Week 4- skeletal muscle structure and function

Question 1

What are the functions of skeletal muscle?

Answer 1

-Force production of locomotion, breathing, postural support
-heat production during cold stress
-acts as an endocrine organ

Question 2

Where is connective tissue found?

Answer 2

Surrounding the entire muscle

Question 3

Where is the epimysium found?

Answer 3

Surrounding the entire muscle

Question 4

Where is the Perimysium found?

Answer 4

surrounds fascicles

Question 5

Where is the endomysium found?

Answer 5

surrounds muscle fibres

Question 6

Where is the Basement found?

Answer 6

just below the endomysium

Question 7

Where is the sarcolemma found?

Answer 7

muscle cell membrane

Question 8

What does myofibrils contain?

Answer 8

contractile proteins actin and myosin

Question 9

What is the use of the sarcoplasmic reticulum?

Answer 9

Storage sites of Ca, terminal cisternae

Question 10

Where do the transverse tubules extend from?

Answer 10

sacrolemma to the sarcoplasmic reticulum

Question 11

What is the key role of satellite cells?

Answer 11

stems cells for growth and repair

Question 12

What happens to satellite cells during exercise?

Answer 12

increase in number of nuclei in mature muscle fibres

Question 13

What does more myonuclear allow for?

Answer 13

greater protein synthesis

Question 14

What does acetylcholine cause when it is release in the neuromuscular junction?

Answer 14

-end-plate potential
-depolarisation of the muscle fibre
-signal for muscle contraction

Question 15

What forms a cross bridge to create a power stroke?

Answer 15

Actin and myosin

Question 16

What breaks down ATP as fibres contract?

Answer 16

Myosin ATPase

Question 17

What is fatigue?

Answer 17

a decline in muscle power output

Question 18

What can cause a decline in muscle power output?

Answer 18

-decrease in muscle force production at cross-bridge level
-decrease in muscle shortening velocity

Question 19

What are the possible causes of fatigue?

Answer 19

• decreased calcium release from the sarcoplasmic reticulum
  -accumulation of metabolites that inhibit myofilament sensitivity to calcium
  -glycogen depletion

Question 20

What are the key metabolites contributing to fatigue?

Answer 20

-Pi and free radicals- modify cross-bridge head and reduce number of cross bridge bound to actin
-H ions bind to Ca binding sites on troponin, preventing Ca binding and contraction

Question 21

What are exercise-associated muscle cramps (EAMC)?

Answer 21

spasmodic, involuntary muscle contractions during exercise

Question 22

What is an isotonic muscle contraction?

Answer 22

muscle tension remains unchanged where muscle length decreases

Question 23

What is an isokinetic muscle contraction?

Answer 23

Muscle length decreases with constant velocity

Question 24

What is a concentric muscle contraction?

Answer 24

muscle shortens, greater force

Question 25

What is an eccentric muscle contraction?

Answer 25

muscle lengthens, lesser force

Question 26

what is an isometric muscle contraction?

Answer 26

muscle contracts but does not change in length

Question 27

What is a dynamic exercise?

Answer 27

concentric, eccentric action leading to muscle length increase and decrease

Question 28

What is a static exercise?

Answer 28

isometric action, no change in muscle length

Question 29

what is oxidative capacity?

Answer 29

quantity of mitochondrial, capillaries and myoglobin in and around the fibre

Question 30

What is speed of contraction regulated by?

Answer 30

myosin ATPase activity

Question 31

What is the maximal power equation?

Answer 31

maximal power output = force X shortening velocity

Question 32

What is muscle fibre efficiency?

Answer 32

lower amount of ATP used to generate force

Question 33

what does muscle contraction speed depend on?

Answer 33

the rate of cross bridge cycling which depends on the myosin ATPase isoform

Question 34

What happens after stimulation?

Answer 34

short latent period to correspond with the depolarisation of muscle fibre

Question 35

What occurs during muscle contraction?

Answer 35

calcium release from SR and tension is developed due to cross bridge binding

Question 36

what occurs at relaxation of the muscle?

Answer 36

reuptake of calcium to SR- cross bridge detachement

Question 37

What does it mean when more motor units are recruited?

Answer 37

greater force

Question 38

What does it mean when faster motor units are recruited?

Answer 38

greater and faster force

Question 39

What occurs when muscle length changes?

Answer 39

increased cross bridge formation

Question 40

What causes the firing rate of motor neurons to increase?

Answer 40

frequency of stimulation- simple twitch, summation, tetanus

Question 41

How many axons innervate a mature muscle fibre?

Answer 41

one

Question 42

How many motor neurons supply a motor unit?

Answer 42

one

Question 43

How many fibre types does a motor unit contain?

Answer 43

one

Question 44

What is the structure of a motor neuron supplying larger faster motor units like compared to motor neurons supplying small motor units?

Answer 44

-larger cell bodies -larger diameter -greater number of axonal branches -sparse afferent innervation -more complex and extensive motor end plate of neuromuscular junction

Question 45

What motor units are harder to excite?

Answer 45

fast motor units

Question 46

How much muscle is lost at the age of 50-80%

Answer 46

50%

Question 47

What is cachexia?

Answer 47

rapid loss of muscle mass