Skeletal Muscle Structure and Function

Question 1

What are qualities of muscles with parallel arrangement?

Answer 1

Rapid shortening but with less tension

Question 2

What are the qualities of muscles with fivers at an angle to the axis of shortening?

Answer 2

Slow shortening but with greater tension

Question 3

What is the order of muscle arrangement from macro to micro?

Answer 3

Muscle-> Fascicle-> Muscle Fiber-> Myofibril-> Sarcomere-> Thick/Thin filaments

Question 4

What does the epimyisium cover?

Answer 4

The whole muscle

Question 5

What does perimysium cover?

Answer 5

The fascicle

Question 6

What does the endomysium cover?

Answer 6

The muscle fiber

Question 7

Where do all three muscle covering connect?

Answer 7

To the tendon

Question 8

What occurs with a single motor unit?

Answer 8

One motor unit innervates all the muscle fibers

Question 9

What occurs with two motor units?

Answer 9

Some of the muscle fibers are innervated by one motor unit and the rest are innervated by the other motor unit; motor units are all the same they can just affect different muscle fibers

Question 10

For fine movements what is true of the motor units?

Answer 10

There are few motor units per muscle fibers

Question 11

What are satellite cells?

Answer 11

Muscle stem cells found between the basement membrane and sarcolemma

Question 12

When are satellite cells activated?

Answer 12

When a muscle is damaged (can be by multiple means)

Question 13

The application of what stains myocyte nuclei blue?

Answer 13

Hemalum

Question 14

What are the three biochemical systems that are the basis of muscle function?

Answer 14

Metabolic system
Calcium regulation
Contractile

Question 15

Where is ATP expended when a myocyte is active?

Answer 15

1/3 to calcium regulation and 2/3 to cross-bridge cycling

Question 16

Where is ATP expended when a myocyte is inactive?

Answer 16

Ion transport and protein synthesis

Question 17

What is titin?

Answer 17

A protein that allows for passive tension (springy); needed for the left ventricle to fill with blood in between contractions

Question 18

What is a main determinant of muscle function?

Answer 18

Myosin isoforms

Question 19

What are Type I fibers?

Answer 19

Slow-oxidative fibers (slow twitch)

Question 20

What are Type II A fibers?

Answer 20

Fast-oxidative fibers (intermediate)

Question 21

What are Type II X fibers?

Answer 21

Fast-glycolytic fibers (fast twitch)

Question 22

The recruitment of muscle motor units occurs in what predetermined sequence?

Answer 22

Type I-> Type IIA-> Type IIX

Question 23

What are the three systems needed for a myocyte to function?

Answer 23

Metabolic
Calcium recycling
Cross-bridge cycling

Question 24

What is the H band?

Answer 24

Zone across the center of the sarcomeres of skeletal muscle; contains only myosin filaments

Question 25

What is the I band?

Answer 25

Light band on each side of Z line; contains only thin (actin) filaments

Question 26

What is the M band?

Answer 26

Runs directly through the center of the A band

Question 27

What is the A band?

Answer 27

Spans the myosin filaments; overlaps with some of the actin filaments

Question 28

What defines one sarcomere?

Answer 28

The segment between two neighboring Z-lines

Question 29

What is the ratio of actin to myosin filaments?

Answer 29

2:1

Question 30

What happens to the bands when a muscle contracts?

Answer 30

H-band shortens I-band is shortened A-band is unchanged

Question 31

What is titin?

Answer 31

A protein needed for passive tension giving muscles a spring-like property; it is important in the filling of blood into the left ventricle

Question 32

What is the clinical association of titin mutations?

Answer 32

Associated with hereditary myopathy with early respiratory failure

Question 33

What is a biomarker for acute MI?

Answer 33

Troponin: TnI and TnC

Question 34

How are different muscle types differentiated in a muscle biopsies?

Answer 34

Myosin heavy chain isoforms

Question 35

What MyHC isoform is found in Type-1 fibers?

Answer 35

MyHC I

Question 36

What MyHC isoforms are found in IIX and IIA muscle forms?

Answer 36

MyHC IIx and MyHC IIa and MyHC IIb (have genes but not expressed in humans)

Question 37

What is the main determinant of muscle function?

Answer 37

Myosin isoforms

Question 38

Which muscle type has the highest and lowest amount of mitochondria respectively?

Answer 38

Type I | Type IIX

Question 39

What implications does the order of motor unit recruitment have?

Answer 39

Rehabilitation