The hypothalamus, anatomy, function and expression of emotions

The hypothalamus is a small structure located at the base of the brain, which plays a fundamental role in the control and regulation of many essential body functions, such as sleep, food, stress and sexual behavior.

Content

• Anatomy of the hypothalamus
• Hypothalamus function
  • The hypothalamus and the endocrine system
  • Function on Somatic Autonomous and Motor Systems
• The hypothalamus and aggressiveness
  • Conclusions
  • References

Anatomy of the hypothalamus

The hypothalamus is located at the bottom of the brain, just above the brainstem and under the thalamus. It is a very small organ, with an approximate size of a cubic centimeter, but its functions are crucial for the proper functioning of the body.

Its anatomy is characterized by an organization in nuclei, each with a specific function.

The hypothalamus is divided into three main regions: The previous hypothalamus, the middle hypothalamus and the posterior hypothalamus. Each region contains specific nuclei that are responsible for controlling different body functions.

He anterior hypothalamus, Also known as the preoptic area, it is involved in sleep regulation, body temperature, thirst, endocrine food and regulation. It contains nuclei such as the medial preoptic nucleus, the lateral preaptic nucleus and the suprachiastic nucleus.

He Middle hypothalamus, also known as the piperal area, is responsible for the regulation of appetite, metabolism and reproductive function. It contains nuclei such as the ventromedial nucleus, the arcuato nucleus and the dorsomedial nucleus.

He posterior hypothalamus, Also known as the mamilar area, it is involved in the regulation of memory and space learning. It contains nuclei such as the supraoptic nucleus and the paraventricular nucleus, which are responsible for the production and release of hypothalamic hormones.

The hypothalamus is connected with other areas of the brain through multiple neuronal pathways, including the mamilemic fascicle, the tecttohypotalamia via and the hypothalamic pathway of the vagus nerve.

In addition, the hypothalamus receives sensory information from several sources, including the flavor, smell and stomach receptors. It also receives information through the autonomic nervous system, which regulates involuntary body functions such as breathing, blood circulation and digestion.

Hypothalamus function

One of the main functions of the hypothalamus is the autonomic nervous system control, that regulates involuntary body functions such as breathing, blood circulation, digestion and excretion. The hypothalamus is also responsible for Regulate body temperature and hormone release.

The hypothalamus is especially important for Regulation of appetite and food consumption. Hypothalamus cells respond to hunger and satiety signals, and can influence food intake and energy spending. Leptin and Grelina hormones, which regulate satiety and hunger, respectively, act in the hypothalamus to help maintain an adequate balance of energy.

In addition, the hypothalamus plays an important role in the regulation of the circadian rhythm of the body, which controls the sleep-vigilia cycle. Melatonin production, the hormone that regulates sleep, is controlled by the hypothalamus and its suprachiamatic nucleus.

Other important functions of the hypothalamus include Regulation of stress response, sexual response and growth hormones. It is also involved in the regulation of the immune system and the inflammatory response.

The hypothalamus and the endocrine system

Two of the most prominent hypothalamic nuclei (because their neurons are large) are the paraventricular nucleus and the supraoptic nucleus. The cells of these nuclei secrete two types hormones in the bloodstream: oxytocin, which causes uterine contraction during birth and induces milk release in females with young and young Antidiuretic hormone (ADH) who travels to the kidneys to help the body retain water by decreasing urinary production.

Other hypothalamic nuclei, located in the anterior area, regulate the blood levels of growth hormone, adrenocortopic hormone (for stress response), thyrotropin (which regulates basal metabolism) and the other hormones that regulate the reproductive organs and Sexual behavior.

Through its connections with the hypophysis, It also plays a key role in the Neuroendocrine secretion control. Hypothalamic neurons participating in endocrine control are, fundamentally, magocellular neurons, supraoptic and paraventricular nuclei, and parvicellular neurons of the periventricular zone.

Function on Somatic Autonomous and Motor Systems

Several hypothalamic nuclei with troncolecencephalic projections regulate and modulate the operation of the Somatic Autonomous System and Motor.

The hypothalamus, however, is not only a brain zone in charge of control of the somatic, motor and endocrine system, but it seems that it is a Coordinating Center, capable of integrating emotional and sensory information, In order to generate an appropriate efferent response for the situation in which the subject is. The hypothalamus coordinates emotional expression through the regulation of neuroendocrine, motor and autonomous systems.

