Exercise 14
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Exercise 14. Microscopic Anatomy, Organization, and Classification of Skeletal Muscle. SKELETAL MUSCLE. Voluntary or involuntary? Striated or not? Multinucleate or uninucleate?. Terminology. “Myo-” or “-Mys-” = muscle “Sarco-” = flesh. Microscopic Anatomy.

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Exercise 14

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Exercise 14

Exercise 14

Microscopic Anatomy, Organization, and

Classification of Skeletal Muscle


Skeletal muscle

SKELETAL MUSCLE

  • Voluntary or involuntary?

  • Striated or not?

  • Multinucleate or uninucleate?


Terminology

Terminology

  • “Myo-” or “-Mys-” = muscle

  • “Sarco-” = flesh


Microscopic anatomy

Microscopic Anatomy

  • Muscle Fiber = long, slender, cylindrical, MULTInucleate cell

  • Nuclei located just under sarcolemma (cell membrane)

Fig. 10-2


Muscle fiber anatomy

Muscle Fiber Anatomy

  • Sarcolemma

    • Plasma membrane of muscle fiber

    • Trans-membrane potential: charge differences on either side

  • Sarcoplasm

    • Cytoplasm of muscle fiber

    • Stored glycogen, mitochondria, myoglobin, actin, myosin


Exercise 14

Fig. 10-3


Exercise 14

  • Transverse tubules

    • T tubules

    • Narrow tubes, continuous with sarcolemma

    • Extend into sarcoplasm, fluid-filled

  • Myofibrils

    • Parallel, extend length of muscle fiber

    • Each muscle fiber contains 100s-1000s

    • Composed of myofilaments

      • Actin (thin filaments) & myosin (thick filaments)


Exercise 14

Fig. 10-3


Exercise 14

  • Sarcoplasmic Reticulum (SR)

    • Smooth ER

    • Tubular network around each myofibril

    • Terminal cisternae: enlarged portion of SR on either side of T tubule

    • Storage/release of Ca

  • Triad = T tubule + 2 terminal cisternae

Fig. 10-3


Exercise 14

  • Muscle contraction begins when Calcium ions are released

    • from the terminal cisternae

    • Into the sarcoplasm

    • ADAM cd-rom


Exercise 14

  • Sarcomeres

    • Organized group of myofilaments

    • Contractile units, smallest functional unit of muscle fiber

    • Z-line to Z-line

Fig. 10-4


Exercise 14

  • Sarcomeres

    • A band: DARK

      • Thick and thin filaments

      • M line is in the middle of the sarcomere/A band

    • I band: LIGHT

      • midline is Z line/disc

      • Thin filaments only

Fig. 10-4


Myofilaments

Myofilaments

  • Thick filaments: myosin

    • Rod-like tail bound to other myosin

    • Head projects outward

      • has binding sites for actin (thin filaments), ATP

      • “cross-bridges”

Contraction: The myosin head changes shape & will grab onto the actin…and pull it toward the M-line

Fig. 10-7


Myofilaments1

Myofilaments

  • Thin filaments: 3 types of protein molecules

    • actin

      • Double helix (2 strands) coil around each other

      • has binding sites for myosin

        • Site is blocked by troponin-tropomyosin complex when muscle’s NOT contracting

    • Tropomyosin

      • Rod-like, coils around actin to stiffen it

      • Covers binding sites

    • Troponin

      • 3 protein-complex

      • One of each binds to: actin, tropomyosin, calcium ions (this one’s empty in a resting cell…see ADAM cd)


Exercise 14

Fig. 10-7


Connective tissue wrappings 3 layers

Connective Tissue Wrappings:3 Layers

  • Epimysium = outer

  • Perimysium = central

  • Endomysium = inner


Connective tissue wrappings

Connective Tissue Wrappings

  • Epimysium

    • Epi = on (outside layer)

    • Surrounds entire muscle

    • Dense layer of collagen fibers, connected to deep fascia

    • Separates muscle from other tissues/organs

Fig. 10-1


Connective tissue wrappings1

Connective Tissue Wrappings

  • Perimysium

    • Peri = around (central layer)

    • Divides muscle into compartments:

      • Fascicle = bundle of muscle fibers (cells)

    • Collagen, elastic fibers

    • Blood vessels, nerves to each fascicle

Fig. 10-1


Connective tissue wrappings2

Connective Tissue Wrappings

  • Endomysium

    • Endo = inside (inner layer)

    • Surrounds individual skeletal muscle cells (fibers)

    • Interconnects adjacent muscle fibers

    • Capillary networks to supply blood to cells, nerve fibers to control muscle

Fig. 10-1


Connective tissues cont

Connective Tissues, cont.

  • Layers are continuous & interwoven – blend into one another

  • Muscle’s ends: layers unite to form

    • Bundle: TENDON

      • Attach skeletal muscles to bones

      • Contraction pulls the bone(s)

    • Broad sheet: APONEUROSIS

      • Attach skeletal muscles to bones or other muscles


Exercise 14

Connective tissue layers!

  • Muscle—covered by epimysium

  • Fascicles—covered by perimysium

  • Fiber (cell)—covered by endomysium

  • Myofibril—covered by sarcoplasmic reticulum

  • Sarcomere—contains thick and thin filaments


Exercise 14

Fig. 10-6


Blood nerve supply

Blood & Nerve Supply

  • Muscles need lots of energy, lots of oxygen

  • Blood vessels supply these

    • Each fiber (cell) has capillary blood supply

  • Contraction stimulated by nerve impulses

    • Axons (nerve fibers) penetrate connective tissue layers, & innervate individual muscle fibers (cells)


How muscles contract adam cd rom

How Muscles Contract: ADAM cd-rom


Neuromuscular junction

Neuromuscular Junction

  • Junction of motor neuron & a muscle fiber

    • Motor neuron sends a signal to cause a movement of a skeletal muscle

  • Neuron—elongated portion = axon

    • Ends in expanded branches (synaptic terminals)

    • synaptic cleft: space between synaptic terminal & muscle fiber’s sarcolemma


Neuromuscular junction1

Neuromuscular Junction

  • Synaptic terminals

    • Contain synaptic vesicles

      • Filled with acetylcholine (ACh)

        • Neurotransmitter: chemical released by neuron

      • Release of ACh triggers muscle contraction

      • Sarcolemma of motor end plate has receptors to bind ACh


Neuromuscular junction2

Neuromuscular Junction

“Motor end plate”

Sarcolemma highly folded

  • Increases surface area

  • Sites of ACh binding

“Action Potential”

Fig. 10-10


Neuromuscular junction3

Neuromuscular Junction

  • Motor unit = A single motor neuron & ALL the muscle fibers it controls

Fig. 10-17


Exercise 14

Fig. 10-10


Exercise 14

Fig. 10-10


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