Lesson overview
Hormones: Why does your heart keep pounding after a fright?
Touch a hot mug and let a tray of cups fall beside a model person, choose the time window that shows each response whole, and read the time to the peak of the heart rate. Then follow adrenaline from the adrenal glands to its target organs and find the glands that secrete four hormones; for the Supplement, watch the liver release glucose and meet glucagon.
Suggested sequence
- Lesson 1 · A reflex and a fright. Nervous and hormonal control compared by speed of action and duration of effect, read from a time course. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- Lesson 2 · Adrenaline at work. A hormone and its target organs; adrenaline in “fight or flight”; (Supplement) adrenaline and metabolic activity. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- Lesson 3 · Glands and their hormones. The adrenal glands, pancreas, testes and ovaries and their hormones; (Supplement) glucagon from the pancreas. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- End of module · final check. 7 new questions, 20–30 min, without hints or notes; pupils check their answers once they have answered them all.
- One to two weeks later · return questions. 7 questions, 15 min, lesson closed.
Learning goals
Part 1: A reflex and a fright
- Compare nervous and hormonal control in terms of speed of action and duration of effect (14.3.4)
Part 2: Adrenaline at work
- 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 (14.3.1)
- Describe adrenaline as the hormone secreted in fight or flight situations, and its effects: increased breathing rate, increased heart rate and increased pupil diameter (14.3.3)
- Supplement: describe the role of adrenaline in the control of metabolic activity: increasing the blood glucose concentration and increasing the heart rate (S14.3.6)
Part 3: Glands and their hormones
- Identify in diagrams and images the adrenal glands, pancreas, testes and ovaries, and state the hormones they secrete: adrenaline, insulin, testosterone and oestrogen (14.3.2)
- Supplement: state that glucagon is secreted by the pancreas (S14.3.5)
Misconceptions to listen for
- “Row A: nervous control is faster and also lasts longer.” — Nervous control is faster, but its effect is short: when the impulses stop, the muscle relaxes. The longer-lasting effect is hormonal.
- “Row B: hormonal control is faster and also lasts longer.” — A hormone lasts longer, but it is slower to act: it must be carried in the blood to its target organs. Impulses act within a fraction of a second.
- “Row D: hormonal control is faster, and nervous control lasts longer.” — Both columns are the wrong way round. Nervous control is faster; hormonal control lasts longer.
- “The heart rate would jump higher in the first second.” — The jump in the first second is caused by nerve impulses, before adrenaline reaches the heart. Slower removal of adrenaline changes the later, longer part.
- “The heart rate would fall back to the resting rate sooner.” — That is the wrong way round. Adrenaline that stays in the blood longer keeps acting longer, so the fall is slower.
- “The heart rate would not change at all after the fright.” — The nerves still make the heart rate jump, and adrenaline is still released. Only its removal is slower.
- “Hormonal control: adrenaline reached her heart.” — Adrenaline causes the slower climb over the next two minutes. In the first second it has not yet been carried to the heart in the blood.
- “Neither: the heart speeds up whenever she walks.” — She was already walking before the horn. The sudden rise came just after the horn, so it is a response to that stimulus.
- “Both kinds of control, equally and at the same moment.” — Both kinds of control take part in a fright, but not at the same moment: the nerves act first, and adrenaline adds to the rise later.
- “59 beats per minute.” — That is half of the peak. The heart rate falls back towards the resting rate of 76, not towards zero.
Scope
Hormones (14.3.1–14.3.6): 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; the adrenal glands and adrenaline, the pancreas and insulin, the testes and testosterone and the ovaries and oestrogen, identified in diagrams and images; adrenaline in “fight or flight” situations and its effects on the breathing rate, the heart rate and the pupil diameter; nervous and hormonal control compared by speed of action and duration of effect; and, for the Supplement, glucagon from the pancreas and the role of adrenaline in metabolic activity (a higher blood glucose concentration and heart rate). What insulin and glucagon do to the blood glucose concentration is in the module on homeostasis; nerves, neurones and the reflex arc are in the module on nerves and reflexes, and the pupil reflex in the module on the eye. Other hormones and glands, and the menstrual cycle, are not covered here.