurons to be activated by stimuli.
In addition, due to its important function as a homeostatic control center in the body, the LC also receives afferent fibers from the hypothalamus . Likewise, the cingulate gyrus and amygdala also innervate the locus coeruleus, allowing distress and emotional pain, and stimuli or stressors to trigger noradrenergic responses.
Finally, the cerebellum and the afferents of the raphe nuclei also send projections towards the locus coeruleus, specifically nucleus raphe pontis and nucleus of the dorsal raphe.
What functions does this brain region play?
Due to the increased production of noradrenaline, the main functions of the nucleus coeruleus are those related to the effects that the sympathetic nervous system exerts on the responses of stress and fear. In addition, recent research also points to the possibility that this brainstem center is of vital importance in the proper functioning of the vigil processes .
In the same way, other studies link the locus coeruleus with Posttraumatic Stress Disorder (PTSD), as well as with the physiopathology of dementias , which are related by the loss of the noradrenergic stimulus.
However, due to the large number of projections found in the LC, this has been related to a large number of functions. Among the most important are:
- Excitement and sleep-wake cycles .
- Attention and memory.
- Behavioral flexibility, inhibition of behavior and psychological aspects of stress.
- Cognitive control .
- Emotions.
- Neuroplasticity
- Postural control and balance .
Pathophysiology of this nucleus: associated disorders
The abnormal or pathological functioning of the locus coeruleus has been associated with a large number of disorders and mental disorders such as clinical depression, panic disorder, anxiety and Parkinson's and Alzheimer's diseases.
In addition, there are a large number of mental or psychological alterations which appear as a consequence of a series of alterations in the norepinephrine-modulating neurocircuits . Among them we find disorders of affect and anxiety, Posttraumatic Stress Disorder (PTSD) or Attention Deficit Hyperactivity Disorder (ADHD).
In addition, it is speculated that certain drugs such as norepinephrine reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors and norepinephrine-dopamine reuptake inhibitors can be very effective in counteracting the effects of deregularization of the locus coeruleus.
Finally, one of the most novel and surprising discoveries is that which suggests a relationship between a dysregulation of the functioning of the locus coeruleus and autism . These investigations suggest that the locus coeruleus system and the noradrenergic system are deregulated by an interrelation of environmental, genetic and epigenetic factors. And that, in addition, the effects of the states of anxiety and stress can also disorganize these systems, especially in the later stages of prenatal development.
