France Première ST2S (health and social sciences) — 1re specialties
Chapters: 4
1. Physics-chemistry for health
Chemical and electrical safety at home · Road safety · Sound waves and hearing · Light and vision · Fluids and blood pressure · Chemistry of biological molecules · Energy needs and diet · Role of biomolecules · Responsible use of natural resources
- Domestic Electric Circuits – A house gets 220 V, 50 Hz AC through a live and a neutral wire; appliances are joined in parallel on separate 5 A and 15 A circuits, and a fuse or MCB in the live wire plus an earth wire keep the house safe.
- Work, Energy and Power – Work is done when a force moves an object: W = F × s, measured in joules (J). Energy is the ability to do work. A moving body has kinetic energy ½mv²; a raised body has potential energy mgh. Energy is never made or destroyed, only changed from one form to another. Power is how fast work is done: P = W ÷ t, in watts. Simple machines like levers and pulleys let a small effort move a big load.
- Sound – Sound is made by vibrating objects. It travels through a medium (air, water, solids) as a longitudinal wave: particles move back and forth, making crowded parts (compressions) and spread-out parts (rarefactions). Frequency (Hz) sets the pitch, amplitude sets the loudness, and speed v = f × λ. Sound cannot travel in vacuum. Humans hear 20 Hz to 20,000 Hz; below is infrasound, above is ultrasound. Reflected sound gives echoes, used and controlled in buildings.
- The Human Eye: Parts, Accommodation and Defects of Vision – The eye is a camera made of living parts. The cornea and eye lens bend light to make a real, upside-down image on the retina. The ciliary muscles change the lens thickness so both far and near things look sharp (accommodation). When the eyeball is too long or too short, or the lens gets stiff, the image misses the retina; the right spectacle lens puts it back.
- Pressure: Force on Each Square Metre – Pressure is the force acting on each unit of area: P = F ÷ A. Its SI unit is the pascal (1 Pa = 1 N/m²). The same force on a smaller area gives a bigger pressure, which is why pins, knives and nails are sharp, and why tractors and camels have wide feet or tyres. Liquids press in all directions, and their pressure grows with depth (P = ρgh). Gases press because their particles keep hitting the walls; squeezing a gas or heating it raises its pressure. The air around us presses with about 101 kPa. Blood pressure is the pressure of blood on the walls of the arteries.
- Carbon and Its Compounds: Bonding, Hydrocarbons and Naming – Carbon has 4 outer electrons, so it shares electrons (covalent bonds) instead of gaining or losing them. Because it bonds to itself (catenation) and always makes 4 bonds (tetravalency), it forms millions of compounds: chains, branches and rings, saturated or unsaturated. Compounds with the same functional group form a homologous series that differs by –CH₂–, and IUPAC names are built from the number of carbons + a suffix or prefix for the functional group.
- Nutrition – Nutrition is how we get and use the substances in food. The body needs six groups of nutrients: carbohydrates and fats (mainly energy), proteins (growth and repair), vitamins and minerals (small amounts to keep the body working), and water, plus fibre for healthy digestion. Carbohydrate and protein give about 17 kJ per gram, fat about 37 kJ per gram. A balanced diet gives all nutrients in the right amounts, and energy in should roughly equal energy out.
- Biomolecules – A cell is mostly water, plus four big families of carbon compounds: proteins, carbohydrates, lipids and nucleic acids. Grinding tissue in acid separates small molecules (acid-soluble pool) from big ones – proteins, polysaccharides and nucleic acids (acid-insoluble pool). Proteins are chains of amino acids folded into four levels of structure. Polysaccharides are chains of sugars; lipids are fatty acids on glycerol; nucleic acids are chains of nucleotides. Enzymes are protein catalysts that bind a substrate at the active site, lower the activation energy, and are affected by temperature, pH, substrate level and inhibitors.
- Water Quality: Safe Drinking Water, Pollution and Soil – Safe drinking water has no harmful germs, is clear, has no bad taste or smell, has pH about 6.5 to 8.5 and has dissolved chemicals (nitrate, arsenic, lead, salts) below set limits. Water gets polluted by farms (fertiliser, pesticide), factories (metals, chemicals) and towns (sewage). Soil helps: its clay and humus hold positive ions and filter particles and germs, but nitrate slips through and soil can fill up.
