Extra Muscle Phys. Q's Flashcards
(8 cards)
What is the crossbridge cycle?
cyclic formation of links b/w actin & myosin causes thin filaments to slide toward the M line of sarcomere. Myosin head undergoes conformational changes, swivelling back & forth =>relies on ATP hydrolysis for energy.
Think of a rowing boat.
List the steps in the crossbridge cycle
- Myosin binds to actin, inorganic P is released.
- Power stroke. Actin pulled toward middle of sarcomere. ADP released
- Rigor (myosin low energy form)
- New ATP binds to myosin head=>unbinding of myosin & actin
- cocking of myosin head
REPEAT. See diagram (L1)
What is the role of Calcium in contraction?
If available=>binds to troponin, moves it, causing movement of tropomyosin, exposing binding sites.
If unavailable=>binding sites blocked
What is excitation-contraction coupling?
Sequence of events describing how an AP in sarcolemma causes contraction. Stimulates Ca release from SR.
List the steps in excitation-contraction coupling
- AP in sarcolemma
- AP down T tubules
- receptors in T tubules open Ca2+ channels in SR
- Ca increases in cytosol
- Ca binds to troponin, shifting tropomyosin, exposing binding sites for myosin & actin
- crossbridge cycling occurs
Name 3 types of skeletal muscle fibres, their order of recruitment & properties
- Slow oxidative (slow to fatigue=>no lactic acid, slow ATPase)
- Fast oxidative (no lactic acid, fast ATPase)
- Fast anaerobic glycolytic (fast to fatigue=>lactic acid, fast ATPase. High force/short term activity)
Name the 2 routes of muscle coordination & feedback control and how they detect things
- muscle spindle fibres=>detect muscle length
2. golgi tendon organ=>detect tension (stretch)
A bit about fast twitch & slow twitch fibres
fast=>relax/contract more rapidly, fatigue more quickly
slow=>relac/contract more slowly, do not fatigue quickly
