An Introduction
The endocrine system in our body is made of several types of glands that secrete chemical messengers called hormones. These hormones circulate and transmit information from a group of cells to another, or between tissues and organs.
The most important glands that comprise the endocrine system include the thyroid, pituitary, the adrenals and the hypothalamus glands. The hypothalamus hormones directly control and regulate a wide variety of bodily processes.
What is 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.
Location of Hypothalamus
The hypothalamus 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
The hypothalamus has a somewhat complex structure and comprises three regions. Each of these is made up of different kinds of nuclei. These nuclei are groups of nerve cells or neurons that carry out many important functions, such as secreting hormones.
The Parts of Hypothalamus are:
Anterior region or Supraoptic region
Middle region or Tuberal region
Posterior region or Mammillary region
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Anterior Region
The anterior region is also known as the supraoptic region. The supraoptic part is made of the supraoptic and paraventricular nuclei. These nuclei mostly secrete hormones that interact with the pituitary gland to form more hormones.
The anterior region secretes some essential hypothalamus hormones. These are:
1. Vasopressin
Vasopressin is also known as the antidiuretic hormone or ADH. It modulates the levels of water in the body.
2. Oxytocin
The hormone oxytocin regulates several emotional responses and behaviour such as recognition, sexual arousal, excitement and trust. It also controls some parts of the reproductive system, such as lactation and childbirth.
3. Thyrotropin-releasing Hormone (TRH)
The TRH signals the pituitary gland to secrete thyroid-stimulating hormone or TSH.
4. Corticotropin-Releasing Hormone
The CRH stimulates the pituitary to secrete the adrenocorticotropic hormone or the ACTH. The ACTH signals the secretion of stress hormone which is known as cortisol.
5. Somatostatin
Somatostatin stops the pituitary gland from secreting some specific hormones.
6. Gonadotropin-Releasing Hormone (GnRH)
GnRH causes the pituitary to secrete reproductive hormones like FSH and LH.
The anterior region also helps maintain the body’s circadian rhythms and body temperature.
Now, let us recapitulate a few concepts with the following exercise.
Pop Quiz 1
1. Where is the Hypothalamus Located?
a. base of the brain and below pituitary gland
b. top of the brain and above pituitary gland
c. base of the brain and above pituitary gland
d. top of the brain and below pituitary gland
Middle Region
Also known as the tuberal region, this middle region of the hypothalamus is mostly made up of the ventromedial and arcuate nuclei. The ventromedial nucleus helps to regulate appetite, and the arcuate plays a role in secreting GHRH or the growth hormone-releasing hormone. It is responsible for the proper growth and development of a body.
Posterior Region
Known as the mammillary region, the posterior region consists of the posterior hypothalamic nucleus and the mammillary nucleus. It helps control and stabilize body temperature and is also believed to play a role in memory and cognition.
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Now we know all about the structure of this hypothalamus. Let us revise our concepts with the following quiz.
Pop Quiz 2
1. Which of these are Hormones Secreted by Hypothalamus?
Oxytocin
Thyrotropin-releasing hormone (TRH)
Corticotropin-releasing hormone
All of these above
Functions of Hypothalamus
The hypothalamus connects to various parts of the central nervous system. It is connected to the brainstem, the part of the brain that carries information from the peripheral nerves and spinal cord to the upper part of the brain. The brainstem contains parts of the midbrain and hindbrain. The hypothalamus is also connected to the peripheral nervous system. With these connections, the hypothalamus can affect many autonomic or involuntary functions.
Besides the hypothalamus hormones, the hypothalamus also features osmotic sensors that react to concentrations of chloride, carbon dioxide, potassium and sodium. These osmotic sensors signal the kidneys to store or release water depending on their respective levels. The role of hypothalamus is an essential one and includes these following activities:
Maintaining sleep cycles
Connects the nervous and endocrine systems
Balances body fluids
Regulates blood pressure and heart rate
Autonomic function control
Maintains homeostasis, such as regulating body temperature, appetite and body weight, heart rate and blood pressure, etc.
Motor function check
Eating and Drinking
Emotion control
Disorders of Hypothalamus
Besides these, the hypothalamus secretes hormones that are involved in many other functions such as appetite and thirst control. Optimum levels of hormones in the bloodstream are necessary for the body to function properly. Low or high levels of a particular hormone could lead to hypothalamus disorders. These include:
Insomnia
Frequent urination
Infertility
Fluctuations in appetite and thirst
Unusually high or low blood pressure
Diabetes insipidus
It is important to eat a balanced diet and ensure that the hypothalamus is healthy and functional.
For more on the work of hypothalamus and other glands in the endocrine system, refer to our PDF notes and solved question papers. Install the Vedantu app today and discover an exciting world of learning with easy access to study materials and online interactive sessions.
FAQs on Hypothalamus
1. What is the Hypothalamus?
The hypothalamus is a tiny gland located towards the base of the brain and lies above the pituitary gland. It forms a direct link between the endocrine system and the nervous system through this pituitary gland.
2. The Antidiuretic Hormone is Secreted by which Gland?
The anterior part of the hypothalamus releases the ADH.
3. What is the Function of the Hypothalamus?
The functions of the hypothalamus include quite a few activities like maintaining sleep cycles, maintaining homeostasis, connecting the nervous and endocrine systems, balancing body fluids, regulating blood pressure and heart rate, etc. It plays an important role in many important functions including hormone release, control of body temperature, maintaining a daily physiological cycle, controlling appetite such as eating and drinking, etc.
4. What is sexual dimorphism?
Certain hypothalamic nuclei are sexually dimorphic; which means there are evident variations in both form and operation between males and females. Some variations are obvious even in gross neuroanatomy: most prominent is the sexually dimorphic nucleus inside the preoptic area, in which the variances include minor alterations in the connection and chemical sensitivity of certain groupings of neurons. The relevance of these alterations can be identified by functional differences between males and females. For example, males of most species prefer the odor and look of females over males, which is crucial in promoting male sexual activity. If the sexually dimorphic nucleus is lesioned, this inclination for females by men declines. Also, the pattern of release of growth hormone is sexually dimorphic. This is why in many animals, mature males are obviously dissimilar sizes from females.
5. What is Incertohypothalamic?
The incertohypothalamic route is a short dopaminergic pathway from the zona incerta to the hypothalamus of the brain. It plays a function in the control of fear and the integration of autonomic and neuroendocrine responses to particular sensory inputs, for example during sexual conduct. Dopaminergic cell groups are clusters of neurons in the central nervous system that produce the neurotransmitter dopamine. In the 1960s, dopamine neurons were originally found and named by Annica Dahlström and SV. Kjell Fuxe, who employed histochemical fluorescence. The successive finding of genes encoding enzymes that replicate dopamine. The transporters integrate dopamine into synaptic vesicles or reclaim it after synaptic release. This helped scientists to study the dopaminergic neurons. Labeling gene or protein expression that is specific to these neurons enables more understanding. In the mammalian brain, dopaminergic neurons constitute a semi-continuous population. This spans from the midbrain through the forebrain, with eleven identified clusters within them.
6. What is the function of the posterior region?
Posterior region is also called mammillary region helps in regulating body temperature, memory, learning, arousal, pupil dilation etc.
7. What is the function of Oxytocin hormone secreted by Hypothalamus?
Oxytocin hormone is a peptide hormone which is released in women during labour or childbirth and lactation. It helps in increasing the contractions of the muscles of the uterus, reduces the excess flow of blood after childbirth, increases milk movement into the mammary glands. In males, it helps in production of testosterone and movement of sperms.
