Ukraine 8 клас Biology

Chapters: 11

1. Introduction: human biology

Humans in the living world

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).

Levels of organisation of the body

Tissues: Plant and Animal Tissues – A tissue is a group of similar cells that do one job together. Cells form tissues, tissues form organs, organs form organ systems and systems form an organism. Plants have dividing meristematic tissue and non-dividing permanent tissue, including xylem (water up) and phloem (food both ways). Animals have epithelial, connective, muscular and nervous tissue. Bones, muscles and joints need good posture, exercise and food rich in calcium.

Nervous system · Endocrine system

Coming soon

Skeleton · Muscles

Muscle Physiology: How Muscles Contract – A skeletal muscle is made of long cells called fibres. Each fibre holds chains of tiny units called sarcomeres. In a sarcomere, thin actin filaments and thick myosin filaments overlap. A nerve signal releases calcium, myosin heads grab actin and pull it to the middle, and the muscle shortens. Every pull uses ATP. ATP comes from creatine phosphate (seconds), fermentation that makes lactate (up to about two minutes) and aerobic respiration (long exercise). When ATP runs low the muscle tires.

Digestive system · Metabolism and nutrition

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.
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.

Blood · Circulation · Lymph and immunity

Transportation in Humans: Heart, Blood Vessels, Blood and Lymph – The heart is a four-chambered muscular pump. Blood passes through it twice in one full round: once to the lungs to pick up oxygen, and once to the rest of the body. This is double circulation. Arteries carry blood away from the heart, veins bring it back and capillaries do the exchange. Blood (plasma, RBCs, WBCs, platelets) and lymph together carry food, gases, hormones and wastes.
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).

Breathing

Respiration: Aerobic, Anaerobic and the Human Lungs – Respiration is the breakdown of food, usually glucose, inside cells to release energy, stored as ATP. With oxygen (aerobic) glucose is fully broken into carbon dioxide and water and gives much energy; without oxygen (anaerobic) it gives little energy and makes ethanol (yeast) or lactic acid (muscles). Our lungs bring oxygen to the blood through millions of alveoli.

Urinary system · Skin and thermoregulation

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.

Analysers

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.

Behaviour and mind

Coming soon

Human reproduction

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.