Chapter 10 muscle tissue
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CHAPTER 10 “ Muscle Tissue”. Objectives Describe and identify the 3 major muscle groups (skeletal, cardiac and, smooth). Describe the general anatomy of muscles. Describe the ultra-structure of skeletal muscle and its role in muscle contraction.

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CHAPTER 10 “ Muscle Tissue”

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CHAPTER 10“Muscle Tissue”


Describe and identify the 3 major muscle groups (skeletal, cardiac and, smooth).

Describe the general anatomy of muscles.

Describe the ultra-structure of skeletal muscle and its role in muscle contraction.

Describe nerve-muscle relationship, the motor unit and the neuromuscular junction.

Define the physiologic fiber types of muscle.

Functions of Muscle

  • Movement: skeletal, cardiac, and smooth muscles

  • Stability: skeletal muscle

  • Communication: skeletal muscle

  • Control of body openings and passages: skeletal and smooth muscles

  • Heat production: skeletal muscles

Properties of Muscles

  • Excitability (responsiveness) respond to chemical, mechanical or electrical stimuli

  • Conductivity initiate events that lead to contraction.

  • Contractility ability to shorten substantially

  • Extensibility able to stretch between contractions.

  • Elasticity ability to return to original length after stretching

Three muscle tissues

  • Skeletal muscle

  • Cardiac muscle

    3. Smooth muscle

Skeletal Muscle

  • Cells are long and cylindrical in shape

  • Cells are multi-nucleated

  • Cross-striations present

  • Under voluntary control

  • Contractile proteins: actin, myosin and tinin.

  • Regulatory proteins: troponin and tropomyosin.

  • Sarcomere is contractile unit of skeletal muscle; defined as the distance between 2 “Z” discs

Connective tissues and fascicles

  • Myofibril- composed of bundles of myofilaments

  • Endomysium- reticular CT covering each muscle fiber and binding it to its neighbors.

  • Perimysium- fibrous CT covering muscle fascicles

  • Fascicles- bundles of muscle fibers surrounded by perimysium

  • Epimysium- covering of dense irregular CT surrounding the entire muscle

Skeletal Muscle

Skeletal Muscle Fascicle Arrangements

  • fusiform – thick in the middle and taper at the ends

  • parallel – muscle fibers are all parallel

  • pennate –fascicles are short and attach obliquely to a central tendon (feather shaped)

  • convergent – spread out as a fan or converge to a point

  • circular – muscle fibers arranged concentrically

Fusiform parallel convergent uni- bi- multipennate circular

Functional Groups of Muscles

  • prime mover or agonist –muscle whose contraction is responsible for a particular movement

  • synergists –muscles that assist the movement of the prime mover or agonist

  • antagonist –muscle whose action opposes that of the prime mover or agonist

  • fixators –stabilize the origin of the prime mover so it can move more efficiently.

    Origin - point of attachment where least movement occurs.

    Insertion – point of attachment with greatest movement.

Intrinsic and extrinsic muscles

  • Muscles are at times grouped as to the regions where they are found and function.

  • Intrinsic muscles are localized to a specific area (i.e. hand, tongue, back, etc.). They function and are contained only within that area.

  • Extrinsic muscles extend into other areas and are responsible for movements of areas other than where they are attached.

Terms to know and identify

  • Sarcolemma - plasma membrane covering each muscle cell.

  • Sarcoplasm - muscle cell cytoplasm.

  • Thick filaments – contractile protein myosin molecules, shaped like a golf club head. Thin filaments slide over thick filaments

  • Thin filaments – contractile protein actin molecules

    (f and G actin) also contain the regulatory proteinstropomyosin and troponin.

  • Elastic filaments - titin (connectin) keep thick and thin filaments aligned over one another for proper contraction to occur; comprise the “Z” line.

Ultrastructure of skeletal muscle: sarcomere = distance between 2 “Z” lines.


Muscle contraction

Every muscle contraction

is preceded by a nerve

impulse from the brain or

spinal cord. The impulse is

transmitted by a motorneuron

to each muscle fiber.

Neuromuscular control

  • Skeletal muscle contraction is controlled by a nerve impulse (action potential) transmitted by the motor nerve from the brain or spinal cord.

  • A motor unit consists of all the muscle fibers controlled by a single motor neuron.

  • Fine control muscles (i.e. eyelid muscles) have fewer muscle fibers/ nerve.

  • A contraction is initiated by an action potential (nerve impulse) and followed by the release a chemical neurotransmitter at the neuromuscular junction (NMJ).

  • Neurotransmitter for skeletal muscle is acetylcholine.

Neuromuscular control

  • Each muscle fiber is innervated by a single motor neuron

  • Contractions may be graded or full due to the number of muscle fibers that respond to the stimulus. The more fibers, the greater the muscle contraction

  • Synapse – functional connection between a nerve fiber and its target cell.

  • Neuromuscular junction – synapse between a motor nerve and a muscle fiber.

Neuromuscular junction

Neuromuscular Junction

Synaptic knob, terminal or bouton – bulbous swelling at the end of a motor nerve above the motor end plate on the muscle fiber.

  • Synaptic cleft – gap between the synaptic knob and the motor end plate.

  • Synaptic vesicles – small packets of neurotransmitter chemical (e.g. acetylcholine, norepinephrine, etc.)

SEM of Neuromuscular Junction

Skeletal muscle fibers

  • Skeletal muscle is composed of 3 different fiber types:

    • Fiber type is based on the process of making ATP and how fast they contract.

    • Type I slow oxidative fibers (dark staining)

    • Type IIa fast oxidative fibers (lighter staining)

    • Type IIx fast glycolytic fibers (pale or no staining)

Skeletal muscle fiber types

Fiber type characteristics

  • Type I Slow oxidative:

    • Appear as thin, dark staining or red in color due to abundant myoglobin

    • Manufacture ATP by aerobic breakdown of glucose

    • Contract slowly and are resistant to fatigue.

    • Ex. back muscles and support muscles

  • Type IIa Fast oxidative:

    • Stain less darkly than Type I but slightly larger

    • Produce ATP via aerobic metabolism like Type I

    • Contract faster and more powerfully than Type I

    • Abundant in lower limbs contract for long periods

Fiber type characteristics

  • Type IIx Fast glycolytic fibers

    • Stain a pale color contain due little myoglobin

    • Larger in diameter than other 2 types

    • Depend on anaerobic glycolysis to make ATP

    • Contract rapidly and fatigue easier

    • More prominent in upper limbs for large work loads

Skeletal muscle fiber types

Cardiac muscle

Characterized by:

- cross-striations

- intercalated discs

- uni-nucleate cells


Cardiac Muscle

Smooth muscle

  • Characterized by:

    • Spindle shaped cells

    • Uni-nucleate cells

    • Involuntary control

    • Found in walls of hollow organs, blood vessels and glands

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