Endocrine System and Adolescence | ICSE Class 8 Biology Notes

This note covers endocrine and exocrine glands, hormones and their actions, the pituitary, thyroid, adrenal glands and pancreas, adolescence and puberty, physical and emotional changes, menstrual hygiene, nutrition, physical activity and stress management.

How do endocrine and exocrine glands differ?

A gland is a structure that produces and releases a substance. This release is called secretion; the word can also mean the substance released. Glands differ in how their secretions leave them and where those secretions act.

Exocrine glands release their secretions through ducts, which are channels carrying the secreted material. Endocrine glands lack ducts, so they are also called ductless glands. They release chemical messengers called hormones into the blood.

What makes a hormone a messenger?

Hormones carry information between cells. They are produced in very small amounts and help regulate body functions. They are not nutrients, meaning substances supplied for nourishment. Their role is communication and regulation, rather than supplying food to the body.

Definition: The endocrine system consists of the endocrine glands and hormone-producing cells and tissues located in different parts of the body. It provides chemical control and coordination of body functions.

Coordination means organising the activities of different body parts so that they work together. Hormonal coordination and nervous coordination both help regulate the body. Nervous coordination uses signals transmitted through nerve cells; hormonal coordination uses chemical messengers.

A gland can have more than one role. The pancreas, a gland in the abdomen, acts as both an exocrine and an endocrine gland. Its endocrine role includes releasing insulin, a hormone that helps regulate the amount of sugar in the blood.

The distinction therefore concerns the route of secretion. The term “ductless” does not mean that an endocrine gland keeps its secretion inside itself. Its hormones enter the blood and can be carried to another part of the body.

How do hormones reach and influence their targets?

A target organ or target tissue is an organ or tissue on which a particular hormone acts. A tissue is a group of cells working together; an organ contains tissues organised to perform functions. Blood transports hormones, but different hormones have specific effects.

How does chemical coordination take place?

1. An endocrine gland produces and releases a hormone. The hormone is a chemical signal involved in regulating a body function.
2. The hormone enters the blood directly, without passing along a glandular duct.
3. The blood carries the hormone to different parts of the body, including its target tissues.
4. At the target tissue, the hormone produces a response, such as changing the activity of the heart or regulating growth.

Adrenaline is a hormone released by the adrenal glands that helps prepare the body for an emergency. The heart is one of its targets. Its action makes the heart beat faster, helping supply more oxygen to the muscles.

Growth hormone, released by the pituitary gland in the head, regulates growth and development. These examples show why naming a hormone is not enough to explain its action: the gland, route of transport and effect are distinct parts of the explanation.

Why does the amount released matter?

Hormones need to be released in suitable quantities and at appropriate times. A feedback mechanism regulates hormone release in response to changes in the body. For example, a rise in blood sugar leads to increased insulin secretion; as blood sugar falls, insulin secretion is reduced.

Feedback links the body's condition to the amount of hormone released. Hormonal control is therefore more than the simple presence of a gland. The release of its secretion must also be regulated.

Where are the principal glands, and what does the pituitary do?

The principal glands considered here are the pituitary in the head, the thyroid in the neck, the paired adrenal glands above the kidneys and the pancreas in the abdomen. Their locations differ, and so do the functions of their hormones.

The pituitary is attached by a stalk to the hypothalamus, a part of the brain that helps regulate the release of pituitary hormones. Growth hormone is one of the hormones secreted by the pituitary. It regulates growth and development of the body.

What happens when growth hormone secretion is disturbed?

A deficiency means an insufficient amount. A deficiency of growth hormone during childhood leads to pituitary dwarfism, a condition involving stunted growth. Excess secretion can produce abnormal growth called gigantism. These are effects of disturbed hormone secretion, not descriptions of ordinary differences between classmates.

The pituitary also produces hormones that stimulate other glands. One is thyroid-stimulating hormone, whose function is to stimulate the thyroid to make and release its hormones. Its name describes the gland that it acts on.

Two body outlines show male and female gland locations. The pituitary is labelled in the head, the thyroid in the neck, and the pancreas and adrenal glands in the abdomen. The adrenal glands are drawn above the kidneys.

See Fig. 6.7 in your NCERT textbook

How does the thyroid support growth and metabolism?

The thyroid gland has two lobes, meaning two main parts, positioned on either side of the trachea, or windpipe. A thin band of tissue connects the lobes. The gland releases thyroid hormones, including thyroxin, also spelt thyroxine.

