6.3 Muscles Flashcards
How do mucles work
- Act in antagonistic pairs
- Work across joints
- Both contract to keep joints at certian angles (isometiric contraction)
What is isometric contraction
When an antagonistic pair of muscles both contract to keep joints at certian angles
What pairs do skeletal muscles work in
Antagonistic
Where do mucles work
Across joints
What is the smaller component arranged end to end that form the myofibril
Sarcomeres
What does ‘M-line’ represent
Middle of sarcomere
What does ‘Z-line’ represent
End of sarcomere
What does H band represent
Length of myosin only
What does I band represent
Length of actin
What does A band represent
Entire length of myosin
Change during contraction: M line
no change
Change during contraction: Z line
Move closer together
Change during contraction: H band
Narrows
Change during contraction: I band
Narrows
Role of phosphocreatine
Provides phosphates to synthesise ATP
Change during contraction: A band
No change
Describe and explain the events of myofibril contraction
- Calcium ion diffuse into myofibrils from sacroplasmic reticulum
- Calcium ions cause movement of tropomyosin on actin filament
- Binding sites on actin are now exposed
- Myosin heads attatch to exposed binding sites on actin (crossbridge formation)
- ATP attatched to myosin head is hydrolysed by ATP hydrolase, releasing energy causing the head to bend
- Pulls actin filament
- Attatchment of another ATP molecule to myosin head causes myosin heads to move and detach from actin filament binding site (Re-set)
Describe the role of myosin
- Myosin head attaches to actin binding site (crossbridge formation)
- Pulls actin filament
- Detaches from actin binding site and re-sets
Describe and explain the role of calcium ions in myofibril contraction
- Diffuse into myofibrils from sarcoplasmic reticulum
- Cause movement of tropomyosin on actin filament
- Exposes myosin binding sites on actin
- Myosin heads attach to exposed binding site (crossbridge formation)
Role of ATP in myofibril contraction
- Attatched to myosin head is hydrolysed by ATP hydrolase, causing myosin head to bend
- Attachemnt of another ATP molecule to myosin head causes myosin heads to move and detach from actin binding site (re-set)
Role of tropomyosin
- Blocks myosin binding site on actin
- Moves out of the way when calcium ions present
- Allow myosin heads to bind to actin (crossbridge formation)
Secondary role of ATP in myofibril contraction
Active transport of calcium ions
Role of phosphocreatine in myofibril contraction
Provides phosphates to synthesise ATP
Slow muscle fibres: contraction
Less powerful
