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The basic element of the nervous system is the nerve cell, or neuron. In combination, neurons form nerves, fibers that transmit impulses throughout the body. A protective covering of myelin, a fatty substance, insulates parts of the fibers.

The action of nerve cells is both electrical and chemical. At the ends of each nerve cell there are specialized regions called synaptic terminals, which contain large numbers of tiny membranous sacs that hold neurotransmitter chemicals. These chemicals transmit nerve impulses from one nerve cell to another. After an electrical nerve impulse has traveled along a neuron, it reaches the terminal and stimulates the release of neurotransmitters from their sacs.

The neurotransmitters travel across the synapse (the junction between the neighboring neurons) and stimulate the production of an electrical charge, which carries the nerve impulse forward. This process is repeated over and over again until a muscle is moved or relaxed or a sensory impression is noted by the brain. These electrochemical events can be considered the "language" of the nervous system, by which information is transmitted from one part of the body to another.

There are two major divisions of the nervous system: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and the spinal cord. The brain lies within the skull and governs body functions by sending and receiving messages through the spinal cord. Protecting the brain and spinal cord are bones, layers of tissue, and cerebrospinal fluid.

Once messages leave the central nervous system, they are carried by the peripheral nervous system. The peripheral system includes the cranial nerves (nerves branching from the brain) and the spinal nerves (nerves branching from the spinal cord). These nerves convey sensory messages from receptor cells in the body to the central nervous system. They also transport motor impulses from the central system out to the body, where muscles and glands can respond to the impulses.

The autonomic nervous system, which is part of the peripheral nervous system, reg-ulates all activity that is involuntary but necessary for life, including activity of the internal organs and glands.

Working together, these divisions coordinate adjustment and reaction of the body to internal and external environmental conditions.

Now that we've covered the nervous system, let's discuss the brain, cerebrospinal fluid, and other related elements in the next section.

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The basic element of the nervous system is the nerve cell, or neuron. In combination, neurons form nerves, fibers that transmit impulses throughout the body. A protective covering of myelin, a fatty substance, insulates parts of the fibers. The action of nerve cells is both electrical and chemical.

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How do you remember the way to your friend's house? Why do your eyes blink without you ever thinking about it? Where do dreams come from? Your brain is in charge of these things and a lot more.

In fact, your brain is the boss of your body. It runs the show and controls just about everything you do, even when you're asleep. Not bad for something that looks like a big, wrinkly, gray sponge.

Your brain has many different parts that work together. We're going to talk about these five parts, which are key players on the brain team:

1. cerebrum (say: suh-REE-brum)

2. cerebellum (say: sair-uh-BELL-um)

3. brain stem

4. pituitary (say: puh-TOO-uh-ter-ee) gland

5. hypothalamus (say: hy-po-THAL-uh-mus)

The Biggest Part: the Cerebrum

The biggest part of the brain is the cerebrum. The cerebrum makes up 85% of the brain's weight, and it's easy to see why. The cerebrum is the thinking part of the brain and it controls your voluntary muscles - the ones that move when you want them to. So you can't dance - or kick a soccer ball - without your cerebrum.

When you're thinking hard, you're using your cerebrum. You need it to solve math problems, figure out a video game, and draw a picture. Your memory lives in the cerebrum - both short-term memory (what you ate for dinner last night) and long-term memory (the name of that roller-coaster you rode on two summers ago). The cerebrum also helps you reason, like when you figure out that you'd better do your homework now because your mom is taking you to a movie later.

The cerebrum has two halves, with one on either side of the head. Scientists think that the right half helps you think about abstract things like music, colors, and shapes. The left half is said to be more analytical, helping you with math, logic, and speech. Scientists do know for sure that the right half of the cerebrum controls the left side of your body, and the left half controls the right side.

The Cerebellum's Balancing Act

Next up is the cerebellum. The cerebellum is at the back of the brain, below the cerebrum. It's a lot smaller than the cerebrum at only 1/8 of its size. But it's a very important part of the brain. It controls balance, movement, and coordination (how your muscles work together).

Because of your cerebellum, you can stand upright, keep your balance, and move around. Think about a surfer riding the waves on his board. What does he need most to stay balanced? The best surfboard? The coolest wetsuit? Nope - he needs his cerebellum!

