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Mechanism of hormone action is one of the most significant mechanisms that goes on inside the human body. The body consists of an endocrine gland which is mainly responsible for secreting hormones that travel across the body through blood vessels. These hormones are further responsible for triggering the intercellular signals by binding themselves through the target cells. These signals are seen in a variety of forms of human activities such as activating specific genes to build in new protein, modifying the permeability of the membranes, etc. In this article, we will discuss the meaning and the details of the hormone and its actions respectively, along with other associated concepts.
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Key Takeaways: Hormones, activities, homeostasis, chemical composition, endocrine gland, pituitary gland, thyroxin, blood sugar level, lipid membrane, action mechanisms
What are Hormones?
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Hormones are the minuscule group of chemical compositions which serve as an important functionary element in the human body. These hormones are released from the endocrine gland and are transported across the body through the bloodstream. Every organ and system of the human body is under the influence of specific hormones which regulate multiple functions and actions. Such as, the actions like thinking, feeling (happiness, sadness, guilt, fear, etc.), eating, and so on, occur due to the actions of several hormones.
Hormones
In general, these hormones are classified in the group of two on the basis of their chemical composition, such as
- Protein Hormone– This is a group of hormones that can easily dissolve in water or can be said that these are water-soluble hormones and can easily move across the body through the blood stream. For example, Adrenaline, noradrenaline, etc.
- Steroid Hormone- This is a group of hormones that cannot be dissolved in water or can be said that these hormones are not soluble in water and therefore work by binding themselves to the plasma protein after which they are released into the target organs. For example, Thyroid hormone from the thyroid gland.
What is Hormone Action?
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Hormones are nothing but chemical substances which are meant to perform various functions in the human body. Moreover, hormones help in keeping the human body in a state of homeostasis.
- Hormones generally work according to the receptors which receive the signals from the acting stimulus and receptors trigger the hormones to act in a specific way.
- These receptors could be of multiple types such as some are present in the cytoplasm or on the surface of the cell membrane, etc. Therefore, different receptors trigger very different hormones, thus, leading to individual-specific actions.
- Some hormones directly act according to the membrane-bound receptors and generate the second messenger to activate the cellular metabolism.
- However, there are also other types of hormones that interact with the intracellular receptors like that of the hormone-receptor complex with the genome and are known for regulating the gene expressions and the chromosome functions.
Hormone Action
Mechanism of Hormone Action
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The mechanism of hormone action can be classified into two different types, such as
1. Fixed Membrane Receptor Mechanism
- The water-soluble hormones which cannot move through the lipid membrane are mainly involved in this type of mechanism.
- Hormones like oxytocin, growth hormone, etc, are rich in amino acids or proteins, therefore, are known for binding themselves to the target cell membranes through the receptors.
- This binding helps the enzyme adenyl cyclase in the cell membrane to get activated which in turn produces the cyclic AMP (cAMP).
- Now, this cAMP serves the function of the secondary messenger and further, gets diffused through the cell membrane and helps in activating several types of enzymes that control the enzymatic reactions to cause biochemical changes.
- Later, the changes are seen in different organs of the body through the target cells, and cAMP is deactivated by the further production of the enzyme phosphodiesterase.
Mechanism of Hormone Action
2. Mobile Receptor Mechanism
- The hormones which can easily pass through the lipid membranes or are lipid-soluble are mainly involved in this type of mechanism.
- Hormones like fatty acids or other types of steroid hormones are known for easily moving across the plasma membrane and therefore, they possess intracellular receptors.
- Such hormones bind themselves to the target receptors which are further responsible for activating the enzymatic activities of the cells and this brings into force the biochemical changes.
- Later, the hormone-receptor complex initiates the transcription of DNA as mRNA is translated into the protein.
- The protein so produced then leads to the biochemical changes inside the cells influencing the overall human action.
Hormones as Regulators
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Hormones act as a regulator of other hormones and this process is known as the feedback mechanism. This mechanism could be classified into two types, such as
- Positive Feedback Control: This control mechanism occurs in the continuous loop of one after another action. In this case, the end action is known for initiating another product. For instance, the menstrual cycle.
- Negative Feedback Mechanism: This type of mechanism is simply a one-step process which after fulfilling the demand of the present existing stimulus, reduces it and completes the action. For instance, blood sugar level regulation.
Thyroid Gland
Hormones as Messengers
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Hormones are known for acting as a messenger for one another. For instance, the neurohormones are secreted into the bloodstream from the hypothalamus with the help of the neurosecretory cells and these hormones are further carried into the pituitary gland. After reaching the pituitary gland, the hormones satisfy the stimulus through specific actions of other hormones. As a result, hormones are also known as the “releasing factors”.
Hormones as Messengers
Hormonal Imbalance
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When the hormone is not produced in the body as per the required quantity, it is known as hormonal imbalance. There could be multiple reasons for this imbalance, such as quick gain of body fat or quick loss of body fat, improper diet, malnourishment, etc. Further, this imbalance of hormones also causes multiple diseases like thyroid, diabetes, delayed menstruations, etc.
