[Biology Class Notes] on Hormones Pdf for EXAM

Hormones are chemical substances that act like messenger molecules that stream through the bloodstream. Hormones carry chemical messages from the glands where they are produced to cells in different parts of the human body. These chemical messages help to turn on or turn off cellular processes that control stress, appetite, growth, sleep cycles, blood sugar, sex drive, and sexual function. 

The importance of hormones in the proper functioning of the human body is immense. They control the functions of organs and influence their growth, reproduction and sexual characteristics.

Moreover, hormones also affect the way a human body stores and uses energy and regulates the volume of fluids as well as the level of sugar and salt in the blood. Thus, a small amount of hormone can trigger a significant response in the human body.

 

What are Hormones?

Hormones are various chemicals released within the human body that regulate and control the activities of multiple organs. The introduction of hormones to the blood takes place via endocrine glands.

 

What Is the Function of Hormones?

Hormones act as a messenger which is released into the blood. Blood transmits them to various organs and tissues of the human body. After reaching a target site, hormones bind to the receptors. Once this process is complete, hormones then transmit the message which causes an organ or tissue to perform a specific action.

 

The following are some important functions of hormones:

• Regulating mood and cognitive functions

• Growth and development

• Food metabolism

• Maintaining body temperature

• Controlling thirst and hunger

• Initiating and maintaining sexual development and reproduction

 

Hormone Regulation

Hormones may be regulated by glands and organs, by a negative feedback mechanism, or by other hormones. Hormones that regulate the release of other hormones are defined as tropic hormones, which are secreted by the anterior pituitary in the brain. 

Hormones During Pregnancy

Many hormone levels are affected in the body during pregnancy. Several hormones play major roles during pregnancy such as Estrogen, Progesterone, human chorionic gonadotropin hormone (hCG), and Human placental lactogen (hPL). 

Chemical Nature of Hormones

Hormones may be chemically classified as either proteins or steroids. All of the hormones in the human body, except the sex hormones and those from the adrenal cortex, are proteins or protein derivatives.

 

What are The Properties of Hormones?

The significant properties of hormones are –

1. They have a low molecular weight; thus, they can easily pass through capillaries.

2. Hormones always act in low concentration.

3. They are soluble in water so that they can be transported via blood.

4. The importance of hormones is that they are non-antigenic. They are organic catalysts. Hormones act as coenzymes of other enzymes in the human body.

5. Hormones, in their first action, cause a limited number of reactions and do not influence any metabolic activities of a cell directly.

6. A significant characteristic of hormones is that, after their function is over, they are readily destroyed, excreted or inactivated.

7. Hormonal activities are not hereditary.

 

What Are Hormones Made Of?

Hormones are made of a diverse range of chemicals, but they are classified into three classes –

1. Eicosanoids

2. Amino acid/protein derivatives (amines, proteins, and peptides)

3. Steroids

 

Important Hormones of the human body

• Melatonin: It primarily controls the circadian rhythm or sleep cycles.

• Estrogen: This is the main sex hormone present in women which bring about puberty, prepares the uterus and body for pregnancy and even regulates the menstrual cycle. Estrogen level changes during menopause because of which women experience many uncomfortable symptoms.

• Cortisol: It has been named the “stress hormone” as it helps the body in responding to stress. This is done by increasing the heart rate, elevating blood sugar levels etc.

• Progesterone: It is a female sex hormone also responsible for the menstrual cycle, pregnancy and embryogenesis.

• Testosterone: This is the most important sex hormone synthesized in men, which cause puberty, muscle mass growth, and strengthen the bones and muscles, increase bone density and controls facial hair growth.

 

Some hormones, such as serotonin and dopamine, also function as neurotransmitters, which are chemicals that relay messages between nerve cells in the brain and from neurons to muscles. 

 

How Many Types of Hormones are There in a Human Body?

Even though there are several types of hormones in a human body, they are primarily classified into three categories based on their chemical structure. These are –

1. Lipid-Derived Hormones

Lipid-derived hormones are primarily derived from cholesterol, and they share a similarity in terms of their structure. Steroid hormones are the primary lipid hormones in the human body, and chemically they are either ketones or alcohols. Examples of steroid hormones are cortisol and aldosterone. 

2. Amino Acid-Derived Hormones

These classes of hormones originate from amino acids, tyrosine and tryptophan. Examples of such hormones as norepinephrine and epinephrine. The medulla section of the adrenal glands produces these. Moreover, the pineal gland in the brain synthesizes melatonin, which controls the sleep cycle.

3. Peptide Hormones

The structure of the peptide hormone is similar to that of the polypeptide chain (chain of amino acids). A popular example of peptide hormone is insulin produced by the pancreas. 

 

Name of Hormones and Their Functions

Here is a list of some important hormones and their functions –

• Insulin: Produced by the pancreas, this hormone helps the human body to synthesize glucose from food intake for energy. Additionally, it controls the blood sugar level in the human body.

• Cortisol: It is a steroid hormone synthesized in the cortex of adrenal glands. Furthermore, this hormone is also called stress hormone as it helps the human body to deal with any pressure. 

• Melatonin: The pineal gland in the human brain produces this hormone. It primarily controls the sleep cycle.

• Progesterone: This female hormone is responsible for embryogenesis, menstrual cycle, and pregnancy. It is produced in the corpus luteum section of the ovary. 

 

Examples of Hormones

• Insulin is a hormone that’s made by the beta cells in the pancreas. When it is released into the blood, insulin helps regulate how the cells of the body use glucose (a type of sugar) for energy.

• Androgens are responsible for male sex characteristics. Testosterone, the sex hormone produced by the testicles, is an androgen.

• Estrogens are the group of hormones responsible for female sexual development. They are produced primarily by the ovaries and in small amounts by the adrenal glands.

• The thyroid gland secretes two main hormones, thyroxine and triiodothyronine, into the bloodstream. These thyroid hormones stimulate all the cells in the body and control biological processes such as growth, reproduction, development, and metabolism.

 

The importance of hormones in the human body is that it helps the body to function properly. This article aims to provide a comprehensive take on this chapter of biology. Furthermore, students can download the app to access other chapters of biology.