3.28 The Muscular System Lesson for Kids
The muscular system protects the body and is responsible for the body’s movement. Explore the muscular system, and learn about the three types of muscles, such as the skeletal muscles, smooth muscles, and cardiac muscles.
The Muscular System
Who has more muscles: a first grader or an adult bodybuilder? Muscles can grow but, surprisingly, every person has the same number of muscles – more than 600. These muscles make up your muscular system, and they can be categorized into three different types: skeletal, smooth, and cardiac.
1. Main Points:
Everyone has the same number of muscles, more than 600, and these muscles can be divided into three types: skeletal, smooth, and cardiac.
2. Questions:
- Content Analysis: How many types of muscles are there and what are they?
- Thematic Analysis: What is the key theme or topic being addressed in the text?
3. Further Discussion:
Why do you think it’s important to know that both a first-grader and a bodybuilder have the same number of muscles?
4. Answers:
- Content Analysis: There are “three different types: skeletal, smooth, and cardiac.”
- Thematic Analysis: The key theme is the “muscular system” and its components.
What do you think? Isn’t it fascinating that whether you’re a first-grader or a bodybuilder, you still have the same number of muscles? Why do you think that’s the case?
Skeletal Muscles
When you think about your muscles, you probably think about the ones that make you run fast and lift heavy things. These are your skeletal muscles. Skeletal muscles are sometimes called voluntary muscles because you choose to move them.
For example, when you want to kick a soccer ball into the goal, you tell your leg muscles to kick. Skeletal muscles are attached to your bones by tendons. When you decide to kick, your brain sends an electrical signal down your nerves to your leg muscle. This electrical message tells your muscle to contract or shorten. The contracting muscle pulls on the bone and makes it move. This is what allows you to score that goal.
You have skeletal muscles all over your body. The ones in your back help you stand up straight. Skeletal muscles in your face contract to make you smile. You even have small skeletal muscles in your eyes that let you look up and down.
1. Main points:
Skeletal muscles help us perform voluntary movements like running, lifting, and smiling, and they’re controlled by electrical signals from the brain.
2. Questions:
- Content Analysis: What are skeletal muscles and what do they help you do?
- Contextual Analysis: Where are skeletal muscles located in the body?
- Thematic Analysis: What is the role of electrical signals from the brain in controlling skeletal muscles?
3. Further Discussion:
How do you think skeletal muscles are different from other types of muscles in the body?
4. Answers:
- What are skeletal muscles and what do they help you do?
“These are your skeletal muscles. Skeletal muscles are sometimes called voluntary muscles because you choose to move them.” - Where are skeletal muscles located in the body?
“You have skeletal muscles all over your body. The ones in your back help you stand up straight.” - What is the role of electrical signals from the brain in controlling skeletal muscles?
“When you decide to kick, your brain sends an electrical signal down your nerves to your leg muscle. This electrical message tells your muscle to contract or shorten.”
Smooth Muscles
You can’t tell your smooth muscles what to do because they’re involuntary muscles. Smooth muscles are found in organs, like your stomach, intestines, and bladder.
Smooth muscles help you with automatic functions in your body, such as digestion. Smooth muscles in the walls of your esophagus, stomach, and intestines contract and relax, pushing food in a one-way path through your digestive tract.
Sometimes when you’re sick, smooth muscles make food go the other way, and you throw up! When you throw up, smooth muscles in your digestive tract contract to force the irritating food out of your stomach, up your esophagus, and out your mouth. Yuck!
1. Main points:
Smooth muscles are involuntary and are found in organs like the stomach and intestines, helping with automatic functions like digestion.
2. Questions:
- Content Analysis: What are smooth muscles and where are they located?
- Contextual Analysis: When do smooth muscles work in a way that’s different from their usual function?
- Thematic Analysis: What automatic functions are smooth muscles responsible for?
3. Further Discussion:
How do you think smooth muscles help you without you even noticing?
4. Answers:
- What are smooth muscles and where are they located?
“You can’t tell your smooth muscles what to do because they’re involuntary muscles. Smooth muscles are found in organs, like your stomach, intestines, and bladder.” - When do smooth muscles work in a way that’s different from their usual function?
“Sometimes when you’re sick, smooth muscles make food go the other way, and you throw up!” - What automatic functions are smooth muscles responsible for?
“Smooth muscles help you with automatic functions in your body, such as digestion.”
Isn’t the human body amazing, especially how smooth muscles work automatically? What else would you like to know?
Cardiac Muscle
Cardiac muscle is the third type of muscle in your body. Like smooth muscle, cardiac muscle is involuntary. Cardiac is a fancy word for heart, so I bet you can guess what this type of muscle does. It’s the muscle that makes up your heart. It contracts and relaxes to pump blood around your body. Your heart beats about 70 times per minute when you’re sitting still. Can you imagine if you had to tell your heart to beat 70 times each minute? You couldn’t get anything else done!
1. Main Points:
Cardiac muscle is involuntary and makes up the heart, which contracts and relaxes to pump blood; it beats about 70 times per minute when at rest.
2. Questions:
- Content Analysis: What is the main function of cardiac muscle?
- Thematic Analysis: What is the main topic or focus of this part of the text?
3. Further Discussion:
Why do you think it’s a good thing that we don’t have to tell our heart to beat?
4. Answers:
- Content Analysis: The main function of cardiac muscle is to “contracts and relaxes to pump blood around your body.”
- Thematic Analysis: The main topic or focus is “Cardiac muscle” and how it works to keep your heart beating.
Isn’t it amazing that our heart muscle works all by itself to keep us alive? Imagine if you had to remind your heart to beat every time—phew, you’d be so busy! What other things in your body do you think work without you having to think about them?
Lesson Summary
Okay, let’s quickly review what we’ve learned in this lesson about your muscles.
The muscles of your body make up your muscular system. Skeletal muscles are sometimes called voluntary muscles because you choose to move them. Smooth muscles in your organs and cardiac muscle in your heart are involuntary muscles. Think about this next time you’re kicking a ball toward a goal.