Thyroxin regulates metabolism, the chemical processes through which the body uses and changes substances. In particular, it regulates carbohydrate, protein and fat metabolism to provide a suitable balance for growth. These nutrients have roles in nourishment; thyroxin regulates their processing.

Why is iodine important?

Iodine is an element needed by the thyroid to make thyroxin. Iodised salt is salt enriched with iodine. The link is therefore between a dietary requirement, hormone production and the regulation of body functions.

If iodine is deficient in the diet, there is a possibility of developing goitre, an enlargement of the thyroid gland. A swollen neck is one of its symptoms. Dietary iodine deficiency does not mean that everyone will develop a visibly swollen neck.

The front view shows the two thyroid lobes beside the trachea, joined across its front. The labels identify the thyroid, trachea and vocal cord, a structure involved in producing the voice. A second view shows the back of the thyroid region.

See Fig. 19.3 in your NCERT textbook

The vocal cords are structures involved in producing the voice. The thyroid diagram places its gland close to the voice-producing region, but these structures have different functions. The thyroid makes hormones; the windpipe carries air, and the voice-producing structures help make sound.

How do the adrenal glands prepare the body for an emergency?

There is one adrenal gland above each kidney. Each gland has an outer region called the adrenal cortex and an inner region called the adrenal medulla. The medulla secretes adrenaline, a hormone involved in preparing the body for emergency situations.

Adrenaline is sometimes called an emergency hormone. The expression fight or flight describes preparation either to confront a threat or move away from it. The body's response involves several organs acting together rather than one isolated change.

What sequence connects hormone release to readiness?

1. Adrenaline is released from the adrenal glands directly into the blood in response to an emergency.
2. The blood carries it to target tissues, including the heart, where it increases the rate of heartbeat.
3. Blood flow to the digestive system and skin is reduced, diverting blood towards the skeletal muscles, which move the body.
4. Breathing becomes faster through the action of the diaphragm, a breathing muscle below the lungs, and the rib muscles.
5. Together, the increased supply of oxygen to muscles and the other responses prepare the body to deal with the situation.

One drawing shows an adrenal gland sitting above a kidney. An arrow leads to an enlarged section of the gland, with the outer adrenal cortex and inner adrenal medulla labelled.

See Fig. 19.4 in your NCERT textbook

The diagram separates the gland from the kidney beneath it. The kidney is a landmark for locating the adrenal gland; the two structures should not be treated as a single gland. Similarly, the outer cortex and inner medulla are regions within the adrenal gland.

The important relationship is between chemical signalling and coordinated action. Adrenaline travels in the blood, while the responses include changes in circulation and breathing that help prepare the muscles for activity.

How does the pancreas regulate blood sugar?

The pancreas has both endocrine and exocrine functions. Its endocrine tissue releases insulin, a hormone that helps regulate glucose, a sugar present in the blood. Blood sugar regulation depends partly on changing the quantity of insulin released.

Insulin promotes the uptake and use of glucose by target cells. It also promotes the conversion of glucose into glycogen, a storage form of carbohydrate. These actions help lower the amount of glucose in the blood.

How does insulin feedback work?

1. The amount of sugar in the blood rises.
2. Cells in the pancreas detect the rise in blood sugar.
3. The pancreas responds by producing more insulin, helping lower blood sugar.
4. As the blood sugar level falls, insulin secretion is reduced.

This process is an example of feedback because the condition being regulated influences the release of the hormone. The response changes as blood sugar changes. It is inaccurate to describe insulin as being released in one unchanging quantity regardless of the body's condition.

If insulin is not secreted in proper amounts, blood sugar rises and can have harmful effects. Diabetes mellitus is a disorder involving prolonged high blood glucose. Some patients receive insulin as part of their treatment.

The pancreas also releases glucagon, another hormone involved in blood glucose regulation. Glucagon raises blood glucose, while insulin lowers it. Their different actions contribute together to maintaining blood glucose levels.

Note: A hormone and the gland producing it are different things. The pancreas is a gland; insulin and glucagon are hormones. Similarly, the thyroid is a gland and thyroxin is one of its hormones.

What are adolescence and puberty?

Adolescence is the period of development between childhood and adulthood. It typically occurs between the ages of 10 and 19. It is a time of rapid growth and development, during which the body prepares for adulthood.

