Chapter 9: Muscles and Muscle Tissue. 2 Governor Arnold Schwarzenegger.

Chapter 9:Muscles and Muscle

Tissue

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Governor Arnold Schwarzenegger

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Muscle Functions• Producing Movement• Maintaining Posture• Stabilizing Joints• Generating Heat

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3 Types of Muscle•Skeletal Muscle

•Cardiac Muscle

•Smooth Muscle

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Skeletal Muscle•attaches to

bones which form levers

•used for bodily movement

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Cardiac Muscle• forms the

heart• used to pump

blood through circulatory system

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Smooth Muscle• lines gut and blood

vessels• controls diameter

of these tubes and in gut helps to propel the digested food

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 Property SkeletalMuscle

 CardiacMuscle

 SmoothMuscle

 Striations?  Yes Yes  No

 Nuclei per Cell  Many  Single  Single

 Cells Connected byIntercalated

Discs or Gap Junctions?

 No  Yes  Yes

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 Relative Speed of Contraction

Fast   Intermediate  Slow

 Voluntary Control?

Yes  No No

 Control of Contraction

 Nerves

 Beats spontaneously

but modulated by nerves

 NervesHormones

Stretch

 Property SkeletalMuscle

 CardiacMuscle

 SmoothMuscle

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Muscle cells• Large, long cells called FIBERS • Contain two types of proteins--actin

and myosin• Excitable (irritable), contractile,

extensible, and elastic • Myo-, mys, or Sarco code for muscle

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Skeletal Muscle Anatomy

•Rich blood supply to center of muscle, branch to capillaries sheathing cells

•Rich nerve supply, branching into each muscle, ending one branch to each muscle fiber

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Structure of Skeletal Muscle

• Cigar shaped, multinucleate cells • Packed with myofilaments made

of actin and myosin creating visible bands (striations)

• Varied length, may be over a foot long

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Structure cont.• Surrounded by dense, fibrous

Connective tissue (CT) sheaths• Endomysium around each fiber • Perimysium around bundles of

fibers (fascicles) • Epimysium around all fascicles

14Figure 6.1 Connective tissue wrappings of skeletal muscle.

© 2000  The Benjamin/Cummings Publishing Company

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Microscopic structure• Muscle fibers filled with Sarcoplasm

– Glycogen and myoglobin

• Nuclei pushed to the edge of sarcolemma by long protein strands that run length of the cell, myofibrils

• Composed of contractile units, sarcomeres, made of myofilaments

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Figure 6.3 Anatomy of a skeletal muscle cell (fiber). (a) A portion of a muscle fiber. One myofibril has been extended. (b) Enlarged view of a myofibril showing its banding pattern. (c) Enlarged view of one sarcomere (contractile unit) of a myofibril. (d) Structure of the thick and thin myofilaments found in the sarcomeres.

© 2000  The Benjamin/Cummings Publishing Company

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Myofilaments• Two types--actin and myosin -Filaments are clusters of actin and myosin • Actin forms thin filaments • Myosin forms thick filaments

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Sarcomere structure

• Alternating dark and light bands • Lateral dark bands--A-band • End in light I-bands, with Z-line in

center marking joint with next sarcomere on each side

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Muscle Contraction

• Sarcomere - basic unit of muscle contraction

• Skeletal and cardiac muscle are striated

• The striations are caused by alignment of bands: the most prominent are the A and I bands and the Z line

• The unit between 2 Z lines is called the sarcomere

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Muscle Contraction-Sarcomere

• In the A band the 2 proteins overlap • The I band contains only the actin protein

• When muscle contracts the sarcomere shortens and

the Z lines move closer together

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Muscle Contraction-relaxed state

• When Muscle Contracts Protein Filaments Slide Together

• Thin filaments: actin, attached to Z line, found in both A and I bands

• Thick filaments: myosin, found in A band • Relaxed state:

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Muscle Contraction-Contracted state

• When muscle contracts the actin filaments slide into the A band, overlapping with myosin

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Muscle Contraction-Contracted state

• Notice what happens when muscle contracts: – a) the Z lines move closer together – b) the I band becomes shorter – c) the A band stays at the same length

• This is called the "sliding filament" model of muscle contraction

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Muscle Contraction-Crossbridge

• The filaments slide together because myosin attaches to actin and pulls on it

• myosin head(H) attaches to actin filament (A), forming a crossbridge

• After the crossbridge is formed the myosin head bends, pulling on the actin filaments and causing them to slide:

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Actin Molecule

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