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A&P II

Lecture 2--Muscle Physiology

QuestionAnswer
Slide 1--Introduction *Muscle provides movement, heat generation and correct posture *Over 600 muscles in the body *innervated by motor neurons; muscle is excitable *There are three types of muscle -skeletal -smooth -Cardiac
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Slide 2--Features of Muscle *Muscle is excitable-It is able to be stimulated *Contractility-the ability to contract or shorten; pull on bones to allow movement *Extensibility-ability to extend or stretch
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Slide 3- Skeletal Muscle *Attached to bone by tendons *Surronded by a protactive sheath called the empimysum *muscle is comprised of multiple fasicles surrounded by the endomysium *Each fasicle sis surrounded by the endomysium *Muscle fiber=Muscle cell
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Slide 4--Skeletal Muscle-Overview (pt 1) *Sarcolemma; the plasma membrane *Sarcoplasm: the muscle fiber's cytoplasm *Sarcoplamic Reticulum: the muscle fiber's version of an endoplasmic retoculum -StoresCalsium (Ca++)
Slide 4--Skeletal Muscle-Overview (pt 2) *T tubules or "Transverse tubules" carry electrical impulses from the sarcolemma into the muscle fiber *Muscle fibers are comprised of mofibrils
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Slide 6--Skeletal Muscle-Myofibrils Myofibrils are composed of two myofilments: 1)thick myofilaments: myosin heads that interact with thin myofilament: requires ATP 2) Thin myofilaments: comprised actin, troponin, and tropomosin
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Slide 8--Skeletal Muscle--Myofibril Anatomy (Pt 1) *Z-line/disk: Anchors or tethers myofibrils together *Sarcomere: A segment of myofibrils between two successive Z-line *A band: A segment that runs the entire length of thick filament
Slide 8--Skeletal Muscle--Myofibril Anatomy (Pt 2) *I Band: includes the thin filaments and Z-line/disc (but not the thich filaments *H Zone: Middle region of thick filaments (But not where thin filaments overlap)
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Slide 10 (pt 1) * Thick filaments: are comprised of mostly myosin heads that are chemically attracted to the actin on thin filaments -Myosin heads are called "cross Bridges" when attached to actin 1)Actin-Serves as binding sites for mypsin
Slide 10 (pt 2) 2) Tropomyosin-Serve to block the interaction between myosin heads and actin 3) Troponin- a protein that controls the position of tropomysin; calcium sensitive
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Slide 11- Skeletal Muscle- Thin Filament (Pt 1) Troponin-Tropinin molecules have binding sites for calcium ions. When a calcium ion fills this site it causes a change in the shape and position of TROPONIN and when TROPONIN shifts it pulls the TROPOMYOSIN to which it is attached.
Slide 11- Skeletal Muscle- Thin Filament (Pt 2) When TROPOMYOSIN is moved the MYOSIN head that was touching the tropomyosin now comes in ctact with an underlying actin molecule.
Slide 11- Skeletal Muscle- Thin Filament (Pt 3) Actin- when action combines with myosin head the ATP assocaited with the head breaks down into ADP. This reaction releasedenergy that causes the myosin head to contract the thin filament
Slide 11- Skeletal Muscle- Thin Filament (Pt 4) Tropomyosin- is a relaxed muscle, the myosin heads of the thick myofilament lie against tropomyosin molecules of the thin myofilament as longas the myosin heads remain in contact with tropomyosin nothing happens (i,e muscle stays relaxed)
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Slide 13- Acetylocholine *First neurotransmitter discovered *Often abbreviated as "ACh" for the neurotransmitter "AchR" for the receptor *Motor neurons connect to the sarcolemma at the motor end plate
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Slide 16- Skeletal Muscle-Contraction (Pt 1) 1) ACh is released by the motor neuron 2) Ach diffuses across the synaptic cleft, binding the receptors on the motor end plate 3)Binding generates an action potential ("Nerve Impulses")
Slide 16 * 17- Skeletal Muscle-Contraction (Pt 2) 4)Impules travels along the sarcolemma down the t tubes and insdie the muscle fiber (cell) 5) as the impulse travels down the T tubules, calcium is released into the sarcoplasm
Slide 16 * 17- Skeletal Muscle-Contraction (Pt 3) 6) Calcium binds to troponin causing the proten to "pull" on tropomyosin, revealing actin binding sites 7) Myosin heads immediately bind to exposed actin
Slide 16 * 17- Skeletal Muscle-Contraction (Pt 4) 8) myosin uses ATP to contract thin filaments releases, binds to the next exposed actin and pulls again 9) the Entire myofibrill shortens
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Created by: ghadeer123