The duration of this stage and the timing of its changes vary between individuals. Each person experiences adolescence at their own pace. An age range describes a typical pattern; it does not make every change begin on the same birthday.

How is puberty related to adolescence?

Puberty is the stage in which external and internal changes develop the adolescent body into an adult body capable of reproduction. Reproduction means producing young ones. Reproductive capability develops as the body grows and matures.

Adolescence includes physical changes as well as emotional and behavioural changes. Puberty focuses on the changes leading to reproductive maturity. Some changes can be seen from outside, while others take place internally and may go unnoticed.

Secondary sexual characteristics are features that help distinguish males from females but are not directly involved in reproduction. Examples include facial hair in boys and breast development in girls. These characteristics are natural signs that the body is preparing for adulthood.

What causes these changes?

The changes of adolescence are primarily controlled by hormones produced in the body. Testosterone, a hormone secreted by the testes, the male reproductive glands, and oestrogen, secreted by the ovaries, the female reproductive glands, are associated with changes at puberty.

Some hormones also influence mood and behaviour. Adolescence therefore cannot be understood through height or appearance alone. Visible changes, internal maturation and changing emotions all belong to this stage of development.

What physical changes can occur during adolescence?

Growth in height becomes more prominent during adolescence. Boys and girls also experience changes in weight and body structure. Among boys, the shoulders might become a bit broader and the chest may become wider. Girls experience changes including breast development.

How do voice and hair change?

The voice box is a structure in the throat that helps produce speech. In adolescent boys, its growth leads to a hoarse-sounding voice. Its growth may appear as a bump called the Adam's apple, but this is not noticeable in every individual.

The voice box also grows in girls, but it is not as large as in boys, leading to only slight changes in voice. This does not mean that girls experience no voice change. The degree of change differs.

Both boys and girls develop hair in the armpits and pubic region, the region around the external reproductive organs. Boys often develop facial hair, later forming a moustache and beard. Some boys may develop chest and back hair, though a few may have no significant hair growth.

Why can pimples appear?

Acne is a skin condition in which small reddish pimples appear, commonly on the face. Increased oily secretions during adolescence can block skin pores, the small openings in the skin, and lead to infections. Pimples are visible manifestations of acne.

The timing, nature and extent of these changes vary between individuals. These variations are completely normal. A comparison table describes changes; it must not be used as a fixed timetable that every adolescent must follow.

What does the onset of menstruation indicate?

Adolescence includes maturation of the parts involved in reproduction. An important internal change in girls is the start of the menstrual cycle, a recurring process associated with reproductive capability. It is an important natural process and one sign of good reproductive health.

Menstruation is the phase of the cycle in which blood is discharged from the body. It is commonly called a period. The menstrual cycle and menstruation are related terms, but menstruation refers specifically to the bleeding phase.

What variation in timing is normal?

The menstrual cycle recurs generally every 28 to 30 days. Many healthy girls may have longer or shorter cycles ranging from 21 to 35 days. Menstruation may last for three to seven days. Some girls may feel pain or discomfort in the lower abdomen during these days.

These ranges should not be changed into a rule that every cycle has the same length. A healthy person may have a cycle longer or shorter than the general 28 to 30 day interval.

Menstruation usually stops naturally by the age of 45 to 55, marking the end of reproductive capability. This later change is distinct from the onset of menstruation at puberty.

Note: Menstruation is a natural process. Beliefs that lead to unnecessary fear, shame or physical isolation of menstruating girls have no scientific basis. Understanding the process and supporting menstrual hygiene promote a healthier approach.

How can adolescents understand emotions and manage stress?

Adolescence is often marked by stronger emotions than childhood. Mood swings are changes in emotional state. Increased sensitivity and strong emotions can influence behaviour. Adolescents may also develop deeper interests in new areas or take part in activities supporting others.

These changes are not all difficulties. Curiosity, creative activities and involvement in social work can provide positive opportunities. Understanding the connection between feelings and behaviour helps a person respond to situations thoughtfully.

What is stress management?

Stress means a feeling of strain or pressure when facing demands or difficulties. Stress management means using ways of coping with this pressure. It includes activities and habits that help a person respond constructively.

Ways of tackling stress include yoga, a practice involving postures and related exercises; meditation, a practice of focusing attention; time management, meaning organising time for activities; sports; hobbies; and rational thinking, meaning considering situations through reason.

Music, dance and sports can provide positive activities during emotional changes. A hobby is an activity pursued for interest or enjoyment. These activities offer ways to develop interests and participate constructively in everyday life.

