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Understanding the Muscle System: Structure, Function, and Terminology

Explore the intricate structure and vital functions of the muscle system, including contraction, thermogenesis, and neuromuscular junction. Learn about muscle fiber organization, attachments, and the roles of agonist, synergist, and antagonist muscles.

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Understanding the Muscle System: Structure, Function, and Terminology

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  1. The Muscle System I Structure and Function

  2. Functions • Contraction (shortening) – the result of which is body movement, posture. • Thermogenesis – generation of heat ATP ADP + P + energy (work and heat)

  3. Structure • Each skeletal muscle has four layers of CT • Each skeletal muscle is comprised of muscle cells called muscle fibers • The muscle fibers are organized into bundles called fascicles

  4. Structure • Fascia – CT surrounding each muscle and separating muscles from each other

  5. Structure • Epimysium – dense CT that surrounds the entire muscle…. just deep to the fascia • Perimysium – CT that surrounds and separates the fascicles • Endomysium – CT that surrounds each muscle fiber (muscle cell)

  6. Structure of Muscle Fiber (cell) • Myofibrils – bundles of myofilaments • Myofilaments – actin and myosin….contractile proteins

  7. Neuromuscular Junction (NMJ) • One of the properties of muscle is excitability or responsive to input • Nerve cells (neurons) provide the input that causes a muscle cell (fiber) to respond (contract) • The interface between the muscle fiber and the neuron is the NMJ • Every muscle fiber has a branch of a neuron that is control of it.

  8. NMJ • How does a nerve impulse cause excitability in a muscle?

  9. NMJ • Nerve releases neurotransmitters into synaptic cleft • Neurotransmitters bind to receptors on surface of muscle fibers and cause contraction of muscle • Acetylcholine (ACh) is the most common neurotransmitter

  10. Muscle Terminology • Every muscle has 2 Attachments • Origin and insertion • When the muscle shortens one attachment moves and the other one doesn’t • Origin – the attachment that does not move • Insertion – the attachment that does move

  11. Muscle Terminology • Agonist – the one muscle in a group of muscles that produces the most forceful reaction • Synergist – the other muscles that “help” the agonist do the same movement • Antagonist – a muscle whose action opposes that of another muscle.

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