11. Muscle Contraction Flashcards
What is the role of ATP in muscle contraction? (Helping the filaments slide over each other)
- Energy source
- Enable the formation of cross-bridges
- Release myosin heads from their binding sites
What is the role of calcium ions in muscle contraction?
- Cause myosin to hydrolyse ATP
- Cause change in shape of tropinin
- Cause tropomyosin to detach from actin filament/ expose binding site
Name the protein found in the H zone
Myosin
What happens to the width of the A band when the muscle contracts?
Stays the same
What happens to the width of the I band when the muscle contracts?
Narrows
Suggest two functions of energy released by mitochondria in the synaptic knob
- Active transport of ions/ ionic pump (reject A.T of ACh)
- Synthesis of acetylcholine/ reform vacuole
- Reabsorption of ACh from cleft
- Movement of vesicles to membrane
- Synthesis of acetylcholinesterase
Describe how the appearance of a muscle fibre would change when the fibril is stimulated by the neurotransmitter
- Shortening of terminal light bands
- Central H zone disappears/ reduced
- Overall shortening of fibril/ sarcomere
Describe how the stimulation of a muscle by a nerve impulse starts the cycle of contraction (myosin heads moving along actin)
- Bind to/ displace tropomyosin
- Reveal actin binding site
- Myosin binds to exposed sites on actin
- Crossbridges formed
- Activates ATPase
Graph- Time taken for phosphocreatine to reform against age. As age increases, the time taken for the regeneration of phosphocreatine increases.
Use your knowledge of fast muscle fibres to explain the data.
- Phosphocreatine takes longer to reform as people get older (from graph)
- Fast muscle fibres used for rapid./ brief/ powerful/ strong contractions
- Phosphocreatine used up rapidly during contraction to make ATP
- Anaerobic respiration involved
- (As people get older) Slower metabolic rate/ slower ATP production/ slower respiration
- ATP used to reform phosphocreatine
- Lots of phosphocreatine in fast fibres
What are the three types of muscle and where are they found?
- Cardiac muscle- exclusively found in the heart
- Smooth muscle- found in the walls of the blood vessels and the gut
- Skeletal (striated muscle)- is the bulk of body muscle in most vertebrates. Attached to bone and is under conscious, voluntary control
What is a myofobril?
Tiny muscle fibres making up striated muscle.
How are myofibrils arranged in skeletal muscle?
Small units bundled into progressively larger ones
What are the two types of protein filament that myofibrils are made up of
- Actin- thinner, two strands twisted around one another
- Myosin-thicker, long rod shaped fibres with bulbous heads that project to the sides
What are the two different bands and why are they different colours?
- Isotropic (I) bands- light bands because actin and myosin do not overlap in these regions
- Anisotropic (A) bands- dark bands because actin and myosin filaments overlap in this region
What is a H zone?
A lighter region at the centre of the anisotropic band