Human endocrine system & Control of blood glucose concentration

SPEC 4.5.3.1 + 4.5.3.2 • PAPER 2 • BOTH TIERS

⭐ HIGH-PRIORITY LESSON • COMBINED SCIENCE TOO

Endocrine System & Blood Glucose

How hormones travel through the blood to control the body — six named glands, the pituitary as master gland, and the insulin/glucagon system that controls blood glucose (plus Type 1 and Type 2 diabetes).

Why This Lesson Wins Marks

Hormones and blood glucose are one of the most frequently examined topics on AQA Paper 2 — appearing in nearly every series. Questions hit predictable angles: name a gland, name a hormone, describe insulin's effect, compare Type 1 vs Type 2 diabetes, interpret a blood glucose graph. Memorise the spec wording and bank these marks.

6

Named Glands

2

Diabetes Types

P2

Paper 2 Only

For Everyone

Unlike Lessons 5.03 and 5.04, this content is not biology only. Combined Science students need this too. Both Foundation and Higher Tier students get tested on the basics; HT adds glucagon and the negative feedback cycle.

By The End You'll Be Able To…

Part A — Endocrine System

1. Describe

Describe how the endocrine system uses hormones to coordinate body functions, and compare it to the nervous system.

2. Identify

Identify the six named glands (pituitary, pancreas, thyroid, adrenal, ovary, testes) on a diagram of the body — and explain why the pituitary is called the master gland.

Part B — Blood Glucose

3. Explain

Explain how the pancreas controls blood glucose using insulin, and compare Type 1 and Type 2 diabetes + their treatments.

4. Explain HT

Explain how glucagon interacts with insulin in a negative feedback cycle to keep blood glucose at the right level.

The Endocrine System — Principles

Spec Definition

The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream. The blood carries the hormone to a target organ where it produces an effect.

Hormones are chemical messengers. Glands make them and release them straight into the blood — not into ducts (that's the digestive/exocrine system). The blood acts as a delivery system, reaching every part of the body, but only the target organ responds.

vs The Nervous System (Spec Comparison)

"Compared to the nervous system, the effects are slower but act for longer."

Nervous SystemEndocrine System

SpeedVery fastSlower

DurationShort-livedActs for longer

MethodElectrical impulses along neuronesHormones via the bloodstream

TargetSpecific muscle / glandSpecific target organ

The Six Named Glands

The spec requires you to identify these six glands on a diagram of the human body. Memorise their positions: AQA exam questions often show a body diagram with letters and ask you to name each gland.

Memory Anchor — Top To Bottom

Pituitary (brain) → Thyroid (neck) → Adrenal (above kidneys) → Pancreas (abdomen) → Ovary/Testes (reproductive system). Both ovaries and testes are on the spec — they're the sex-specific reproductive glands.

What Each Gland Does

You're not expected to memorise every hormone each gland makes — but a brief idea of each gland's role helps. The pancreas and pituitary are the most exam-relevant.

Pituitary

The master gland in the brain — secretes hormones that control other glands

Thyroid

Produces hormones that control growth and metabolism (covered in 5.09)

Adrenal

Sits on top of each kidney — produces hormones for the "fight or flight" response (covered in 5.09)

Pancreas

Controls blood glucose concentration via insulin (and glucagon — HT)

Ovary

Produces oestrogen in females — controls the menstrual cycle (covered in 5.07)

Testes

Produce testosterone in males — controls sperm production (covered in 5.07)

Scope Reminder

For this lesson, focus on the pancreas + insulin/glucagon mechanism. The other glands' specific hormones (adrenaline, thyroxine, oestrogen, testosterone) are covered in detail in Lessons 5.07 and 5.09 — don't write about them in detail here.

The Pituitary — Master Gland

Spec Wording

The pituitary gland in the brain is a 'master gland' which secretes several hormones into the blood in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects.

Cascade Effect

Pituitary detects a change in body conditions

Pituitary secretes a hormone into the blood

Blood carries the hormone to another gland (target)

That gland releases its own hormone

That second hormone produces the effect on the body

Exam Phrasing

The pituitary doesn't directly cause every effect — it triggers OTHER glands. AQA mark schemes credit answers that mention "acts on other glands" or "stimulates other glands to release hormones". Saying "the pituitary controls everything" is too vague.

Blood Glucose Control — Insulin

Spec Wording

Blood glucose concentration is monitored and controlled by the pancreas.

After you eat carbohydrates, glucose enters the blood and the concentration rises. The pancreas detects this and releases insulin to bring blood glucose back to normal.

