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Chapter 12

BIOL 1344 Chapter Notes - Chapter 12: Skeletal Muscle, Myocyte, Broad Sheet Glass

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BIOL 1344
Wayne Chad

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Lab 12: Skeletal Muscle Histology
- Skeletal muscle functions
o Pulling on bones to produce movement of skeleton at joints
o Maintaining posture
o Supporting and protecting soft tissues of the abdomen and pelvis
o Controlling entrances and exits of the digestive and urinary system
o Producing heat to maintain internal body temperature
o Serving as reservoir for amino acids that can be used in times of poor nutrition
- Tendon
o Rope-like bundle of dense regular connective tissue
o Located at the ends of a muscle
o Contains collagen fibers from all other connective tissue layers associated with the
o Heavy in collagen fibers
o Attaches muscle to bone
o If tendon is a broad sheet, it is called aponeurosis
- Fascicle: bundle of muscle fibers within a skeletal muscle, surrounded by perimysium
o Muscle fiber: a single, multinucleate muscle cell that I wrapped in endomysium
- Endomysium
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o Delicate connective tissue layer
o Encases individual muscle fibers
o Connects together adjacent muscle fibers within the fascicle
o Contains capillaries and neurons associated with its muscle fiber
- Perimysium
o Fibrous connective tissue rich in collagen and elastin
o Divides muscle into compartments called fascicles
o Nerves and blood vessels run through muscle in this layer of connective tissue
- Epimysium
o Outermost layer merges with tendon
- Skeletal muscle cell/fiber
o Sarcomere s
Functional subunit of myofibril
Overlapping thick and thin filaments slide past each other to produce
Extends from one z disc to the next
- Plasma membrane of muscle fiber sarcolemma
- Sarcomere structure
o I band: light region at each end; contains only thin filaments. The z disc is in the
middle of this band
o A band: dense central region, contains thick and thin filaments
o H zone: lighter region around M line; contains only thick filaments
o M line: connects thick filaments tail to tail in the center of the sarcomere
o Z disc: end line of sarcomere; thin filaments anchored to it
- Proteins associated with sarcomere
o Actinin: connects actin filaments to Z disc
o Tropomyosin: covers myosin binding sites on the actin filaments
o Troponin: causes muscle contraction by binding calcium ions
o Titin: is responsive for passive elasticity of muscle fiber
o Dystrophin: protects muscle fibers against damage during contraction
- Myofilaments
o Thick myofilament
Composed primarily of myosin
Creates banded pattern within sarcomere
o Thin myofilament
Composed primarily of actin
Creates banded pattern within sarcomere
- Myofibril
o Subunit of muscle fiber
o Consists of a series of sarcomeres
o Appears banded under microscope due to arrangement of myofilaments
- Transverse tubule
o Continuous with sarcolemma
o Forms network through muscle fiber
o Carries wave of depolarization throughout muscle fiber
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