3.2 - Skeletal Muscle

Question 1

What % of the body weight do the skeletal muscles make up?

Answer 1

around 40%

Question 2

What is the function of the skeletal muscles?

Answer 2

to position and move the skeleton

Question 3

Muscles are attached to bones via _____

Answer 3

tendons

Question 4

What are tendons composed of?

Answer 4

dense regular connective tissue = collagen

Question 5

What is collagen?

Answer 5

protein arranged into cable-like fibers

Question 6

What is the outer connective tissue surrounding the whole skeletal muscle?

Answer 6

epimysium

Question 7

What are fascicles?

Answer 7

bundles of muscle tissue

Question 8

Fascicles are covered by a connective tissue sheath called _____

Answer 8

perimysium

Question 9

What are muscle fibers covered by?

Answer 9

endomysium

Question 10

What are myofibrils?

Answer 10

functional units of skeletal muscle, contractile and elastic protein bundles

Question 11

What is the shape of a muscle fiber?

Answer 11

long and cylindrical

Question 12

The cell membrane of a muscle fiber is called the ____

Answer 12

sarcolemma

Question 13

The specialized endoplasmic reticulum of the muscle fiber is called _____

Answer 13

sarcoplasmic reticulum

Question 14

What are T-tubules?

Answer 14

transverse tubules

branching tubes associated with the SR

Question 15

What is the function of the terminal cisternae?

Answer 15

sequester Ca2+ with the help of Ca2+ ATPase in SR membrane

Question 16

What is a triad?

Answer 16

1 t-tubules with flanking cisternae

Question 17

What are the muscle equivalent of these terms?

• muscle cell
• cell membrane
• cytoplasm
• modified endoplasmic reticulum

Answer 17

• muscle fiber
• sarcolemma
• sarcoplasm
• SR

Question 18

What structures occupy most space in the muscle fiber?

Answer 18

contractile structures of the myofibril

Question 19

Myofibrils are made up of proteins. Name the:

1. Contractile proteins
2. Regulatory proteins
3. Accessory proteins

Answer 19

contractile proteins:

• myosin
• actin

Regulatory proteins:

• tropomyosin
• troponin

Accessory proteins:

• nebulin
• titin
• others

Question 20

The repeated patters of striations in a muscle fibre forms a _____

Answer 20

sarcomere

Question 21

What is a sarcomere made up of?

Answer 21

z-line

I-band = isotropic = reflects light uniformly

A-band = anisotropic = scatters light unevenly

H zone = lighter part of A band

M line = middle

Question 22

What causes these striations?

Answer 22

the organization of the protein components of the myofibrils

Question 23

What is the structure of myosin?

Answer 23

• consists of 2 coiled protein chains/mols
• head and tail region
• tails are together, heads are at the ends

Question 24

About 250 myosin mols join to form the _____

Answer 24

thick filament

Question 25

What are the individual actin subunits called?

Answer 25

G-actin (globular)

Question 26

G actin subunits polymerize to form ____

Answer 26

F-actin chains | f for filamentous

Question 27

What forms the basis of a thin filament?

Answer 27

When 2 F-actin chains twist together

Question 28

The F-actin associates with _____

Answer 28

regulatory proteins; troponin and tropomyosin

Question 29

What are known as crossbridges?

Answer 29

The direct interaction of myosin heads with actin filaments

Question 30

What forms a completed thin filament?

Answer 30

coiled F actin + troponin + tropomyosin

Question 31

The I band contains:

Answer 31

ONLY thin filaments

Question 32

TRUE OR FALSE: The Z-line is the attachment site for ____ and the M-line is the attachment site for ____

Answer 32

z-line: thin filaments m-line: thick filaments

Question 33

The H-zone contains _____

Answer 33

only thick filaments

Question 34

How are cross sections taken at the outer edge of an A band lined out?

Answer 34

each thin filament is surrounded by 3 thick filaments | 6 thin filaments surround 1 think filament

Question 35

Accessory proteins ensure that ____

Answer 35

filaments are properly aligned within a sarcomere

Question 36

What is the function of titin?

Answer 36

- stabilizes position of contractile filaments | - returns stretched muscles to their resting length

Question 37

What is titin?

Answer 37

largest known elastic protein stretching from z line to m line

Question 38

What is nebulin?

Answer 38

non-elastic protein

Question 39

Where does nebulin attach?

Answer 39

z disc

Question 40

What is the function of nebulin?

Answer 40

helps to align actin filaments in the sarcomere