Things to Remember
- Oestrogen and testosterone are known as the female and the male sex hormones. However, the body of both females and males require these hormones and their imbalance leads to various reproductive problems in both the sex.
- These two hormones, that is, estrogen and testosterone also control memory, cognitions, and other thinking capacities.
- The hormones in the human body stimulate most of the functions varying from body fat to that of the menstrual cycle in females. Balanced and nutritious diets play a significant role in regulating the secretion of such hormones.
- The pituitary gland is known as the major organ in the human body which releases multiple hormones for various kinds of functions.
- The production of insulin and the management of the blood sugar level in the human body is regulated by the pancreas through the production of various specific hormones including insulin.
Sample Questions
Ques. What are hormones? Explain their functions. (5 marks)
Ans. Hormones are chemical substances that are produced in the human body itself, mainly from multiple organs like the pituitary gland or the endocrine gland. However, sometimes, one hormone also regulates the presence of others. Some of the hormones are adrenaline, noradrenaline, thyroxin, etc. These hormones serve various functions, such as
- Hormones secreted by the glands help in regulating the functions of various organs and systems in the human body. For example, the production of oestrogen and progesterone helps in regulating the reproductive system.
- Proper secretion of hormones prevents the occurrence of various diseases like the balanced production of insulin prevents diabetes, thyroxin hormone controls the thyroid, and so on.
- Hormones act as regulators which further leads to the positive and negative feedback control mechanisms. The continuous occurrence of the menstrual cycle is in particular maintained by the production of one hormone, further, activating another in a continuous loop.
- Hormones also act as the releasing factor, as seen in the case of neurohormones where one hormone stimulates the functions of another in the human body.
Ques. What is the positive and the negative feedback mechanism? (3 marks)
Ans. The positive and the negative feedback mechanisms are the functions of hormones where they act as the regulators.
The positive feedback control occurs in the continuous loop of one after another action. Here, the end action is known for initiating another product. For instance, the menstrual cycle.
A negative feedback mechanism, on the other hand, is simply a one-step process which after fulfilling the demand of the present existing stimulus, reduces it and completes the action.
In this, the hormones mainly silence the stimulus after the actions are completed through required actions. For instance, blood sugar level regulation.
Ques. Explain any three types of hormones in terms of their functions. (4 marks)
Ans. The three types of hormones are as follows.
- Insulin: It is released by the pancreas and helps the body organs, livers, and fat to absorb the glucose. Its imbalance leads to the accumulation of blood sugar, thus, causing diabetes.
- Melatonin: It is released by the pineal gland of the human brain. It mainly regulates the biological clock of human beings. The body gets ready to sleep as soon as the lights in the surroundings get darker. The natural sleep pattern might get affected due to its imbalance.
- Oestrogen: It is also known as the female sex hormone and is released by the ovaries of women. Functions like breast development, regulating pubic hair, blood clotting, menstrual cycle, etc. are performed by this hormone. Its imbalance leads to low libido, weight gain, menopause, etc.
Ques. Define the significance of cortisol. (2 marks)
Ans. It is a natural alert system that makes the body aware of the possible danger in its surroundings. Cortisol is also known as the stress hormone, as the continuous release of cortisol leads to anxiety, migraine, heart problems, sleep disturbances, etc. This hormone is essential to prevent the human body from danger by making the organs react to the existing dangerous stimulus and therefore it acts as the natural alert system.
Ques. Which hormone is responsible for pregnancy? (2 marks)
Ans. The human chorionic gonadotropin hormone (HCG) is mainly responsible for the pregnancy. This hormone is secreted only during the pregnancy in the placenta of the mother. Further, the hormone is circulated all over the body of the female through the bloodstream and is responsible for most of the functions in the female body during pregnancy.
Ques. Explain the fixed–membrane receptor mechanism. (3 marks)
Ans. The fixed–membrane receptor mechanism is found in the water-soluble hormones which cannot move through the lipid membrane, for example. oxytocin, growth hormone, etc. Such hormones are rich in amino acids or proteins, therefore, are known for binding themselves to the target cell membranes through the receptors which help the enzyme adenyl cyclase in the cell membrane to get activated and leads to the production of the cyclic AMP (cAMP). This cAMP serves the function of the secondary messenger and further, gets diffuses through the cell membrane, and helps in activating the enzymes for controlling the enzymatic reactions to cause the required biochemical changes.
Ques. What is homeostasis? (2 marks)
Ans. Homeostasis is a self–regulating process which helps in maintaining stability in the human body. This stability or the equilibrium of chemicals in the body is maintained by the proper secretion of another chemical composition known as the hormones. For instance, the secretion of insulin by the pancreas controls the accumulation of blood sugar thus preventing diabetes.
Ques. Mention a few of the happiness hormones. (2 marks)
Ans. The human body produces various types of hormones that are responsible for making us happy. Such as, dopamine is secreted in the body on its own and makes us feel good. Another happiness hormone is serotonin which helps in releasing depression and the endorphins make the individuals happy by reducing the physical pain.
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