9.3 Muscle Fiber Anatomy

Question 1

long, cylindrical cells with multiple nuclei

Answer 1

Skeletal muscle fibers

Question 2

muscle fiber plasma membrane

Answer 2

Sarcolemma

Question 3

muscle fiber cytoplasm

Answer 3

Sarcoplasm

Question 4

many of these in the sarcoplasm; used for glycogen storage

Answer 4

Glycosomes

Question 5

many of these in the sarcoplasm; used for O2 storage

Answer 5

Myoglobin

Question 6

densely packed, rod-like elements

Answer 6

Myofibrils

Question 7

stripes formed from repeating series of dark and light bands along length of each myofibril

Answer 7

Striations

Question 8

dark regions

Answer 8

A bands

Question 9

lighter region in middle of a dark A band

Answer 9

H zone

Question 10

line of protein (myomesin) that bisects H zone vertically

Answer 10

M line

Question 11

lighter regions

Answer 11

I bands

Question 12

coin-shaped sheet of proteins on midline of light I band

Answer 12

Z disc (line)

Question 13

smallest contractile unit (functional unit) of muscle fiber

-contains A band with half of an I band at each end

Answer 13

Sarcomere

Question 14

orderly arrangement of actin and myosin myofilaments within a sarcomere

Answer 14

Myofilaments

Question 15

thin filaments

-extend across I band and partway in A band

Answer 15

Actin myofilaments

Question 16

thick filaments

• extend length of A band
• connected at M line

Answer 16

Myosin myofilaments

Question 17

network of smooth endoplasmic reticulum tubules surrounding each myofibril

• functions in regulation of intracellular Ca2+ levels
• stores and releases Ca2+

Answer 17

Sarcoplasmic reticulum

Question 18

tube formed by a protrusion of sarcolemma deep into cell interior
-penetrate cell’s interior at each A-I band junction between terminal cisterns

Answer 18

T tubules

Question 19

area formed from terminal cistern of one sarcomere, T tubule, and terminal cistern of neighboring sarcomere

Answer 19

Triad

Question 20

when an electrical impulse passes by, T tubule proteins change shape, causing SR proteins to change shape, causing release of calcium into cytoplasm

Answer 20

Triad relationships

Question 21

during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more

Answer 21

Sliding filament model of contraction

Question 22

the activation of cross bridges to generate force

Answer 22

Contraction

Question 23

form when myosin heads bind to actin, causing sliding (contraction) process to begin

Answer 23

Cross bridges