Why does support matter?

Seeking support and guidance when needed helps adolescents manage changes. Parents and teachers can provide guidance, including in social interactions. Strong emotions do not require facing every situation alone or making a decision immediately without thought.

Respectful behaviour towards others helps create a favourable and safe environment. Adolescents may feel attracted to peers, meaning others of a similar age, and may imitate their behaviour. Thoughtful choices remain important in both face-to-face and online interactions.

Why are personal and menstrual hygiene important?

Personal hygiene means habits that maintain the cleanliness of the body. During adolescence, attention to body hygiene, particularly the armpits and pubic region, may protect against potential infections. Hygiene is part of caring for the body as it changes.

Menstrual hygiene means practices that support cleanliness, comfort and health during menstruation. Suitable materials include sanitary pads and reusable cloth pads designed for the purpose. A sanitary pad is a product used to absorb menstrual discharge.

How should used sanitary pads be handled?

Used sanitary pads should be wrapped in newspaper and placed inside a dustbin. Proper disposal supports community health and environmental cleanliness. Leaving used pads scattered around a bin does not achieve proper disposal.

Necessary facilities in schools and public places help support menstrual hygiene. Reducing the stigma, or unfair shame, associated with sanitary products is also important. Menstruation should be discussed with respect and a scientific understanding.

Cleanliness and respectful treatment work together. Maintaining hygiene does not justify treating menstruating girls as unclean or requiring their isolation. Menstruation is a natural process, and myths surrounding it have no scientific basis.

How are hygiene and nutrition connected to well-being?

Nutrition supplies the body with substances required for growth and functioning; hygiene concerns cleanliness and care. Both are important during adolescence. Neither replaces the other: a nutritious diet and appropriate hygiene habits address different needs.

Good personal care also involves understanding normal changes. For example, increased oily skin secretions can contribute to acne, while menstrual hygiene concerns the management of menstrual discharge. Identifying the change helps connect it to the relevant care practice.

Which daily choices support a healthy adolescence?

A nutritious diet supplies substances needed for growth, development and body functions. Adolescents need proteins and carbohydrates, together with adequate fats, vitamins and minerals. These are groups of nutrients required as part of a healthy diet.

Proteins support growth, while carbohydrates are energy-providing nutrients. Calcium, a mineral, supports bone growth. Foods listed as sources of calcium, proteins and fats include milk, millets, curd, cheese and paneer.

Iron is a mineral involved in the formation of blood. Spinach, kidney beans and dried fruits such as raisins and figs are iron-containing foods. Adolescents, especially girls, may sometimes experience blood-related health problems because of iron or vitamin B12 deficiency.

Why include physical activity?

Regular exercise, games and sports help keep the body and mind fit. They build stamina, the capacity to sustain activity, and boost mood. Physical activity is therefore relevant to both physical fitness and emotional well-being.

How can harmful pressures be handled?

Tobacco, alcohol and illegal drugs can harm physical and mental health and are addictive. Addiction involves a strong urge to consume a substance repeatedly. Curiosity and pressure from others might influence adolescents to try these substances.

Refusing harmful substances firmly and confidently is important. If someone becomes involved in substance abuse, recognising the problem and seeking help are important steps. Depending on the substance, use can cause breathing difficulties, memory loss or lung damage.

Online behaviour also requires care. Cyberbullying means harassment using digital devices or online platforms. Seeking help from parents and teachers, protecting privacy and being cautious about sharing personal information support responsible social interaction.

Glossary

• Endocrine gland — A ductless gland that releases hormones into the blood to help regulate body functions.
• Exocrine gland — A gland that releases its secretions through ducts carrying them to their destination.
• Hormone — A chemical messenger produced in small amounts that helps coordinate and regulate body functions.
• Target tissue — A tissue on which a particular hormone acts to produce its specific effects.
• Pituitary gland — A gland attached to the hypothalamus that secretes growth hormone and other regulatory hormones.
• Thyroxin — A thyroid hormone that regulates carbohydrate, protein and fat metabolism to support balanced growth.
• Adrenaline — An adrenal hormone that helps prepare the body to respond to an emergency situation.
• Insulin — A pancreatic hormone that helps lower blood glucose and regulate its level in the blood.
• Feedback mechanism — A process in which changes in a body condition regulate the release of a hormone.
• Adolescence — The period of development between childhood and adulthood, typically occurring between ages 10 and 19.
• Puberty — The stage involving external and internal changes through which the body develops reproductive capability.
• Secondary sexual characteristics — Features helping distinguish males and females that are not directly involved in reproduction.
• Menstruation — The phase of the menstrual cycle during which blood is discharged from the body.
• Acne — A skin condition with reddish pimples, associated with increased oily secretions that can block skin pores.
• Stress management — Ways of coping with pressure, including yoga, meditation, time management, sports, hobbies and rational thinking.