Brain Stem Keeps You Breathing - and More

Another brain part that's small but mighty is the brain stem. The brain stem sits beneath the cerebrum and in front of the cerebellum. It connects the rest of the brain to the spinal cord, which runs down your neck and back. The brain stem is in charge of all the functions your body needs to stay alive, like breathing air, digesting food, and circulating blood.

Part of the brain stem's job is to control your involuntary muscles - the ones that work automatically, without you even thinking about it. There are involuntary muscles in the heart and stomach, and it's the brain stem that tells your heart to pump more blood when you're biking or your stomach to start digesting your lunch. The brain stem also sorts through the millions of messages that the brain and the rest of the body send back and forth. Whew! It's a big job being the brain's secretary!

Pituitary Gland Controls Growth

The pituitary gland is very small - only about the size of a pea! Its job is to produce and release hormones into your body. If your clothes from last year are too small, it's because your pituitary gland released special hormones that made you grow. This gland is a big player in puberty too. This is the time when boys' and girls' bodies go through major changes as they slowly become men and women, all thanks to hormones released by the pituitary gland.

This little gland also plays a role with lots of other hormones, like ones that control the amount of sugars and water in your body. And it helps keep your metabolism (say: muh-TA-buh-lih-zum) going. Your metabolism is everything that goes on in your body to keep it alive and growing and supplied with energy, like breathing, digesting food, and moving your blood around.

Hypothalamus Controls Temperature

The hypothalamus is like your brain's inner thermostat (that little box on the wall that controls the heat in your house). The hypothalamus knows what temperature your body should be (about 98.6°F or 37°C). If your body is too hot, the hypothalamus tells it to sweat. If you're too cold, the hypothalamus gets you shivering. Both shivering and sweating are attempts to get your body's temperature back where it needs to be.

You Have Some Nerve!

So the brain is boss, but it can't do it alone. It needs some nerves - actually a lot of them. And it needs the spinal cord, which is a long bundle of nerves inside your spinal column, the vertebrae that protect it. It's the spinal cord and nerves - known as the nervous system - that let messages flow back and forth between the brain and body.

If a spiky cactus falls off a shelf headed right for your best friend, your nerves and brain communicate so that you jump up and yell for your friend to get out of the way. If you're really good, maybe you're able to catch the plant before it hits your friend!

But you might wonder about these nerves, which you can't see without a microscope. What are they anyway? The nervous system is made up of millions and millions of neurons (say: NUR-onz), which are microscopic cells. Each neuron has tiny branches coming off it that let it connect to many other neurons.

When you were born, your brain came with all the neurons it will ever have, but many of them were not connected to each other. When you learn things, the messages travel from one neuron to another, over and over. Eventually, the brain starts to create connections (or pathways) between the neurons, so things become easier and you can do them better and better.

Think back to the first time you rode a bike. Your brain had to think about pedaling, staying balanced, steering with the handlebars, watching the road, and maybe even hitting the brakes - all at once. Hard work, right? But eventually, as you got more practice, the neurons sent messages back and forth until a pathway was created in your brain. Now you can ride your bike without thinking about it because the neurons have successfully created a "bike riding" pathway.

Emotion Location

With all the other things it does, is it any surprise that the brain runs your emotions? Maybe you got the exact toy you wanted for your birthday and you were really happy. Or your friend is sick and you feel sad. Or your little brother messed up your room, so you're really angry! Where do those feelings come from? Your brain, of course.

Your brain has a little bunch of cells on each side called the amygdala (say: uh-MIG-duh-luh). The word amygdala is Latin for almond, and that's what this area looks like. Scientists believe that the amygdala is responsible for emotion. It's normal to feel all different kinds of emotions, good and bad. Sometimes you might feel a little sad, and other times you might feel scared, or silly, or glad.

Be Good to Your Brain

So what can you do for your brain? Plenty.

Eat healthy foods. They contain potassium and calcium, two minerals that are important for the nervous system.

Get a lot of playtime (exercise).

Wear a helmet when you ride your bike or play other sports that require head protection.

Don't drink alcohol, take drugs, or use tobacco.

Use your brain by doing challenging activities, such as puzzles, reading, playing music, making art, or anything else that gives your brain a workout!

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How do you remember the way to your friend's house? Why do your eyes blink without you ever thinking about it? Where do dreams come from? Your brain is in charge of these things and a lot more. In fact, your brain is the boss of your body.

