Week 4 Muscle Excitation- Trachte Flashcards Preview

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Flashcards in Week 4 Muscle Excitation- Trachte Deck (21)
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Lou Gehrig's Disease/ Amyotropic lateral sclerosis

degeneration of motor neurons



auto-antibodies against calcium channels in motor neurons resulting in an inability to relase acetylcholine



prevents acetylcholine relases by cleaving synaptic associated proteins (SNAPS)


Myathenia Gravis

autoantibodies against nicotinic receptors in skeletal muscle


Malignant Hyperthermia

mutation of the ryanodine receptor allowing excessive release of calcium, usually triggered by anesthetics


Duchenne's muscular dystrophy

a mutation in dystrophin, a skeletal muscle support protein


What happens to the A band and I band during a muscle contraction?

The A band remains the same, the I band decreases in width


What causes the power stroke in a muscle contraction?

Release of the phosphate causes the angle of the myosin head to revert to 45 degrees


Describe the process of a muscle contraction

-Ca+ is released and binds to troponin causing a conformational change in the tropomyosin, exposing the myosin binding site on the actin

-ATP hydrolysis cocks the myosin head so it is ready to attach to actin

-Myosin cross bridge binds Actin

-Phosphate is released causing the power stroke (moves the head from 90 to 45 degrees toward M line)

- ATP is required to myosin head to detach from actin


What is required for muscle relaxation?

-sequestration of calcium (this required ATP) by Ca ATPases

-this allows troponin-tropomyosin complex to inhibit bind of myosin


***What is the amount of force generated by a muscle directly proportional to?

the number of actin-myosin crossbridges per cross-sectional area


When do muscles work best?

Muscles work best when there is considerable overlap between actin and myosin


What is an isometric contraction?

when the load is larger than the muscle's ability to move it (the muscle contracts enough to pull the tendon taut but does not actually move the body attachment)

-trying to move something that won't move


What is an isotonic contraction

if the load on the muscle is constant


Slow twitch fibers

Type 1 fibers
slower myosin ATPase enzyme
contain a lot of myoglobin
Red fibers
*Need myoglobin because they require lots of oxygen to maintain


fast twitch fiber

Type II fibers
Faster myosin ATPase enyme
White fibers (less myoglobin)
Adapted for anaerobic metabolism


Concentric contraction

muscle contracts resulting in shortening (typical biceps curl)



muscle lengthens while attempting to shorten
(dropping a curl with resistance, running down a hill)
more damage to muscle with this type of contraction


What are some big differences between cardiac and skeletal muscle?

-Cardiac does not required innervation to contract, has autorhythmicity
-more dependent on extra-cellular calcium


Why is smooth muscle unique?

-not striated
-contraction not controlled by troponin or topomyosin
-initiated by calcium interacting with a calcium-dependent myosin light chain kinase
-oftenhas autorhythmicity (like intestinal muscle)


What is the speed of a muscle contraction dependent on?

myosin ATPase activity