Flashcards in Week 4 Muscle Excitation- Trachte Deck (21):
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)
autoantibodies against nicotinic receptors in skeletal muscle
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
*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
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?
-contraction not controlled by troponin or topomyosin
-initiated by calcium interacting with a calcium-dependent myosin light chain kinase
-oftenhas autorhythmicity (like intestinal muscle)