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A&P Chapter 9


Muscle is... an organ, covered by fascia and epimysium
Fascicle is... a tissue covered by perimysium
Motor unit one nerve cell + attached muscle cells, contractions are "all or none" as a unit when stimulated
Fiber is... 1 muscle cell, up to 1 ft long, multinucleate, and covered by endomysium
Myofibril is... 1 contracting organelle, full length of cell, covered by sarcoplasmic reticulum
what is a contracting section of a myofibril, attached end-to-end by z-discs a Sarcomere
what is a "thin" filament at each end (think AMY) Actin filament
what is a "thick" filament in the middle (think KARKOW) Myosin
Actin filament is an assembly of what three proteins? 1. Actin protein: has attachment sites for myosin 2. Tropomysin: forms long strands to cover actin sites 3. Troponin: binds Ca to move tropomyosin and expose attachment sites on actin
Myosin filament is an assembly of what? Myosin proteins. Myosin proteins have a head capable of forming cross-bridges t othe actin sites
When can cross bridges form? only when Ca is present and the actin sites are exposed.
What does the Sliding Filament Theory say? That actin filaments are grabbed by myosin heads and slide toward each other - to contract you need to "get your actin together" -Each sarcomere pulls on its neighbor like tug-o-war - This makes the whole myofibril shorten and the cell contracts.
How do the striations correspond? A Band= dark striation: myosin filament length I Band= light striation: 2 ends of "bare" actin H Band= light mid-band" middle of "bare" myosin
Depolarization causes what in the muscle twitch sequence? Ca Entry
What is myofilament? A thread of bundled proteins (actin and myosin)
Skeletal movement is done by... pulling only
posture is maintained by... by maintaining tone-partial contraction
what do sphincters control? "openings" such as your rectum
how is heat generated? by shivering
A muscle twitch involves what? one motor units, and begins with an axon of a neuron caring an action potential (AP)
In the muscle twitch sequence what does the AP (action potential) cause? The AP causes axon terminal depolarization
ACh (acetylcholine) vesicles undergo what? Exocytosis
where is there ACh (acetylcholine) diffusion at? Across the synaptic cleft
what causes the Na entry in the muscle twitch sequence?
Created by: mheidenreich