When Blood Glucose Is Too High

The pancreas detects high blood glucose

The pancreas produces the hormone insulin

Insulin causes glucose to move from the blood into the cells

Once in cells, glucose can be used in respiration OR (in liver and muscle cells) excess glucose is converted to glycogen for storage

Blood glucose concentration drops back to normal

Three Accepted Effects Of Insulin

AQA mark schemes (e.g. Jun 2022 P2) credit any of these three: (1) glucose moves from blood into cells · (2) glucose is converted to glycogen (in liver/muscle) · (3) glucose is used in respiration. Mentioning multiple effects in your answer maximises marks.

Glucose vs Glycogen — Two Different Words!

The monosaccharide glucose (a sugar) is what's in your blood. Glycogen is the storage form — a polymer of glucose stored in liver/muscle cells. They're spelled similarly but they're different molecules. AQA frequently catches students mixing them up.

When Blood Glucose Is Too Low HT Only

Spec Wording (HT)

If the blood glucose concentration is too low, the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.

When Blood Glucose Is Too Low (e.g. between meals, after exercise)

The pancreas detects low blood glucose

The pancreas produces the hormone glucagon

Glucagon causes glycogen (stored in liver and muscle) to be converted back into glucose

This glucose is released into the blood

Blood glucose concentration rises back to normal

Glucagon vs Glycogen — Two Different Things

Glucagon = the hormone released by the pancreas when glucose is too low. Glycogen = the stored polysaccharide made of glucose. Glucagon causes glycogen to break down. Spelling and meaning are different — read carefully in exam Qs.

Negative Feedback Cycle HT Only

Spec Wording (HT)

Students should be able to explain how glucagon interacts with insulin in a negative feedback cycle to control blood glucose levels in the body.

Negative Feedback Defined

When blood glucose moves away from normal, the body produces the opposite hormone to bring it back. High → insulin pulls it down. Low → glucagon pushes it up. The response opposes the change — this is the definition of negative feedback.

Type 1 Diabetes

Spec Wording

Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections.

Cause

The pancreas doesn't produce enough insulin. Often diagnosed in childhood. The spec doesn't require you to know the underlying biological reason — just that the pancreas fails to make sufficient insulin.

Effect

Without insulin, glucose can't move from blood into cells. Blood glucose stays uncontrollably high after eating, which causes long-term damage to organs.

Treatment

Insulin injections — usually before meals to handle the glucose rise. Modern systems include insulin pumps and continuous glucose monitors, but the spec just says "insulin injections".

Type 2 Diabetes

Spec Wording

In Type 2 diabetes, the body cells no longer respond to insulin produced by the pancreas. A carbohydrate-controlled diet and an exercise regime are common treatments. Obesity is a risk factor for Type 2 diabetes.

Cause

The pancreas DOES make insulin, but the body cells become resistant — they no longer respond to it. So even though insulin is present, glucose can't move from blood into cells properly.

Risk Factor

Obesity is a risk factor — being overweight increases the likelihood of developing Type 2 diabetes. (Not the only cause; other factors include age, ethnicity, family history — but obesity is the one the spec names explicitly.)

Treatment

Carbohydrate-controlled diet + exercise regime. These are the spec's named treatments. AQA mark schemes also credit weight loss as an additional/related treatment. Insulin injections are not the primary treatment for Type 2 (key contrast with Type 1).

Type 1 vs Type 2 — Side By Side

The spec asks you to compare Type 1 and Type 2 diabetes and explain how they can be treated. Memorise this table.

Type 1 DiabetesType 2 Diabetes

CausePancreas fails to produce sufficient insulinBody cells no longer respond to insulin

Insulin levelToo little or noneNormal, but cells don't respond

Typical onsetOften childhoodUsually adulthood

Risk factorsNot listed in specObesity (spec wording)

TreatmentInsulin injectionsCarbohydrate-controlled diet + exercise (weight loss also credited)

Common 4-Mark Question

"Compare Type 1 and Type 2 diabetes." Structure your answer: cause (different for each), insulin response (none vs no cell response), treatment (injections vs diet+exercise). 1 mark for each clear contrast. Don't just describe one — make them comparison statements ("Type 1 is X; Type 2 is Y").

Evaluating Obesity & Diabetes (WS 1.3)

The spec WS 1.3 skill asks you to evaluate information around obesity and diabetes and make recommendations, considering social and ethical issues. Often appears as a 4–6 mark question with data.

The Evidence

Obesity is a clear risk factor for Type 2 diabetes

Rates of Type 2 have risen alongside rising obesity rates

Lifestyle interventions (diet, exercise) reduce risk and can manage existing diabetes

Possible Recommendations

Public health campaigns on diet and exercise

Sugar / fat taxes on unhealthy foods

Restricting advertising of unhealthy foods to children

Better access to affordable healthy foods

Social & Ethical Considerations

Individual freedom vs government intervention — should the state control what people eat?