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Information about the human brain, the parts and how they work for kids k - 6. Includes how the emotions work.

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There are very few things in this world that you can honestly say you can't live without. Your digestive system is definitely one of those things. Simply put, this system is in charge of absorbing and transporting all the nutrients your body needs in order to thrive -- and it gets rid of all the waste the body doesn't need. As you read this article, your digestive system is chugging along, all its parts working together as a team (well, at least we hope it is).

This digestive team is composed of a bunch of hollow passageways that start at your mouth and end at your anus. These organs are aided by a couple of friends, the liver and the pancreas, with a few cameos from the brain and nerves.

Everything you eat takes a long journey through your body -- if stretched out, the system would measure about 30 feet, most of it the winding intestines [source: Kids Health: Digestive System]. And the entire ride is usually over in a matter of hours. Of course, there can be bumps in the digestive road, but we'll get to those later.

So how exactly do all of these organs work together? Let's begin by following the topsy-turvy journey of a ham and cheese sandwich.

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There are very few things in this world that you can honestly say you can't live without. Your digestive system is definitely one of those things. Simply put, this system is in charge of absorbing and transporting all the nutrients your body needs in order to thrive -- and it gets rid of all the waste the body doesn't need.

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The human body is an incredible machine. It runs so well most of the time that we don't have to pay much attention to any of the life-sustaining systems that are in motion around the clock, humming along without our mindful involvement.

Right now, your body is performing vital and complicated tasks nearly too numerous to comprehend. Fortunately, our bodies don't demand our comprehension in order to pump the heart, oxygenate blood, regulate hormone production, interpret sensory data and carry out every other process that keeps our biological boats afloat.

In this article, we'll discuss one of the systems that makes life possible: the skeletal system.

Bones prevent you from puddling on the floor in the form of a jellyfish, but what else do they do? Bones rebuild themselves, they produce blood cells, they protect our brains and our organs, they provide a giant system of levers that allow us to move ourselves around, and bones also help maintain a steady amount of calcium in our bodies.

And, even if you never make your mark on the world (or in the history books), your bones will stick around long after you have otherwise vanished to declare to the world: "These skeletal remains once supported skin and tissue and organs! This person once existed!" And as the construction crew that unearthed your bones reels back in horror, every life choice you ever made will seem -- if but for a moment before you are shoveled into a Dumpster -- very much worthwhile.

Before we leave behind our skeletal remains to freak out future generations, we should first learn some basics about bones: What are bones made of? What happens when they break? And just how many of them do you have, anyway?

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If you didn't have bones, you'd be puddled on the floor like a jellyfish with skin -- and your ability to impress people on the dancefloor would be severely compromised. What else are skeletons for, besides decorating your house for Halloween?

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Muscles are one of those things that most of us take completely for granted, but they are incredibly important for two key reasons:

Muscles are the "engine" that your body uses to propel itself. Although they work differently than a car engine or an electric motor, muscles do the same thing -- they turn energy into motion.

It would be impossible for you to do anything without your muscles. Absolutely everything that you conceive of with your brain is expressed as muscular motion. The only ways for you to express an idea are with the muscles of your larynx, mouth and tongue (spoken words), with the muscles of your fingers (written words or "talking with your hands") or with the skeletal muscles (body language, dancing, running, building or fighting, to name a few).

Because muscles are so crucial to any animal, they are incredibly sophisticated. They are efficient at turning fuel into motion, they are long-lasting, they are self-healing and they are able to grow stronger with practice. They do everything from allowing you to walk to keeping your blood flowing!

When most people think of "muscles," they think about the muscles that we can see. For example, most of us know about the biceps muscles in our arms. But there are three unique kinds of muscle in any mammal's body:

Skeletal muscle is the type of muscle that we can see and feel. When a body builder works out to increase muscle mass, skeletal muscle is what is being exercised. Skeletal muscles attach to the skeleton and come in pairs -- one muscle to move the bone in one direction and another to move it back the other way. These muscles usually contract voluntarily, meaning that you think about contracting them and your nervous system tells them to do so. They can do a short, single contraction (twitch) or a long, sustained contraction (tetanus).

Smooth muscle is found in your digestive system, blood vessels, bladder, airways and, in a female, the uterus. Smooth muscle has the ability to stretch and maintain tension for long periods of time. It contracts involuntarily, meaning that you do not have to think about contracting it because your nervous system controls it automatically. For example, your stomach and intestines do their muscular thing all day long, and, for the most part, you never know what's going on in there.