In 1932, Stephen Ranson implemented electrodes in different areas of the hypothalamus. Through the electrical stimulation of the different regions of the hypothalamus, Ranson generated various autonomic reactions to experimental animals, such as alterations in capillary erection, alterations in gastrointestinal and bladder motility, blood pressure or heart rate, among others.

The hypothalamus and aggressiveness

It is believed that the Hypothalam also has a very important role in the regulation of emotion. Specifically, its lateral areas seem to be involved with pleasure and anger, while the middle part is mainly connected to the aversion, disgust and the tendency to uncontrollable and strong laughter. However, in general terms, the hypothalamus has more to do with the expression (symptomatic manifestation) of emotions that with the genesis of affective states.

In the twenties, different experimental studies with cats and dogs showed that the rear half injury of the hypothalamus prevented the manifestation, in the same animals, of aggressive behaviors induced by removal of the cerebral hemispheres.

A researcher at the University of Zurich, Walter R. HESS, showed that the electrical stimulation of several locations of the hypothalamus could induce different attack and defense responses.

Darwin's engraving that illustrates a cat's emotional response to the threat of a dog.

W.R. HESS studied the effects of the electrical stimulation of several areas of the diencephalon and found a variety of responses depending on the concrete stimulated area. Thus, this researcher showed that The electrical stimulation of the hypothalamus was able to generate in the animals characteristic of emotional responses of fear and fury. In 1949, HESS received the Nobel Prize for his works on the role of the hypothalamus in the coordination and functional regulation of the internal organs.

In 1971, Panksepp found that when The electrical stimulation of the hypothalamus generated predatory aggression, This stimulation was reinforcing by animal, while when it generated threat behaviors, it turned out to be aversive. PANKSEPP came to this conclusion because in the first case the rats easily learned to self -apply stimulation currents in the lateral hypothalamus through a lever, while in the second they learned very easily to disconnect electrical stimulation when it was provided in the medial hypothalamus.

In the seventies, the researcher at the University of Yale Medicine, John Flynn, saw that Electrical stimulation of medial hypothalamus could generate attack threat behaviors in cats; These behaviors were accompanied by a high activity of the sympathetic branch of the autonomic nervous system. When stimulation was, however, of lateral hypothalamus a predatory aggression was caused without this high sympathetic activity.

The stimulation of the medial hypothalamus in cats generates threat behaviors that warn the adversary that it will be subject to aggression if it is still present in the situation.
Source: m.F. Bear, b.W. Connors, m. TO. Paradiso to: Neuroscience. Exploring The Brain. (2001). Ed .: Lippinott Williams & Wilkins.

The stimulation of the lateral hypothalamus generates predatory attacks by a member of a species towards a member of another.
Source: m.F. Bear, b.W. Connors, m. TO. Paradiso to: Neuroscience. Exploring The Brain. (2001). Ed .: Lippinott Williams & Wilkins.

Experiments carried out by Shaikh, Siegel and collaborators have revealed the interconnections between the amygdala, the hypothalamus and the peri -eductal gray substance For the development, both of the aggression of the threat of attack (called by some authors and affective aggression, due to the high sympathetic activity observed in behavioral patterns), and of the predatory aggression.

Conclusions

As we can see, the hypothalamus is a small but vital structure in the brain that plays a key role in the regulation of many essential body functions. It is responsible for maintaining adequate energy, regulating the circadian rhythm of the body, controlling the response to stress and sexual function, Regulates behavioral patterns aggressive through two anatomically differentiated pathways and has a very important role in coordinating the peripheral expression of emotional states and is involved in the regulation of the immune system.

Functionally, The hypothalamus is related to aspects such as homeostatic regulation, motivated behaviors or emotions. For this reason, its complex interaction with other areas of the brain makes it an important research objective in neuroscience and the treatment of neurological disorders.

References

• Bradford, h.F. (1988). Fundamentals of neurochemistry. Barcelona: Labor.
• Carlson, n.R. (1999). Behavior Physiology. Barcelona: Ariel Psychology.
• Guyton, a.C. (1994) Anatomy and Physiology of the Nervous System. Basic neuroscience. Madrid: Pan American Medical Editorial.
• Kandel, e.R.; Shwartz, J.H. And Jesell, T.M. (eds) (1997) Neuroscience and behavior. Madrid: Prentice Hall.
• Martin, J.H. (1998) Neuroanatomy. Madrid: Prentice Hall.
• Nolte, J. (1994) The human brain: Introduction to functional anatomy. Madrid: Mosby-Doyma.