Muscle Terms

Question 1

Definition of

Striated muscle (def)

Answer 1

“striped” (alternating light & dark bands in micrographs) - skeletal & cardiac muscle

Question 2

Definition of

Triad (def)

Answer 2

T-tubule and flanking terminal cisternae (in skeletal muscle)

Question 3

Definition of

Muscle (def)

Answer 3

Bundle of fascicles

Question 4

Definition of

Smooth muscle (def)

Answer 4

Non-striated muscle

Question 5

Definition of

Z disk (sarcomere) (def)

Answer 5

Band at end of sarcomere to which terminal actin molecules on adjacent sarcomeres are bound

Question 6

Definition of

Motor Endplate (def)

Answer 6

Highly excitable region of the sarcolemma, at the neuromuscular junction

Question 7

Definition of

Muscle fiber (def)

Answer 7

Bundle of myofibrils (one cell, surrounded by sarcolemma, containing sarcoplasm)

Question 8

Definition of

Terminal cisterna(e) (def)

Answer 8

Chamber(s) of SR alongside (adjacent to) T-tubule

Question 9

Definition of

Perimysium (def)

Answer 9

Collagenous connective tissue surrounding one fascicle

Question 10

Definition of

Myosin filament (def)

Answer 10

Many 100’s of myosin molecules

Question 11

Definition of

Basal lamina (def)

Answer 11

Matrix with glycoproteins and collagen, between the endomysium and muscle fiber plasma membrane

Question 12

Definition of

Sarcomere (def)

Answer 12

Contractile unit of myofibril; contains alternating actin & myosin filaments; ends “capped” by Z-disks

Question 13

Definition of

M line (sarcomere) (def)

Answer 13

Center line of sarcomere

Question 14

Definition of

Epimysium (def)

Answer 14

Dense collagenous connective tissue; surrounds one muscle

Question 15

Definition of

Sarcolemma (def)

Answer 15

Myofiber plasma membrane

Question 16

Definition of

T-tubule (def)

Answer 16

Sarcolemma invagination, perpendicular to myofibrils

Question 17

Definition of

Muscle Fascicle (def)

Answer 17

Bundle of myofibers; surrounded by perimysium

Question 18

Definition of

Myofilament (def)

Answer 18

Actin, myosin (and intermediate filaments)

Question 19

Definition of

Endomysium (def)

Answer 19

Fine (fuzzy-looking) connective tissue surrounding one muscle fiber

Question 20

Definition of

A-band (sarcomere) (def)

Answer 20

Along entire length of myosin filaments (in middle of cell)

Question 21

Definition of

Ryanodin receptor (def)

Answer 21

Ca++ gated Ca++ release channel, located on SR (on cisternae adjacent to T-tubule in striated muscle (in contact); beneath caveolae in smooth muscle (not in contact but very close))

Question 22

Definition of

I band (sarcomere) (def)

Answer 22

Region where there are actin filaments only - no over-lapping myosin filaments (ends of each sarcomere)

Question 23

Definition of

Myosin molecule (def)

Answer 23

4 light chains and 2 heavy chains; 2 heads with 2 active sites each (one for ATP, one for actin)

Question 24

Definition of

Arrows (w.r.t. myotendinous junction) (def)

Answer 24

Projections of myofibers inserted into connective tissue

Question 25

# Definition of Sarcoplasm (def)

Answer 25

Myofiber cytoplasm

Question 26

# Definition of Dihydropyridine receptor (def)

Answer 26

Voltage-gated Ca++ channel, on T-tubules

Question 27

# Definition of Myofibril (def)

Answer 27

Sarcomeres lined end-to-end

Question 28

# Definition of H zone (sarcomere) (def)

Answer 28

Region where there are myosin filaments only - no overlapping actin filaments (middle of each sarcomere)

Question 29

# Definition of Myocardium (def)

Answer 29

Thick layer of cardiac muscle in heart

Question 30

# Definition of Caveola(e) (def)

Answer 30

Smooth muscle: goblet-shaped plasma membrane invagination (instead of T-tubules)

Question 31

# Definition of Dense body (def)

Answer 31

Anchor point for filaments in smooth muscle, located in sarcoplasm

Question 32

# Definition of Zonula adherens (def)

Answer 32

Component of transverse region of intercalated disks; bind f-actin of terminal sarcomeres to plasma membrane

Question 33

# Definition of Calmodulin (def)

Answer 33

Smooth muscle protein; binds Ca++ released from SR, then binds MLCK

Question 34

# Definition of Dense plaque (def)

Answer 34

Anchor point for filaments in smooth muscle, located on sarcolemma

Question 35

# Definition of Intercalated disk (def)

Answer 35

Junctional complex between cardiomyocytes

Question 36

# Definition of Desmosomes (def)

Answer 36

Component of transverse region of intercalated disks; keeps adjacent fibers together during contraction

Question 37

# Definition of MLCK (def)

Answer 37

Myosin light chain kinase; when activated (by binding Ca++/calmodulin), phosphorylates 2 myosin light chains to permit myosin contraction

Question 38

# Definition of Varicosity (def)

Answer 38

Swelling in autonomic smooth muscle motor neuron; contains mitochondria and vesicles of neurotransmitter