Skeletal Muscle Physiology - Case Study

1. Skeletal muscle uses ATP to contract. ATP is broken down into ADP and P, which releases energy (heat).

2.

a. sarcoplasmic reticulum = SR (the smooth endoplasmic reticulum of muscle cells)

b. Step 1: Action potential transmitted across sarcolemma (plasma membrane of muscle cell)

Step 2: Action potential transmitted into muscle cell through T-tubules (Transverse tubules)

Step 3: Action potential transmits impulse to Ryanodine receptors on the terminal cisternae of the SR to release calcium

3. –

c. Step 1: Calcium binds to troponin (troponin C to be specific)

Step 2: This causes the unwinding of the tropomyosin-actin complex, which uncovers the myosin-head binding sites

Step 3: Myosin head binds to actin at those sites and forms a cross-bridge

Step 4: ATP generates a series of steps on the myosin head for contraction

4. Glycolysis and the TCA (also known as Citric Acid and Kreb's) Cycle. TCA produces 6 CO2's per glucose.

5. a) ATP binds to the myosin head to help release it from actin and then is broken down in a cycle to put it into the cross-bridge configuration to pull on actin

b) ATP fuels the primary active transport pump for sodium and potassium. The pump maintains a positive voltage on the exterior of the cell and negative on the interior.

c) ATP pumps calcium back into the SR after muscle contraction so that it does not remain bound to troponin or else a state of tetanus (stiff contraction) will happen.

6. Dantrolene inhibits the calcium channel (Ryanodine receptor) on the SR and therefore prevents the release of calcium from the SR. Basically it is inhibiting Step 3 above in question #1. With no calcium in the sarcoplasm (cytoplasm of the muscle cell), it will not bind to tropinin and continue the rest of the steps mentioned above.