7. Regulation of Muscle Contraction

Question 1

Describe excitation-contraction coupling in muscle

Answer 1

1. Action Potential propagates along the sarcolema and T system
2. Increases Ca conc
3. Troponin binds Ca allowing cross bridge formation with actin
   Release of ADP and phosphate from myosin ATPase
4. Further charges move the crossbridges
   Drag actin filaments towards centre of the A band
5. Myosin ATPase binds ATP
   Dissociation of crossbridges
   Return to ‘cocked position’ for next cycle

Question 2

What is malignant hyperthermia?

Answer 2

Abnormal ryanodine receptor
Anaesthesia causes rapid increase in temperature, muscle rigidity and damage and death
Excessive Ca in sarcoplasm
Dantrolene to treat

Question 3

Where does the energy for contraction come from?

Answer 3

1. ATP
2. ADP and phosphocreatine
3. Anaerobic glycolysis
4. Fat and protein

Question 4

Why does rigor mortis occur?

Answer 4

No ATP is produced after death
Myosin heads are stuck on actin
Constant contraction

Question 5

What is isotonic contraction?

Answer 5

Tension increases until it reaches the weight of the object being lifted
Muscle shortens and tension stays constant

Question 6

What is isometric contraction?

Answer 6

Weight is too heavy to be lifted
Tendon lengthens and muscle shortens
Overall remains the same length

Question 7

What is eccentric contraction

Answer 7

Muscle lengthens
Different force is acting eg. gravity
Causes more damage to the muscle fibre

Question 8

What is calsequestrin?

Answer 8

A protein which loosely binds Ca ions

Makes it easier for Ca pump to work

Question 9

What do high serum levels of creatine kinase suggest?

Answer 9

Muscle disease

Released by the break down of muscle