Common errors and misconceptions

• Misconception: Endocrine glands release hormones through ducts. Correct: Endocrine glands are ductless and release hormones into the blood; exocrine glands use ducts.
• Misconception: Insulin is the name of a gland. Correct: Insulin is a hormone produced by the pancreas, which has both endocrine and exocrine functions.
• Misconception: Every adolescent changes at the same age and rate. Correct: The timing, nature and extent of adolescent changes vary between individuals; these variations are completely normal.
• Misconception: Girls experience no change in voice. Correct: Their voice box also grows, but the growth is smaller than in boys and leads to only slight voice changes.
• Misconception: Every menstrual cycle lasts exactly 28 days. Correct: Cycles generally recur every 28 to 30 days, and many healthy girls may have cycles ranging from 21 to 35 days.
• Misconception: Menstruation requires physical isolation. Correct: Menstruation is natural, and such myths have no scientific basis. Appropriate hygiene and respectful treatment are important.
• Misconception: Adolescence involves only physical growth. Correct: It also includes reproductive maturation and emotional and behavioural changes, some of which may not be visible externally.
• Misconception: The pancreas releases a fixed amount of insulin regardless of blood sugar. Correct: Rising blood sugar stimulates more insulin release, while falling blood sugar reduces secretion.

Exam-style questions with model answers

Q1. Endocrine glands lack ducts and release hormones into blood. Exocrine glands release their secretions through ducts. State two linked differences between them: the presence of ducts and the route of secretion. [2 marks]

1. Endocrine glands are ductless, whereas exocrine glands possess ducts.
2. Endocrine secretions enter the blood directly; exocrine secretions pass along ducts.

Q2. Iodine is needed to make thyroxin. Thyroxin regulates carbohydrate, protein and fat metabolism to support balanced growth. Dietary iodine deficiency creates a possibility of goitre, an enlarged thyroid with a swollen neck as one symptom. Explain the iodine-hormone link, thyroxin's function and the possible deficiency effect. [3 marks]

1. Iodine is required by the thyroid gland to make thyroxin, so the dietary supply of iodine is connected to hormone production.
2. Thyroxin regulates the metabolism of carbohydrates, proteins and fats, helping provide a suitable balance for growth.
3. With dietary iodine deficiency, there is a possibility of goitre. This involves thyroid enlargement, with a swollen neck as one symptom.

Q3. Pancreatic cells detect rising blood sugar and respond by producing more insulin. Insulin helps lower blood sugar. As blood sugar falls, insulin secretion is reduced. Explain this feedback process in four stages, starting with the rise. [4 marks]

1. The process begins with a rise in the sugar level of the blood, which is the change requiring regulation.
2. Cells in the pancreas detect this rise and respond by producing a larger amount of insulin.
3. The increased insulin helps lower blood sugar, changing the condition that triggered the increased secretion.
4. As the blood sugar level falls, insulin secretion is reduced. The changing condition therefore regulates the hormone's release.

Q4. In an emergency, the adrenal glands release adrenaline into blood. It reaches targets including the heart, increases heartbeat, diverts blood from the digestive system and skin to skeletal muscles, and increases breathing. These changes increase oxygen supply to muscles and prepare the body to respond. Explain the response in five points. [5 marks]

1. The adrenal glands release adrenaline directly into the blood. This begins a chemical response that helps prepare the body for an emergency.
2. Blood carries adrenaline to its target tissues, including the heart. The heart beats faster as a result of the hormone's action.
3. Blood flow to the digestive system and skin is reduced. Blood is diverted towards the skeletal muscles involved in moving the body.
4. The breathing rate also increases. Together with the changes in circulation, this helps increase the supply of oxygen to the muscles.
5. The combined responses prepare the body to deal with the emergency, showing how a hormone coordinates changes involving several different parts of the body.

