Coaching Centre
Body systems review
A summary of the whole Body Systems chapter, key words, and a mixed test covering the nervous and endocrine systems, reflexes, the brain, homeostasis, the senses, systems working together, infectious disease, immunity and non-infectious disease.
Use this page to check the whole chapter. Read the summary, make sure you can explain every key word, then do the test without looking back.
Chapter summary
| Topic | What you need to know |
|---|---|
| 4A Nervous system | Stimulus → receptor → control centre → effector → response. Neuron: dendrites, cell body, axon, myelin, axon terminals. Sensory, inter- and motor neurons. Synapses and neurotransmitters. CNS (brain, spinal cord) and PNS (somatic; autonomic: sympathetic and parasympathetic). About 86 billion neurons in the brain. MS damages myelin. |
| 4B Reflexes | Fast, automatic, protective. Reflex arc: receptor, sensory neuron, interneuron in spinal cord, motor neuron, effector. Brain told afterwards. Reaction time from a dropped ruler: t = √(2d ÷ 9.8). Average many trials. |
| 4C Brain and spinal cord | Protected by skull, meninges, cerebrospinal fluid, vertebrae. Frontal (planning, personality, movement, speech), parietal (touch), occipital (vision), temporal (hearing, memory). Cerebellum (balance, coordination), brain stem (breathing, heart rate), hypothalamus. Each side controls the opposite side of the body. Neuroplasticity. Paraplegia and tetraplegia; C3–C5 control breathing. |
| 4D Endocrine system | Glands release hormones into the blood; only target cells with receptors respond. Pituitary (growth hormone, ADH), pineal (melatonin), thyroid (thyroxine), adrenal (adrenaline), pancreas (insulin, glucagon), ovaries, testes. Hormones slower and longer-lasting than nerves. Fight or flight. Diabetes types 1 and 2; goitre and iodised salt. |
| 4E Homeostasis | Keeping the internal environment constant by negative feedback: stimulus, receptor, control centre, effector, response. Temperature: vasodilation and sweating; vasoconstriction and shivering. Heat stroke above 40 °C, hypothermia below 35 °C, fever raises the set point. Positive feedback in childbirth. Endotherms and ectotherms. |
| 4F Senses | Photo-, mechano-, chemo-, thermo- and pain receptors. More than five senses: balance, proprioception. Eye: cornea, iris, pupil, lens, retina (rods and cones), optic nerve, blind spot. Ear: cochlea, semicircular canals. Five tastes; flavour is mostly smell. Two-point test. Platypus electroreception. Plant tropisms. |
| 4G Systems together | Digestive and respiratory supply glucose and oxygen; circulatory delivers; excretory removes wastes; nervous and endocrine coordinate. Exercise: faster, deeper breathing, faster heart, blood diverted to muscles, sweating. Anaerobic respiration makes lactic acid. Fitness lowers resting heart rate. Anaemia. |
| 4H Infectious disease | Pathogens: bacteria, viruses, fungi, protozoa, macroparasites, prions. Spread by air, contact, surfaces, food and water, body fluids, vectors, animals. Virulence (severity) vs transmissibility (spread). Pandemics: 1918 flu, COVID-19. Hendra, Phytophthora dieback, devil facial tumour disease. Hygiene, quarantine, biosecurity. Bundjalung use of tea tree. |
| 4I Immunity | First line: skin, mucus, acid. Second: inflammation, phagocytes, fever. Third: lymphocytes, antibodies fit antigens, killer T cells, memory cells. Primary and secondary responses. Active and passive, natural and artificial immunity. Vaccines including mRNA. Antibiotics (Fleming, Florey) and resistance. Allergies, autoimmune disease, HIV. |
| 4J Non-infectious disease | Genetic, lifestyle, diet, environmental, ageing causes. Cancer: several mutations, uncontrolled division; benign vs malignant; metastasis. UV and tobacco as mutagens. Slip! Slop! Slap!, plain packaging. Asbestos and mesothelioma. Rheumatic heart disease. Spray-on skin. |
Putting it together
The whole chapter is about one question: how does a body made of trillions of cells keep every one of them alive? Each cell needs a steady supply of glucose, oxygen and water, a narrow range of temperature, and its wastes taken away. The digestive, respiratory, circulatory and excretory systems do the supplying and removing, but only because the nervous and endocrine systems are constantly checking conditions and adjusting them. Nerves give fast, precise responses; hormones give slower, longer, widespread ones; and the hypothalamus links the two.
