Body Systems Reading: HS-LS1-2 and 1-3.

Introduction to Body Systems

The human body is made up of different systems that work together to help the body function properly. These systems are important for tasks like digesting food, breathing, moving, and keeping the body in balance. Let's take a look at some of the main body systems and how they work together to keep us healthy.

1. The Digestive System:

The digestive system helps break down food and absorb nutrients that the body needs to stay alive and healthy. When we eat, the food travels through the mouth, esophagus, and stomach, where it is broken down. In the small intestine, tiny structures called villi help the body absorb nutrients, including glucose, which is a sugar that provides energy. The circulatory system carries glucose and other nutrients to the rest of the body to be used for energy.

Glucose is important because the body needs it to make energy through a process called cellular respiration. Cellular respiration takes place in the mitochondria of our cells and uses glucose (and oxygen from the respiratory system) to create energy that the body can use for movement, growth, and other important functions. When we exercise, our bodies need more energy, so the digestive and respiratory systems work harder to bring in more glucose and oxygen.

2. The Respiratory System:

The respiratory system helps the body get oxygen and get rid of carbon dioxide (CO2). Oxygen is needed by the cells for cellular respiration to make energy. The lungs are the main organs for breathing. Inside the lungs are tiny air sacs called alveoli that help oxygen pass into the blood. The diaphragm, a muscle, helps the lungs expand and contract to bring in air.

When we exercise or do something that requires more energy, the body needs more oxygen to keep up with the increased energy demand. At the same time, the body produces more carbon dioxide (CO2) as a waste product from cellular respiration, so the respiratory system also helps remove CO2 by exhaling it.

3. The Circulatory System:

The circulatory system moves blood throughout the body, carrying oxygen, nutrients, and waste products. The heart pumps blood, and it travels through arteries, veins, and tiny capillaries. The circulatory system works closely with the respiratory and digestive systems to make sure oxygen, glucose, and other nutrients are delivered to cells for energy, and that waste products like CO2 are carried away to be removed.

4. The Excretory System:

The excretory system helps the body remove waste, like excess water, salt, and toxins. The kidneys filter the blood, and the liver helps break down waste. The skin also helps remove some waste through sweating.

5. The Nervous System:

The nervous system controls and coordinates all of the body's activities. It includes the brain, spinal cord, and neurons (nerve cells). The brain receives information from the body through sensory neurons and sends signals to the muscles and organs through motor neurons. This allows us to move, think, feel, and respond to changes in our environment.

There are two main parts of the nervous system:

• Central Nervous System (CNS): This includes the brain and spinal cord, which process information and make decisions.

• Peripheral Nervous System (PNS): This includes the nerves that carry messages between the CNS and the rest of the body, such as the sensory neurons that send information to the CNS and motor neurons that send signals from the CNS to muscles and organs.

Homeostasis: Keeping the Body in Balance

Homeostasis is the process the body uses to maintain a stable and balanced internal environment, even when the outside environment changes. For example, the body needs to keep things like oxygen levels, blood sugar, water balance, and body temperature at certain levels for everything to work well. If one of these factors goes out of balance, the body will take steps to bring it back to normal.

Examples of Homeostasis:

• Oxygen and Carbon Dioxide: The body needs enough oxygen to make energy (through cellular respiration). If the oxygen level gets too low, the respiratory system increases breathing rate to bring in more oxygen. Similarly, if there is too much carbon dioxide in the blood, the body will breathe faster to release the excess CO2.

• Water Balance: The body needs to maintain a certain amount of water. If the body becomes too hot or if we don’t drink enough, the body can sweat to cool down and release excess heat. Sweating also helps release excess salt and water.

• Temperature: The body needs to stay at a certain temperature (around 98.6°F or 37°C). If the body gets too hot, the body will sweat to cool down. If it gets too cold, the body will shiver to generate heat and warm up.

• Blood Sugar: When you eat, glucose (sugar) enters the bloodstream. If the blood sugar gets too high, the body releases insulin to bring the levels back down. If it gets too low, the body releases other hormones to raise blood sugar levels.

In all these examples, the body uses feedback mechanisms to keep things in balance. Negative feedback helps bring things back to normal, like when insulin lowers high blood sugar. Positive feedback helps things move in the same direction, like when blood clotting speeds up after an injury.

Vocabulary List

• Digestive System: The system that breaks down food and absorbs nutrients.

  • Example: The stomach is part of the digestive system.

• Glucose: A type of sugar the body uses for energy.

  • Example: The body uses glucose for energy during exercise.

• Cellular Respiration: The process by which cells create energy from glucose and oxygen.

  • Example: Cellular respiration takes place in the mitochondria.

• Respiratory System: The system that brings oxygen into the body and removes carbon dioxide.

  • Example: The lungs are part of the respiratory system.

• Alveoli: Tiny air sacs in the lungs where oxygen is exchanged with the blood.

  • Example: Alveoli help oxygen move into the blood.

• Diaphragm: A muscle that helps the lungs expand and contract during breathing.

  • Example: The diaphragm moves down when you breathe in.

• Circulatory System: The system that moves blood, oxygen, and nutrients throughout the body.

  • Example: The heart is part of the circulatory system.

• Heart: The organ that pumps blood throughout the body.

  • Example: The heart pumps oxygen-rich blood to the body.

• Kidneys: Organs that filter waste from the blood.

  • Example: The kidneys help remove excess water and waste.

• Nervous System: The system that controls and coordinates body activities.

  • Example: The brain and spinal cord are part of the nervous system.

• Neurons: Nerve cells that send messages through the body.

  • Example: Neurons carry signals to help you move or feel.

• Homeostasis: The process the body uses to keep internal conditions stable.

  • Example: Sweating helps the body stay cool and maintain homeostasis.

• Negative Feedback: A process that slows or stops a stimulus to bring things back to normal.

  • Example: Negative feedback helps reduce high blood sugar.

• Positive Feedback: A process that strengthens or increases a stimulus.

  • Example: Positive feedback helps blood clotting during an injury.