exam 2: skeletal muscle

Question 1

the dark band

Answer 1

a-band
thick and thin

Question 2

light band

Answer 2

I-band
only thin

Question 3

functional unit of cardiac and skeletal muscle

Answer 3

sarcomere

Question 4

when the sarcomere shortens, what moves and what stays

Answer 4

I-band shrinks during contractions (H-zone)
and
A-band remains the same

Question 5

alternating A-bands and I-bands create the _________ appearance in skeletal and cardiac muscle

Answer 5

striated appearance

Question 6

entire length of thick filament

Answer 6

a-band (dark)

Question 7

includes only the thin filament

Answer 7

I-band (light)

Question 8

only thick filament

Answer 8

H-zone

Question 9

thin filaments anchored here

Answer 9

z-line

Question 10

link the central regions of thick filaments

Answer 10

m-line

Question 11

during contraction what decreases:

Answer 11

H-zone and I-band

Question 12

why doesnt a-band change in size

Answer 12

because its the same length as the thick filament

Question 13

thin filaments are composed of____
, ______, and _____

Answer 13

actin, tropomyosin, and troponin

Question 14

(with G-actin molecules, the active site which bind myosin)

Answer 14

actin

Question 15

(which binds actin, tropomyosin and calcium)

Answer 15

troponin

Question 16

covers up myosin binding site of actin

Answer 16

tropomyosin

Question 17

troponin has 3 globular proteins:

Answer 17

T, C and I

Question 18

_____(thick) filaments has multiple cross-bridges where the “heads” can bind to the

Answer 18

myosin

g-actin molecule

Question 19

myosin also functions as the

Answer 19

ATPase enzyme

Question 20

this connects thin filaments to glycoproteins in sarcolemma

Answer 20

dystrophin protein

Question 21

provides scaffolding for sarcomeres

Answer 21

dysotrophin protein

Question 22

muscular dystrophies:

Answer 22

1. duchenne (x-linked)
2. beckers (milder phenotype)
3. myotonic
4. oculopharyngeal
5. limb girdle

Question 23

what is muscular dystrophy

Answer 23

not enough dystrophin

Question 24

excitation/contraction coupling.

the alpha motor neuron (LMN) releases _____ which binds to a nicotinic ACh receptor on the muscle fiber

this is happening at the motor end plate or aka

Answer 24

ACh

aka neuromuscular junction

Question 25

this inhibits the release of ACh at the neuromuscular junction. it can be used in dentistry

Answer 25

botulinism toxin A

Question 26

muscle twitch has 3 phases in order:

Answer 26

1. latent period= muscle Action potential (really fast) 2. contraction= muscle increase 3. relaxation= of muscle

Question 27

what ap is first and what is right after that is second

Answer 27

1. AP of alpha motor neuron is first 2. ap of muscle is right after (Na and K out)

Question 28

for contraction to happen, the intracellular _____ in the muscle fiber must increase

Answer 28

calcium

Question 29

in resting muscle, _______ prevents a strong bond between the myosin head and g-actin molecules

Answer 29

tropomyosin

Question 30

when troponin binds to cytosolic Ca2+, tropomyosin is:

Answer 30

pulled away from myosin binding site and allows for the power stroke (myosin heads can then attach to actin)

Question 31

calcium is released from

Answer 31

the sarcoplasmic reticulum

Question 32

modified ER that sequesters(hide away) Ca2+

Answer 32

sarcoplasmic reticulum (SR)

Question 33

invaginations of sarcolemma

Answer 33

transverse (T)-tubules

Question 34

portion of SR that contact t-tubules

Answer 34

terminal cisternae

Question 35

the action potential travels down the membrane, down T-tubules and activates: which are on the t-tubules

Answer 35

sensitive dihydropyridine (DHP) receptors

Question 36

DHP in turn open_____ on the SR. calicum goes from SR to the sarcoplasm

Answer 36

calcium channels (ryanodine receptors)

Question 37

the intracellular structure of_________ ensures spread of action potential (and calcium) throughout the cell

Answer 37

myocytes

Question 38

what is necessary for contraction?

