He Hypothalamus Is a small brain structure that lies beneath the thalamus and forms part of the floor of the third ventricle of the brain.
It comes from the Greek"ὑπό", meaning"below"and"θάλαμος"which would be"thalamus"(a term referring to"bed").
This structure is cone-shaped, and projects downward from the brain , Ending in the pituitary gland . With this gland it maintains a complex interaction.
The hypothalamus performs very important functions, integrating a great variety of information. It is considered an essential part of the nervous system and the endocrine system. It is responsible for releasing hormones and other substances that regulate different cells and organs.
The hormones of the hypothalamus maintain the homeostasis in the organism, that is, it ensures its correct functioning by correcting certain mismatches.
In this way you can control physiological functions like thirst, hunger, sleep, temperature, mood, sexual desire... As well as other body hormones.
In addition, the hypothalamus is also involved in metabolism, growth, and even certain involuntary behaviors.
It is linked to another endocrine gland called Pituitary or pituitary gland . In particular, the hypothalamus sends signals to the gland to release certain hormones from the body.
The hypothalamus is composed of several neuronal nuclei that have different functions.
Where is the hypothetical?
The hypothalamus is a subcortical structure that is located in the interior of our brain. Its location is practically central, allowing it to establish relations with many areas of the brain. It is present in all vertebrates, and in humans its size is similar to that of an almond.
It is part of Diencephalon , A set of structures of the Encephalon .
On the hypothalamus lies the hypothalamic groove, the thalamus, and the choroid plexus of the third ventricle.
Below this is the recess and the supraoptic crest, the Brain stem , And the pituitary gland (pituitary gland).
In the anterior part of the hypothalamus, the anterior commissure and the terminal lamina are located. While thereafter, there are the mammillary bodies, the perforated substance, the cerebral peduncle, and The aqueduct of Silvio .
Parts of the hypothalamus
The hypothalamus can be divided into three structurally different parts. These are the anterior, middle, and posterior regions. They are also commonly known as supraoptic, tuberal and mammillary regions.
All these areas work together to produce different hormones and important chemicals to modulate the activity of the various organs of the body.
In addition, each area has specific functions that are explained in the following sections.
Anterior or supraoptic region
As its name indicates, it is located just above the optic chiasma . The most prominent nuclei in this area are the paraventricular and the supraoptic. Other nuclei that may be found are the preoptic, the anterior hypothalamus and the suprachiasmatic.
The latter work together to secrete hormones such as Oxytocin , Vasopressin, somatostatin and corticotropin-releasing hormone.
Thanks to the supraoptic region, you can control circadian rhythms, thermoregulation of the body, sweating and development of the sexual characteristics of the body. Later on, the functions in which the hypothalamus intervenes will be discussed in more detail.
Middle or tuberal region
The middle region of the hypothalamus lies in the Tuber cinereum . It is divided into two parts, the medial and lateral.
In the medial, the dorsomedial and ventromedial nuclei influence the control of the feeding impulse. The dorsomedial nucleus is related to appetite. The ventromedial nucleus, the major and one of the most important, is responsible for regulating the sensation of fullness or satiety.
In this region is also the arched nucleus, which blocks milk production in women by inhibiting the release of a hormone called prolactin.
Other functions associated with the middle or tubal region are blood pressure, heart rate, and gastrointestinal activity.
Posterior region or nipple
This area is also divided into two parts: medial and lateral. The medial zone includes two classes of hypothalamic nuclei, called the mamillary nucleus and the posterior nucleus.
These nuclei intervene in functions such as blood pressure, tremors, energy balance, hunger, sleep, and activation. As well as memory and learning.
Functions
The main function of the hypothalamus is to maintain homeostasis or balance the entire body. This structure plays a multitude of functions essential for a normal functioning of the organism.
For example, it is the reason we know when we are thirsty or hungry, or why we always maintain a constant temperature.
The hypothalamus receives information from almost the entire nervous system, and is involved in a multitude of Functions of the autonomic nervous system . Each of the functions of this structure is explained below.
Endocrine functions
The hypothalamus acts as an intermediary between the nervous system and the endocrine system. Its fundamental endocrine function is the control of the pituitary gland so that it releases hormones in the necessary moments. This gland is essential since it modulates all other endocrine glands in the body.
This system is known as the hypothalamic-pituitary axis. When the hypothalamus receives certain signals from the nervous system, it releases substances called neurohormones. These stimulate or inhibit the secretion of hormones from the pituitary gland, which will in turn control the release of hormones from other glands in the body.
The hypothalamus has neurons that release and capture norepinephrine, serotonin and dopamine, allowing the regulation of hormone levels.
The Hormones of the hypothalamus Most outstanding are:
- Corticotropin releasing hormone. As the name implies, it promotes the release of corticotropin. In this way, it sends signals to the pituitary gland to stimulate the adrenal glands. The latter release corticosteroids (cortisol), a substance important for metabolism and the immune system.
When the levels of Cortisol Are reduced, fatigue, weakness, hypoglycemia, Lack of sexual desire And decreased body hair.
- Antidiuretic hormone , Also called arginine vasopressin. It controls the amount of fluids, glucose and salts in the blood. In addition to producing a greater concentration in the urine, as well as a decrease in its quantity.
