Objective 10

Question 0

Linking the electrical signal to cross-bridge formation (which causes the contraction) is known as what?

Answer 0

excitation-contraction coupling

Question 1

What must a skeletal muscle do in order to contract?

Answer 1

• be stimulated by a nerve ending with propagation of an AP along its sarcolemma
• Have a brief rise in intracellular Ca2+ levels, which is the final trigger for contraction

Question 2

Excitation-Contraction Coupling:

Where does the action potential propagate? And then by what path does it travel?

Answer 2

The action potential propagates along the sarcolemma and travels down the T tubules

Question 3

Excitation-Contraction Coupling:

After the AP travels down the T tubules, what happens next?

Answer 3

The AP triggers Ca2+ release from the SR terminal cisternae

Question 4

Excitation-Contraction Coupling:

After the SR terminal cisternae releases Ca2+, what happens next?

Answer 4

Ca2+ binds to troponin and removes the blocking action of tropomyosin.
- Actin acctivve binding sites are exposed and ready for myosin binding

Question 5

What’s it called when high-energy (cocked) myosin head attaches to actin filament?

Answer 5

Cross bridge formation

Question 6

What is it called when the myosin head pivots and pulls actin filament toward M line?

Answer 6

Working (power) stroke

Question 7

What is it called when the ATP attaches to myosin head and the cross bridge detaches?

Answer 7

Cross bridge detachment

Question 8

What happens to cause “cocking” of the myosin head?

Answer 8

When energy from hydrolysis of ATP cocks the myosin head into the high-energy state

Question 9

What happens when nerve stimulation stops?

Answer 9

Ca2+ is pumped back into the SR (active transport)

Question 10

What happens when muscle contraction ends?

Answer 10

Tropomyosin blocks again blocks actin binding sites