Hypothalamus

Table of Contents

What is Hypothalamus?

Hypothalamus is a minute region, almost the size of an almond, present at the centre of the human brain, near the pituitary gland.

It consists of three main regions:

• The anterior region.
• The middle region.
• The posterior region.

It plays a vital role in the production of hormones. Maintaining the hypothalamus health is very important. Its improper functioning causes several disorders.

Also Refer: Endocrine glands and Hormones

Structure of Hypothalamus

The structure of hypothalamus is made up of three main regions:

• Anterior region
• Middle region
• Posterior region

Anterior Region

1. The anterior region is also known as the supraoptic region.
2. It regulates body temperature and maintains the circadian rhythm.
3. There are several small nuclei in the hypothalamus. The major hypothalamic nuclei include supraoptic and paraventricular nuclei.
4. The nuclei in this region are involved in the hormone secretion.

Following are the hormones secreted by the anterior region of the hypothalamus:

• Corticotropin-releasing hormone
• Thyrotropin-releasing hormone
• Gonadotropin-releasing hormone
• Oxytocin
• Vasopressin
• Somatostatin

Middle Region

1. This is known as the tuberal region.
2. It consists of ventromedial and arcuate nuclei.
3. The ventromedial nuclei control the appetite, whereas the arcuate nuclei secrete the growth hormone responsible for the growth and development of the body.

Posterior Region

1. This region is also known as the mammillary region.
2. The major nuclei include posterior hypothalamic nucleus and mammillary nuclei.
3. The posterior hypothalamic nuclei cause shivering and blockage of sweat and thus regulates the body temperature.
4. The mammillary nuclei, on the contrary, are believed to be involved in the memory function.

Functions of Hypothalamus

The hypothalamus contains osmotic sensors that react to the concentration of sodium, potassium, carbon dioxide, and chloride. When the blood pressure is very low these osmotic sensors and baroreceptors intimate the kidneys to store or release water to maintain the concentration of these substances.

Following are the important functions of the hypothalamus:

• Its main function is maintaining the body’s internal balance- homeostasis.
• It also connects the endocrine and the nervous system.
• Hypothalamus stimulates or inhibits many of the body’s activities in order to maintain homeostasis, such as regulating body temperature, appetite and body weight, heart rate and blood pressure, etc.
• It is involved in many essential functions of the body, including:

1. Childbirth.
2. Emotions.
3. Sleep cycles.
4. Balancing body fluids.
5. Appetite and thirst control.
6. Blood pressure and heart rate.

Also Check: Diagram of Hypothalamus and Pituitary

Hormones Secreted by Hypothalamus

The anterior region of the hypothalamus is responsible for hormone secretion. The nuclei present in this region lead the process. The important hormones secreted by hypothalamus are:

1. Corticotropin-Releasing Hormone: This hormone is responsible for the regulation of metabolic and immune response.
2. Thyrotropin Releasing Hormone: It triggers the pituitary gland to release a thyroid-stimulating hormone which plays a major role in the functioning of organs of the body such as heart, muscles, etc.
3. Gonadotropin-Releasing Hormone: It stimulates the pituitary gland to release several reproductive hormones.
4. Oxytocin: It is involved in several processes such as lactation, childbirth, regulating sleep cycles, maintaining body temperature.
5. Somatostatin: This hormone is also known as Growth Hormone Inhibiting Hormone. It regulates the endocrine system and affects the neurotransmission and cell proliferation by interacting with G-protein coupled receptors.

The middle region of hypothalamus stimulates the release of Growth Hormone Releasing Hormone. This hormone plays a major role in the growth and development of the body.

Let us know more about the Oxytocin and ADH hormone.

Oxytocin

Oxytocin is a peptide hormone, released during childbirth and lactation. In females, it is mainly involved in stimulating the growth of prostaglandins, increasing the contractions of the muscles of the uterus,  reduces the excess blood flow post-childbirth, promotes milk movement into the mammary glands. In males, oxytocin helps in the production of testosterone and aids in the movement of sperm. It also plays a role in social behaviour and various aspects around it.

