Contraction and Relaxation

Question 0

Outline muscle contraction

Answer 0

1) tropomyosin (held by Troponin) prevents myosin head
2) signal
3) ca2+ ions from EP, tropomyosin detached from actin binding site
4) myosin head attaches
5) myosin head changes angle pulling actin filament along, releasing ADP(and energy) (ATP HYDROLYSIS)
6) ATP fixes to myosin head, so it detaches from binding site
7) hydrolysis of ATP provides energy for myosin head to resume normal position
8) process repeated further along actin filament

Question 1

First …

Answer 1

Muscle stimulation (action potential) —> acetylcholine causing depolarisation

Question 2

Muscle relaxation…

Answer 2

1) nervous stimulation ceases
2) ca2+ ions actively transported back into ER, using energy from ATP hydrolysis
3) absence of Ca = tropomyosin blocks binding sites
4) myosin head cannot bind to actin

Therefore relaxation

Question 3

ATP HYDROLYSIS

Answer 3

ATP —> ADP + Pi + energy

Question 4

ATP energy needed in contraction and relaxation for …

Answer 4

Movement of myosin heads

Reabsorption of Ca ions into ER (active transport)