L8 Intro to Muscle

Question 1

Skeletal Muscles - Structure

Answer 1

Muscle fibres - long cells
Sarcolemma - mucke fibre cell membrane
folds to form T(transverse ) tubules - help spread electrical forces through sarcoplasm so all parts of muscle fibre is reached
internal membrane - Sarcoplasmic Retinaculum - stores and releases Ca
mitochondria - phosphorylation of ATP
Multinucleated
myofibrils- special proteins - v good for contractions

Question 2

Myofibrils

Answer 2

contain thick & thin filaments
thick; myosin, A-Band, dark, M line, H-Zone
thin;actin, I band, light, Z endings
sarcomeres; actin & myosin filaments

Question 3

Muscle contraction Process

Answer 3

1. Formation of AMCB:
   - myosin has 2 binding sites: for ATP and actin
   actin has a binding site for myosin also
   BUT: it has 2 other proteins that are attached together: troponin and tropomyosin, the latter of which blocks this binding site = problems
2. AP fixes it
   - AP stimulates the muscle fibres
   - travels through the sarcolemma, and t-tubules makes sure AP travels throughout the whole muscle
   - causes the SR to release Ca ions
   - Ca binds to troponin, tropomyosin moves away = free binding site
   - AMCB forms !

Question 4

NB of ATP during muscle contraction

Answer 4

ATP provides energy needed to move myosin head
ATP - ADP & Pi
this moves myosin head and pulls actin with it in a rowing motion

ATP provides energy to break actin-myosin CBB
This bond is constantly being broken and myosin head re attatches to different site along actin filament
???/ another ACTIVE site???/??

Question 5

What must happen to make muscle contraction stop

Answer 5

Ca ions leave troponin by ACTIVE transport & return to Sarcoplasmic reticulum.
Tropomyosin and Troponin come together
Binding site - blocked.
AMCB Bond canNOT form
Actin filaments return to original position & sarcomeres lengthen

Question 6

Slow twitch muscle fibres features

Answer 6

• contract slowly
• good for endurance
• can work for a long time w/o getting tired
• energy - released slowly through aerobic respiration
  (mitochondria & blood vessels supply muscles with 02)
  muscles you use - POSTURE
  RED in colour - contain myoglobin - protein that stores 02

Question 7

fast twitch fibres

Answer 7

• contract quickly
• good for sprints
• get tired easily
• energy released by ANAEROBIC respiration (using glycogen- stored glucose as doesn’t have time to wait for 02 to be produced I think)
  WHITE in colour