The Endocrine System, Blood Glucose & Diabetes
The endocrine system is a network of glands that secrete chemical messengers called hormones directly into the bloodstream, carrying signals to specific target organs to coordinate long-lasting physiological processes. A essential homeostatic role of the endocrine system is regulating blood glucose concentration via a negative feedback loop controlled by the pancreas using the hormones insulin and glucagon. Examiners frequently test the comparison between nervous and hormonal coordination, the exact mechanism of insulin and glucagon action on the liver, and the differences between Type 1 and Type 2 diabetes.
- Major Endocrine Glands
- 1. Pituitary gland ('learn gland' in brain). 2. Thyroid gland (neck; secretes thyroxine). 3. Pancreas (abdomen; secretes insulin and glucagon). 4. Adrenal glands (top of kidneys; secrete adrenaline). 5. Ovaries (female; secrete oestrogen and progesterone). 6. Testes (male; secrete testosterone).
- High Blood Glucose & Insulin Action
- When blood glucose concentration rises too high (e.g., after a carbohydrate-rich meal), the pancreas detects this and secretes the hormone insulin into the blood. Insulin causes muscle and liver cells to absorb glucose from the blood and convert soluble glucose into insoluble glycogen for storage, lowering blood glucose back to normal.
- Low Blood Glucose & Glucagon Action (Higher Tier)
- When blood glucose concentration falls too low (e.g., during fasting or exercise), the pancreas secretes the hormone glucagon into the blood. Glucagon stimulates liver cells to break stored glycogen back down into soluble glucose and release it into the bloodstream, raising blood glucose back to normal.
Interactive Human Body & Cell Structure Explorer
Click any internal organ or organelle to inspect its structure, toggle organs on/off to see what happens, or test yourself in Quiz Mode.
Heart (Double Circulatory Pump)
Structure & Function:
Pumps blood in a double circulatory system: the right ventricle pumps deoxygenated blood to the lungs, and the thick muscular left ventricle pumps oxygenated blood at high pressure around the whole body.
Key Exam Mark-Scheme Point:
Exam tip: The left ventricle has a much thicker muscular wall than the right ventricle because it must pump blood at high pressure all the way around the entire body, not just to the lungs.
What happens if this organ fails or is removed?
Without pressure from the heart, blood flow stops immediately. Oxygen and glucose cannot reach tissues, and waste carbon dioxide cannot be removed.
Tip: Use the “Simulate Organ Failure” button above to see how each organ system depends on the others to maintain homeostasis and cellular respiration.
Key Concepts & Exam Definitions (6)
- Major Endocrine Glands
- 1. Pituitary gland ('learn gland' in brain). 2. Thyroid gland (neck; secretes thyroxine). 3. Pancreas (abdomen; secretes insulin and glucagon). 4. Adrenal glands (top of kidneys; secrete adrenaline). 5. Ovaries (female; secrete oestrogen and progesterone). 6. Testes (male; secrete testosterone).
- High Blood Glucose & Insulin Action
- When blood glucose concentration rises too high (e.g., after a carbohydrate-rich meal), the pancreas detects this and secretes the hormone insulin into the blood. Insulin causes muscle and liver cells to absorb glucose from the blood and convert soluble glucose into insoluble glycogen for storage, lowering blood glucose back to normal.
- Low Blood Glucose & Glucagon Action (Higher Tier)
- When blood glucose concentration falls too low (e.g., during fasting or exercise), the pancreas secretes the hormone glucagon into the blood. Glucagon stimulates liver cells to break stored glycogen back down into soluble glucose and release it into the bloodstream, raising blood glucose back to normal.
- Type 1 vs Type 2 Diabetes
- Type 1: Pancreas produces little or no insulin, causing dangerously high blood glucose levels; treated by injecting insulin before meals and monitoring blood sugar. Type 2: Liver and muscle cells no longer respond to insulin produced by the pancreas; obesity is a major risk factor; treated with a low-sugar/carbohydrate-controlled diet and exercise.
- Thyroxine & Negative Feedback (Higher Tier)
- Thyroxine (from the thyroid gland) stimulates the basal metabolic rate and is important for growth and development. Controlled by negative feedback: when blood thyroxine falls low, the pituitary gland releases TSH (Thyroid Stimulating Hormone), stimulating the thyroid to release more thyroxine, which then inhibits further TSH release.
- Adrenaline & the Fight-or-Flight Response (Higher Tier)
- Secreted by the adrenal glands in times of fear or stress without a negative feedback loop. Adrenaline increases heart rate and breathing rate, boosting the delivery of oxygen and glucose to the brain and skeletal muscles, and stimulates glycogen breakdown in the liver, preparing the body for 'fight or flight'.
Quick-Fire Flashcards (6)
Click any card to check the answer, then mark it as Known to track your progress.
Why must excess glucose be stored as glycogen in liver and muscle cells rather than remaining dissolved as glucose?
Explain how the pancreas restores normal blood glucose levels after a person eats a sweet meal.
What is negative feedback?
How does the pituitary gland regulate low thyroxine levels in the blood?
Why is insulin injected rather than taken as a tablet by mouth?
How does adrenaline prepare the body for 'fight or flight'?
Exam-Style Questions & Mark Schemes (4)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
Explain how insulin and glucagon interact in a negative feedback cycle to keep blood glucose concentration constant. [5 marks]
Click “Check Mark Scheme” to compare your answer, 1. When blood glucose rises above the normal level, the pancreas detects the rise and secretes insulin into the bloodstream [1 mark]. 2. Insulin stimulates liver and muscle cells to absorb glucose from the blood and convert it into insoluble glycogen for storage, lowering blood glucose back to normal [1 mark]. 3. When blood glucose falls below the normal level, the pancreas detects the drop and secretes glucagon into the bloodstream [1 mark]. 4. Glucagon stimulates liver cells to break stored glycogen back down into glucose and release it into the blood [1 mark]. 5. This raises blood glucose back to normal, completing the negative feedback loop [1 mark].
