Lecture 5: Skeletal Muscle

Question 1

skeletal muscle converts ___energy to __ energy

Answer 1

electrical; mechanical

Question 2

the process of converting electrical energy to mechanical energy is called __

Answer 2

excitation-contraction coupling

Question 3

an individual muscle cell is called a

Answer 3

muscle fiber

Question 4

t/f the movement of skeletal muscle is under conscious control

Answer 4

true

Question 5

skeletal muscle is striated and multinucleate (t/f)

Answer 5

true

Question 6

myofibrils are the ___ elements

Answer 6

contractile

Question 7

t/f myofibrils run the entire length of of a muscle

Answer 7

true

Question 8

myofibrils contain a regular repeated pattern of ___

Answer 8

protein filaments

Question 9

protein filaments interact with each other in an ___ pattern

Answer 9

interdigitating

Question 10

what are the 3 zones/bands in a myofibril?

Answer 10

I band, H zone, A band

Question 11

what happens to thick and thin filaments during muscle contraction?

Answer 11

they slide against us

Question 12

t/f filaments change shape when they slide over each other

Answer 12

false

Question 13

how does the A band change during muscle contraction?

Answer 13

doesn’t change

Question 14

how does the I band change during muscle contraction?

Answer 14

gets shorter

Question 15

how does the H band change during muscle contraction?

Answer 15

gets shorter until it almost disappears

Question 16

thick protein filaments are made of ___

Answer 16

myosin

Question 17

a myosin filament consists of 2 ___ chains and 2 ___ chains

Answer 17

heavy; light

Question 18

what are the 2 binding sites on a myosin head?

Answer 18

atp and actin binding sites

Question 19

myosin heads have ___ activity

Answer 19

atpase

Question 20

what is the energy source for filament movement?

Answer 20

atp hydrolysis at myosin head

Question 21

thin protein filaments are made of __ , ___ and __

Answer 21

actin, tropomyosin, and troponin

Question 22

actin is made of ___ that are strung together to make __

Answer 22

g actin. f actin

Question 23

troponin are ___ proteins

Answer 23

globular

Question 24

tropomyosin are __ proteins

Answer 24

filamentous

Question 25

explain the steps of the powerstroke

Answer 25

1. myosin head hydrolyses ATP and becomes energized and cocked 2. the myosin binds to the actin, forming a crossbridge 3. the myosin cross bridge pivots, puling the thin filament past the thick filament toward the centre of the sarcomere 4. atp binds to myosin head and head detaches from actin

Question 26

calcium is the __ for muscle contraction

Answer 26

trigger

Question 27

explain the role of calcium in muscle contraction

Answer 27

ca binds to troponin, which causes tropomyosin to move and reveal the actin binding sites so myosin can bind

Question 28

the sarcoplasmic reticulum has a high concentration of __

Answer 28

calcium ions

Question 29

the T-tubule network is an extension of the ___

Answer 29

cell membrane

Question 30

what allows an action potential to penetrate into a muscle fibre?

Answer 30

t-tubule

Question 31

the t-tubule comes in close contact with ___

Answer 31

sarcoplasmic reticulum

Question 32

the t-tubule network is filled with ___

Answer 32

extracellular fluid

Question 33

what is the purpose of the T tubule network?

Answer 33

allow action potential into muscle fibre to stimulate the release of ca from the sarcoplasmic reticulum

Question 34

t/f dihydropyridine receptors are functional ca channels

Answer 34

false

Question 35

t/f ryanodine receptors are functional ca channels

Answer 35

true

Question 36

what is the function of the dihydropyridine receptors?

Answer 36

detect action potentials and activate ryanidine receptors

Question 37

t/f calcium atpase is constantly pumping calcium in by using atp

Answer 37

true

Question 38

what happens when ryanidine receptors are activated?

Answer 38

they allow ca to be released from the sarcoplasm reticulum

Question 39

list the 9 steps in EC coupling

Answer 39

1. ach release from nerve 2. ach induced endplate potential leading to muscle ap 3. acetylcholinesterase destroys ach 4. ap causes ca to be released from sr 5. ca binds to troponin 6. cross bridge cycling ; contraction 7. ca reuptake by SR 8. tropomyosin prevents cross bridge formation 9. relaxation

Question 40

after an action potential there is a brief ___ period before actual contraction that is caused by ___

Answer 40

latent; sliding filaments taking up slack

Question 41

what causes a muscle twitch?

Answer 41

single action potential

Question 42

t/f a twitch is the smallest single unit muscle contraction

Answer 42

true

Question 43

the number of cross bridges formed is proportional to the amount of ___ generated

Answer 43

tension

Question 44

___ is when max tension is reached and all cross bridges are formed

Answer 44

fused tetanus

Question 45

unfunded tetanus occurs when:

Answer 45

multiple action potentials sequentially (wave summation)

Question 46

why is there less muscle tension when a muscle is overstretched?

Answer 46

less overlap of thick and thin to make cross bridges required for tension

Question 47

why is there less muscle tension when a muscle is under stretched?

Answer 47

too much overlap, causing thin filaments to overlap with each other instead and preventing cross bridge formation