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Muscle Cell actoin potential
A brief change in muscle cell voltage from negative to positive to negative. (normal is negative)
True or False: Muscle cell action potetial, travels along the suface of muscle cells very quickly, probably more thea 100 m/sec or about the speed of and Indy reacecar.
Remember that skeletal and __________ muscle have a series of _________ _________ (T tubules) that help the action potential penetrate deep into the muscle ________.
cardiac, trasnvers tubules, fiber
From Action ptential to Calcium release
- Muscle cell action potenial travels along muscle surface
- Penetrates into the interior of the muscle cell at transvers tubules
- Remember T tubules arein a triad with two sacs of sarcoplaspic reticulum
- Sarcoplasmic reticulum releases calcium into the cytoplasm of the muscle cell
From Calcium Release to contraciton
Calcium released from SR them binds to troponin; this moves tropomyosin aside and exposes binding sites for myosin on the actin filament
True or False : The calcium released from the sarcoplasmic reticulum interacts with a special protien, found only in muscle cells
When calcium binds to the protein called troponin...
...it changes shape, and pushes another specialized protien called tropomyosin
- "moving muscle protein"
- normally covers a myosin binding site ont e actin molecule
- keeps myosin (which wants to bind actin) from being able to reach its binding site on actin.
When _________ is present, and troponin shoves topomyosin and topomyosin moves away from the _______ ______, myosin can grab _______.
calcium, binding site, actin
True or false : Stereograms don't work when projected on a screen.
true.see objective 14 p.446- 447
The cross-bridge cycle
- 6a. calcium binds to troponin; troponin choves tropomyosin; tropomyosin moves, exposing the myosin binding site on actin.
- 6b. Myosin brings a piggy backed molecule of ATP which is split to form ADP and the loose phosphate is released as myosin binds actin
- 6c. Power stroke: the shape of myosin changes; the head region flexes and moves the actin filament a tiny amount. this releases ADP and opens a site for ATP to bind again
- 6d. ATP binds, myosin release the actin filament, and the cycle can begin agian.
- A dead person uses up their ATPin a matterof minutes ore hours depending on the temperature, and muscles are "locked" in position
- Later, again cepending on temperature , cirobes break down muscle tissue to the point where muscle becomes loose again.
What happens if ATP is absent from the cross-bridge cycle?
- Myosin remains permanently bound to actin, muscles cannot move
- -miuscle stuck between step 5 and 1
- Rigor motis results
- Eventually , ensymes and microbes destroy muscle structure and corps becomes "loose" again.
Three terms used to describe muscle anatomy.
the place where a muscle "begins," where it attaches to a relatively immoveable point
.-usually, this is proximal
- the place where a muscle "ends," where it attaches to a moveable part.
- -usually, this is distal
what the muscle does when it contracts.
Names of muscle function
prime mover (agonist)
Prime Mover (Agonist):
muscle that does most of the work in the action being discussed.
oppose action of agonist
aid agonist in creating movement.
stabalizes the muscle origin.
Example: fixators in the shoulder girdle help to stop rotation of the shoulder joint during the motions of the triceps and biceps.