Orexin: What is it? Functions, Relationship with Narcolepsy and Sleep Physiology

It is one of the hormones responsible for regulating sleep.

When there is a deficiency of orexin in the body, neurological disorders can be generated , even being so severe that narcolepsy is caused .

Orexin is also known as hypocretins and intervenes as a protein in neuronal function, acting in the central nervous system to regulate various cellular processes.

This hormone is a neuropeptide, therefore two types are known:

  • Orexina A.
  • Orexina B.

Among the characteristics that differentiate them are:

  • Type A orexin: it is composed of 33 amino acids
  • Orexin B: is made up of 28 amino acids.

The brain structure that synthesizes the participation of orexins A and B is described as follows:

  • Orexin A or hypocretin 1 receptor.
  • Orexin B or hypocretin 2 receptor.

Functions of orexin

This hormone apart from its main function of regulating the sleep cycle , the hypocretin-orexin system is involved in the fluidity or maintenance of wakefulness. This characteristic has high levels of motor activity.

These levels of maintenance of wakefulness tend to decrease as the depth of sleep appears.

Some studies suggest that orexin stabilizes the wakefulness circuit by promoting the neuronal connections of monoamines, such as:

  • Dopamine.
  • Norepinephrine.

These monoamines are responsible for keeping the body in a state of alert.

Among the other functions that orexins have are:

  • The regulation of stress .
  • The regulation of eating behavior.
  • Thermoregulation.
  • It is involved in motivational behaviors.

Narcolepsy and orexin

Narcolepsy is a neuronal disease better known as a sleep disorder.

It has various levels of severity, to the point of causing the affected person to fall asleep in strange circumstances, that is, due to unusual stimuli, generally emotional, that cause a sudden and deep sleep regardless of the place, time or circumstance in which the individual is found.

This disease is caused by an alteration in the cycle of sleep or wakefulness.

Narcolepsy-generated dream attacks can be triggered by:

  • Extreme happiness
  • Uncontrollable laughter.
  • Deep sadness.
  • Uncontrolled crying.

This disease, when it is at its highest level, is usually accompanied by a cataplexy crisis, which is a loss or reluctance of the muscles, which generates sudden falls without being able to mobilize the body.

Narcolepsy can also be accompanied by:

  • Hypnagogic hallucinations.
  • Hypnopompic hallucinations.

Hypnagogic hallucinations are generated when the person is in the process of falling asleep.

While hypnopompic hallucinations occur while the sufferer is waking up.

Patients who suffer from this condition tend to suffer from several episodes of body paralysis, before or after falling asleep and it is usually very uncomfortable, even traumatic when it occurs in public spaces.

As this condition is linked to a defect in the functioning of the orexin or hypocretin system, its pathophysiological mechanism is quite complex, which causes the levels of the hormone orexin to become undetectable.

The alteration of the hormone can even cause the affected person to enter a stage of deep sleep, less known as REM sleep.

Sleep physiology

The state of relaxation that the body acquires when it is at rest or sleeping harbors an active cellular process with a regulation of multiple molecules and neurotransmitters.

In this way, the physiological levels have a circadian rhythm of 24.

Although it may seem that sleep is a process of disconnection and cessation of cellular processes, it is a very complex active process. It is regulated by a multitude of molecules and neurotransmitters.

That is why one of the brain structures involved is the hypothalamus, where there are neuronal nuclei involved with sleep, which are:

  • Wake Center.
  • Sleep center.

The waking center is located in the posterior hypothalamus.

Instead, the sleep center is located in the anterior hypothalamus, right in the preoptic region.

These centers are only two of the multiple neural connections that the brain structure presents related to alertness and drowsiness, but they are very important in the sleep-wake cycle.

People who suffer from a sleep-related disorder should seek specialist help, because if the body does not rest enough, diseases involving the central nervous system may later occur.