Answer 38

atp

Question 39

ATP binding to the myosin head:

Answer 39

breaks the cross-bridge (connection between actin and myosin)

Question 40

energy released from ATP hydrolysis by the myosin head provides: ATP-> ADP + Pi+energy

Answer 40

energy for cocking the myosin head (myosin is now in the high energy form)

Question 41

release of what from the myosin head provides energy for the POWER STROKE? which leads to

Answer 41

inorganic phosphate (myosin head pulling actin towards the center of the sarcomere) leads to sarcomere shortening

Question 42

muscle cells only have enough ATP for ~ _____ twitches

Answer 42

8 twitches

Question 43

cross-bridge cycling will stop only when

Answer 43

you run out of atp or ca2+

Question 44

both ___ and ___ produce ATP for muscle fibers

Answer 44

aerobic and anaerobic metabolism

Question 45

both aerobic and anaerobic metabolism produce ATP for muscle fibers. however, the contribution of each in a specific muscle fiber depends on: 1. 2.

Answer 45

1. the metabolic enzymes are present in the cell (glycolytic vs. oxidative fibers) 2. the intensity of the exercise

Question 46

when muscles are resting, they build up a bunch of: which can use by adding ADP and CK to for ATP

Answer 46

phosphocreatine

Question 47

measurements of this in the blood is down to determine if damage to muscle tissue (skeletal and cardiac) has occurred

Answer 47

creatine kinase (CK)

Question 48

what happens if atp runs out

Answer 48

fatigue

Question 49

fatigue muscles:

Answer 49

1. have decreased tension generation 2. take longer to contract 3. relax more slowly and may not completely relax

Question 50

theories for fatigue:

Answer 50

1. change in membrane potential 2. decreased ACH 3. blockage of blood flow 4. central fatigue 5. increased metabolic byproducts (lactic acid or high K+ in ECF) 6. depleted glycogen

Question 51

what 2 things must be present for cross-bridge cycling

Answer 51

both Ca and ATP

Question 52

cross-bridge cycling. prior to atp binding, when myosin and actin are tightly bound

Answer 52

rigor state

Question 53

cross-bridge cycling. step two, atp binds to ____, decreases its affinity for actin and the two separate

Answer 53

atp binds to myosin head

Question 54

cross-bridge cycling. step 3, myosin head moves in the direction of the ______, ATP is_____

Answer 54

direction of the z-line atp is hydrolyzed

Question 55

cross-bridge cycling. step 4 myosin binds the next actin (one closer to z-line) and _____ occurs (pulls actin towards M-line

Answer 55

power stroke

Question 56

cross-bridge cycling. step 5._____ is released and the actin and myosin resume to the rigor state

Answer 56

ADP

Question 57

to get relaxation of skeletal muscle, ______ must stop firing and ____ must decrease but ____ must be present to remove myosin from actin

Answer 57

alpha motor neuron stop firing and cytosolic (intracellular) calcium concen. decrease atp must be present

Question 58

relaxation of skeletal muscle. what removes calcium from cystol on SR

Answer 58

calcium ATPase

Question 59

what happens when atp is lost and myosin is stuck to actin

Answer 59

rigor mortis

Question 60

relaxation of skeletal muscle. ____ moves and covers actin's myosin-binding site

Answer 60

tropomyosin

Question 61

relaxation of skeletal muscle. actin slowly slides back to its original resting place and the ____ returns to its original length

Answer 61

sarcomere

Question 62

where is DHP? where is ryanodine?

Answer 62

dhp= muscle membrane ryanodine= SR

Question 63

botox works by

Answer 63

blocking ACH release

Question 64

what provides energy for power stroke

Answer 64

release of phosphate