CIE iGCSE Co-ordinated Sciences-B13.2 Hormones - Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-B13.2 Hormones – Study Notes
CIE iGCSE Co-ordinated Sciences-B13.2 Hormones – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Describe a hormone as a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
- Identify in diagrams and images specific endocrine glands and state the hormones they secrete, limited to:
(a) adrenal glands and adrenaline
(b) pancreas and insulin
(c) testes and testosterone
(d) ovaries and oestrogen - Describe adrenaline as the hormone secreted in ‘fight or flight’ situations and its effects, limited to:
(a) increased breathing rate
(b) increased heart rate
(c) increased pupil diameter
Supplement
- State that glucagon is secreted by the pancreas
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Hormones
📌 Definition
A hormone is a chemical substance, produced by a gland, carried in the blood, which alters the activity of one or more specific target organs.
🌱 Key Features of Hormones
- Made by endocrine glands (e.g. pancreas, adrenal, pituitary).
- Travel in the bloodstream (not along nerves).
- Each hormone affects only its specific target organ(s).
- Cause slower but longer-lasting effects compared to nerve impulses.
📊 Examples
| Hormone | Gland | Target organ | Effect |
|---|---|---|---|
| Insulin | Pancreas | Liver, muscles | Lowers blood glucose |
| Adrenaline | Adrenal gland | Heart, muscles | Prepares body for “fight or flight” |
| Testosterone | Testes | Male reproductive system | Controls development of male features |
| Oestrogen | Ovaries | Female reproductive system | Controls menstrual cycle, female features |
⚡ Quick Recap
Hormone = chemical messenger.
Made in glands → carried in blood → affects target organ.
Works slower than nerves but lasts longer.
Memory tip: “Hormones hurry through blood to organs.”
Endocrine Glands and Their Hormones
📌 Introduction
Endocrine glands release hormones directly into the blood. These hormones act on specific target organs to control body functions.
🌱 Key Endocrine Glands
(a) Adrenal glands
- Location: On top of the kidneys.
- Hormone: Adrenaline.
- Role: Prepares body for “fight or flight” – increases heart rate, breathing rate, and glucose release.
(b) Pancreas
- Location: Below the stomach.
- Hormone: Insulin.
- Role: Lowers blood glucose by converting glucose into glycogen in the liver and muscles.
(c) Testes (in males)
- Hormone: Testosterone.
- Role: Controls development of male secondary sexual characteristics (voice deepening, muscle growth, hair growth) and sperm production.
(d) Ovaries (in females)
- Hormone: Oestrogen.
- Role: Controls development of female secondary sexual characteristics and regulates the menstrual cycle.
📊 Summary Table
| Endocrine gland | Hormone | Main effect |
|---|---|---|
| Adrenal glands | Adrenaline | Prepares body for fight/flight |
| Pancreas | Insulin | Lowers blood glucose |
| Testes | Testosterone | Male sexual development & sperm production |
| Ovaries | Oestrogen | Female sexual development & menstrual cycle |
⚡ Quick Recap
Adrenal → Adrenaline → fight/flight
Pancreas → Insulin → lowers glucose
Testes → Testosterone → male features
Ovaries → Oestrogen → female features & cycle
Memory tip: “APTO” = Adrenal, Pancreas, Testes, Ovaries.
Adrenaline – The “Fight or Flight” Hormone
📌 Introduction
Adrenaline is a hormone secreted by the adrenal glands (on top of the kidneys) during stressful, exciting, or emergency (‘fight or flight’) situations. It prepares the body for rapid action.
🌱 Key Effects of Adrenaline
(a) Increased breathing rate
Allows more oxygen to enter the blood.
Supplies muscles with extra oxygen for respiration → more energy for action.
(b) Increased heart rate
Pumps blood faster.
Delivers oxygen and glucose more quickly to muscles.
Removes carbon dioxide faster.
(c) Increased pupil diameter
Pupils widen (dilate).
Allows more light into the eyes → improves vision, especially in dim conditions.
📊 Summary Table
| Effect | Purpose in “fight or flight” |
|---|---|
| ↑ Breathing rate | More oxygen into blood |
| ↑ Heart rate | Faster delivery of O₂ + glucose to muscles |
| ↑ Pupil diameter | Better vision to detect danger |
⚡ Quick Recap
Adrenaline = emergency hormone.
Triggered in fight or flight.
Key effects: breathing ↑, heart rate ↑, pupils widen.
Memory tip: “Adrenaline = Air (breathing), Blood (heart), Eyes (pupil).”
Glucagon
📌 Definition
Glucagon is a hormone secreted by the pancreas.
🌱 Key Points
- Made in the pancreas (by special cells called alpha cells in the islets of Langerhans).
- Works as the opposite of insulin.
- Function: Raises blood glucose by stimulating the liver to convert stored glycogen → glucose, which is released into the blood.
📊 Glucagon vs Insulin
| Hormone | Secreted by | Effect on blood glucose |
|---|---|---|
| Insulin | Pancreas (beta cells) | Lowers glucose (stores it as glycogen) |
| Glucagon | Pancreas (alpha cells) | Raises glucose (breaks down glycogen) |
⚡ Quick Recap
Glucagon = pancreas hormone.
Role = increase blood sugar.
Opposite to insulin.
Memory tip: “Glucagon is gone? → glucose comes on!”