Poland Szkoła podstawowa, klasa VII Biology
Chapters: 2
1. III. The human body
Skin · Movement system · Digestive system and nutrition · Circulatory system · Immune system · Respiratory system · Urinary system and excretion · Nervous system · Sense organs · Endocrine system · Reproduction and development
- Human Skin: Layers, Jobs and Sun Safety – Skin is the largest organ of the body. It has three layers: the epidermis (outer, waterproof, holds melanin), the dermis (blood vessels, nerves, glands, hair roots) and a fat layer underneath. It protects, senses touch and pain, controls body temperature with sweat and blood flow, and makes vitamin D in sunlight. Too much UV light harms skin cells, speeds ageing and can cause skin cancer such as melanoma.
- The Immune System: How Your Body Fights Germs – Germs (pathogens) cause infectious disease. The body has three lines of defence: barriers (skin, mucus, acid), a fast general (innate) response (inflammation, fever, phagocytes) and a slow, specific (adaptive) response (B cells make antibodies, T cells kill infected cells). Memory cells make the second attack fast. Vaccines create memory safely. Immunity can go wrong: allergy, autoimmune disease, immunodeficiency (e.g. HIV).
- Sense Organs – Sense organs let us pick up changes around us (stimuli). The eye senses light, the ear sound and balance, the nose smell, the tongue taste, and the skin touch, pressure, heat, cold and pain. Each has receptor cells that turn the stimulus into nerve signals. The signal goes along a sensory nerve to the brain or spinal cord, which sends an order to a muscle: the response.
- Reproduction in Human Beings and Reproductive Health – At puberty, hormones from the brain make the testes and ovaries start working. The male system makes and carries sperm; the female system makes eggs and provides a place (uterus) where a baby develops. Fertilisation happens in the oviduct, and the embryo is fed through the placenta. Reproductive health includes safe choices, contraception, avoiding female foeticide, and preventing sexually transmitted diseases such as HIV/AIDS.
2. IV. Homeostasis
Keeping the internal environment stable · Safe use of medicines
- Homeostasis – Homeostasis is how the body keeps its internal environment (blood and tissue fluid) steady even when the outside world changes. It controls body temperature (about 37 °C), blood glucose (about 4–6 mmol/L), water and salt, and blood pH (about 7.4). It mostly uses negative feedback: a receptor senses a change, a control centre decides, and an effector brings the level back to its set point.
- Health and Disease – Health is complete physical, mental and social well-being, not just the absence of disease. Communicable diseases are caused by pathogens (bacteria, viruses, fungi, protists) and spread from person to person, through air, water, food, touch or animals. Non-communicable diseases such as heart disease, diabetes, many cancers and high blood pressure do not spread; they are linked to genes, age and lifestyle. We prevent disease with hygiene, clean water, vaccines, a balanced diet, exercise, sleep, not smoking, and regular check-ups and self-checks. Antibiotics kill bacteria but not viruses; misusing them breeds resistant bacteria. Medicines must be taken as the leaflet or doctor says.