Hormone — the three-part definition
A hormone is a chemical substance, produced by a gland, carried by the blood, that alters the activity of one or more specific target organs. Three linked elements — chemical, gland, blood — and every one of them has to appear for full credit. The gland is an endocrine gland: no duct, hormone released straight into the bloodstream. The target organ is where the change actually happens, and it is often a long way from the gland that made the hormone.
Four glands, four hormones to name
Adrenal gland — adrenaline. Pancreas — insulin (Core), plus glucagon at Extended. Testes — testosterone. Ovaries — oestrogen. The full table sits in the study note; the discipline is direction. Given a gland, name only that gland's hormone; given a hormone, name only the gland that makes it. The pancreas is the one gland on the list with two named hormones, so a question naming it may be asking for both. All four are endocrine glands, releasing directly into the blood.
Adrenaline — the fight or flight hormone
Adrenaline is released by the adrenal gland into the blood in response to stress, fear, excitement or danger, preparing the body for vigorous physical action. Three named effects: increased breathing rate (more oxygen enters the blood), increased heart rate (oxygen and glucose reach the muscles and brain faster) and increased pupil diameter (more light enters the eye, sharpening vision). All three are increases — the syllabus lists no decrease.
Drawn from real examiner reports.
Vague hormone definitions score zero
"A hormone is a chemical that affects the body" earns nothing. It omits where the hormone comes from (a gland) and how it reaches the place it acts (carried by the blood). Chemical, gland, blood, target organ — dropping any one of the four is the commonest way marks are lost on a "define a hormone" question.
Digest B13 (general finding, all four sittings): the required definition is "a hormone is made by a gland, carried in blood, acts on target organs" — candidates repeatedly drop one of these elements.
Adrenaline widens pupils, not narrows
Adrenaline increases pupil diameter — the pupils dilate, they get wider. "Narrows" or "constricts" is the opposite of the syllabus fact and scores zero. Add the reason too: wider pupils let more light into the eye, so danger is seen more clearly. If the direction will not come to mind, reason from the purpose — fight or flight sharpens the senses, it does not dull them.
Digest B13: "many think adrenaline narrows pupils" — Jun 2023 P13 Q9; Nov 2023 P42 Q10(iii).
A hormone is not an enzyme
A hormone is a chemical messenger: made by a gland, carried by the blood, it alters the activity of a target organ. An enzyme is a biological catalyst — a protein that speeds up a reaction and is not used up. Writing that a hormone "speeds up a reaction" describes an enzyme instead and gets no credit, however fluent the rest of the answer.
Hormones travel in blood, not ducts
An endocrine gland has no duct — it releases its hormone straight into the bloodstream, and the blood carries it to target organs all over the body. A gland with a duct, such as a salivary gland, sends its product down a tube to one place instead. Saying adrenaline reaches its target organ "through a duct" contradicts the definition of an endocrine gland.
Testosterone and oestrogen swapped
Testes produce testosterone; ovaries produce oestrogen. Swapping the pair is a frequent slip, and a right fact written against the wrong gland scores nothing — the mark is for the pairing, not for the word on its own. Keep the ovary (a gland, makes oestrogen) separate from the uterus (where an embryo develops); the uterus is not a gland at all.
The pancreas makes two hormones
The pancreas is the only gland on this list with two named hormones: insulin (Core) and glucagon (Extended). Naming just insulin when an Extended question asks what the pancreas secretes throws away a mark. Both come from the same gland, so a question that asks which gland produces either hormone has the same one-word answer — the pancreas.
Percentage change uses the resting value
For a rate change caused by adrenaline, divide the change by the original (resting) value, never by the new raised one. A resting heart rate of 72 rising to 108 beats per minute gives (108 − 72) / 72 × 100 = 50%, not 36 / 108 ≈ 33%. Reaching for the new figure as the denominator is the standard error here, and it turns a correct subtraction into a wrong answer.
Match the effects to the tariff
A 3-mark "describe the effects of adrenaline" question wants three separate named effects — increased breathing rate, increased heart rate, increased pupil diameter. One effect explained at length still earns one mark. Count the marks, then count your points, before writing.
Build the gland-blood-organ chain
For explain questions, run one fixed route every time: the adrenal gland makes adrenaline, the blood carries it, the target organs respond, the body is ready to fight or flee. Listing the effects without the route loses the explain marks even when every effect named is correct.
Say endocrine, not just gland
When a one-mark question asks for the type of gland that has no duct and secretes into the blood, the answer is endocrine. Writing just "gland" repeats the question back and earns nothing. Name specific glands precisely too — "adrenal gland", not "a gland near the kidney".
State the direction, then the benefit
For pupil diameter, say wider / dilated first and only then explain that more light enters the eye and vision sharpens. The direction carries its own mark, and a well-argued benefit attached to the wrong direction scores nothing at all.
| Gland | Hormone(s) |
|---|---|
| Adrenal gland (sits on top of each kidney) | Adrenaline |
| Pancreas | Insulin (Core); glucagon (Extended) |
| Testes | Testosterone |
| Ovaries | Oestrogen |
Define an endocrine gland.
Name the hormone produced by each of the following glands: the adrenal gland, the pancreas (name both hormones), the testes, and the ovaries. (5 marks)
