Skeletal, Muscular, and Integumentary Systems Section 3

Bellringer

Alternately bend and stretch your legs while feeling the muscles in the front and the back.

What do you feel when the leg is straightened and what you feel when the leg is bent?

Skeletal, Muscular, and Integumentary Systems Section 3

Key Ideas

• What types of muscles are in the body?• How do muscle pairs work? • What are skeletal muscles made of?• How do muscles contract?• How do muscles produce energy for movement?• What diseases or conditions affect muscles?

Skeletal, Muscular, and Integumentary Systems Section 3

Three Types of Muscle Tissues (p. 848)

1. Skeletal-- designed to pullpull on bonesA. Voluntary -- you can control; learned actionsB. Attached to bonesC. “Striated” -- long fibers with perpendicular stripes

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Skeletal, Muscular, and Integumentary Systems Section 3

Types of Muscles, continued

2. Smooth muscle• Surrounds hollow organs (blood

vessels, digestive organs)• Involuntary

3. Cardiac muscle -- in heart only• Involuntary muscle• “Self-contracting”

-- no nerve signal needed

Skeletal, Muscular, and Integumentary Systems Section 3

Movement and Muscle (p. 849)

• Tendons attach muscles to two bones.– “Origin” -- connects to bone that doesn’t

move– “Insertion” -- connects to bone that moves

• Muscles work in pairs– Work oppositely (one contracts while the

other relaxes)– Flexor muscles cause a joint to bend.– Extensor muscles causes a joint to

straighten.

• Warning! Flexors can extend, and Extensors can flex

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Skeletal, Muscular, and Integumentary Systems Section 3

Muscle Pairs

• Where is the origin?• Where is the insertion?• Which is the flexor

muscle?• Which is the extensor

muscle?

Skeletal, Muscular, and Integumentary Systems Section 3

Structure of Muscles

• Muscle cells are called muscle fibers.

• A group of parallel muscle fibers is called a bundle.

• A group of bundles makes up a muscle.

fibers bundles muscles

Skeletal, Muscular, and Integumentary Systems Section 3

Structure of Muscles, cont.

• Muscle cells are made of myofibrils.

• Myofibrils are made of sarcomeres linked end-to-end.

• Sarcomeres make muscles looked striped.

• Sarcomeres contain myosin and actin proteins.

Skeletal, Muscular, and Integumentary Systems Section 3

Muscle Contraction

Skeletal, Muscular, and Integumentary Systems Section 3

Steps of Muscle Contraction

1. Nerve signal reaches relaxed muscle fiber

2. Sarcomeres absorb calcium

3. Myosin and actin pull on each other sarcomere shortens whole muscle contracts

4. ATP supplies energy for fiber to keep pulling