Muscular System (week 3)

Question 1

state 4 basic facts about muscles (general)

Answer 1

1. only part of MS system that can actively generate force
2. active organs which can be stimulated both voluntarily and involuntarily
3. create internal forces to hold the position of the body or create movement
4. make up approx. 40% total body weight

Question 2

state the names of the ‘4 characteristics’ of muscle

Answer 2

1. excitability
2. extensibility (passive)
3. elasticity (passive)
4. contractility (active)

Question 3

state what it is meant by the key term - excitability

Answer 3

excitability the ability of a muscle to respond to stimulation

Question 4

state what it is meant by the key term - extensibility

Answer 4

extensibility refers to muscles ability to stretch beyond it’s resting length (passive)

Question 5

state what it is meant by the key term - elasticity

Answer 5

elasticity refers to a muscles ability to return to it’s resting length (passive)

Question 6

state what it is meant by the key term - contractility

Answer 6

contractility refers to the ability of muscles to contract and generate tension at the ends (active)

Question 7

what percentage of a muscles resting length can it lengthen and shorten by

Answer 7

40-50 %

Question 8

state 4 general facts about the Muscle Tendon Unit (MTU)

Answer 8

1. tendinous tissue runs through the whole muscle and is called aponeurosis
2. muscle belly = force production = active + passive
3. tendon = force transfer = passive
4. the force production of a muscle is transferred to the tendinous tissue and then to the skeleton

Question 9

fascia = …

Answer 9

Fascia = Epimysium + Perimysium + Endomysium

Question 10

state the 7 layer hierarchical structure of muscle

Answer 10

1. muscle
2. fibre bundle
3. fascicle
4. muscle fibre/cell
5. myofibrils
6. filament
7. sarcomere

Question 11

what is the difference between the epimysium, perimysium and endomysium

Answer 11

1. epimysium - surrounds the whole muscle
2. perimysium - surrounds the individual muscle fibres/cells
3. endomysium - surrounds sarcolemma + myofibrils (contained within sarcolemma)

Question 12

state 3 structural characteristics of muscle cells

Answer 12

1. the membranous system is made of the SR and TT’s
2. the sarcomere is the contractile machinery of the cell
3. muscle cells are multinucleate
4. the sarcoplasm is the cytoplasm of the muscle cell. it contains glycogen and other fuels

Question 13

state 4 facts about isometric contractions

Answer 13

1. static - no change in length of the MTU
2. can happen during partial or maximal muscle contraction
3. can occur at end or during a dynamic movement
4. muscle belly shortens, tendon lengths, MTU stays the same

Question 14

state 3 facts about concentric contractions

Answer 14

1. muscle shortens
2. contraction velocity is positive
3. muscle belly shortens, tendon lengthens, MTU shortens

Question 15

state 3 facts about eccentric contractions

Answer 15

1. muscle lengthens
2. contraction velocity is negative
3. muscle belly lengthens, tendon lengthens, MTU lengthens

Question 16

state 3 facts about actin

Answer 16

1. a contractile protein
2. structure like pearls strung together by string and then the strands of pearls are twisted together
3. each actin has a binding site for myosin

Question 17

state 2 facts about tropomyosin

Answer 17

1. a regulatory protein

2. overlaps binding sites on actin for myosin and inhibits binding when muscle is in it’s relaxed state

Question 18

state 2 facts about troponin

Answer 18

1. a regulatory protein
2. troponin binds reversibly to Ca2+ and once bound, changes conformation to pull tropomyosin away from myosin binding site

Question 19

state the first 3 steps of the excitation-coupling contraction reaction

Answer 19

1. muscle AP propagated into TT’s
2. Ca2+ released from lateral sac of SR
3. CA2+ binding to troponin removes blocking action of tropomyosin

Question 20

state the 4th step of the excitation-coupling contraction reaction

Answer 20

1. cross bridges form between actin + myosin and generate force
2. cross bridge moves through power stroke sliding actin past myosin
3. ATP causes release of myosin heads + return to normal state
4. if Ca2+ and ATP are still present, myosin head will attach to a new actin binding site

Question 21

state the 5th and 6th step (final 2 steps) of the excitation-coupling contraction reaction

Answer 21

1. when the AP ceases, SR re-uptakes Ca2+

2. CA2+ removal from troponin restores tropomyosin’s regulatory function