Cardiac muscle is found only in your heart, and its big features are endurance and consistency. It can stretch in a limited way, like smooth muscle, and contract with the force of a skeletal muscle. It is a twitch muscle only and contracts involuntarily.

In this article, we will look at the different types of muscles in your body and the amazing technology that allows them to work so well. From here on, we will focus on skeletal muscle. The basic molecular processes are the same in all three types.

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Muscles are one of those things that most of us take completely for granted, but they are incredibly important for two key reasons: Muscles are the "engine" that your body uses to propel itself. Although they work differently than a car engine or an electric motor, muscles do the same thing -- they turn energy into motion.

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You breathe in and out anywhere from 15 to 25 times per minute without even thinking about it. When you exercise, your breathing rate goes up -- again, without you thinking about it. You breathe so regularly that it is easy to take your lungs for granted. You can't even stop yourself from breathing if you try!

Your lungs are complex organs, but what they do is take a gas that your body needs to get rid of (carbon dioxide) and exchange it for a gas that your body can use (oxygen).

In this article, we will take a close look at how your lungs work and how they keep your body's cells supplied with oxygen and get rid of the carbon dioxide waste. We will explain some of the conditions and diseases that make breathing harder and cause the lungs
to fail. We will also explain why you can't hold your breath for a long
time and why you cough or hiccup.

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You breathe in and out anywhere from 15 to 25 times per minute without even thinking about it -- it just happens naturally. Learn all about your lungs, various conditions and diseases, and what makes the breath of life so crucial.

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Muscle Facts for Kids

Learn some fun muscle facts for kids. The muscles in our body are responsible for keeping our heart beating and for all our physical movements.

How many muscles do we have? What are the different types of muscles? What are the strongest muscles in our body? Read on and enjoy these interesting facts about our muscles.

Muscle is a soft tissue in the body of humans and animals. Its main purpose is to produce force and motion.

Muscles are responsible for maintaining posture, physical movement (sitting, walking, eating, etc), and movement of internal organs (such as keeping the heart pumping to circulate blood and moving food through the digestive system).

The word muscle is derived from the Latin term musculus, meaning "little mouse". This Latin term could be due to the shape of some muscles or because muscles contracting under the skin can look like a mouse moving under a rug.

Tendons connect our soft contracting muscle to our hard bones.

There are around 650 skeletal muscles in the human body.

There are three types of muscle, skeletal, cardiac, and smooth.

Skeletal muscles (or striated) are voluntary muscles that control nearly every action a person intentionally performs. Tendons attach the muscle to two bones across a joint, as one muscle contracts the other relaxes which moves the bones.

Skeletal muscle can be further divided into two types, slow twitch and fast twitch.

Slow twitch (Type I) muscle contain proteins that give it a rich red color. This muscle carries more oxygen efficiently and using fats, proteins or carbs as energy slow twitch muscle fibers contract over a long period of time.

Therefore type I muscle fiber works well for aerobic sports such as long distance running and cycling.

Fast twitch (Type II) muscle is whiter in color as it has less myoglobin (a oxygen carrying protein). Fast twitch fibers contract quickly and powerfully, however they fatigue rapidly.

Therefore type II muscle fiber is useful for anaerobic exercise such as sprinting or for strength sports like weightlifting.

Smooth muscle (or visceral) is involuntary, its not controlled by our conscious mind. It is found on the walls of many organs and structures such as the esophagus, stomach, intestines, bladder, and blood vessels. Smooth muscles contract to move substances such as food through the organ.

Cardiac muscle is also an involuntary muscle. It is only found in the heart and is responsible for keeping the heart pumping.

Muscle makes up around half of the total human body weight. Muscle tissue is also around 15% denser than fat tissue.

It takes 17 muscles in the face for us to smile and 43 muscles to frown.

If muscle strength is regarded as the ability to use force on something then the jaw muscle (masseter) is the strongest in the body.

The strongest muscles in relation to the job they have to do is the external muscles of the eye which are large and about 100 times stronger than they need to be in relation to the small size and weight of the eyeball.

The tongue has 8 muscles, so is technically not the strongest muscle in the body.

The heart cardiac muscle does the most work of any muscle over a lifetime.

