muscle contraction - topic 7

Question 1

name the thick and thin filaments in a myofibril

Answer 1

thick - myosin
thin - actin

Question 2

describe the structure of actin in a myofibril

Answer 2

• two actin twist together forming a chain
• tropmyosin twists around chain
• troponin is attatched at regular intervals

Question 3

what movements occur in muscle contraction ?

Answer 3

• sarcomeres shorten
• z discs pulled together
• myosin and actin do not change length they just slide over eachother

Question 4

describe the processes that occur during muscle contraction (5)

Answer 4

• action potential arrives at neuromusclular junction
• ca2+ releases from sarcoplasmic recticulum
• Ca2+ binds to troponin changing its shape
  -moving tropomyosin exposing myosin binding sites on actin
• myosin heads bind forming cross bridges
• heads nod forward causing actin to slide over myosin
• releases ADP + P
• ATP binds to mysosin head changing its shape
• myosin head releases from actin