Physiology Quiz: How the Body Works

Twenty questions on how the body works, from the heart’s pacemaker to how the kidney concentrates urine. Easy to hard. Tap an answer to see if you’re right.

  1. Question 1 of 20

    What is the heart’s natural pacemaker?

    1. Bundle of His
    2. Sinoatrial (SA) node
    3. Purkinje fibres
    4. Atrioventricular (AV) node
    Show answer

    Answer: Sinoatrial (SA) node. A cluster of cells in the right atrium that fires about 60 to 100 times a minute and sets the rhythm.

  2. Question 2 of 20

    Where does gas exchange happen in the lungs?

    1. Alveoli
    2. Pleura
    3. Bronchi
    4. Trachea
    Show answer

    Answer: Alveoli. About 300 million tiny air sacs with walls one cell thick, wrapped in capillaries.

  3. Question 3 of 20

    Which blood cells carry oxygen?

    1. White blood cells
    2. Plasma cells
    3. Red blood cells
    4. Platelets
    Show answer

    Answer: Red blood cells. Each one is packed with haemoglobin, which binds oxygen in the lungs and releases it in the tissues.

  4. Question 4 of 20

    What is a normal adult resting heart rate?

    1. 40 to 50 a minute
    2. 20 to 30 a minute
    3. 100 to 140 a minute
    4. 60 to 100 a minute
    Show answer

    Answer: 60 to 100 a minute. Fit people often sit below 60, which is normal for them.

  5. Question 5 of 20

    Which hormone lowers blood sugar?

    1. Glucagon
    2. Adrenaline
    3. Insulin
    4. Cortisol
    Show answer

    Answer: Insulin. Insulin from the pancreas lets cells take in glucose. Glucagon, adrenaline and cortisol all push sugar up.

  6. Question 6 of 20

    What is the filtering unit of the kidney called?

    1. Nephron
    2. Villus
    3. Alveolus
    4. Neuron
    Show answer

    Answer: Nephron. Each kidney has about a million nephrons, filtering around 180 litres of blood plasma a day.

  7. Question 7 of 20

    Which muscle does most of the work of quiet breathing?

    1. Intercostals
    2. Sternocleidomastoid
    3. Abdominal muscles
    4. Diaphragm
    Show answer

    Answer: Diaphragm. It contracts and flattens, pulling air in. Breathing out at rest is passive.

  8. Question 8 of 20

    Where are most nutrients absorbed?

    1. Stomach
    2. Small intestine
    3. Oesophagus
    4. Large intestine
    Show answer

    Answer: Small intestine. Its folds, villi and microvilli give it a surface area of roughly a tennis court.

  9. Question 9 of 20

    Where is bile made?

    1. Gallbladder
    2. Liver
    3. Stomach
    4. Pancreas
    Show answer

    Answer: Liver. The liver makes it; the gallbladder stores and concentrates it, then squeezes it out after a fatty meal.

  10. Question 10 of 20

    Which hormone from the kidneys tells the bone marrow to make red blood cells?

    1. Erythropoietin (EPO)
    2. Renin
    3. Aldosterone
    4. Thyroxine
    Show answer

    Answer: Erythropoietin (EPO). Low oxygen triggers EPO release. People with kidney failure often become anaemic because they make less.

  11. Question 11 of 20

    Cardiac output equals heart rate multiplied by what?

    1. Respiratory rate
    2. Ejection fraction
    3. Blood pressure
    4. Stroke volume
    Show answer

    Answer: Stroke volume. About 70 beats x 70 mL is roughly 5 litres a minute at rest.

  12. Question 12 of 20

    What senses blood pressure in the carotid arteries and aortic arch?

    1. Nociceptors
    2. Chemoreceptors
    3. Baroreceptors
    4. Proprioceptors
    Show answer

    Answer: Baroreceptors. Stretch sensors that adjust heart rate and vessel tone within seconds, like when you stand up.

  13. Question 13 of 20

    What does antidiuretic hormone (ADH) do?

    1. Makes the kidneys pass more water
    2. Makes the kidneys hold on to water
    3. Makes red blood cells
    4. Raises blood sugar
    Show answer

    Answer: Makes the kidneys hold on to water. Released from the pituitary when you’re dehydrated. Alcohol blocks it, which is why you wee more.

  14. Question 14 of 20

    In healthy people, what mainly drives the urge to breathe?

    1. Falling carbon dioxide
    2. Falling oxygen
    3. Rising carbon dioxide
    4. Heart rate
    Show answer

    Answer: Rising carbon dioxide. Chemoreceptors sense CO2 (through blood acidity). Low oxygen only becomes the main drive when it’s quite low.

  15. Question 15 of 20

    The Frank-Starling law says the more the heart muscle is stretched by filling, the more…

    1. Weakly it contracts
    2. Irregularly it beats
    3. Slowly it beats
    4. Forcefully it contracts
    Show answer

    Answer: Forcefully it contracts. More blood in means more blood out, up to a point. Beyond that, an overstretched failing heart weakens.

  16. Question 16 of 20

    In exercising muscle, extra heat, acid and carbon dioxide make haemoglobin do what?

    1. Release oxygen more easily
    2. Stop carrying oxygen
    3. Carry more carbon monoxide
    4. Hold on to oxygen more tightly
    Show answer

    Answer: Release oxygen more easily. The Bohr effect shifts the oxygen curve to the right, so busy tissues get more oxygen.

  17. Question 17 of 20

    Where is renin released from?

    1. Adrenal cortex
    2. Juxtaglomerular cells in the kidney
    3. Liver
    4. Pituitary gland
    Show answer

    Answer: Juxtaglomerular cells in the kidney. Low blood pressure or low salt reaching the kidney triggers renin, which starts the renin-angiotensin-aldosterone system.

  18. Question 18 of 20

    What does aldosterone do in the kidney?

    1. Gets rid of sodium and keeps potassium
    2. Gets rid of glucose
    3. Keeps sodium and gets rid of potassium
    4. Keeps calcium
    Show answer

    Answer: Keeps sodium and gets rid of potassium. Water follows the sodium, raising blood pressure. Too much aldosterone causes high blood pressure and low potassium.

  19. Question 19 of 20

    A nerve cell’s resting voltage mainly depends on which ion leaking out?

    1. Calcium
    2. Sodium
    3. Chloride
    4. Potassium
    Show answer

    Answer: Potassium. Potassium leaks out through open channels, leaving the inside around −70 mV. That’s why high or low potassium affects the heart.

  20. Question 20 of 20

    Which part of the nephron builds the salty gradient that lets the kidney concentrate urine?

    1. Loop of Henle
    2. Proximal tubule
    3. Bowman’s capsule
    4. Glomerulus
    Show answer

    Answer: Loop of Henle. The countercurrent multiplier. Animals with longer loops, like desert rodents, make far more concentrated urine.

Want the parts too? Try the anatomy quizzes, with diagrams of every system.

Common questions

What is the difference between anatomy and physiology?

Anatomy is the structure of the body (what and where). Physiology is how it works (what it does and how).

How do I study for an anatomy and physiology exam?

Test yourself often with short quizzes, link each structure to its job, draw systems from memory, and space your revision over days rather than cramming.

More medical quizzes

Updated 16 November 2026. General education, not medical advice. General education, not personal medical advice.