Q5. Adolescence typically occurs from ages 10 to 19, with timing varying between people. Height growth becomes prominent; voice changes and body hair develop; reproductive parts mature; and emotional and behavioural changes occur. Puberty develops reproductive capability. Use these facts to explain adolescence, puberty and the limits of a fixed growth timetable in five points. [5 marks]

1. Adolescence is the period between childhood and adulthood. It typically occurs from ages 10 to 19, but this range describes a general pattern.
2. Physical development includes a more prominent increase in height, changes in voice and the growth of body hair, rather than height change alone.
3. Reproductive parts also mature internally. Puberty refers to changes through which the body develops into an adult body capable of reproduction.
4. Emotional and behavioural changes are also part of adolescence. A description limited to external appearance would therefore leave out important aspects of development.
5. The timing varies between individuals. A fixed timetable expecting all adolescents to show the same changes simultaneously would not reflect this variation.

Q6. Menstrual cycles generally recur every 28 to 30 days; many healthy girls may have cycles of 21 to 35 days. Menstruation may last three to seven days. Pads or purpose-designed cloth pads support hygiene, and used sanitary pads should be wrapped in newspaper and placed inside a dustbin to support community health and environmental cleanliness. State four conclusions about timing and hygiene. [4 marks]

1. The general interval is 28 to 30 days, but healthy cycles may range from 21 to 35 days, so timing is not identical for everyone.
2. Menstruation is the bleeding phase and may last three to seven days; this is different from the length of the whole cycle.
3. Sanitary pads or cloth pads designed for menstruation can support hygiene, comfort and health.
4. Used sanitary pads should be wrapped in newspaper and placed inside a dustbin to support community health and environmental cleanliness.

Q7. Adolescence is often marked by strong emotions. Music, dance and sports offer positive activities. Ways to tackle stress include yoga, meditation, time management, hobbies and rational thinking; support from parents and teachers can help. State three approaches to managing emotional changes using this information. [3 marks]

1. Take part in positive activities such as music, dance or sports, giving strong emotions a constructive place within daily life.
2. Use ways of tackling stress such as yoga, meditation, time management, hobbies and rational thinking to respond to pressure constructively.
3. Seek guidance and support from parents or teachers when needed, rather than assuming that every emotional change must be managed alone.

Q8. Hormones regulate development. Boys often develop facial hair, but its timing and extent vary; an Adam's apple is not noticeable in every individual. Explain why facial hair and a visible Adam's apple cannot form a fixed checklist for every adolescent boy. [2 marks]

1. Facial hair often develops, but its timing and extent vary between individuals.
2. An Adam's apple is not noticeable in every individual, so visibility is not universal.

Key takeaways

• Endocrine glands release hormones into the blood, while exocrine glands release their secretions through ducts.
• Hormones are chemical messengers with specific actions, and feedback helps regulate their timing and quantity of release.
• The pituitary regulates growth through growth hormone; the thyroid makes thyroxin and requires iodine for its production.
• Adrenaline prepares the body for an emergency by coordinating changes in heartbeat, blood flow and breathing.
• The pancreas releases insulin to help lower blood sugar, with insulin secretion changing as blood sugar changes.
• Adolescence includes physical, reproductive, emotional and behavioural changes, whose timing and extent vary between individuals.
• Menstruation is a natural process with variation in cycle length; appropriate hygiene and respectful treatment are important.
• Nutritious food, physical activity, personal hygiene, supportive relationships and constructive stress management help support healthy adolescent development.

Test yourself

Why are endocrine glands called ductless glands?

They lack ducts and release their hormones directly into the blood.

What distinguishes a hormone from its gland?

A gland is a structure that produces a secretion; a hormone is a chemical messenger released by it.

What connects dietary iodine with the thyroid?

The thyroid needs iodine to make thyroxin, which regulates carbohydrate, protein and fat metabolism.

Where are the adrenal glands situated?

There is a pair of adrenal glands, with one located above each kidney.

What happens to insulin secretion as blood sugar falls?

Insulin secretion is reduced as the blood sugar level falls, illustrating hormonal feedback.

How does puberty differ from the broader idea of adolescence?

Puberty concerns the development of reproductive capability. Adolescence is the transition towards adulthood, including physical, emotional and behavioural development.

Why is “girls have no voice change” inaccurate?

Their voice box also grows during adolescence, although this leads to only slight changes in voice.

Which activities can be used to tackle stress?

Yoga, meditation, time management, sports, hobbies and rational thinking are ways of tackling stress.