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The Muscular System The Skeletal Muscles.

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Presentation on theme: "The Muscular System The Skeletal Muscles."— Presentation transcript:

1 The Muscular System The Skeletal Muscles

2 Types of Muscle Smooth - lines blood vessels and other organs (ex. Stomach) (involuntary) Cardiac - found in heart (involuntary) Skeletal - attached to skeleton to create movement (voluntary)

3 Functions of skeletal muscle
Movement Posture Stabilize joints Generate heat

4 Origin* - Attachment to less moveable bone
Origin and Insertion Origin* - Attachment to less moveable bone *Muscles are attached to bones by tendons Insertion* - point of attachment to moveable bone

5 Flexors and Extensors Flexor - decreases angle between bones at a joint (ex.curling forearm towards upper arm) Extensor - increases angle between bones at a joint (ex. straightening arm)

6 Prime mover/Agonist vs. Antagonist
Prime movers are muscles that produce the most force for a give movement Antagonists oppose the force of the prime mover, but are not activated during the movement

7 Types of Muscle Contractions
Isometric - muscle contracts, but does not shorten or lengthen Isotonic - muscle contracts, and either shortens or lengthens Concentric - muscle contracts as it shortens Eccentric - muscle contracts as it lengthens

8 Muscle Contraction Muscle contraction is stimulated by motor neurons
Motor neurons are nerve cells that stimulate skeletal muscle Each muscle is innervated by at least one motor nerve A motor neuron and the muscle fibers it controls are called a motor unit

9 Motor Units Motor units are activated during contraction
To exert more force (i.e. moving a heavy weight or moving very quickly) more motor units must be recruited

10 Parts of a Muscle Fiber (a.k.a. muscle cell)
Sarcolemma - cell membrane of muscle fiber Sarcoplasm - cytoplasm of muscle fiber Sarcoplasmic reticulum - endoplasmic reticulum of muscle fiber (stores Ca2+ ions) T-tubules - folding in of the sarcolemma (allows nerve impulses to reach into the interior of a fiber)

11 Muscle Contraction (cellular level)
Motor neuron sends nerve impulse to muscle fibers Impulse travels along sarcolemma of fiber and down T-tubules Calcium ions are released from the sarcoplasmic reticulum Ca2+ allow myosin heads to attach to actin binding sites forming a cross-bridge Using the energy of ATP, myosin pulls on actin, causing the muscle to shorten along its length

12 Sarcomere - smallest contractile unit of skeletal muscle
A Band - area occupied by myosin filaments (dark) H zone - area between actin filaments Z disk - proteins marking the beginning and end of the sarcomere I band - area where there is no mysoin (light)


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