Hypothalamus

The hypothalamus is that part of the brain that is situated slightly below the thalamus and just above the brain stem. It is shaped like an almond. It predominantly functions as an organ that connects the nervous system to the endocrine system via the pituitary gland. As far as the location is concerned, it is available in a ventral position when compared to that of diencephalon.

The hypothalamus performs a number of vital functions. Some of them are discussed below:

Homeostasis:

• One of the most critical functions of the hypothalamus is homeostasis. Homeostasis is defined as the maintenance and balance of varied factors of the body. In most instances such factors don’t waiver from a stable set-point. The several factors that are preserved at all time of homeostasis include blood pressure, body temperature, fluid balance, electrolyte balance and weight of the body.
• The hypothalamus has two parts, i.e. the posterior or heating part and the anterior or cooling part. The body temperature is regulated by these two parts of the hypothalamus. When the temperature of blood present in the arteries rises, it results in the activation of hypothalamus receptors which are sensitive to heat. Such receptors are present in posterior part of hypothalamus and known as thermo-receptors.
• This leads to a response by the autonomous nervous system which results in the following two reactions, i.e. cutaneous vasodilation and sweating. This causes the temperature of the body to dip and thus cool down.
• As opposed to above, when the temperature of the body goes down, then the receptors that are present in the anterior part of the hypothalamus get activated. Such receptors are sensitive to low temperatures and are also known as thermo-receptors.
• The autonomic nervous system responds to the dip in body temperature with a number of reactions such as increased heart rate, shivering, rising of basal metabolic rate, assembly of carbohydrate reserves and cutaneous vasoconstriction.

Water balance:

• The water balance of the body is maintained by the paraventricular and supraoptic nuclei present in the hypothalamus.
• When the water levels present in the body become low, then it leads to an increase in the salt concentration levels in the blood. The hypothalamus has osmoreceptors that detect the presence of such a condition in the body. This causes them to release vasopressin into the capillaries of neurohypophysis.
• Vasopressin release causes the kidneys to retain the water, which eventually leads to reduction in the concentration of salt.
• Conversely, increase in the levels of water in the body results in decreased salt concentration in blood. This activates the osmoreceptors present in the hypothalamus, which in turn inhibit the secretion of vasopressin into the neurohypophysis capillaries. Such an absence of vasopressin causes the kidneys to absorb the available quantity of water and release it in the form of urine. The water levels are thus brought down to balanced levels, which increased the salt concentration in the blood to normal levels.

Other broad functions:

• The hypothalamus has a regulatory role in several important functions such as body metabolism, control of endocrine hormonal levels and sensory processing.

Specific functions of the hypothalamus

The details discussed above provide an overall summary of the broad functions of the hypothalamus. Discussed below are functions that are specific to this region of the brain.

• The hypothalamus governs the autonomic nervous system. Such control of the hypothalamus includes the process of regulating the subconscious tasks as well as the automatic functions of the nervous system
• The hypothalamus controls the output by secreting a few types of chemicals to the front lobe of the pituitary gland

The following points will assist in understanding the role of hypothalamus in the endocrine system:

• The hypothalamus plays an important role in the regulation and control of emotional behavior and thus becomes a vital cog in the governance of the endocrine system.
• The hypothalamus performs the important function of maintaining the balance of the circadian rhythms. The suprachiasmatic nucleus is present in the anterior part of the hypothalamus. This nucleus assists in the setting of the biological clock of the body. The suprachiasmatic nucleus gets the information about the different times of day or night from the retinohypothalamic tract.

Function of lateral hypothalamus

• This area of the hypothalamus is related to hunger. One will certainly feel hungry when this part of the hypothalamus or brain is stimulated. Trauma or injury to lateral hypothalamus results in reduced desire to consume food.
• The glucostatic receptors send signals to the hypothalamus that convey the messages of any drop in the blood sugar levels. Upon receiving such a message, some types of specific neurons present in the brain get stimulated. This leads to sensations of hunger and the desire to consume food.
• The functions of the ventromedial hypothalamus are similar to those of lateral hypothalamus. When an individual is eating or has finished eating, the blood sugar levels rise. This message of increase in glucose levels are carried by the glucostatic receptors to the ventromedial hypothalamus. The successful delivery of this message leads to a feeling of satiety or fullness within the individual.