January 13, 2015
1. Calcium:
a. Where is calcium stored in a muscle cell?
cistern
b. What makes the calcium leave its storage area?
action potential triggers release (makes cisterns permeable)
c. How does the calcium get back into the storage area?
enzyme pumps (ATP)
d. What happens when the calcium is put back into the storage area?
muscle relaxes because binding sites no longer exposed to myosin
sidearms; if calcium remains, myosin can keep attaching for power stroke
e. Where else is calcium involved in muscle movement? nerve end bulb
2. muscle functioning:
a. Explain why muscles can only pull, not push.
power stroke can only shorten muscle, only way to lengthen muscle again is
for antagonist to pull
b. What is treppe? muscle gets stronger as it's first contracting, due to fact it
takes time to get enough calcium out to uncover all binding sites; fast shortening
or early in shortening process means less time for all the bridges to attach so not
as strong
c. What is complete tetany and what has to happen to bring it about?
applying stimuli at a rate that doesn't allow muscle cell any relaxation, action
potentials keep coming so neurotransmitter continuously released and signal
keeps going down t-tubule, calcium levels kept up in sarcoplasm
d. What explains the all-or-nothing principle? Why can’t muscles contract ½way? no mechanism for stopping power strokes once they start, once binding
sites exposed
January 13, 2015
3.muscle cells and their microstructure:
a. Why is there so little room for sarcoplasm in a muscle cell? lots of myofibrils
b. How big are muscle cells? 1/10 -- 1/100 mm, 1 ft. long
c. What is sarcoplasm? cytoplasm of muscle cell
d.What are terminal cisterns an extension of? SR
e. What are t-tubules an extension of? sarcolemma
f. What cartoon step could explain the need to reach threshold? (What
might need to happen a number of times before the muscle can begin to
contract?) enough neurotransmitters must cross cleft to open gates and
enough sodium must cross the membrane to change polarization
4.
a. Why do muscle cells look striped (like they have bands)?
areas where there's both actin and myosin are dark, other areas are
lighter
b. Draw a relaxed and a contracted sarcomere.
c. What is a sarcomere?
repeating unit of thick and thin myofilaments in a myofibril
d. How many muscles do we have? 600+
e. How are muscles organized? Each muscle is divided into fascicles
which are divided into…..
f. What is the difference between a myofibril and a myofilament?
fibers= muscle cells, fibrils = bundle of filaments, myofilament = actin
and myosin
g. Which is the “thick” filament and which is the “thin” one?
thick = myosin, thin = actin
January 13, 2015
5. Muscle fibers
a. What are the 3 types of muscle fibers? type 1, 2A and 2B
b. What are the differences and similarities among them?
type 1 -- aerobic, slow but endurance
2B -- anaerobic, fast, tires easily
c. Which can you change into another type? 2B to 2A
d. Which is “dark meat” and why is it dark? type 1, has myoglobin
e. Which can carry out anaerobic respiration and which can carry out
only aerobic? (What are aerobic and anaerobic respiration?)
6. muscle force
a. Which step in your cartoon makes the muscle contract?
b. The cross-bridges are so little. How can they provide enough force
to shorten a muscle cell?
c. What is a motor unit?
d. Why are some motor units bigger than others?
e. Draw a motor unit, showing the axon, the branches of the axon, and
the muscle cells attached.
January 13, 2015
cramps have many causes, including dehydration, lack of ATP, electrolyte imbalance, muscle
fatigue
January 13, 2015
g. How does the sliding filament theory explain muscle movement?
(You should have this step by step in your cartoon)
h. Why do you need ATP for both contracting and relaxing?
need ATP for power stroke and to release myosin arm
i. Why can’t cross –bridges always attach to actin? sometimes binding
site is covered by tropomyosin