Disease is what happens when this system is pushed beyond what it can correct. Pathogens invade from outside, and the immune system, another coordinated system of cells and chemical signals, fights back and remembers. Non-infectious diseases come from inside: faulty genes, mutations that build up over a lifetime, or damage from how we live. Science has given us vaccines, antibiotics, screening and campaigns that change behaviour, but as rheumatic heart disease shows, health also depends on fair access to housing and care.
Key words
adrenaline · antibiotic · antibody · antigen · axon · cerebellum · effector · endocrine gland · homeostasis · hormone · hypothalamus · immunity · interneuron · lymphocyte · memory cell · metastasis · motor neuron · mutation · myelin · negative feedback · neuron · pathogen · phagocyte · receptor · reflex arc · sensory neuron · set point · stimulus · synapse · target cell · transmissibility · vaccine · vector · virulence
Test yourself
Which order does a message follow in a reflex arc?
The message passes inward to the spinal cord, then out to the effector.
Which part of the brain coordinates balance and smooth movement?
The cerebellum coordinates movement and balance.
Insulin is released by the pancreas and travels in the blood. This is an example of
Hormones are chemical messengers carried in the blood.
When you are too cold, which response helps bring your temperature back up?
Shivering muscles release heat from respiration.
Which cells in the retina detect colour?
Three types of cone detect colour in bright light.
During hard exercise, which change does not happen?
Blood is diverted away from the gut to the muscles.
Which pathogen is a misfolded protein?
Prions are not alive; they are misfolded proteins.
A vaccine protects you mainly by causing your body to produce
Memory cells give a fast secondary response when the real pathogen arrives.
Why are antibiotics prescribed less often than they used to be?
Every use selects for resistant bacteria.
Cancer develops when
Several mutations lead to uncontrolled division.
Name the three types of neuron.
Label the regions of the brain.
Label the endocrine glands.
Label the eye.
Name the three lines of defence.
Which system is responsible?
Put the steps of the temperature feedback loop in order, starting when you get too hot.
The gap between two neurons is a . The links the nervous and endocrine systems. Keeping internal conditions steady is called . A foreign molecule that triggers an immune response is an . An animal such as a mosquito that carries a pathogen is a . The spread of cancer to other parts of the body is .
Compare how the nervous and endocrine systems send messages. Use the fight-or-flight response to show how they work together.
The nervous system sends electrical impulses along neurons to exact places, so its responses are very fast but short-lived. The endocrine system releases hormones into the blood; they reach every part of the body but only affect target cells with receptors, and their effects are slower to start and last longer. In fight or flight, sympathetic nerves speed up the heart and breathing within a fraction of a second. They also trigger the adrenal glands to release adrenaline, which keeps the heart racing, makes the liver release glucose and sends more blood to the muscles for several minutes, even after the danger has passed.
A new strain of flu appears. Explain how a person's body defends itself if they are infected, and why a person who received this year's flu vaccine is likely to recover more quickly.
The flu virus is breathed in. Mucus and cilia in the airways trap and remove many virus particles, but some infect cells lining the airways. Infected cells trigger inflammation, and phagocytes arrive and engulf viruses and debris. The body may also raise its temperature (fever) to slow the virus and speed up immune cells. Meanwhile, lymphocytes whose receptors match the flu antigens are activated and multiply. B cells make antibodies that bind to the virus and stop it entering more cells, and killer T cells destroy infected cells. In an unvaccinated person this primary response takes about a week, so the virus multiplies and they are sick for several days. Memory cells are left afterwards. A person vaccinated with this year's vaccine has already been exposed to these flu antigens, so they already have memory cells. These produce a fast, large secondary response, so the virus is controlled sooner and the illness is milder and shorter. Because flu viruses change their antigens, the vaccine is updated every year to match.