Also Read: Lactation

Effects Of Oxytocin

Consumption of oxytocin can have adverse side-effects. Such as:

• Higher levels of oxytocin have been related to Benign prostatic hyperplasia
• Lack of oxytocin can prevent breastfeeding by milk-ejection reflex
• Low oxytocin levels have also been linked to autistic disorders (Asperger’s syndrome). It also leads to depressive symptoms
• Fetal heart rate deceleration, pulmonary oedema, and uterine hyperstimulation are other conditions caused due to oxytocin
• Vomiting, nausea, jaundice, neonatal hyperbilirubinemia, sinus bradycardia are also caused due to abnormal oxytocin levels
• Oxytocin imbalance in the body causes seizures in the neurons

Functions Of Oxytocin

• Affects gland growth.
• Acts as a neurotransmitter in the brain.
• Stimulates contractility of the epididymis, prostate gland, and seminiferous tubules.
• Oxytocin plays a role in maternal and sexual behaviour, memory-related, yawning, feeding, thermoregulation and cardiovascular regulation.
• Stimulates uterine muscle contractions. During childbirth, fetal-ejection reflex produces oxytocin, which causes contractions of muscles of the uterus.

ADH-  Anti-diuretic Hormone

ADH, also known as arginine vasopressin, is a hormone produced by the hypothalamus and stored in the posterior pituitary gland. It is made up of special nerve cells found at the base of the hypothalamus. The hormone is transported to the pituitary gland via axons, where it is released into the bloodstream. It regulates and balances the amount of water in the blood.

Functions Of ADH

• It acts on the kidneys and the blood vessels and functions to control the blood pressure. Higher concentrations of ADH constrict the blood vessels which increases the blood pressure.
• It allows the water in the urine to be taken back in a specific area in the kidney and thus reduces the amount of water excreted through the urine thereby conserving the volume of the fluid in the body.
• It is mainly responsible for homeostasis.

Also read: Regulation of Kidney Function

Regulation Of ADH

The release of ADH into the bloodstream is regulated by a number of factors:

• The decrease in the blood volume or blood pressure is detected by the large blood vessels and the receptors present in the heart, which stimulate the release of ADH.
• The increase in the concentration of salts in the bloodstream also controls the secretion of ADH which is identified by special nerve cells in the hypothalamus.
• Alcohol prevents the release of ADH. This causes dehydration and an increase in urine production.

If the levels of ADH are higher, the water is retained by the kidney in the body. If excess ADH is released when not required, the blood gets diluted due to excess water retention. The salt concentration in the blood thus decreases. High levels of ADH may be caused due to the side-effects of drugs, lung diseases, etc. Increased ADH is associated with leukaemia, lymphoma, bladder cancer, brain cancer, etc.

If the levels of ADH are lower, a lot of water is excreted by the kidneys. This increases urine volume and lowers blood pressure. Low levels of ADH indicate primary polydipsia and damage to the hypothalamus or pituitary gland. Diabetes insipidus is related to low levels of ADH.

Also read: Hormones in Animals

Hypothalamic Disorders

Every hormone should be secreted at accurate levels. Very high or very low secretions can lead to hypothalamic disorders. Hypothalamic disorders can be due to the following problems:

• Head injuries
• Genetic disorders
• Tumours in the hypothalamus
• Disorders in eating
• Brain surgeries
• Autoimmune disorders

The symptoms that indicate a hypothalamic disorder include:

• Body temperature fluctuations
• Infertility
• Unusually high or low blood pressure
• Insomnia
• Change in appetite
• Frequent urination
• Delayed puberty

Overall, the hypothalamus is a small region present in the centre of the brain, which plays a major role in signalling the Pituitary Gland to release hormones to the rest of the endocrine system.

Also Read: Endocrine gland and its disorders

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Frequently Asked Questions

What are Hormones?

Hormones are the chemical substances produced by endocrine glands, which synchronize biological processes including the growth of an individual.

Which gland secretes oxytocin?

Oxytocin is a hormone secreted into the bloodstream by the posterior pituitary gland and produced in the hypothalamus.

How do the Hormones functions in our body?

Endocrine glands release hormones directly into the bloodstream. Hormones act as mediators, communicating messages across the body, controlling and coordinating the body activities. Different hormones affect the body differently, while some hormones are quickly generated to carry out a biological process at a faster pace, some other processes work over a period of time and hence require doses of these hormones at regular intervals.

Which hormone is called the happy hormone?

Serotonin is a chemical messenger that has a wide variety of functions in the human body. It is also called the happy hormone as it contributes to well-being and happiness.

What is ADH?

ADH refers to Anti-diuretic Hormone. It is also called arginine vasopressin. This hormone increases the amount of water absorbed in the blood by the kidneys and regulates and balances the amount of water in your blood. It is produced by the hypothalamus in the brain.