muscle cell structure

Question 1

What are the three types of muscle tissue?

Answer 1

skeletal muscle, cardiac, and smooth

Question 2

1. found in voluntary muscles
2. cells are called muscle fibers - these are long and cylindrical
3. multinucleate

Answer 2

skeletal muscle tissue

Question 3

contraction of skeletal muscle tissue is dependent on stimulation by somatic motor neurons, these form a chemical synapse called what?

Answer 3

neuromuscular junction

Question 4

release of __________ induces an action potential, which stimulates contraction of the muscle. (in skeletal muscle)

Answer 4

acetylcholine

Question 5

1. located int he heart
2. short, irregular- shaped cells
3. single nucleus

Answer 5

cardiac muscle tissue

Question 6

in cardiac muscle, cells are connected by gap junctions that are located within the __________ ____________

Answer 6

intercalated discs

Question 7

cardiac muscle is _____________ , meaning that action potentials arise within the muscle tissue itself.

Answer 7

autorhythmic

Question 8

action potentials within cardiac muscle are transmitted cell to cell via

Answer 8

electrical synapses

Question 9

1. located in the viscera and involved in reflexes
2. spindle-shaped and smaller than muscle fibers
3. single nucleus

Answer 9

smooth muscle tissue

Question 10

what are the 2 types of smooth muscle tissue?

Answer 10

single-unit and multi-unit

Question 11

located in the uterus, GI tract, and small-diameter blood vessels.
- connected by electrical synapses
- autorhythmic

Answer 11

single-unit smooth muscle tissue

Question 12

-located in large arteries, respiratory airways, iris of the eye, arrector pili muscles of skin
-not connected by electrical synapses
- contraction stimulated by depolarizing postsynaptic potentials
- do not produce action potentials

Answer 12

multi-unit smooth muscle tissue

Question 13

the plasma membrane of the muscle cell

Answer 13

sarcolemma

Question 14

the cytosol (ICF) of muscle cell

Answer 14

sarcoplasm

Question 15

cylindrical structures that extend the length of the muscle fiber and contain the sarcomeres.

Answer 15

myofibrils

Question 16

what causes the contraction of the muscle fiber?

Answer 16

contraction of sarcomeres

Question 17

specialized portion of the ER that acts as a calcium ion storage organelle

Answer 17

sarcoplasm reticulum

Question 18

propagate action potentials from the sarcolemma to the interior of the muscle fiber

Answer 18

transverse tubules (T tubules)

Question 19

dark crosswire striations on a myofibril

Answer 19

A bands

Question 20

light crosswire striations on a myofibril

Answer 20

I bands

Question 21

What gives the myofibrils a striated appearance?

Answer 21

the A and I bands between myofibrils

Question 22

What are the proteins in the myofibrils organized into?

Answer 22

thick or thin filaments

Question 23

Thick filaments are surrounded on all sides by thin filaments

Answer 23

yes

Question 24

Where are thick filaments located?

Answer 24

in the A bands

Question 25

What is found in the center of each A band?

Answer 25

M line

Question 26

The central area of an A band (lighter area flanked by darker areas)

Answer 26

H zone

Question 27

What are the dark areas that flank the H zone?

Answer 27

where the thick and thin filaments meet

Question 28

Only what kind of filaments are found within the H zone?

Answer 28

thick

Question 29

Where are thin filaments located?

Answer 29

I band and overlap w A band

Question 30

What is found in the center of each I band?

Answer 30

Z disk

Question 31

contractile unit of a myofibril, area between two adjacent Z disks

Answer 31

sarcomere

Question 32

a chain of Z disks arranged end-to-end

Answer 32

myofibril

Question 33

What are thin filaments made of?

Answer 33

G-actin, tropomyosin, troponin

Question 34

a globular protein that can polymerize to form long chains

Answer 34

g-actin

Question 35

two g-actin chains coiled together form

Answer 35

F-actin

Question 36

Each G-actin has one

Answer 36

myosin-binding site

Question 37

A filamentous protein that lies along F-actin, and has the ability to block myosin-binding sites

Answer 37

tropomyosin

Question 38

Troponin consists of what 3 subunits?

Answer 38

troponin T, troponin I, and Troponin C

Question 39

which troponin subunits can interact w tropomyosin and alter its position w respect to the myosin-binding sites?

Answer 39

troponins I and T

Question 40

can bind to calcium ions and regulates the activity of troponins I and T

Answer 40

troponin C

Question 41

made primarily of the protein myosin

Answer 41

thick filament

Question 42

what is myosin made of? (its characteristics)

Answer 42

long, thin tail and two heads at the end of the protein

Question 43

Myosin is composed of how many polypeptides? What are they called and how many are there?

Answer 43

6; 2 heavy chains; 4 light chains

Question 44

What do the heavy chains form in myosin?

Answer 44

the tails and heads

Question 45

what do the light chains make up?

Answer 45

they contribute to the head and form a flexible hinge region bw the head and tail.

Question 46

What sites does the head have on each myosin?

Answer 46

an ATPase site and one G-actin binding site

Question 47

consists on 200-400 myosin molecules bundled together

Answer 47

1 thick filament

Question 48

the heads that project from the thick filament are called _______________ because they interact w surrounding thin filaments

Answer 48

cross-bridges

Question 49

the middle of a thick filament lacks cross-bridges and is referred to as the

Answer 49

bare zone