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Body Lab 3-5 / Week 03 / Thursday
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Week 03 · Muscles

Thursday

Three kinds of muscle
// The pullers that move you
⏱ about 15 min

Thursday: Three Kinds of Muscle

Rocket sits very still. "I am resting every muscle," he says proudly.

Raven puts a hand on her chest. "What do you notice? Is your heart resting?"

Rocket feels a steady thump. "Oops! It is still going."

Nova hovers close. "Some muscles work without asking you first," she says. "How many kinds might there be?"

Three kinds

KindWhere it isDo you control it?
skeletal muscleattached to bones, like in arms and legsyes, it is voluntary
smooth musclewalls of the stomach, intestines and blood vesselsno, it is involuntary
cardiac musclethe heartno, it is involuntary

Skeletal muscle moves your bones when you choose to move.

Under a microscope, skeletal muscle looks striped.

Smooth muscle in the stomach and intestines squeezes to move food along.

Cardiac muscle is in the heart. It squeezes to pump blood out of the heart.

A part of the brain called the brain stem controls involuntary muscles.

WHICH KIND?
  • Read the question.
  • Tap your answer.
You kick a ball. Which kind of muscle did that?
Your stomach moves food along. Which kind of muscle?
Your heart beats all day and all night. Which kind of muscle?
What is the name for heart muscle?
WHY THIS EXERCISECardiac muscle is the muscle of the heart.
A muscle you control is called ____.
A muscle that works on its own is called ____.
StatementTrue or false?
You can choose to stop your heart muscle.?
Skeletal muscle looks striped under a microscope.?
Smooth muscle helps move food through the body.?
The brain stem controls involuntary muscles.?
WHY THIS EXERCISEHeart and smooth muscle are involuntary. Skeletal muscle is voluntary.

Muscles that do not tire

Skeletal muscles can contract quickly and powerfully. But they tire easily.

Smooth muscles contract more slowly. They do not tire easily.

That is why you need rests when you run, but your stomach keeps working.

TIRED OR NOT?
  • Read the question.
  • Tap your answer.
Which kind of muscle tires easily?
Which kind of muscle does not tire easily?
Try it
Sit still for ten seconds. Try to keep every arm and leg muscle relaxed.
Which muscles kept working anyway?
Think about your breathing and your heart.
FOOD ON THE MOVE
  • ?Food reaches the stomach.
  • ?Smooth muscle in the stomach wall squeezes.
  • ?Food moves on into the intestines.
  • ?Smooth muscle there keeps squeezing it along.
WHY THIS EXERCISESmooth muscle squeezes food along without you thinking about it.

Super sorting! Tomorrow we put muscles, tendons and bones together into one team.

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