Muscle Contraction

Question 1

• What is the purpose of the sarcoplasmic reticulum?

Answer 1

Run parallel to myofibrils, release calcium for troponin/tropomyosin to contract muscle

Question 2

• What is the purpose of the t-tubules?

Answer 2

extension of plasmalemma; pass laterally through muscle fiber to help transmit nerve impulses to myofibrals

Question 3

• What is the importance of the sarcomeres?

Answer 3

contain the proteins needed for contraction, basic functional unit for muscle contraction

Question 4

• Review the filaments within the sarcomere.

Answer 4

Thick- Mysoin w/ myosin head

Thin- Troponin/Tropomyosin, actin

Question 5

• Review the types of bands within the sarcomeres.

Answer 5

I band: light, thin only
A-Band: dark, thick and thin
H-zone: center of A band, thick only
M-Line: titan stabilize sarcomere

Question 6

• Review the specific proteins in the sarcomere used for muscle contraction.

Answer 6

Thin:
actin- backbone of filament
Tropomyosin: twists around actin strand
Troponin: attached at intervals of the strand

Thick: myosin and titan (T is z-mline)

Question 7

discuss/list the process of muscle contraction from beginning to end; including how the action potential is sent and received, as well as how ATP is broken down and used.

Answer 7

1. Ready state: myosin head at 45 angle
2. ATP binds to myosin, myosin release from actin
3. ATPase hydrolyzes ATP to get energy, moves away from actin, ADP & Pi remain on myosin
4. myosin moves to 90 and binds to new actin molecule
5. myosin release Pi, causes power stroke, tilts back to 45, pulling actin to center of sacromere
6. myosin release ADP and back to ready state

Question 8

• What is titin and why is it important?

Answer 8

stabilizing sarcomeres; activated by calcium ion influx, winds around thin filaments, rotating them. explains the force when muscle is stretched; resist active stretching

Question 9

• How and when does muscle relaxation occur?

Answer 9

zdisk reaches myosin/AP stops; calcium returned to SP and tropomin/tropomyosin return to resting position

Question 10

• What order are fibers recruited in?

Answer 10

small->large

Question 11

• What are the different types of muscle contraction?

Answer 11

Concentric: shortening of the muscle; dynamic due to joint movement

Static: muscle generates force, length stays the same; isometric due to no joint movement

Eccentric: legthining, dynamic, extend elbow slowly to lower weight with bicep

Question 12

• What are the factors for generating force?

Answer 12

number/type of motor units activated, frequency of stimulation for each motor unit, size of muscle, muscle fiber and sarcomere length, speed of contraction

Question 13

• Know the definition of hypertrophy (chronic & transient), as well as the mechanisms that are associated with increasing it.

Answer 13

Chronic: long term; reflects structural change in muscle; fiber growth

Transient: due to edema from plasma fluid, gone in hours

Question 14

• Know the definition of hyperplasia and how it may occur.

Answer 14

fiber splitting due to intense strength training