Reaching the Age of Adolescence class 8 notes: Class 8 science ch 7 notes
| Textbook | Ncert |
| Class | Class 8 |
| Subject | Science |
| Chapter | Chapter 7 |
| Chapter Name | Reaching the Age of Adolescence |
| Medium | English |
Are you looking for Class 8 Science chapter 7 notes? Now you can download Reaching the Age of Adolescence class 8 notes pdf from here. In this chapter, we learn about adolescence, puberty, and changes during adolescence. It includes physical, emotional, and mental changes in boys and girls. The chapter discusses the role of hormones in initiating puberty, secondary sexual characteristics, and the endocrine system. It also covers reproductive health, sex determination, and the importance of personal hygiene and balanced diet during adolescence.
👦👧 Adolescence :-
The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age.
🧑🤝🧑 Teenagers :-
Since this period covers the ‘teens’ (13 to 18 or 19 years of age), adolescents are also called ‘teenagers’.
⚡ Puberty :-
Puberty is the period during which the human body undergoes physical and hormonal changes that lead to sexual and reproductive maturity.
🔄 Changes During Adolescence :-
Children gain height during adolescence. The onset of puberty brings about growth of the reproductive organs. Hair grow at various places on the body. Breasts develop in girls and facial hair (moustache and beard) appear in boys. Voice of boys becomes hoarse as voice box enlarges during adolescence.
🧬 Changes at Puberty :-
- Increase in Height – Rapid growth in height during puberty.
- Change in Body Shape – Boys develop broader shoulders; girls develop wider hips.
- Voice Change – Boys’ voice becomes deep; girls’ voice becomes slightly shrill.
- Increased Activity of Sweat and Sebaceous Glands – Causes body odor and pimples.
- Development of Sex Organs – Testes and ovaries mature; start producing gametes.
- Reaching Mental, Emotional, and Social Maturity – Improved thinking, reasoning, and emotional stability.
- Development of Secondary Sexual Characters – Facial hair in boys; breast development in girls; growth of hair in underarms and pubic areas.
Adam’s Apple :-
The growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple.
🧪 Thyroxine :-
Thyroxine is a hormone secreted from the thyroid gland.
🎙️ Voice Box :-
Voice producing part of the throat is called voice box or larynx.
🚻 Secondary sexual characters :-
In girls, breasts begin to develop at puberty and boys begin to grow facial hair, that is, moustaches and beard. As these features help to distinguish the male from the female they are called secondary sexual characters.
🧪 Hormones :-
Hormones are chemical substances. These are secretions from endocrine glands, or endocrine system. The changes which occur at adolescence are controlled by hormones.
📋 Important Hormones :-
👦 Testosterone: Testosterone is the male hormone released by the testes at the onset of puberty. It causes changes in boys such as the growth of facial hair.
👧 Estrogen: Estrogen is the female hormone produced by the ovaries once puberty is reached in girls. It leads to the development of breasts and mammary glands.
🧠 Pituitary Gland :-
The pituitary gland is an endocrine gland that secretes several important hormones, including the growth hormone. It also produces hormones that control other endocrine glands such as the testes, ovaries, thyroid, and adrenal glands, stimulating them to release their own hormones.
🎯 Target sites :-
Endocrine glands release hormones into the bloodstream to reach a particular body part called Target Site.
🧬 Reproductive Phase in Humans:
👩 Females: In females, the reproductive phase of life begins at puberty (10 to 12 years of age) and generally lasts till the age of approximately 45 to 50 years.
👨 Males: Starts from around 13 to 14 years and continues throughout life, though sperm production may decrease with age.
🩸 Menstruation :-
If fertilisation does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women which is called menstruation. Menstruation occurs once in about 28 to 30 days.
🩷 Menarche :-
The first menstrual flow begins at puberty and is termed menarche.
🌸 Menopause :-
At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is termed menopause.
🧬 Chromosomes :-
Chromosomes are thread-like structures present inside the nucleus of a cell. They carry genetic instructions, including those that determine the sex of a baby, and pass information from one generation to the next. All human beings have 23 pairs of chromosomes in the nuclei of their cells.
🧒👧 How is the Sex of the Baby Determined?
The sex of a child is determined at the time of fertilisation. The sperm can carry either an X or a Y sex chromosome, while the ovum (egg) always carries an X chromosome.
If a sperm carrying an X chromosome fertilises the egg (X), the resulting zygote will have XX chromosomes — the child will be female.
If a sperm carrying a Y chromosome fertilises the egg (X), the resulting zygote will have XY chromosomes — the child will be male.
💉 Insulin :-
Insulin is a hormone secreted by the pancreas. It helps regulate blood sugar levels by allowing glucose to enter the cells, where it is used for energy or stored for future use.
⚠️ Adrenalin :-
It is the hormone secreted by Adrenalin glands that helps the body to adjust to stress when one is very angry, embarrassed or worried.
❤️🩹 Reproductive Health :-
Reproductive health refers to the physical and mental well-being of an individual in all matters related to the reproductive system. It includes maintaining personal hygiene, eating a balanced diet, and staying physically active—especially during adolescence when the body is undergoing rapid growth and development.
🥗 Balanced Diet :-
A diet which contains all the necessary nutrients such as proteins, carbohydrates, fats and vitamins in proper proportions is called a balanced diet.
✅ Conditions to Maintain Good Reproductive Health :-
- Eat a Balanced Diet – Include proteins, vitamins, and minerals.
- Maintain Personal Hygiene – Regular bathing and keeping private parts clean.
- Exercise Regularly – Helps in proper physical and mental development.
- Avoid Drug and Alcohol Use – These harm body and brain development.
- Stay Mentally Healthy – Manage stress and talk to trusted adults when needed.
- Get Proper Knowledge – Be aware of bodily changes and reproductive health.
🛡️ HIV and AIDS Awareness :-
AIDS is a serious disease caused by the HIV virus. HIV can spread from an infected person to a healthy one through sharing needles, especially when injecting drugs. It can also be transmitted through unprotected sexual contact with an infected person or from mother to baby through breast milk. Preventing drug use and being aware of safe practices can help protect against HIV/AIDS.