Skeletal Muscle Contraction Flashcards Preview

physiology IV > Skeletal Muscle Contraction > Flashcards

Flashcards in Skeletal Muscle Contraction Deck (29):
1

What is the Z line?

The boundary between two sarcomeres

2

What is the I band?

Composed of only actin filaments
-extends from Z towards center of sarcomere
-appears light

3

What is the A band?

Composed of myosin thick filaments
-appears dark

4

What is the H zone?

location of NO overlap between actin and myosin

5

What is the M-line?

The center of the sarcomere
-site where thick filaments are linked with eachother

6

What occurs to the Z lines, A bands, I bands during muscle contraction?

1. Z lines move closer together
2. Length of A band is constant
3. Length of I band shortens

7

What is a myosin molecule made up of?

-2 heavy chains
-4 light chains
2 regulatory chains
2 essential or alkali chains

8

What is a myosin filament made up of ?

200 or more individual myosin molecules
-equal to the length of the A band

9

What are the 6 steps involved in excitation coupling (innervation) of a skeletal muscle ?

1. Motor AP travels along motor neuron to motor endplate at neuromusc junction
2. ACh released – acts on sarcolemma
3. Trigger AP in muscle
4. Propagates down T-tubule membranes into interior of muscle fibers
5. causes release of ca2+ sequestered in SR (inside the cell)
6. Leads to shortening of sarcomere

10

How is a muscle lengthened?

By innervation and contraction of an antagonist muscle

11

What does each bind to:
1.Troponin C
2. Tropoinin I
3. Troponin T

1. c binds calcium
2. I binds actin - inhibits actomyosin ATPase
3. T binds to tropomyosin

12

What is the cycle of contraction in a sarcomere, starting when the myosin head is in an attached state? (5 steps)

1. ATP binds to myosin head -dissociation
2. ATP is hydrolyzed-myosin heads to return to resting conformation
3. A crossbridge forms and myosin head binds to new position on actin
4. P is released. Myosin heads change conformation
5. ADP is released

13

How much energy is stored in ATP as it is transformed into mechanical work in the crossbridge cycle?

30%!!

14

What is the contraction generated by a single action potential called?

A twitch

15

What is genetically distinct between the slow twitch, and two fast twitch fibers?

They differ in the myosin heavy chain they encode for
-different rates of ATP hydrolysis
-influence speed of crossbridge cycle and muscle contraction

16

Describe the phases of a graph for an isometric contraction - tension vs time

1. latent period
2. contraction phase
3. relaxation phase

17

What is the active tension ?

The difference between total tension and passive tension

18

When is tension of the muscle the greatest?

When there is maximal overlap between thick and thin filaments - number of crossbridges is the greatest

19

At which two states does zero tension exist in a muscle?

-When the muscle is stretched beyond the optimal length and there is no thin and thick overlap

-When the thick filaments contact the Z lines

20

What are satellite cells?

-Quiescent undifferentiated cells which mediate repair and growth

21

How do satellite cells assist in growth of skeletal muscle?

-They fuse into existing multinucleate myofibers and increase myofibril protein production

22

What is the result of a loss of myostatin in the mice experiment?

-uncontrolled hypertrophy
-altered satellite activation

23

What is the drug MYO-029?

-recombinant human AB that binds to inhibit myostatin activity
-used to treat muscular dystrophy

24

Describe a slow twitch fiber:
1. other name
2. Fatigue
3. Color

1. Type I
2. resistant
3. red - myoglobin

25

Describe a fast twitch iia fiber:
1. Fatigue
2. color

1. Resistant
2. Red-myoglobin

26

Describe a fast twitch IIB fiber:
1. fatigue
2. color

1. fatigable
2. white - low myoglobin

27

Describe a slow twitch fiber:
1. metabolism
2. mitochondria content
3. glycogen level

1. oxidative
2. high
3. low

28

Describe a fast twitch IIA fiber:
1. metabolism
2. mitochondria content
3. glycogen level

1. Oxidative
2. Highest
3. abundant

29

Describe a fast twitch IIb fiber:
1. metabolism
2. mitochondria content
3. glycogen level

1. Glycolytic
2. few
3. high