Hypothalamus – Class 11 | Chapter – 22 | Biology Short Notes Series PDF

Hypothalamus: The hypothalamus is a tiny gland located towards the base of the brain and lies above the pituitary gland. The function of hypothalamus in the brain is a vital one; it forms a direct link between the endocrine system and the nervous system through the pituitary gland.

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It consists of three main regions:

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

Location of Hypothalamus

Location of Hypothalamus

It is a small organ located in the brain that controls secretions from the pituitary gland which sends hormones to different organs. The brain is a mass of nervous tissue at the front end of an organism that functions as the “command and control system” of our body. The human brain is classified into three different main parts: the forebrain, the midbrain, and the hindbrain. The hypothalamus is  part of the forebrain and is at the base of the thalamus bordered on the sides by temporal lobes and optic tracts. It includes many centers that control not only our body temperature, but also our daily activities.

Structure of Hypothalamus

  • 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:
    • Childbirth.
    • Emotions.
    • Sleep cycles.
    • Balancing body fluids.
    • Appetite and thirst control.
    • Blood pressure and heart rate.

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:

  • Corticotropin-Releasing Hormone: This hormone is responsible for the regulation of metabolic and immune response.
  • 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.
  • Gonadotropin-Releasing Hormone: It stimulates the pituitary gland to release several reproductive hormones.
  • Oxytocin: It is involved in several processes such as lactation, childbirth, regulating sleep cycles, maintaining body temperature.
  • 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.

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By Team Learning Mantras