Cerebral palsy is a disorder that affects balance and motor functions, while muscular dystrophy is a genetic disease that damages muscle fibers.

Muscle memory is created by practising an action over and over again. Our muscles fine tune themselves, becoming more precise and exact in what they do. So practice is very important when learning a sport!!

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Fun Muscle Facts for Kids - Interesting Information about Human Muscles

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Muscle Facts for Kids Learn some fun muscle facts for kids. The muscles in our body are responsible for keeping our heart beating and for all our physical movements. How many muscles do we have? What are the different types of muscles? What are the strongest muscles in our body?

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Human Circulatory System Video - Heart, Arteries, Capillaries, Blood & Veins

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Learn how the heart, arteries, capillaries and veins work together to pump oxygen rich blood around the human body.

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Human Respiratory System Video - Breathing, Lungs, Oxygen, Diaphragm

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See how the diaphragm facilitates the breathing process through inhalation and exhalation, learn how oxygen from the air is exchanged for carbon dioxide produced by the body, understand the important role the lungs play and more.

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Digestive System Facts

Learn some interesting digestive system facts for kids. The digestive system of humans and other animals plays a vital role in how the body processes the food we eat.

There are many components of the digestive system from saliva and chewing food through to the stomach and intestines. Read on to find out how the digestive system works, why we get that grumbling sound in the pit of our stomachs and many other interesting facts.

The digestive system is responsible for breaking down food we eat into smaller components so that nutrients can be easily absorbed by the body and the waste discarded.

There are two types of digestion. Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces through, chewing (mastication). While chemical digestion uses enzymes to break down this food mass further into small molecules which the body can separate and use.

Saliva in our mouths plays a key role in initial digestion by moistening the food to help with the mechanical chewing and swallowing process. Saliva also contains an enzyme which starts the chemical digestion of starchy foods.

Our salivary glands produce around 1.5 litres of saliva each day!

Bolus is the name of the small round slurry mass produced for swallowing as a result of chewing and starch digestion.

The pharynx, at the back of the throat, has a flap of tissue called the epiglottis that closes during swallowing to prevent food going down the trachea (windpipe).

Once swallowed, bolus (food) travels down through the esophagus to the stomach, taking about 7 seconds to get there.

Muscles in the esophagus tighten and relax to create a wave-like process called peristalsis which pushes food down the small tube, which is why your food never falls back out if you happen to be eating and swallowing upside down!

Enzymes called proteases break down proteins within the stomach and small intestine. While in saliva, amylases break down carbohydrates and lipases break down fats.

The adult stomach has a very small volume when empty but can expand to hold up to 1.5 litres of food when full.

The inner wall of the stomach secretes hydrochloric acid to help kill bacteria and, along with proteases enzymes, aids in the digestion of food. To protect itself from the corrosive acid, the stomach lining must create a thick coating of mucus.

Stomach rumblings (borborygmi) are caused by wave-like muscular contractions (peristalsis) at the walls of the stomach and small intestine. These are normal digestion movements, however the process is louder and more noticeable when the stomach is empty as the sound is not muffled.

Some animals such as cows, giraffes and deer have stomachs with multiple compartments (not multiple stomachs as is commonly believed). While others like seahorses, lungfishes and platypuses have no stomachs at all.

The small intestine is composed of a duodenum, jejunum, and ileum.

Most of the digestion and absorption of food nutrients actually takes place in the small intestine. The stomach passes on a thick liquid called chyme and enzymes continue to break this down in the small intestine which absorbs the nutrients into the bloodstream.

The pancreas secretes enzymes for use by the small intestine.

On average, the human adult male's small intestine is 6.9 m (22 ft 6 in) long, and the female's 7.1 m (23 ft 4 in).

The large intestine includes the cecum, appendix, colon, and rectum. It is the final part of the digestive system. It absorbs water from the remaining indigestible food matter, and passes any un-needed waste from the body.

The large intestine is approximately 1.5 m (4.9 ft) long.

The liver produces bile for the digestive system and processes the nutrients.

The gall bladder stores the bile used to break down dietary fat.

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Digestive System Facts for Kids - Stomach, Intestines, Saliva, Esophagus

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Digestive System Facts Learn some interesting digestive system facts for kids. The digestive system of humans and other animals plays a vital role in how the body processes the food we eat. There are many components of the digestive system from saliva and chewing food through to the stomach and intestines.

