Biology

PowerPoint® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community College

C H A P T E R

© 2013 Pearson Education, Inc.

© Annie Leibovitz/Contact Press Images

9

Muscles and Muscle Tissue: Part A

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Muscle Tissue

  • Nearly half of body’s mass
  • Transforms chemical energy (ATP) to directed mechanical energy  exerts force
  • Three types
  • Skeletal
  • Cardiac
  • Smooth
  • Myo, mys, and sarco – prefixes for muscle

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Types of Muscle Tissue

  • Skeletal muscles
  • Organs attached to bones and skin
  • Elongated cells called muscle fibers
  • Striated (striped)
  • Voluntary (i.e., conscious control)
  • Contract rapidly; tire easily; powerful
  • Require nervous system stimulation

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Types of Muscle Tissue

  • Cardiac muscle
  • Only in heart; bulk of heart walls
  • Striated
  • Can contract without nervous system stimulation
  • Involuntary

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Types of Muscle Tissue

  • Smooth muscle
  • In walls of hollow organs, e.g., stomach, urinary bladder, and airways
  • Not striated
  • Can contract without nervous system stimulation
  • Involuntary

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Table 9.3 Comparison of Skeletal, Cardiac, and Smooth Muscle (1 of 4)

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Special Characteristics of Muscle Tissue

  • Excitability (responsiveness): ability to receive and respond to stimuli
  • Contractility: ability to shorten forcibly when stimulated
  • Extensibility: ability to be stretched
  • Elasticity: ability to recoil to resting length

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Muscle Functions

  • Four important functions
  • Movement of bones or fluids (e.g., blood)
  • Maintaining posture and body position
  • Stabilizing joints
  • Heat generation (especially skeletal muscle)
  • Additional functions
  • Protects organs, forms valves, controls pupil size, causes “goosebumps”

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Skeletal Muscle

  • Connective tissue sheaths of skeletal muscle
  • Support cells; reinforce whole muscle
  • External to internal
  • Epimysium: dense irregular connective tissue surrounding entire muscle; may blend with fascia
  • Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers)
  • Endomysium: fine areolar connective tissue surrounding each muscle fiber

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Figure 9.1 Connective tissue sheaths of skeletal muscle: epimysium, perimysium, and endomysium.

Bone

Tendon

Epimysium

Epimysium

Perimysium

Endomysium

Muscle fiber

in middle of

a fascicle

Blood vessel

Perimysium

wrapping a fascicle

Endomysium

(between individual

muscle fibers)

Muscle

fiber

Perimysium

Fascicle

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Table 9.1 Structure and Organizational Levels of Skeletal Muscle (1 of 3)

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Table 9.1 Structure and Organizational Levels of Skeletal Muscle (2 of 3)

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Table 9.1 Structure and Organizational Levels of Skeletal Muscle (3 of 3)

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Microscopic Anatomy of a Skeletal Muscle Fiber

  • Long, cylindrical cell
  • 10 to 100 µm in diameter; up to 30 cm long
  • Multiple peripheral nuclei
  • Sarcolemma = plasma membrane
  • Sarcoplasm = cytoplasm
  • Glycosomes for glycogen storage, myoglobin for O2 storage
  • Modified structures: myofibrils, sarcoplasmic reticulum, and T tubules

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© 2013 Pearson Education, Inc.

Myofibrils

  • Densely packed, rodlike elements
  • ~80% of cell volume
  • Contain sarcomeres – contractile units
  • Sarcomeres contain myofilaments
  • Exhibit striations – perfectly aligned repeating series of dark A bands and light I bands

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Figure 9.2b Microscopic anatomy of a skeletal muscle fiber.

Diagram of part of a muscle fiber showing

the myofibrils. One myofibril extends from the cut end of the fiber.

Sarcolemma

Mitochondrion

Myofibril

Nucleus

Light

I band

Dark

A band

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© 2013 Pearson Education, Inc.

Striations

  • H zone: lighter region in midsection of dark A band where filaments do not overlap
  • M line: line of protein myomesin bisects H zone
  • Z disc (line): coin-shaped sheet of proteins on midline of light I band that anchors thin filaments and connects myofibrils to one another
  • Thick filaments: run entire length of an A band
  • Thin filaments: run length of I band and partway into A band
  • Sarcomere: region between two successive Z discs

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Sarcomere

  • Smallest contractile unit (functional unit) of muscle fiber
  • Align along myofibril like boxcars of train
  • Contains A band with ½ I band at each end
  • Composed of thick and thin myofilaments made of contractile proteins

© 2013 Pearson Education, Inc.

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© 2013 Pearson Education, Inc.

Figure 9.2c Microscopic anatomy of a skeletal muscle fiber.

Small part of one

myofibril

enlarged to show

the myofilaments

responsible for the

banding pattern.

Each sarcomere

extends from one Z

disc to the next.

Thin (actin)

filament

Z disc

H zone

Z disc

Thick

(myosin)

filament

I band

A band

I band

M line

Sarcomere

© 2013 Pearson Education, Inc.

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