Physioreview48A(Skeletal/smooth Muscle)

Front 1

What are the components of a skeletal muscle fiber?

Back 1

Bundles of myofibrils
Surrounding sarcoplasmic reticulum
Tranverse(T) tubules

Front 2

What is a sarcomere?

Back 2

Myofibril unit

Front 3

How are the filaments in a sarcomere arranged in skeletal muscle?

Back 3

Longitudinally

Front 4

What does the arrangement of sarcomeres produce on a macroscopic scale in skeletal muscle?

Back 4

Striation pattern

Front 5

What are thick filaments made up of?

Back 5

Myosin

Front 6

What are the components of myosin?

Back 6

Six polypeptide chains
(two heavy and four light chains)

Front 7

What are the thin filaments made up of?

Back 7

Actin
Tropomysin
Troponin

Front 8

What are the components of troponin and what are their functions?

Back 8

Troponin C: Binds Ca+ and allows interaction of actin and myosin
Troponin I: Inhibits interaction of actin and myosin
Troponin T: Attaches troponin to tropomysin

Front 9

What are the functions of the SR?

Back 9

Stores and releases Ca+ in excitation-contraction coupling and maintains low intracellular{Ca+2]

Front 10

How are the SR and T tubule connected?

Back 10

At terminal cisternae

Front 11

How is Ca+ stored in the SR?

Back 11

Loosely bound to calsequestrin

Front 12

How is Ca+ transported into the SR?

Back 12

Ca+2-ATPase pump on the SR membrane

Front 13

How does Ca+2 exit the SR?

Back 13

Via the ryanodine receptor Ca+ channel

Front 14

What are the functions of T tubules?

Back 14

Carry depolarization from the muscle cell membrane into the myofibrils

Front 15

Describe the steps in excitation-contraction coupling that permit the cross bridge cycle for muscle contraction.

Back 15

1.Action potential occurs
2. T tubules depolarize
3. Ca+ channels open on SR membrane
4. Intracellular[CA2+] increaases
5. Ca= bind to troponin C
6. Troponin undergoes conformational change moving tropomyosin from the myosin-binding site on actin
7. Cross bridge cycle occurs

Front 16

Describe the steps in the cross bridge cycle that produces muscle contraction?

Back 16

1. Myosin has no ATP bound and is tightly attached to actin
2. ATP binds to myosin causing a conformational change that releases actin
3. Hydrolysis of ATP into ADP
and inorganic phosphate(pi) displace myosin toward the plus end of actin
4. Myosin binds to a new site on actin, which generates the power for contraction
5. ADP is released, returning myosin to its tightly bound state

Front 17

What limits the cross bridge cycle?

Back 17

Ca= being bound to troponin C and exposing the myosin binding sites on actin

Front 18

What causes muscle relaxation?

Back 18

Reuptake of Ca+ by the SR

Front 19

What would occur if the intracellular Ca+ remained high in a skeletal muscle cell?

Back 19

The muscle would not be able to relax(tetanus)

Front 20

What is an isometeric contraction?
What is isotonic contraction?

Back 20

Force is generated without the muscle
Muscle fiber shortens at a constant afterload