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Did you give your friends valentines and little heart-shaped candies on Valentine's Day? Do you ever cross your heart when making a promise that you really, really mean? Or turn on the radio to hear a guy singing about his broken heart?

We see and hear about hearts everywhere. A long time ago, people even thought that their emotions came from their hearts, maybe because the heart beats faster when a person is scared or excited. Now we know that emotions come from the brain, and in this case, the brain tells the heart to speed up. So what's the heart up to, then? How does it keep busy? What does it look like? Let's find out.

Working That Muscle

Your heart is really a muscle. It's located a little to the left of the middle of your chest, and it's about the size of your fist. There are lots of muscles all over your body - in your arms, in your legs, in your back, even in your behind.

But the heart muscle is special because of what it does. The heart sends blood around your body. The blood provides your body with the oxygen and nutrients it needs. It also carries away waste.

Your heart is sort of like a pump, or two pumps in one. The right side of your heart receives blood from the body and pumps it to the lungs. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body.

We Got the Beat

How does the heart beat? Before each beat, your heart fills with blood. Then its muscle contracts to squirt the blood along. When the heart contracts, it squeezes - try squeezing your hand into a fist. That's sort of like what your heart does so it can squirt out the blood. Your heart does this all day and all night, all the time. The heart is one hard worker!

Heart Parts

The heart is made up of four different blood-filled areas, and each of these areas is called a chamber. There are two chambers on each side of the heart. One chamber is on the top and one chamber is on the bottom. The two chambers on top are called the atria (say: AY-tree-uh). If you're talking only about one, call it an atrium. The atria are the chambers that fill with the blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium.

The two chambers on the bottom are called the ventricles (say: VEN-trih-kulz). The heart has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and lungs. Running down the middle of the heart is a thick wall of muscle called the septum (say: SEP-tum). The septum's job is to separate the left side and the right side of the heart.

The atria and ventricles work as a team - the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles are squeezing, the atria refill and get ready for the next contraction. So when the blood gets pumped, how does it know which way to go?

Well, your blood relies on four special valves inside the heart. A valve lets something in and keeps it there by closing - think of walking through a door. The door shuts behind you and keeps you from going backward.

Two of the heart valves are the mitral (say: MY-trul) valve and the tricuspid (say: try-KUS-pid) valve. They let blood flow from the atria to the ventricles. The other two are called the aortic (say: ay-OR-tik) valve and pulmonary (say: PUL-muh-ner-ee) valve, and they're in charge of controlling the flow as the blood leaves the heart. These valves all work to keep the blood flowing forward. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward.

It's Great to Circulate

You probably guessed that the blood just doesn't slosh around your body once it leaves the heart. It moves through many tubes called arteries and veins, which together are called blood vessels. These blood vessels are attached to the heart. The blood vessels that carry blood away from the heart are called arteries. The ones that carry blood back to the heart are called veins.

The movement of the blood through the heart and around the body is called circulation (say: sur-kyoo-LAY-shun), and your heart is really good at it - it takes less than 60 seconds to pump blood to every cell in your body.

Your body needs this steady supply of blood to keep it working right. Blood delivers oxygen to all the body's cells. To stay alive, a person needs healthy, living cells. Without oxygen, these cells would die. If that oxygen-rich blood doesn't circulate as it should, a person could die.

The left side of your heart sends that oxygen-rich blood out to the body. The body takes the oxygen out of the blood and uses it in your body's cells. When the cells use the oxygen, they make carbon dioxide and other stuff that gets carried away by the blood. It's like the blood delivers lunch to the cells and then has to pick up the trash!

The returning blood enters the right side of the heart. The right ventricle pumps the blood to the lungs for a little freshening up. In the lungs, carbon dioxide is removed from the blood and sent out of the body when we exhale. What's next? An inhale, of course, and a fresh breath of oxygen that can enter the blood to start the process again. And remember, it all happens in about a minute!

Listen to the Lub-Dub

When you go for a checkup, your doctor uses a stethoscope to listen carefully to your heart. A healthy heart makes a lub-dub sound with each beat. This sound comes from the valves shutting on the blood inside the heart.

The first sound (the lub) happens when the mitral and tricuspid valves close. The next sound (the dub) happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart. Next time you go to the doctor, ask if you can listen to the lub-dub, too.

Pretty Cool - It's My Pulse!

