Skeletal Muscle: Molecular Basis

Question 1

What are Transvers Tubules?

Answer 1

• Invaginations of sarcolemma into the center of the cell
• Contain voltage gated L type DHPR Ca channels
• Many other types of Na,K, and Ca channels and pumps.

Question 2

What is the SR?

Answer 2

• system of tubular sacs
• stores high concentrations of Ca
• Contains DHPR activated channels (Ryanodine receptors)
• Release Ca to trigger muscle contraction and SERCA to pump Calcium back in

Question 3

What is a sarcomere?

Answer 3

The Contractile Unit of muscle made of myofilament proteins

Question 4

What is the role of nebulin Nd other Z disc proteins??

Answer 4

Anchor thin filaments in place

Question 5

What is the role of Titian?

Answer 5

Large protein which spans entire sarcomere which helps to prevent pulling apart and in elastic recoil

Question 6

What is the troponin complex, and what are its components?

Answer 6

Protein which regulates beginning and end of contraction based on calcium iron concentrations

Troponin C - Calcium binding unit
Troponin I - Inhibitory subunit which regulates actin-tropomysoin interaction
Troponin T: Tropomyosin binding subunit

Question 7

What events follow Ca binding to troponin?

Answer 7

1. Troponin-tropomyosin move and allow myosin to interact with actin
2. Myosin produces contraction (shortening)
3. Ca is pumped back into SR/out of cell
4. Relaxation occurs when Ca unbind from troponin which results in troponin-tropomyosin preventing myosin from binding actin

Question 8

What is the role ofATP in Muscle contraction?

Answer 8

During Contraction, ATP binds to myosin causing dissociation of myosin from actin

Question 9

Describe the sliding filament model of muscle contraction.

Answer 9

• “swinging lover arm”
• Shortening occurs due to movement of actin filament over myosin
• Formation of crossbridges btwn actin and myosin makes power stroke