As soon as possible would be great!

part a: put these parts of muscles in order from 1 (largest) to 6 (smallest)

part b: put these steps in muscle contraction in sequence by numbering the steps in order

if the pic is hard to read let me know and i can add another one

Answer:

Part A  

6 actin filament

3 muscle fiber = muscle cell

1 muscle

2 bundle of muscle fibers

4 myofibril

5 myosin filament

Part B

1 Action potential in motor neuron

11 Myosin head releases ADP

6 Troponin shifts tropomyosin, exposing myosin binding sites on actin

7 Myosin head extends

8 Myosin’s ATP is hydrolyzed to form ADP-P

15 Troponin loses calcium, so tropomyosin shifts and covers myosin binding site on actin

5 Calcium binds troponin

9 Myosin head with ADP-P binds to actin

2 Action potential in neuromuscular junction

13 Muscle excitation ends so calcium release from sarcoplasmic reticulum ends

10 Myosin head releases P, causing myosin head to flex, pulling filaments past each other = the power stroke

4 Action potential in muscle fiber cell membrane and T-tubules

12 Myosin head binds ATP and realeases actin

14 Calcium pumps of sarcoplasmic reticulum take up calcium and reduce its concentration in sarcoplasm

3 Release of calcium from sarcoplasmic reticulum into sarcoplasm surrounding myofibril