Even though your heart is inside you, there is a cool way to know it's working from the outside. It's your pulse. You can find your pulse by lightly pressing on the skin anywhere there's a large artery running just beneath your skin. Two good places to find it are on the side of your neck and the inside of your wrist, just below the thumb.

You'll know that you've found your pulse when you can feel a small beat under your skin. Each beat is caused by the contraction (squeezing) of your heart. If you want to find out what your heart rate is, use a watch with a second hand and count how many beats you feel in 1 minute. When you are resting, you will probably feel between 70 and 100 beats per minute.

When you run around a lot, your body needs a lot more oxygen-filled blood. Your heart pumps faster to supply the oxygen-filled blood that your body needs. You may even feel your heart pounding in your chest. Try running in place or jumping rope for a few minutes and taking your pulse again - now how many beats do you count in 1 minute?

Keep Your Heart Happy

Most kids are born with a healthy heart and it's important to keep yours in good shape. Here are some things that you can do to help keep your heart happy:

Remember that your heart is a muscle. If you want it to be strong, you need to exercise it. How do you do it? By being active in a way that gets you huffing and puffing, like jumping rope, dancing, or playing basketball. Try to be active every day for at least 30 minutes! An hour would be even better for your heart!

Eat a variety of healthy foods and avoid foods high in unhealthy fats, such as saturated fats and trans fats (reading the labels on foods can help you figure out if your favorite snacks contain these unhealthy ingredients).

Try to eat at least five servings of fruits and vegetables each day.

Avoid sugary soft drinks and fruit drinks.

Don't smoke. It can damage the heart and blood vessels.

So now you know that your heart doesn't look like a valentine, but it sure deserves to be loved for all the work it does. It started pumping blood before you were born and will continue pumping throughout your whole life.

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Did you give your friends valentines and little heart-shaped candies on Valentine's Day? Do you ever cross your heart when making a promise that you really, really mean? Or turn on the radio to hear a guy singing about his broken heart? We see and hear about hearts everywhere.

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The digestive system breaks down the food you eat. Learn how in this article for kids.

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Where would you be without your bones? Learn more about the skeletal system in this article for kids.

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What's something kids are doing all day, every day? Breathing! Your lungs are large and in charge of breathing, so read all about them in this article.

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What Do Muscles Do?

Did you know you have more than 600 muscles in your body? They do everything from pumping blood throughout your body to helping you lift your heavy backpack. You control some of your muscles, while others - like your heart - do their jobs without you thinking about them at all.

Muscles are all made of the same material, a type of elastic tissue (sort of like the material in a rubber band). Thousands, or even tens of thousands, of small fibers make up each muscle.

What Are the Three Types of Muscles?

You have three different types of muscles in your body:

smooth muscle

cardiac (say: KAR-dee-ak) muscle, and

skeletal (say: SKEL-uh-tul) muscle

What Are Smooth Muscles?

Smooth muscles - sometimes also called involuntary muscles - are usually in sheets, or layers, with one layer of muscle behind the other. You can't control this type of muscle. Your brain and body tell these muscles what to do without you even thinking about it. You can't use your smooth muscles to make a muscle in your arm or jump into the air.

But smooth muscles are at work all over your body. In your stomach and digestive system, they contract (tighten up) and relax to allow food to make its journey through the body. Your smooth muscles come in handy if you're sick and you need to throw up. The muscles push the food back out of the stomach so it comes up through the esophagus (say: ih-SAH-fuh-gus) and out of the mouth.

Smooth muscles are also found in your bladder. When they're relaxed, they allow you to hold in urine (pee) until you can get to the bathroom. Then they contract so that you can push the urine out. These muscles are also in a woman's uterus, which is where a baby develops. There they help to push the baby out of the mother's body when it's time to be born.

You'll find smooth muscles at work behind the scenes in your eyes, too. These muscles keep the eyes focused.

What's the Cardiac (Heart) Muscle?

The muscle that makes up the heart is called cardiac muscle. It is also known as the myocardium (say: my-uh-KAR-dee-um). The thick muscles of the heart contract to pump blood out and then relax to let blood back in after it has circulated through the body.

Just like smooth muscle, cardiac muscle works all by itself with no help from you. A special group of cells within the heart are known as the pacemaker of the heart because it controls the heartbeat.

What Are the Skeletal (Striated) Muscles?

