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5. Homeostasis and response

How the body keeps its internal conditions steady, and how humans and plants respond to change: the nervous system, the brain and eye, hormones, blood glucose, temperature, water balance and the kidneys, reproductive hormones and plant hormones.

Homeostasis

1 lesson
5.1 Homeostasis and control systems What homeostasis is, why cells need steady conditions, and how receptors, coordination centres and effectors use negative feedback to keep levels near their optimum. AQA Edexcel OCR

The nervous system

5 lessons
5.2 The nervous system and neurones How the nervous system carries electrical impulses from receptors to the CNS and on to effectors, and how sensory, relay and motor neurones are adapted to do it. AQA Edexcel OCR 5.3 Synapses and reflex arcs How impulses cross synapses using neurotransmitters, and how a reflex arc produces a fast, automatic response that protects the body. AQA Edexcel OCR 5.4 Investigating reaction time How to plan and carry out a ruler-drop investigation into a factor that affects human reaction time, convert distances into times, and evaluate the results. AQA Edexcel OCR 5.5 The brain The main regions of the brain (cerebral cortex, cerebellum, medulla, hypothalamus and pituitary gland) and what each one controls. Separate only AQA Edexcel OCR 5.6 Investigating and treating the brain How scientists map brain function (patients with brain damage, electrical stimulation, MRI, CT and PET scans) and why brain and spinal injuries are so hard to treat. Higher only Separate only AQA Edexcel OCR

The eye

3 lessons
5.7 Structure of the eye The parts of the eye and their jobs: cornea, iris, pupil, lens, ciliary muscles, suspensory ligaments, retina (rods and cones), sclera and optic nerve, plus the iris reflex. Separate only AQA Edexcel OCR 5.8 Accommodation: focusing near and far How the ciliary muscles and suspensory ligaments change the shape of the lens so the eye can focus on near and distant objects. Separate only AQA Edexcel OCR 5.9 Defects of the eye Short sight, long sight, cataracts and colour blindness: what causes them, ray diagrams, and how glasses, contact lenses, laser surgery and lens replacement correct them. Separate only AQA Edexcel OCR

Hormones

2 lessons
5.10 The endocrine system How endocrine glands release hormones into the blood to act on target organs, where the main glands are, and how hormonal control compares with the nervous system. AQA Edexcel OCR 5.11 Adrenaline and thyroxine How adrenaline prepares the body for fight or flight, and how thyroxine controls metabolic rate through negative feedback involving TRH and TSH. Higher only AQA Edexcel OCR

Blood glucose

2 lessons
5.12 Controlling blood glucose How the pancreas controls blood glucose: insulin moves glucose into liver and muscle cells to be stored as glycogen, and (Higher) glucagon turns glycogen back into glucose. AQA Edexcel OCR 5.13 Diabetes Type 1 and type 2 diabetes compared: causes, treatments, reading glucose graphs, and the link between obesity, BMI, waist:hip ratio and type 2 diabetes. AQA Edexcel OCR

Temperature and water balance

6 lessons
5.14 Controlling body temperature How the thermoregulatory centre in the brain and the skin keep body temperature near 37 °C, using sweating, vasodilation, vasoconstriction and shivering. Separate only AQA Edexcel OCR 5.15 Water, urea and osmosis in the body How water, ions and urea leave the body, why cells are damaged if body fluids become too dilute or too concentrated, and how the liver turns excess amino acids into urea. Separate only AQA Edexcel OCR 5.16 How the kidneys make urine The urinary system, and how the kidneys make urine by filtering the blood and selectively reabsorbing glucose, some ions and water, with data on what is in plasma, filtrate and urine. Separate only AQA Edexcel OCR 5.17 The nephron The structure of a nephron (glomerulus, Bowman's capsule, convoluted tubules, loop of Henle, collecting duct) and how each part filters the blood or reabsorbs glucose and water. Separate only Edexcel OCR 5.18 ADH and water balance How ADH from the pituitary gland changes how permeable the kidney tubules are to water, controlling the water content of the blood by negative feedback, and how the body copes with dehydration, excess water and salt. Higher only Separate only AQA Edexcel OCR 5.19 Kidney failure: dialysis and transplants What happens when kidneys fail, how a dialysis machine cleans the blood, how kidney transplants work, and how to compare the two treatments. Separate only AQA Edexcel

Reproductive hormones

4 lessons
5.20 Hormones and the menstrual cycle How testosterone and oestrogen bring about puberty, the stages of the 28-day menstrual cycle, and the jobs of FSH, LH, oestrogen and progesterone. AQA Edexcel OCR 5.21 How the menstrual cycle hormones interact How FSH, oestrogen, LH and progesterone switch each other on and off to control the menstrual cycle, and how to read a graph of hormone levels. Higher only AQA Edexcel OCR 5.22 Contraception How hormonal and non-hormonal methods of contraception prevent pregnancy, how effective each one is, and how to evaluate them. AQA Edexcel OCR 5.23 Treating infertility How hormones are used to treat infertility: fertility drugs containing FSH and LH, clomifene, and the steps of IVF, with the benefits, risks and ethical issues. Higher only AQA Edexcel OCR

Plant hormones

3 lessons
5.24 Auxin and tropisms How unequal amounts of auxin make shoots grow towards light and roots grow towards gravity, and what gibberellins and ethene do in plants. Separate only AQA Edexcel OCR 5.25 Investigating plant growth responses How to investigate the effect of light or gravity on newly germinated seedlings: methods, variables, measurements, biological drawings and evaluation. Separate only AQA Edexcel OCR 5.26 Uses of plant hormones How people use auxins (weedkillers, rooting powders, tissue culture), gibberellins (dormancy, flowering, bigger and seedless fruit) and ethene (ripening) in farming and food. Higher only Separate only AQA Edexcel OCR