Muscle Architecture

Question 1

Orientation of Muscles

Answer 1

epimysium -> perimysium -> endomysium -> sarcolemma -> sarcoplasmic reticulum

Question 2

Epimysium

Answer 2

surrounds entire muscle; also known as fascia

Question 3

Perimysium

Answer 3

surrounds fasciculi

Question 4

Endomysium

Answer 4

surrounds myocytes (mus cells/mus fibers)

Question 5

Sarcolema

Answer 5

muscle cell membrane; underlies the endomysium

Question 6

Transverse (T-) Tubules

Answer 6

invaginations of sarcolemma
Transmit action potential into interior mus cell
closely apposed to SR

Question 7

SR

Answer 7

membranous sac underlying the sarcolemma
responsible for Ca+ storage (release and uptake)
integral to mus contraction

Question 8

Terminal Cisternae

Answer 8

bulbous enlargements of SR

store and release Ca

Question 9

Sarcolemma

Answer 9

mus cell membrane;

contains sarcoplasm, cellular proteins, organelles, and myofibrils

Question 10

Myofibrils

Answer 10

divided into individual contractile units (myosin and actin)

Question 11

Thick Filaments

Answer 11

myosin

Question 12

think filaments

Answer 12

actin

Question 13

location of troponin and tropomyosin

Answer 13

actin filament

Question 14

Zone of Sarcomere

Answer 14

from Z-disc to Z-disc

Question 15

M Line

Answer 15

myofibril

Question 16

H Zone

Answer 16

contains just myosin

Question 17

I Band

Answer 17

contains just actin

Question 18

Zone of Overlap

Answer 18

contains both myosin and actin

Question 19

A Band

Answer 19

2 overlaps and H zone

Question 20

Titin/Connectin

Answer 20

molecular blueprint
molecular spring
contribution to signal transduction

Question 21

How is titin a molecular blueprint?

Answer 21

specifies and coordinates assembly of structural, regulatory and contractile proteins

Question 22

How is titin a molecular spring?

Answer 22

links z-disk to M band
maintains relative position of actin and myosin
contributes ot mus extensibility and passive force development

Question 23

Nebulin

Answer 23

molecular ruler

Question 24

how is nebulin a molecular ruler?

Answer 24

incorporated into and co-extensive with actin
extens form z-disk to end of actin myofilament
precisely regulates actin length

Question 25

Obscurin

Answer 25

intimately surrounds sarcomere, primarily at Z-disk and M-band regions coordinates assembly and organization of SR with myofilament

Question 26

Myosin Chains

Answer 26

2 heavy and 2 light polypeptides

Question 27

2 heavy myosin chains

Answer 27

light meromyosin | heavy meromyosin

Question 28

What does the light meromyosin do?

Answer 28

intertwine in double helix formation to form molecular backbone

Question 29

what does the heavy meromyosin do?

Answer 29

project outward to form neck (S2) and globular head (S1)

Question 30

what are the two light chain myosin polypeptides

Answer 30

1 essential and 1 regulatory chain for each S1/S2 complex | isoforms fine tune contraction velocity

Question 31

Actin

Answer 31

thin double helix contains mysoin binding site

Question 32

Tropomyosin

Answer 32

resides in groove along length of actin protein

Question 33

what is the purpose of tropomyosin in the absence of Ca+?

Answer 33

blocks the myosin binding site

Question 34

Troponin

Answer 34

``` spaced at regular intervals along length of actin protein 3 subunits (Ti, Tc, Tt) ```

Question 35

what does troponin do in resting state

Answer 35

regulates position of tropomyosin relative to myosin binding site

Question 36

What is the sequence of events for muscle contraction

Answer 36

1) action potential propogated along sarcolemma and into T-Tubes 2) Stim release of Ca+ from SR 3) Ca+ binds to Tc - conformation change that pulls tropomyosin away from myosin binding site 4*) hydrolysis of ATP cocks myosin head 5) cocked head binds to action and CONTRACTION OCCURS 6) hydrolysis of ATP detaches myosin head from actin 7) With action potential and thus Ca+ present, cycle keeps on 8) No AP and No Ca+ --> toponin and tropomyosin return and block binding site

Question 37

Slow Twitch Fibers

Answer 37

low myosin-ATPase activity associates with lower max contraction and longer time to peak tension

Question 38

Fast Twitch Fibers

Answer 38

high myosin-ATPase activity associates with higher max contraction and shorter time to peak tension

Question 39

Type I Fibers

Answer 39

slow oxidative

Question 40

Type IIa Fibers

Answer 40

fast oxidative-glycolytic

Question 41

Type IIb (or IIx) Fibers

Answer 41

fast glycolytic

Question 42

Myoplasticity

Answer 42

changes in use and environment can generate alterations in structural and enzymatic protein content

Question 43

what predomenately changes fibers according to myoplasticity?

Answer 43

gene expression | Levels: structure, type, metabolism, energy storage, cap den, fxn

Question 44

What causes myoplastic adaptations in endurance training?

Answer 44

delayed onset of metabolic acidosis increased fatigue resistance increased O2 consumption

Question 45

What are the adaptations in endurance training?

Answer 45

- increased oxidative capacity - increased mitochondrial density - increased expression of type I - decreased expression type IIa (takes years) - decreased expression type IIb (takes days)

Question 46

What causes myoplasitc adaptations in resistance training?

Answer 46

increase contractibility improved elasticity improved neuromotor recruitment

Question 47

What are the adaptations in resistance training?

Answer 47

- increased CSA in all fibers - increased nuclei/cell - decreased mitochondria density - decreased type I - decreased type IIb - increased type IIa - little cap change

Question 48

DMD

Answer 48

dystrophin ~5% of cytoskeletal membrane X-linked recessive inability to produce dystrophin

Question 49

DMD intervention

Answer 49

emphasis on mobility develop large mus groups and improve strength and increase endurance avoid joint contractures - rom, stretching, braces strengthen - resistance, pool