Unit 6 Muscles

Question 1

What do muscles do

Answer 1

• Act as antagonistic pairs against an incompressible skeleton to create movement can be autonomic as part of relfex response or controlled by conscious thought

Question 2

Outline the structure of a Myofiril

Answer 2

• Known as sarcoplasm and high number of mitochondria
• Made up of 2 types of protein, myosin and actin which form sarcomere

Question 3

Outline gross and microscopic strcture of skeletal muscle

Answer 3

• A band = overlap of actin and myosin[no change in contraction]
• I band = Only actin [shortens in contraction]
• H zone = Only myosin[shortens in contraction]
• Z line = boundary ebtween sarcomere [moves closer together in contraction]
• m line in middle

Question 4

Outline the process in myofibril contraction

Answer 4

• Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum and calcium ions cause movement of tropomyosin on actin
• This movement causes exposure of the binding sites on the actin
• Myosin heads with ADP attached attach to binding sites on actin to form cross bridge (actinomyosin bridge)
• Myosin heads change shape, filaments slide past each other & ADP released
• ATP attaches to each myosin head causes myosin heads to detach from actin sites.
• Hydrolysis of ATP by ATPase on myosin heads causes myosin heads to return to original position

Question 5

Outline the role of ATP and phosphocreatine

Answer 5

• Active muscle require high concentration of ATP
• When aerobic respiration cannot create enough ATP to meet this demand, anaerobic respiration occurs.
• Phosphocreatine, which is stored in muscles, provides phosphate to regenerate ATP from ADP.

Question 6

Describe fast and slow twitch muscle fibres work

Answer 6