Affordability — healthy food is sometimes more expensive; this affects lower-income groups disproportionately

Stigma — focusing on obesity can stigmatise people with diabetes who aren't overweight

NHS cost — treating Type 2 diabetes is expensive; prevention saves resources

Exam Pattern

For "evaluate" questions, give at least one benefit and one drawback for any recommendation, then a brief judgement. The judgement often picks up the final mark.

Interpreting Blood Glucose Graphs (MS 2c)

The spec says you should be able to extract information and interpret data from graphs that show the effect of insulin on blood glucose levels — for both people with diabetes and people without. AQA Paper 2 frequently includes such a graph.

Typical Graph Pattern

X-axis: time after a meal · Y-axis: blood glucose concentration. Three curves often shown: person without diabetes (peaks then returns to normal), person with Type 1 (peaks higher, stays elevated), person with Type 1 after insulin injection (peak controlled, returns to normal).

What To Describe

Peak value — how high does blood glucose go?

Time to peak — how long after the meal?

Return to normal — does it return to baseline? How quickly?

Comparison — how does each condition differ?

Quote Numbers From The Graph

"Describe" questions on graphs require specific data points: peak values, times, percentages. Don't write "it goes up and down" — say "blood glucose peaks at X mmol/L after Y minutes". Numerical quotes are often worth marks on their own.

Worked Example & Practice Q

Worked example — original 4-mark question in AQA style:

"Explain how the pancreas controls blood glucose concentration after a person eats a meal containing a lot of carbohydrate." — Practice question · 4 marks · AO1 · Spec 4.5.3.2

1

After the meal, blood glucose concentration rises / becomes too high(1 mark).

2

The pancreas detects this and produces / secretes the hormone insulin(1 mark).

3

Insulin causes glucose to move from the blood into cells(1 mark).

4

In liver and muscle cells, excess glucose is converted to glycogen for storage(1 mark).

Now try this one yourself:

(a) Name the gland that secretes insulin.1 MARK

(b) State one risk factor for Type 2 diabetes.1 MARK

(c) Compare the treatments for Type 1 and Type 2 diabetes.2 MARKS

(d) HT Explain the role of glucagon when blood glucose concentration falls too low.3 MARKS

(a)

Pancreas. (1 mark)

(b)

Obesity. (1 mark — obesity is the spec-named risk factor and the safest answer.)

(c)

Type 1 is treated with insulin injections(1 mark); Type 2 is treated with a carbohydrate-controlled diet and exercise (and/or weight loss) (1 mark).

(d)

The pancreas releases glucagon(1 mark); glucagon causes glycogen (stored in liver / muscle) to be converted into glucose(1 mark); the glucose is released into the blood, raising blood glucose concentration back to normal (1 mark).

⚠️

Mark-loss check: Part (b) — "obesity" is the safest, spec-named answer. Part (c) — must contrast both treatments, not just describe one. Part (d) — must distinguish glucagon (hormone) from glycogen (stored polymer) — spelling matters.

Common Errors & Summary

The single biggest cause of dropped marks here is confusion between similar terms. Memorise the right column.

✗ Wrong

"Glucagon stores glucose."

Confused with insulin AND mixed up with glycogen.

✓ Correct

"Insulin causes glucose to move into cells (and excess is stored as glycogen). Glucagon does the opposite: converts glycogen back to glucose."

✗ Wrong

"Type 2 diabetes is caused by obesity."

Obesity is a risk factor, not a direct cause.

✓ Correct

"Obesity is a risk factor for Type 2 diabetes; the underlying cause is that body cells no longer respond to insulin."

✗ Wrong

"The pituitary makes all the hormones."

Too vague — pituitary triggers OTHER glands.

✓ Correct

"The pituitary acts on other glands, stimulating them to release their own hormones."

Endocrine System (4.5.3.1)

Glands secrete hormones into the bloodstream → travel to target organ → effect

Compared to nervous system: slower but acts for longer

6 named glands: pituitary, pancreas, thyroid, adrenal, ovary, testes

Pituitary = master gland in the brain; triggers other glands

Blood Glucose (4.5.3.2)

Controlled by the pancreas

Too high → insulin → glucose enters cells; excess stored as glycogen (liver/muscle)

Type 1: pancreas can't make enough insulin → insulin injections

Type 2: body cells don't respond to insulin → diet + exercise; obesity is risk factor

HT Only

Too low → glucagon → glycogen converted back to glucose, released into blood

Insulin + glucagon = negative feedback cycle — opposing hormones bring blood glucose back to normal