Now, let's talk about the kind of muscle you think of when we say "muscle" - the ones that show how strong you are and let you boot a soccer ball into the goal. These are your skeletal muscles - sometimes called striated (say: STRY-ay-tud) muscle because the light and dark parts of the muscle fibers make them look striped (striated is a fancy word meaning striped).

Skeletal muscles are voluntary muscles, which means you can control what they do. Your leg won't bend to kick the soccer ball unless you want it to. These muscles help to make up the musculoskeletal (say: mus-kyuh-low-SKEL-uh-tul) system - the combination of your muscles and your skeleton, or bones.

Together, the skeletal muscles work with your bones to give your body power and strength. In most cases, a skeletal muscle is attached to one end of a bone. It stretches all the way across a joint (the place where two bones meet) and then attaches again to another bone.

What Are Tendons?

Skeletal muscles are held to the bones with the help of tendons (say: TEN-dunz). Tendons are cords made of tough tissue, and they work as special connector pieces between bone and muscle. The tendons are attached so well that when you contract one of your muscles, the tendon and bone move along with it.

What Do Face Muscles Do?

You may not think of it as a muscular body part, but your face has plenty of muscles. You can check them out next time you look in the mirror. Facial muscles don't all attach directly to bone like they do in the rest of the body. Instead, many of them attach under the skin. This allows you to contract your facial muscles just a tiny bit and make dozens of different kinds of faces. Even the smallest movement can turn a smile into a frown. You can raise your eyebrow to look surprised or wiggle your nose.

And while you're looking at your face, don't pass over your tongue - a muscle that's attached only at one end! Your tongue is actually made of a group of muscles that work together to allow you to talk and help you chew food. Stick out your tongue and wiggle it around to see those muscles at work.

What Are Some Major Skeletal Muscles?

Skeletal muscles come in many different sizes and shapes to allow them to do many types of jobs. Some of the biggest and most powerful muscles are your calf and thigh muscles. They give your body the power it needs to lift and push things. Muscles in your neck and the top part of your back aren't as large, but they are capable of some pretty amazing things: Try rotating your head around, back and forth, and up and down to feel the power of the muscles in your neck. These muscles also hold your head high.

Because there are so many skeletal muscles in your body, we can't list them all here. But here are a few of the major ones:

What's the Deltoid Muscle?

In each of your shoulders is a deltoid (say: DEL-toyd) muscle. Your deltoid muscles help you move your shoulders every which way - from swinging a softball bat to shrugging your shoulders when you're not sure of an answer.

What Are the Pectoralis Muscles (Pecs)?

The pectoralis (say: pek-tuh-RAH-lus) muscles are found on each side of your upper chest. These are usually called pectorals (say: PEK-tuh-rulz), or pecs, for short. When many boys hit puberty, their pectoral muscles become larger. Many athletes and bodybuilders have large pecs, too.

What Are the Rectus Abdominus Muscles (Abs)?

Below these pectorals, down under your ribcage, are your rectus abdominus (say: REK-tus ab-DAHM-uh-nus) muscles, or abdominals (say: ab-DAHM-uh-nulz). They're often called abs for short.

What Is the Biceps Muscle?

When you make a muscle in your arm, you tense your biceps (say: BYE-seps) muscle. When you contract your biceps muscle, you can actually see it push up under your skin.

What Are the Quadriceps (Quads)?

Your quadriceps (say: KWAD-ruh-seps), or quads, are the muscles on the front of your thighs. Many people who run, bike, or play sports develop large, strong quads.

What Is the Gluteus Maximus?

And when it's time for you to take a seat? You'll be sitting on your gluteus maximus (say: GLOOT-ee-us MAK-suh-mus), the muscle that's under the skin and fat in your behind!

Date reviewed: January 2023

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Listen Play Stop Volume mp3 Settings Close Player Larger text size Large text size Regular text size Did you know you have more than 600 muscles in your body? They do everything from pumping blood throughout your body to helping you lift your heavy backpack.

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Information about the lungs and breathing (the respiratory system) for students K-6

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We couldn’t find the page you were looking for. This is either because:

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Information about the circulatory system for kids K - 6. All about the heart and blood.

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Information about the digestive system for kids K - 6. Includes information about the role of the liver and a video and an online game about the process of digestion

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Facts about muscles and how they work in the body for kids K - 6

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Information about the human skeleton, what our bones do and how to have healthy bones, for kids K - 6