chapter 11

Question 1

What protein is found in thin filaments?

Answer 1

actin

Question 2

What protein is found in thick filaments?

Answer 2

myosin II

Question 3

What is the cytoplasm of muscles cells called?

Answer 3

sarcoplasm

Question 4

this type of muscle is attached to bone and is responsible for movement of the axial and appendicular skeleton and for maintenance of body posture and position

Answer 4

skeletal muscle

Question 5

muscle that is restricted to the soft tissues like the tongue, pharynx, lumbar part of the diaphragm, and upper part of the esophagus

Answer 5

visceral striated muscle

Question 6

type of striated muscle found in the wall of the heart and in the base of the large veins that empty into the heart

Answer 6

cardiac muscle

Question 7

A muscle cell is a multinucleated ____________________________

Answer 7

syncytium

Question 8

A muscle fiber is formed during development by the fusion of small, individual muscle cells called ______________________________

Answer 8

myoblasts

Question 9

consists of the plasma membrane of the muscle cell, its external lamina, and the surrounding reticular lamina

Answer 9

sarcolemma

Question 10

the delicate layer of reticular fibers that immediately surrounds individual muscle fibers

Answer 10

endomysium

Question 11

a thicker connective tissue layer that surrounds a group of fibers to form a fascicle

Answer 11

perimysium

Question 12

functional units of muscle fibers that tend to work together to perform a specific function

Answer 12

fascicle

Question 13

the sheath of dense connective tissue that surrounds a collection of fascicles that constitutes the muscle

Answer 13

epimysium

Question 14

functions primarily to store oxygen in muscle fibers and provides a ready source of oxygen for muscle metabolism

Answer 14

myoglobin

Question 15

-contain many mitochondria and large amounts of myoglobin
-these fibers have great resistance to fatigue but generate less tension than other fibers
-their myosin ATPase reaction velocity is the slowest of all of the fiber types
-typically found in the limb muscles of mammals and in the breast muscle of migrating birds

Answer 15

Type I or slow oxidative fibers

Question 16

-medium size with many mitochondria and high myoglobin content
-contain large amounts of glycogen and are capable of anaerobic glycolysis
-generate high peak muscle tension

Answer 16

Type IIa or fast oxidative glycolytic fibers

Question 17

-contain less myoglobin and fewer mitochondria
-have a low level of oxidative enzymes but exhibit high anaerobic enzyme activity and store a considerable amount of glycogen
-high peak muscle tension
-myosin ATPase velocity is the fastest of all the fiber types
-fatigue rapidly as a result of production of lactic acid

Answer 17

Type IIb or fast glycolytic fibers

Question 18

the structural and functional subunit of the muscle fiber

Answer 18

myofibril

Question 19

forms a highly organized tubular network around the contractile elements in all striated muscle cells

Answer 19

sarcoplasmic reticulum

Question 20

The basic contractile unit of striated muscle
-the portion of a myofibril between 2 adjacent Z lines

Answer 20

Sarcomere

Question 21

Which portion of the sarcomere are thick filaments restricted to?

Answer 21

central portion or A band

Question 22

What portion of the sarcomere are thin filaments found?

Answer 22

attached to the Z line and extend into the A band to the edge of the H band

Question 23

The Z line and its matrix material anchor the thin filaments from adjacent sarcomeres to the angles of the zigzag by _______________________________, and actin-binding protein.

Answer 23

a-actinin

Question 24

-small molecule that polymerizes to form a double-stranded helix, the F-actin filament
-polar, oriented in the same direction
-has a binding site for myosin

Answer 24

G-actin

Question 25

-64 kDa protein that consists of a double helix of two polypeptides -forms filaments that run in the groove between the F-actin molecules in the thin filament

Answer 25

tropomyosin

Question 26

-the smallest subunit of the troponin complex -binds calcium which is an essential step in the initiation of contraction

Answer 26

Troponin-C (TnC)

Question 27

binds to tropomyosin, anchoring the troponin complex

Answer 27

Troponin-T (TnT)

Question 28

binds to actin, thus inhibiting actin-myosin interaction

Answer 28

Troponin-I (TnI)

Question 29

-small actin-binding protein that is attached to the free end of the thin filament -maintains and regulates the length of the actin filament in the sarcomere

Answer 29

Tropomodulin

Question 30

-an elongated, inelastic protein attached to the Z lines that spans most of the length of the thin filament except for its minus pointed end -acts as a "molecular ruler" for the length of the thin filament because the molecular weight of different isoforms correlates to the length of thin filaments during muscle development -adds stability to the thin filaments anchored by the a-actinin in Z lines

Answer 30

Nebulin

Question 31

Myosin II is composed of _________heavy polypeptide chains and _______light chains

Answer 31

2 heavy 4 light

Question 32

Each globular myosin head represents a heavy chain ___________________________that projects at an approximate right angle at one end of the myosin molecule.

Answer 32

motor domain

Question 33

zone in the middle of thick myosin filaments that does not have globular projections

Answer 33

bare zone

Question 34

-large protein that spans half of the sarcomere -2 spring-like portions of this protein help center the thick filament in the middle between two Z lines -springs prevent excessive stretching of the sarcomere by developing a passive restoring force that helps with its shortening

Answer 34

Titin

Question 35

-short, bipolar, rod-shaped, actin-binding protein that bundles thin filaments into parallel arrays and anchors them at the Z-line

Answer 35

a-actinin

Question 36

intermediate filament that forms a lattice that surrounds the sarcomere at the level of the Z lines, attaching them to one another and to the plasma membrane via linkage protein ankyrin

Answer 36

Desmin

Question 37

What are the names of the M line proteins that hold thick filaments in register at the M line and attach titin molecules to the thick filament?

Answer 37

-myomesin -M-protein -obscurin -muscle creatine phosphatase

Question 38

-protein that contributes to normal assembly and to stabilization of thick filaments -forms several distinct transverse stripes on both sides of the M line that interact with titin molecules

Answer 38

Myosin-binding protein C

Question 39

protein that is thought to link laminin, which resides in the external lamina of the muscle cells, to actin filaments

Answer 39

Dystrophin

Question 40

When a muscle contracts, each sarcomere ______________________, but the myofilaments ___________________________.

Answer 40

shorten remain the same length