Muscle

Question 1

What are the 3 main types of muscles?

Answer 1

1. skeletal
2. Cardiac
3. Smooth (unitary and multi-unit)

Question 2

Describe excitation-contraction coupling:

Answer 2

• Na+ and K+ –> develops action potential
• Ca2+ regulates muscle contraction –> actomyosin –> gives the striated look

Question 3

Described Sarcomere

Answer 3

• 1 sacromere unit = from Z line to Z line
• Z line is in the middle the lighter band, I band
• I band = composed of the light chains –> actin, tropomyosin, and troponin
• Between each I band, there is the A band
• A band = composed of thick filaments (myosin)
  - Has a central lighter area = H band
• H band = region when the muscle is relaxed, the thin and thick filament don’t overlap
• M line is in the middle of H band

Question 4

Isometric vs isotonic contraction

Answer 4

Isometric contraction = contraction without decrease in length
Isotonic contraction = same tension, decrease in length

Question 5

What’s the difference between contraction regulation in smooth vs cardiac & striated muscle?

Answer 5

In smooth muscle, contraction is via actomyosin system
In cardiac and striated muscle, contraction is regulated by Ca2+ though phosphorylation-dephosphorylation reactions

Question 6

How does the Ca2+ fluctuate during cardiac contraction?

Answer 6

Question 7

What are the functions of Troponin T, I, and C?

Answer 7

• Troponin T, I , C –> from skeletal muscles
• Striation in skeletal muscle
• Mostly mysoin II in skeletal muscle –> 2 heads, uses ATP to move
• Troponin T binds tropomysoin
• Troponin I inhibits myosin with actin
• Troponin C binds Ca2+ –> stored in sER

Question 8

Which cation effects the magnitude of the action potential? which effects the resting potential?

Answer 8

• Changes in Na extracellular will effect magnitude of action potential
• Changes in external K affect the resting potential

Question 9

Describe the steps leading to muscle contraction in smooth, skeletal, and cardiac muscle.

Answer 9