2. Human biology and pathophysiology
Organisation of the human body · Locomotor system and movement · Digestive system and nutrition · Cardiovascular system · Respiratory system
- Human Body Systems – Your body is organised in levels: cells make tissues, tissues make organs, organs make organ systems, and all systems together make you, the organism. Each system has a main job: skeletal (frame), muscular (movement), circulatory (transport), respiratory (gas exchange), digestive (food), excretory (waste), nervous and endocrine (control), immune (defence), integumentary (skin, hair, nails) and reproductive. No system works alone: during exercise the muscles, heart, lungs and nerves all change together to keep the inside of the body steady (homeostasis).
- The Skeletal System – The skeleton is the body's frame of 206 bones (adult). It has five main jobs: support and shape, protection, movement (with muscles), making blood cells in red marrow, and storing minerals like calcium. Bones meet at joints; hinge joints (elbow, knee) bend one way, ball-and-socket joints (shoulder, hip) move in all directions. Ligaments join bone to bone, tendons join muscle to bone, cartilage cushions the ends. Muscles only pull, so they work in antagonistic pairs such as biceps and triceps.
- Human Digestive System and Heterotrophic Nutrition – Heterotrophs take ready-made food from other living things. Humans are holozoic: we eat whole food and break it down in a long tube, the alimentary canal. Teeth, saliva, stomach acid, enzymes, bile and pancreatic juice cut big food molecules into small ones that villi in the small intestine absorb into blood.
- Body Fluids and Circulation – Blood and lymph are the body's transport fluids. Blood is plasma (about 55%) plus formed elements: RBCs, WBCs and platelets. Blood groups (ABO, Rh) depend on antigens on RBCs. A clot forms when fibrinogen turns into fibrin threads. The human heart has four chambers and pumps blood through two loops: to the lungs and to the body (double circulation). The SA node starts each beat; one beat is a cardiac cycle of about 0.8 s, recorded as an ECG with P, QRS and T waves. Cardiac output = stroke volume × heart rate ≈ 5 L/min.
- Breathing and Exchange of Gases – Breathing moves air in and out of the lungs. Air travels nose → trachea → bronchi → bronchioles → alveoli. We breathe in when the diaphragm and outer rib muscles contract and make the chest bigger, so pressure inside falls. In the alveoli, oxygen moves into blood and carbon dioxide moves out, always from higher partial pressure to lower. Blood carries O2 mostly on haemoglobin and CO2 mostly as bicarbonate. A centre in the brain sets the rhythm. Lung volumes like tidal volume and vital capacity can be added and measured.
3. Health and social sciences: thematic strand
Health, well-being and social cohesion · Social protection · Social and health interventions
- Public Health – Public health is the work of keeping whole communities healthy: preventing disease, promoting healthy living and making sure everyone can get care. Infectious diseases spread through air, water, food, touch and insects; hygiene, clean water, sanitation and vaccination break the chain. When enough people are immune, herd immunity protects the rest. Health systems work in levels (primary, secondary, tertiary) and use surveillance data to spot outbreaks early.
- The Welfare State and Social Security – A welfare state is a state that protects people against the big risks of life: illness, job loss, old age, disability and poverty. It does this with a safety net made of three parts. Social insurance is paid from contributions taken from wages. Social assistance is paid from taxes to people in need. Public services such as schools and hospitals are open to everyone. Countries mix these parts in different ways: liberal (low tax, small help), conservative (help linked to your job) and social-democratic (high tax, help for all). Today welfare states face ageing populations, rising costs, global competition and many informal workers.
4. Health and social sciences: methods strand
Methods for the health and social sector
- Social Science Methods: How We Study People and Society – Social scientists study people and society the way scientists study nature: ask a clear question, collect evidence (sources, surveys, interviews, observation, statistics, maps), analyse it, check for bias, and draw careful conclusions. Economics, sociology and political science ask different questions but share these tools.