Cell Physiology- Muscle Contraction

Question 1

what are the 3 types of muscle fibers?

Answer 1

smooth, cardiac and skeletal

Question 2

what features are unique to smooth muscle?

Answer 2

1. non-striated appearance (less organized)

2. can contract without action potential

Question 3

What features are unique to cardiac muscle?

Answer 3

1.

Question 4

what features are unique to skeletal muscle?

Answer 4

1.

Question 5

what features are shared by all three fibers?

Answer 5

1. require Ca to contract

2. contain myosin

Question 6

what features are shared by skeletal and cardiac?

Answer 6

1. T-tubule system

2. Need action potential to contract

Question 7

1

Answer 7

1

Question 8

1

Answer 8

1

Question 9

Correct sequence for excitation-contraction coupling in skeletal muscle

Answer 9

1. action potential in the muscle membrane
2. depolarization of the T-tubules?
   2a. Opens SR Ca++ release channels (ryanodine receptors)
3. increase in intracellular Ca++
4. binding of Ca to troponin C
5. Tropomyosin moves and allows for interaction of actin and myosin
6. Cross bridge formation and force generation
7. Ca++ reaccumulated by SR –> relaxation. splitting of ATP

Question 10

what properties are shared by cardiac and smooth muscle?

Answer 10

both are interconnected by gap junctions which allow for the spread of an electrical depolarization

Question 11

only striated muscle contains T-tubules? T or F

Answer 11

True

Question 12

smooth muscles are connected by _____

Answer 12

gap junctions

Question 13

smooth muscles do not have sarcomeres. T or F?

Answer 13

True

Question 14

which band shortens during a muscle contraction?

Answer 14

• I band

- this is the band that contains the titin which compresses?

Question 15

A band is

Answer 15

• located in the middle and contains the thick myosin filaments.
• does not change length during contraction or relaxation

Question 16

Z line

Answer 16

demarcates the separation of sarcomeres?

Question 17

H zone

Answer 17

• this is the bare region
• there are no thin filaments here and thus there cannot be any overlap of thin and thick filaments or cross-bridge formation in this region

Question 18

M line

Answer 18

• think M for middle

- bisects the H zone (bare zone)

Question 19

T tubules

Answer 19

invaginations of the muscle cell plasma membrane that carry the plasma membrane depolarization deep within the cell and very close to the sites of the terminal cisternae of the sarcoplasmic reticulum, located within the cytoplasm of the muscle fiber (cell).

Question 20

Duchenne Muscular Dystrophy

Answer 20

involves a decline in skeletal muscle function, due to a genetic defect in an important structural protein (dystrophin) that is located inside skeletal muscle fibers. This disease is a associated with a decerase in the mass of some of the muscle fibers but this decline is not uniform. Muscle tissue can be replaced bybyconnective tissue; indeed the increase in connective tissue can more than make up for the mass of muscle fibers lost and hence the muscle can actually increase in size at the same time it is losing functional capacity.

Question 21

gap junctions

Answer 21

responsible for the spread of a depolarization in smooth and cardiac myocytes

Question 22

excitation-contraction coupling

Answer 22

events occurring between the action potential in the muscle fiber and contraction of the muscle fiber

Question 23

myosin

Answer 23

• thick filaments comprising a large molecular weight protein
• has one heavy chain and two pairs of light chains

Question 24

2 “heads” on the myosin molecule

Answer 24

• formed by the four light chains and the N terminus of each heavy chain

Question 25

tropomyosin

Answer 25

• a filamentous protein that runs along the length of each twisted actin filament

Question 26

3 globular proteins of troponin

Answer 26

• T - troponin T
• I - troponin I - for inhibition - inhibits the interaction of actin and myosin by covering the myosin binding site of actin
• C- Troponin C - Calcium binding protein
• located at regular intervals along the tropomyosin binding filaments

Question 27

sarcomere

Answer 27

the basic contractile unit; is delineated by the Z disks

Question 28

I band

Answer 28

• located on either side of the A bands and appear light when viewed under polarized light
• contain thin (actin) filaments, intermediate filamentous proteins, and Z disks

Question 29

dystrophin

Answer 29

• an actin binding protein that anchors the entire myofibrillar array to the cell membrane

Question 30

titin

Answer 30

• a large molecular weight protein that extends from the M line to the Z disks
• associated with thick filaments

Question 31

Transverse T tubules

Answer 31

• extensive network of muscle cell membrane (sarcolemmal membrane) that invaginates deep into the muscle fiber

Question 32

dihydropyridine receptor

Answer 32

voltage sensitive protein located on the T-tubules

Question 33

sarcoplasmic reticulum

Answer 33

• an internal tubular structure which is the site of storage and release of calcium for excitation-contraction coupling

Question 34

ryanodine receptor

Answer 34

• Ca++ release channel contained in the sarcoplasmic reticulum

Question 35

Ca++ ATPase (SERCA)

Answer 35

• accumulates Ca++ in the sarcoplasmic reticulum

Question 36

tetanus

Answer 36

• a sustained contraction rather than a single twitch as a result of high levels of Ca++ due to repeated stimulation of the muscle

Question 37

length tension relationship in muscle-

Answer 37

• refers to the effect of muscle fiber length on the amount of tension the fiber can develop