Lecture 3

Question 1

Muscle Types?

Answer 1

-Skeletal
-Smooth
-Cardiac

Question 2

Skeletal Muscle is Not Uniform?

Answer 2

True

Question 3

Skeletal is Striated, thus it?

Answer 3

Appears to have stripes
(myocyte –> myofibril –> sarcomere –> actin/myosin)

Question 4

Large Bundles of muscle are composed of individual muscle cells that each contain many?

Answer 4

Myofibrils

Question 5

Myofibrils each contain many?

Answer 5

Sarcomeres that are arranged end-to-end in series

Question 6

Each Sarcomere is composed of?

Answer 6

(smallest functioning unit of muscle)
Actin, Myosin, and other molecular machinery

Question 7

Actin?

Answer 7

Thin

Question 8

Myosin?

Answer 8

Thick

Question 9

Thin Filaments?

Answer 9

Actin helix with tropomyosin and troponin complex attached

Question 10

Thick Filaments?

Answer 10

Myosin II = ATPase because breakdown ATP for energy

Question 11

Thin and Thick filaments interact to produce?

Answer 11

Force

Question 12

AChR causes?

Answer 12

Depolarization in skeletal muscle cells

Question 13

Neuromuscular Junction?

Answer 13

1) Nerve axon innervating each muscle fiber
2) Release actylcholine (ACh)
3) ACh binds to AChR which is permeable to Na+, K+, and Ca2+

Question 14

Each Muscle Cell innervated by?

Answer 14

1 Nerve

Question 15

Initiation of Skeletal Muscle Contraction?

Answer 15

1) Ca2+ release from SR
2) Ca2+ binds to Troponin C and initiates a conformational change
3) Tropomyosin slides into groove between actin strands
4) Myosin can now bind actin

Question 16

Muscle Relaxed?

Answer 16

-Z-bands become wider
-I-bands widen
-A-bands remain the same
-H-bands widen

Question 17

Muscle Contraction?

Answer 17

-Z-bands move closer together
-I-bands narrow
-A-bands remain the same
-H-bands narrow

Question 18

(Skeletal Muscle Relaxation) SERCA?

Answer 18

(Sarcoplasmic Endoplasmic Reticulum ATPase)
-A calcium pump that sequesters myoplasmic Ca2+ into SR
-Pumps 2 Ca2+ into lumen/ATP while extruding 2 H+

Question 19

(Skeletal Muscle Relaxation) Calsequestrin?

Answer 19

Ca2+ binding protein near RyR (holds Ca2+ into SR in preparation for next contraction)

Question 20

(Skeletal Muscle Relaxation) Sarcalumenin?

Answer 20

Transfers Ca2+ from uptake sites to release sites (transport of Ca2+ from SERCA to RyR)

Question 21

(Initiation of Smooth Muscle Contraction) Ca2+ initiates smooth muscle contraction by?
Myosin light chain kinase (MLCK) is required to?

Answer 21

-Binding to calmodulin (can bind 4 molecules of Ca2+)

Question 22

Skeletal Muscle: T-tubules carry charge to SR to stimulate?

Answer 22

Ca2+ release from internal stores

Question 23

Smooth Muscle: Caveolae bring?

Answer 23

External Ca2+ to the SR (when refills SR)

Question 24

Factors Affecting Force Production in Skeletal Muscle?

Answer 24

1) Initial Length of Muscle Fiber
2) Fiber Type
3) Motor Unit Recruitment
4) Speed of Contraction
5) Muscle Fiber Arrangement

Question 25

Dynamic Actions?

Answer 25

-Concentric -Eccentric

Question 26

Concentric?

Answer 26

-Muscle develops Tension and Muscle shortens and pulls weight up -Muscle Force > External Force

Question 27

Eccentric?

Answer 27

-Muscle develops Tension and Muscle lengthens lowering weight gently -Braking Action= hiking downhill, spring-like storage of energy -Muscle Force < External Force

Question 28

Static Action - Isometric?

Answer 28

-Muscle develops Tension with no change in Length -Muscle Force = External Force

Question 29

Passive Force is Mediated by Titin?

Answer 29

(largest known protein) -Elastic protein that runs from Z line to M line of the sarcomere (halfway) -Acts as a molecular spring that is responsible for producing passive force in muscle

Question 30

Increased O2?

Answer 30

Increased ATP

Question 31

Motor Unit?

Answer 31

All Muscle Fibers Innervated by a Single Motor Neuron, all move together when AP fires

Question 32

Summation?

Answer 32

How muscle increases force

Question 33

Temporal Summation?

Answer 33

-Increased frequency of stimulation -Increased AP firing rate -Single AP releases Ca2+ for a short duration to cause a twitch (Tetany)

Question 34

Spatial Summation in Skeletal Muscle?

Answer 34

-All muscle fibers in a motor unit are activated simultaneously -All or None -Not all motor units are available at same time

Question 35

Recruitment?

Answer 35

Not all muscle fibers are participating all the time; some are inactive

Question 36

Tetany?

Answer 36

-Maximum force -Spasmic Muscles -Stimulating a muscle with an AP before muscle has had time to totally relax leads to

Question 37

Tonic?

Answer 37

-Continuously active to maintain a level of tone -Ex. blood vessels, respiratory tract, some sphincters -Multiunit

Question 38

Phasic?

Answer 38

-Rhythmic or intermittent contractions -Ex. GI tract, urogenital, lymphatic -Single unit

Question 39

1 Sarcomere is bounded by 2?

Answer 39

Z-lines

Question 40

I-Band decreases?

Answer 40

Increased overlap (I-Band has only actin)

Question 41

H-Zone decreases?

Answer 41

Increased overlap (H-Zone has only myosin)

Question 42

Sarcoplasmic Reticulum in Myocytes is?

Answer 42

Ca2+ storage cell

Question 43

T-tubules maximize SA of cell membrane contact with SR to couple?

Answer 43

Electrical activity from nerve with Ca2+ release

Question 44

Intermediate filaments desmin or vimentin form a?

Answer 44

Cytoskeleton network connecting dense bodies (dense bodies also contain a-actinin, which binds actin)

Question 45

Smooth Muscle Relaxation?

Answer 45

-Similar to skeletal Muscle, Ca2+ must be resequestered in SR and can also pump Ca2+ out of cell -Additional Step: MLCP (to remove phosphate from myosin to inactivate)

Question 46

Muscle Energy Sources During Exercise?

Answer 46

1) ATP (small but replenishable pool) 2) Creatine Phosphate (ATP buffer system that keeps ATP constant) 3) Glycogen (from muscle cells) 4) Plasma glucose + glycogen 5) Plasma Free Fatty Acids