Skeletal Muscle Contraction

Question 1

sliding filament theory

Answer 1

movement within the myofibrils in which the filaments of actin and myosin slide past one another, shortening the muscle fiber and pulling on its attachments

Question 2

Contractile proteins

Answer 2

actin and myosin

• generate force

Question 3

Regulatory proteins

Answer 3

troponin and tropomyosin

• function as the on/off switch
• attached to actin

Question 4

Structural proteins

Answer 4

titin and actinin

• large protein in body
• keep thick and thin filaments of myofibrils in proper alignment, give myofibrils elasticity and extensibility, and link myofibrils to sarcolemma and extracellular matrix

Question 5

myosin molecule

Answer 5

composed of 2 twisted protein strands

Question 6

heads

Answer 6

globular projections along 2 strands of myosin

Question 7

actin molecule

Answer 7

globular structure with binding site to which the myosin heads can attach forming cross-bridges

Question 8

actin filament

Answer 8

actin molecule twist into a double strand (helix)

Question 9

troponin-tropomyosin complex

Answer 9

cover actin binding sites when at rest or unstimulated to contract

contraction cannot occur as long as these binding sites are covered

Question 10

sarcomere

Answer 10

as thick and thin filaments slide past each other, this shortens

Question 11

ATP in muscle contraction

Answer 11

1. Calcium binds to the troponin, eventually changing its shape and altering the position of the tropomyosin
2. Movement of the trop myosin molecules exposes the binding sites on actin filaments
3. Linkage form between the actin and myosin filaments
4. “power stroke” occurs receiving energy from ATP; it pulls the actin filaments towards the A bands
5. The myosin head possesses stored energy, which will be released when myosin head binds to actin and pulls - recovery stroke

Question 12

ATPase

Answer 12

enzyme that releases energy stored in the terminal phosphate bonds of ATP molecules

• breakdown ATP (adenosine triphosphate) to ADP (adenosine diphosphate) and phosphate
• provides the force with which the cross-bridge pull

Question 13

ATPase binding with ATP

Answer 13

results in splitting into ADP and a phosphate

Question 14

ATP

Answer 14

contains adenine, which provides a carbon and nitrogen basem ribose, which is a 5 carbon sugar and 3 chemical groups called phosphates in a chain

Question 15

creatine phosphate

Answer 15

stores energy

Question 16

cellular respiration

Answer 16

releases energy from organic compounds

Question 17

ATP binding with cross-bridge

Answer 17

causes cross-bridge to release from actin even before ATP splits

• requires fresh ATP attach to myosin ATPase
• binds, but not yet broken down

Question 18

muscle cramp

Answer 18

result from lack of ATP to cause the release of the cross-bridges and/or required to shuttle calcium out