Test II: Muscle Tissue

Question 1

Muscle Tissue

Answer 1

A primary tissue type, divided into:
• Skeletal muscle tissue
• Cardiac muscle tissue
• Smooth muscle tissue

Question 2

How does muscle fibers develop?

Answer 2

Muscle fibers develop through the fusion of

mesodermal cells called myoblasts.

Question 3

Lengthwise subdivisions within muscle fiber
– Made up of bundles of protein filaments
(myofilaments)

Answer 3

myofibrils

Question 4

Protein filaments responsible for muscle contraction

Answer 4

Myofilaments

Question 5

Types of myofilaments:

Answer 5

• Thin filaments
– Made of the protein actin
• Thick filaments
– Made of the protein myosin

Question 6

– The contractile units of muscle
– Structural units of myofibrils
– Form visible patterns within myofibrils

Answer 6

Sarcomeres

Question 7

Alternating dark, thick filaments within myofibrils

Answer 7

A bands

Question 8

light, thin filaments within myofibrils

Answer 8

I bands

Question 9

Parts of the A band

Answer 9

M line
H Band
Zone of overlap

Question 10

– The center of the A band

– At midline of sarcomere

Answer 10

M line

Question 11

– The area around the M line

– Has thick filaments but no thin filaments

Answer 11

H Band

Question 12

– The densest, darkest area on a light micrograph

– Where thick and thin filaments overlap

Answer 12

Zone of overlap

Question 13

Parts of the I band

Answer 13

Z lines and titin

Question 14

– The centers of the I bands

– At two ends of sarcomere

Answer 14

Z lines

Question 15

– Are strands of protein
– Reach from tips of thick filaments to the Z line
– Stabilize the filaments

Answer 15

Titin

Question 16

• Is two twisted rows of globular G-actin

* The active sites on G-actin strands bind to myosin

Answer 16

F-actin (filamentous actin) (Thin Filament)

Question 17

• Holds F-actin strands together

Answer 17

Nebulin (thin filament)

Question 18

• Is a double strand

* Prevents actin–myosin interaction

Answer 18

Tropomyosin (thin filament)

Question 19

• A globular protein
• Binds tropomyosin to G-actin
• Controlled by Ca2+

Answer 19

Troponin (thin filament)

Question 20

– A membranous structure surrounding each
myofibril
– Helps transmit action potential to myofibril
– Similar in structure to smooth endoplasmic
reticulum
– Forms chambers (terminal cisternae) attached
to T tubules

Answer 20

Sarcoplasmic Reticulum (SR)

Question 21

Part of the SR that is formed by one T tubule and two terminal cisternae

Answer 21

Triad

Question 22

function of cisternae

Answer 22

– Concentrate Ca2+ (via ion pumps)
– Release Ca2+ into sarcomeres to begin muscle
contraction

Question 23

Initiating Contraction

Answer 23

– Ca2+ binds to receptor on troponin molecule
– Troponin–tropomyosin complex changes
– Exposes active site of F-actin

Question 24

– Contain about 300 twisted myosin subunits
– Contain titin strands that recoil after
stretching

Answer 24

Thick Filaments

Question 25

The mysosin molecule

Answer 25

The mysosin molecule
• Tail
– Binds to other myosin molecules
• Head
– Made of two globular protein subunits
– Reaches the nearest thin filament

Question 26

Myosin Action

Answer 26

– During contraction, myosin heads:
• Interact with actin filaments, forming crossbridges
• Pivot, producing motion

Question 27

Sliding filament theory

Answer 27

• Thin filaments of sarcomere slide toward M line,
alongside thick filaments
• The width of A zone stays the same
• Z lines move closer together

Question 28

Skeletal Muscle Contraction

Answer 28

The process of contraction
• Neural stimulation of sarcolemma
Causes excitation–contraction
coupling
• Muscle fiber contraction
– Interaction of thick and thin filaments
• Tension production

Question 29

Excitation–Contraction Coupling

Answer 29

– Action potential reaches a triad
• Releasing Ca2+
• Triggering contraction
– Requires myosin heads to be in “cocked”
position
• Loaded by ATP energy