GED Science: Human Body and Health Concepts
Importance ★★★★★ · 20% (estimate)
Overview
This chapter covers how the human body works and stays healthy: body systems, homeostasis, nutrition, and disease. The GED Science test uses these ideas in its Human Health and Living Systems theme, often with a short passage, a food label, or a data table.
Body systems work together. Muscles pull on bones to move the body, and the nervous and endocrine systems send signals that control other organs. Homeostasis is the body's way of keeping inside conditions steady. Most of it works by negative feedback: the body senses a change and responds in the opposite direction, such as sweating when hot or releasing insulin when blood sugar rises.
Food gives the body energy and building materials. Carbohydrates are the main quick energy source, and fat stores the most energy per gram. Vitamins and minerals are needed in small amounts but contain no calories. Diseases are caused by pathogens (germs) that spread through the air, water, food, blood, or contact. They are prevented by methods such as vaccination, hand washing, sanitation, and protective equipment.
Key concepts
Homeostasis
Keeping inside conditions such as body temperature, blood sugar, and water balance steady, even when the outside changes.
Memory tipSweating when hot and shivering when cold are classic examples.
Negative feedback
A response that reverses a change. Blood sugar rises, insulin is released, and blood sugar falls back.
Memory tipNegative feedback = bring it back to normal.
Body systems
Groups of organs that do a job. Muscular and skeletal systems move the body; the circulatory system carries blood; the endocrine system makes hormones.
Memory tipAsk which systems must work together for the job described.
Nutrients and Calories
Fat has about 9 Calories per gram; carbohydrate and protein have about 4 each. Vitamins, minerals, and water have none.
Memory tipMultiply grams by Calories per gram for each nutrient, then add.
Pathogen
A germ that causes disease, such as a virus or bacterium. It can spread through air, water, food, blood, or contact.
Memory tipMatch the precaution to the way the germ spreads.
Vaccine
Trains the immune system to recognize a germ before a person is exposed, so the body can fight it off quickly.
Memory tipVaccines prevent; antibiotics treat bacterial infections.
Often tested
- Sweating cools the body by evaporation; narrowing skin blood vessels saves heat in the cold.
- Insulin lowering blood sugar is negative feedback.
- Gloves protect against bloodborne germs; covering coughs protects against airborne germs.
- A supported conclusion describes what the data show; it does not claim proof from a small study.
Easy to confuse: How diseases spread and how to block them
| Route | Example | Prevention |
|---|---|---|
| Airborne | Flu, colds | Vaccines, covering coughs, fresh air |
| Bloodborne | Hepatitis B, HIV | Gloves, safe disposal of needles |
| Food and water | Food poisoning | Washing hands and food, cooking, clean water |
3 sample questions
Verified practice questions from this unit.
Question 1. On a hot summer job site, a worker's body starts to sweat. What is the main purpose of sweating?
- ① To raise the body's temperature
- ② To cool the body as sweat evaporates from the skin
- ③ To remove extra oxygen from the blood
- ④ To store water in the skin for later
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ② To cool the body as sweat evaporates from the skin
Key point: Sweating cools the body and keeps temperature steady
Sweat is mostly water. When it evaporates (turns into vapor) from the skin, it carries heat away from the body. This helps keep the inside of the body near a normal temperature. Keeping inside conditions steady is called homeostasis.
Wrong choices
- To raise the body's temperature: Sweating does the opposite. It lowers body temperature.
- To remove extra oxygen from the blood: Oxygen is not removed by sweat. Extra carbon dioxide leaves the body through the lungs.
- To store water in the skin for later: Sweating releases water from the body. It does not store water.
Question 2. Which method helps prevent a disease by training the immune system before a person is ever exposed to the germ?
- ① Taking antibiotics after symptoms start
- ② Drinking more water each day
- ③ Wearing sunscreen outdoors
- ④ Getting a vaccine
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ④ Getting a vaccine
Key point: A vaccine trains the immune system before exposure
A vaccine shows the immune system a harmless form or part of a germ. The body learns to recognize that germ and can fight it quickly if the real germ enters later. This is why vaccination is a prevention method.
Wrong choices
- Taking antibiotics after symptoms start: Antibiotics are taken after an infection begins, and they work only on bacteria. They do not train the immune system ahead of time.
- Drinking more water each day: Drinking water is healthy, but it does not teach the immune system to recognize a germ.
- Wearing sunscreen outdoors: Sunscreen protects skin from ultraviolet light. It does not protect against germs.
Question 3. Which two body systems work together most directly to move your arm?
- ① The muscular system and the skeletal system
- ② The respiratory system and the endocrine system
- ③ The immune system and the digestive system
- ④ The digestive system and the excretory system
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ① The muscular system and the skeletal system
Key point: Muscles pull on bones to move the body
Muscles are attached to bones. When a muscle contracts (gets shorter), it pulls on a bone, and the bone moves at a joint. So the muscular system and the skeletal system work together to move the body.
Wrong choices
- The respiratory system and the endocrine system: The respiratory system exchanges gases and the endocrine system makes hormones. Neither one pulls on bones.
- The immune system and the digestive system: The immune system fights germs and the digestive system breaks down food. They do not move the arm.
- The digestive system and the excretory system: These systems break down food and remove wastes. They do not move bones.
AI-written · Verified · Written by AI. Only units that passed a separate AI check (re-reading facts and numbers) are published. Tell us if you find a mistake.