Muscle Architecture & Contraction

Question 1

Epimysium (Fascia)

Answer 1

Surrounds entire muscle

Question 2

Perimysium

Answer 2

Surrounds fasciculi

Question 3

Endomysium

Answer 3

Surround myocytes

Question 4

Sarcolemma

Answer 4

Muscle cell membrane
Underlies endomysium
Contains sarcoplasm, cellular proteins, organelles and myofibrils

Question 5

Transverse Tubules

Answer 5

Invagination of sarcolemma that transmit action potential into interior muscle cell
Closely apposed to SR

Question 6

Sarcoplasmic Reticulum

Answer 6

Membranous sac underlying sarcolemma
Responsible for calcium storage, release and reuptake
Integral to muscle contraction

Question 7

Terminal Cisternae

Answer 7

Store and release calcium

Question 8

Myofibrils

Answer 8

Divided into individual contractile units - sarcomere

Question 9

Myosin

Answer 9

Thick filament

Question 10

Actin

Answer 10

Thin filament

Troponin and tropomyosin located on actin protein

Question 11

Titin/Connectin (Molecular blueprint)

Answer 11

Coordinate assembly of structural/regulator/contractile proteins

Question 12

Titin/Connectin (Molecular spring)

Answer 12

Links z-disk to m-line

Maintains position of actin and myosin

Question 13

Nebulin

Answer 13

Precisely regulates actin length

Question 14

Obscurin

Answer 14

Assembly and organization of SR with myofilaments

Question 15

Myosin - Heavy Chain Polypeptides

Answer 15

Light meromyosin - form molecular backbone
Heavy meromyosin - form globular head (S1) and neck (S2)
Isoforms determined by ATPase activity and contribute to contraction velocity

Question 16

Myosin - Light Chain Polypeptides

Answer 16

Each S1/2 contains essential and regulatory chains

Isoforms fine tune contraction velocity

Question 17

Tropomyosin

Answer 17

Blocks myosin binding sites at rest

Question 18

Troponin

Answer 18

Regulates tropomyosin position

Question 19

Low M-ATPase

Answer 19

Lower max contraction velocity and longer time to peak tension
“Slow twitch”

Question 20

High M-ATPase

Answer 20

Higher max contraction velocity and shorter time to peak tension
“Fast twitch”

Question 21

Type I

Answer 21

Slow oxidative

Question 22

Type IIa

Answer 22

Fast oxidative-glycolytic

Question 23

Type IIb

Answer 23

Fast glycolytic

Question 24

Myosin Isoforms

Answer 24

Genetically determined
Can’t override intrinsic qualities (I II, can’t do)
Can alter depending on training type (IIa IIb)

Question 25

Myoplasticity

Answer 25

Changes in use/environment generating alterations in structural/enzymatic protein content

Question 26

Gene expression influenced by

Answer 26

Loading conditions
Nutrition
Hormones
Environment
Contractile activity

Question 27

Myoplastic adaptation can occur at level of:

Answer 27

Structure (CSA)
Type
Metabolism
Energy storage
Capillary density
Function

Question 28

Endurance Adaptations

Answer 28

Increased oxidative capacity, mitochondrial density and expression of Type I
Reduced expression of Type IIb fibers (days)
Reduced expression of Type IIa fibers (years)

Question 29

Endurance Adaptions result in

Answer 29

Delayed metabolic acidosis

Increased fatigue resistance and oxygen consumption

Question 30

Resistance Adaptations

Answer 30

Increased CSA and number of nuclei/cell
Reduced mitochondrial density and expression of Type I and IIb fibers
Increased expression of Type IIa

Question 31

Resistance Adaptations result in

Answer 31

Increased contractility, elasticity and neuromotor recruitment

Question 32

Duchenne’s PT Interventions

Answer 32

Resistance: delay weakness
ROM: ease severity of joint contracture
Emphasize mobility and maintaining independence