- Gonadotropin-releasing hormone. It is essential for sexual reproduction. This hormone stimulates the pituitary (pituitary) to release two hormones essential for a correct functioning of the ovary or testicles. These are follicle stimulating hormone (FSH) and luteinizing hormone (LH).
- Growth Hormone Releasing Hormone (Somatocrinin) . It secretes growth hormone, which serves to maintain a suitable size and body composition in children. In adults, it is useful for maintaining healthy bones and propitious muscle mass. It also seems to influence the distribution of fat.
The hypothalamus also releases a hormone that has the opposite effect, the growth hormone inhibitory hormone (somatostatin).
- Oxytocin: Is a hormone that has a great variety of functions. It is primarily linked to sexual reproduction, orgasm, delivery, and milk production of the mammary glands.
- Prolactin releasing hormone. Essentially this hormone is useful for the production of breast milk.
- Hormone stimulating thyroid hormones. These regulate energy levels, development and metabolism.
The hypothalamus receives signals from the body that tell it to"give orders"to increase or inhibit the production of certain hormones when necessary.
Basic life functions
On the other hand, it also helps to stimulate or inhibit fundamental processes like: heart rate, blood pressure, or body temperature. It also regulates electrolyte and fluid levels, thirst, appetite, and weight.
Functioning of the gastrointestinal system
The hypothalamus also regulates the glandular secretions of the stomach and intestines.
Biological rhythms
Circadian rhythm control, also known as Biological rhythms . It is a system that regulates our periods of sleep, activity or hunger. For example, thanks to biological rhythms every day we tend to sleep at the same time.
Reproductive, attachment and parenting behaviors
Some areas of the hypothalamus appear to influence the sexual appetite, recognition, protection and feeding of the offspring.
Learning and memory
The hypothalamus is involved in brain circuits that allow the retrieval of information stored in our memory , Mainly its nipple area. It also seems to be involved in learning simple associations.
Emotions
This structure has also been related to emotional expression. In the hypothalamus are grouped several chemical substances that produce emotions In humans, such as sadness, astonishment, anger, affection or sexual satisfaction.
Diseases of the hypothalamus
A physical injury to the head affecting the hypothalamus is one of the most common causes of hypothalamic disease. Malnutrition, inflammation ( meningitis Or encephalitis), neoplasms, Stroke , Or infections.
Hypothalamic tumors appear to be very rare. In the case in which they appear, they can cause hyperactivation or hypoactivation of the pituitary.
On the other hand, it is possible that the hypothalamus is damaged by radiotherapy or surgical procedures performed prior to symptoms.
Disorders of sleep and appetite are the most frequent manifestations, since the hypothalamus regulates these functions.
Sometimes it can be difficult to know if certain symptoms are due to a lesion in the hypothalamus, as it can be confused with injuries in the pituitary gland (for example). Since both are connected and work together to modulate different functions.
When the hypothalamic-pituitary circuit is damaged, these cases are known as hypothalamic-pituitary disorders.
An example of this is hypopituitarism or Panhypopituitarism . In this condition, the hypothalamus does not function properly, inhibiting the hormonal secretions of the pituitary gland. Thus, they affect the basic vital functions of the organism and growth.
Other examples would be gigantism, dwarfism, absence of menstruation or irregular cycles in women, sexual dysfunctions, etc.
Damage to the hypothalamus has been shown to produce some of the following symptoms:
- Lesions in the hypothalamus influence the sleep and wake cycle. This is due to the existing connections between the ocular retina and the suprachiasmatic nucleus, which regulate circadian rhythms. By affecting alertness, damage to the hypothalamus may cause drowsiness and continual fatigue.
- Loss of vision.
- Early puberty, or delayed development.
- Macrocephaly , That is, an exaggerated increase in head size.
- Because the hypothalamus secretes vasopressin (antidiuretic hormone), when damage occurs in it, it is expected to block the production of vasopressin. This leads to the inability of the kidneys to conserve the fluid, a condition called Diabetes insipidus .
- Problems of memory and emotional expression, especially if the mammillary bodies of the hypothalamus are damaged. This is because the hypothalamus is part of the Circuit of Papez , Connecting with regions of the limbic system . This system is fundamental for the memory and experimentation of emotions.
- Hyperthermia, caused by an injury to the anterior nucleus of the hypothalamus. Since this is involved in thermoregulation by the stimulation of the parasympathetic nervous system.
- Malnutrition or extreme starvation conditions such as Anorexia nervosa , May lead to the destruction of the lateral part of the tubal region of the hypothalamus. This area is responsible for regulating appetite and food.
As the hypothalamus regulates appetite and metabolism, it is possible that if there is a failure in this hypothesis there is an increase or decrease in weight.
Related to the above, hypothalamic obesity disorder may also occur. What happens with these patients, is that after making the relevant analyzes to see what their obesity is due to, they only find differences in the thyroid hormones.
However, when they take the medication needed for hormone replacement they feel worse and do not lose weight as they expected.
But with a deeper analysis, you can see that the source of the problem lies in the hypothalamus. The treatment in this case would be behavioral therapy combined with pharmacological therapy for the hypothalamic pathways involved in satiety and metabolism.
References
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- Sargis, R. (April 4, 2015). An Overview of the Hypothalamus. Obtained from Endocrine web: endocrineweb.com.
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- What is Hypothalamus, Parts of Hypothalamus with Pictures. (S.f.). Retrieved on January 27, 2017, from Human Brain Facts: humanbrainfacts.org.