- Q2
Compare the causes, risk factors, and treatments of Type 1 and Type 2 diabetes. [6 marks]
Click “Check Mark Scheme” to compare your answer, 1. Cause of Type 1: The pancreas fails to produce sufficient insulin (an autoimmune condition where insulin-producing cells are destroyed) [1 mark]. 2. Cause of Type 2: The pancreas still produces insulin, but the liver and muscle cell receptors stop responding to it (insulin resistance) [1 mark]. 3. Risk factors: Type 1 is primarily genetic/early onset and not linked to lifestyle, whereas obesity and lack of exercise are major risk factors for Type 2 diabetes [1 mark]. 4. Treatment of Type 1: Patients must inject insulin into subcutaneous fat before meals [1 mark]. 5. Treatment of Type 2: Patients are initially treated with a carbohydrate-controlled diet and regular exercise to lose weight and lower glucose intake [1 mark]. 6. Both types require careful monitoring of blood glucose concentration and diet management to avoid hyperglycaemia or hypoglycaemia [1 mark].
- Q3
Explain how thyroxine levels in the blood are controlled by negative feedback, and suggest why a person with an underactive thyroid gland might gain weight and feel tired. [5 marks]
Click “Check Mark Scheme” to compare your answer, 1. When thyroxine levels in the blood fall below normal, the pituitary gland detects this and secretes more Thyroid Stimulating Hormone (TSH) into the blood [1 mark]. 2. TSH stimulates the thyroid gland to synthesise and release more thyroxine [1 mark]. 3. Once blood thyroxine returns to normal (or rises too high), it inhibits the pituitary gland from secreting TSH, preventing thyroxine from rising further [1 mark]. 4. Thyroxine controls the body's basal metabolic rate (the speed of chemical reactions, including cellular respiration) [1 mark]. 5. With an underactive thyroid (low thyroxine), cellular respiration is slower, so less glucose/fat is broken down (causing weight gain) and less energy is released (causing tiredness) [1 mark].
- Q4
Compare how information is transmitted in the nervous system with how it is transmitted in the endocrine system. [4 marks]
Click “Check Mark Scheme” to compare your answer, 1. Nature of signal: The nervous system uses electrical impulses (and neurotransmitters at synapses), whereas the endocrine system uses chemical messengers (hormones) [1 mark]. 2. Transmission pathway: Nervous impulses travel along neurones (nerve cells), whereas hormones travel dissolved in blood plasma throughout the body [1 mark]. 3. Speed of transmission: Nervous transmission is very fast (milliseconds), whereas hormonal transmission is slower (limited by blood flow) [1 mark]. 4. Duration and specificity of response: Nervous responses are short-lived and act on specific effectors (muscles/glands), whereas hormonal responses are longer-lasting and can act on widespread target tissues [1 mark].
Common Exam Questions (4)
How does hormonal control differ from nervous control?
Nervous impulses are electrical signals transmitted along neurones at very high speed to produce a rapid, short-lived, and localised response (e.g., a muscle twitch). Hormones are chemical messengers carried in the blood plasma; they act more slowly, produce longer-lasting effects, and can affect multiple target organs simultaneously.
Why is the pituitary gland called the 'learn gland'?
The pituitary gland at the base of the brain is called the 'learn gland' because it secretes several hormones into the blood in response to body conditions, and many of these hormones (such as TSH, FSH, and LH) stimulate other endocrine glands (like the thyroid or ovaries) to release their own hormones.
What is the difference between glycogen and glucagon?
Spelling is critical in GCSE Biology exams. Glycogen is the insoluble storage carbohydrate (polymer of glucose) stored inside liver and muscle cells. Glucagon is a hormone secreted by the pancreas when blood glucose falls too low, which stimulates liver cells to break glycogen back down into glucose.
How do Type 1 and Type 2 diabetes differ in their cause and treatment?
Type 1 diabetes is an autoimmune disorder where the pancreas fails to produce sufficient insulin; it usually starts in childhood and is treated with insulin injections. Type 2 diabetes occurs when body cells stop responding properly to the insulin that is produced (insulin resistance); it is strongly linked to obesity and is treated with a carbohydrate-controlled diet and regular exercise.
Need more questions on The Endocrine System, Blood Glucose & Diabetes, or want to organise your own notes?
Type a specific exam question you are stuck on, pick one of the prompts below, or paste your class notes to build a custom set of flashcards and practice questions on this page.
Related study guides
Homeostasis & Body Temperature
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for enzyme action and cell function, in response to internal and external changes. In humans, automatic control systems using nervous and hormonal responses regulate core body temperature, blood glucose concentration, and water levels.
The Nervous System & Reflexes
The human nervous system enables the body to detect changes in its surroundings (stimuli) and coordinate rapid responses. Electrical impulses travel along sensory, relay, and motor neurones through the central nervous system (brain and spinal cord), while chemical neurotransmitters carry signals across synapses.
Hormones in Human Reproduction, Menstrual Cycle & IVF
During puberty, reproductive hormones trigger secondary sexual characteristics: testosterone (produced by the testes) stimulates sperm production in males, while oestrogen (produced by the ovaries) initiates the 28-day menstrual cycle in females. The menstrual cycle is regulated by the interaction of four hormones (FSH, LH, oestrogen, and progesterone) secreted by the pituitary gland and ovaries to mature an egg and prepare the uterus lining for pregnancy. Examiners heavily test how these four hormones stimulate or inhibit each other, enabling both hormonal contraception (inhibiting FSH) and fertility drugs (using FSH and LH in IVF).