Reaching the Age of Adolescence Class 8 Notes Science Chapter 7

Reaching the age of Adolescence

Changes during Puberty

Puberty is a time when a lot of important changes happen in the body. Here are some key points about what happens during puberty:

• Growth and Height: After the age of 10, people start growing taller, and this is one of the most noticeable changes during puberty. Regular exercise and a healthy diet can help increase height, but how tall someone gets also depends on their genetics.
• Body Shape: As boys and girls grow taller during puberty, their bodies start to take on different shapes.
• Voice Changes: In boys, the larynx (voice box) gets bigger during puberty, which makes their voices deeper.
• Sweat and Oil Glands: During puberty, sweat glands become more active, leading to increased sweating. Oil glands also become more active, which can cause pimples or acne.
• Development of Sex Organs: During puberty, the sex organs develop and become active. In boys, the testes start producing sperm, which are the male gametes. In girls, the ovaries grow and mature the ovum, which is the female gamete.
• Mood Changes: Adolescents may experience mood swings during this time.
• Mental and Intellectual Development: This period also contributes to mental and intellectual maturity. The brain is very active during puberty, which helps improve learning abilities.
• Reproductive Maturity: Adolescence marks the beginning of reproductive maturity, which means that adolescents become capable of reproduction.
• Secondary Sexual Characteristics: These are features that help identify males and females. In boys, facial hair such as beards and moustaches starts to grow. In girls, breasts develop during puberty.

Hormones and Reproductive Function

• Hormones are chemical messengers that control various functions in the body. They are released by endocrine glands directly into the bloodstream.
• Sex hormones play a crucial role in triggering puberty and activating reproductive functions. In boys, testosterone is responsible for changes like facial hair growth and voice deepening. In girls, oestrogen drives breast development during puberty.
• By the time of puberty, the levels of sex hormones are sufficient to mature gametes, which are the reproductive cells—sperms in males and ova in females.
• The reproductive life span is generally longer in males than in females.
• Menarche is the term used for the first occurrence of menstruation in females. Menstruation involves the shedding of the uterine lining along with blood. Menopause marks the end of menstruation.
• Fertilisation occurs when a sperm and an ovum unite. The menstrual cycle typically occurs every 28-30 days. The sex chromosomes in sperms determine the gender of the baby.
• Humans have 23 pairs of chromosomes in each cell. A gamete is a mature reproductive cell, either a sperm or an ovum. In India, determining the gender of an unborn baby is illegal.
• Goitre is a condition caused by the enlargement of the thyroid gland. Diabetes is a disorder that occurs due to insulin deficiency. The thyroid gland produces thyroxine and calcitonin. The adrenal glands secrete adrenaline. The pituitary gland is known as the master gland because it controls all other endocrine glands. Hormones also influence the life cycle of the silk moth. Thyroxine is responsible for transforming larvae or tadpoles into adult frogs.

Adolescence and Health

• During adolescence, it is important to avoid junk food and consume a balanced diet for better health. A balanced diet includes the right amounts of carbohydrates, proteins, fats, vitamins, minerals, and water. Healthy foods provide more nutritional value compared to junk foods.
• A person is considered healthy when they are physically and mentally fit. Personal hygiene is crucial for maintaining health, and cleaning private parts is important to prevent infections. Body parts like hair, skin, nails, and feet are susceptible to infections if not kept clean.
• During puberty, the increased activity of sweat glands can lead to body odour. Regular physical exercise is essential for keeping the body fit and healthy. Outdoor games and exercises help in building a strong and muscular body.
• Some individuals may use anabolic steroids to increase body mass, but these can have serious side effects. Peer pressure can be managed through self-confidence and a healthy lifestyle. Adolescents may experience feelings of insecurity and confusion due to the many changes occurring in their bodies and minds.
• Drugs can be addictive and should only be taken with a doctor’s prescription. AIDS is caused by the HIV virus, which can be transmitted through shared syringes. Pregnancy occurs only through sexual contact. In India, the legal age for marriage is 21 years for boys and 18 years for girls.