Skeletal Muscle

Question 1

Epimysium

Answer 1

connective tissue surrounding entire muscle

Question 2

Muscle

Answer 2

made up of multiple fascicles

Question 3

Perimysium

Answer 3

connective tissue surrounding individual fascicle

Question 4

Fascicle

Answer 4

A bundle of myofibers

Question 5

Endomysium

Answer 5

Delicate connective tissue around each myofiber

Question 6

Sarcolemma

Answer 6

also called (plasmalemma) cell membrane of muscle fiber

Question 7

myofiber

Answer 7

muscle cell, individual multinucleated muscle cell

Question 8

myofibril

Answer 8

a chain of sarcomeres within a myofiber

Question 9

Myofilament

Answer 9

actin and myosin filaments that make up a sarcomere

Question 10

Sarcolemma

Answer 10

Plasmalemma containing T-tubules

Question 11

T-tubules

Answer 11

invaginations of carloemma, two per sarcomere

Question 12

Sarcoplasmic reticulum

Answer 12

Endoplasmic reticulum

Question 13

Sarcomere

Answer 13

basic contractile unit consisting of an I band (actin), an A band (myosin + actin), a Z disc indicating sarcomere separation, and an H band consisting of just myosin

Question 14

Z discs

Answer 14

anchor actin filaments

located at each end of a sarcomere

Question 15

I bands

Answer 15

composed entirely of actin

width changes during contraction

Question 16

A bands

Answer 16

composed of actin and myosin

width does not change during contraction

Question 17

H bands

Answer 17

composed entirely of myosin

width changes during contraction

Question 18

Titin

Answer 18

the protein that helps keep the actin and myosin’s side by side relationship stable. act as a framework

Question 19

After acetylcholine triggers an action potential at the sarcolemma…

Answer 19

voltage gated ion channels on T-tubules (dihydropyrodine channels) interact with ryanodine-sensitive calcium ion release channels

Question 20

When voltage gates on _____ _______ are depolarized, they interact with _____ ______ on ______ ______

Answer 20

T-tubules, ryanodine receptors on SR membrane

Question 21

Ryanodine receptor channels =

Answer 21

calcium ion sensitive, located in SR cisternae

Question 22

Ryanodine receptors

Answer 22

release calcium in cytosol, which binds to troponin

Question 23

Calcium binds to

Answer 23

troponin, which moves tropomyosin from myosin binding sites on actin

Question 24

Where would you find ATPase in the sarcomere?

Answer 24

on myosin: splits ATP in order to bind to actin

Question 25

ATP’s role in muscle contraction (2)

Answer 25

ATP used to connect to actin; ATP used to disconnect from actin

Question 26

Power Stroke

Answer 26

this is the “event” caused by the potential energy stored up in myosin from cleaving ATP to ADP+P(i) earlier

Question 27

Cycle of “power stroke” beginning at ATP binding to myosin

Answer 27

ATP binds to myosin to release actin from a previous cycle. Afterward myosins ATPase cleaves a P bond, leaving behind ADP+P(i) on the myosin head
when calcium comes along and causes conformational exposure of the actin binding sites, the myosin is “cocked and loaded”–contains the potential energy needed– and can perform the POWER STROKE, cycle continues

Question 28

“Big picture” beginning at sarcolemma depolarization

Answer 28

Sarcolemma depolarizes—> T-tubule depolarizes —> DHP receptor undergoes conformational change —> causes Ryanodine receptors to change conformation —> causes Ryanodine receptor calcium channels to release traces amount of calcium —-> triggers SR to release tons of calcium into cytoplasm for sarcomere contractions

Question 29

Ryanodine Receptors are located—>

Answer 29

on the cisternae of the sarcoplasmic reticulum

facilitated diffusion followed by active transport to return calcium to SR

Question 30

Dihydropyridine (DHP) receptors are located —->

Answer 30

on sarcolemma t tubules

voltage gated

Question 31

ATP in muscle contraction: where/how

Answer 31

Largely used for contraction (myosin/actin interactions),

pumping calcium ions from sarcoplasm BACK into sarcoplasmic reticulum

pumping sodium and potassium ions through the sarcolemma to reestablish resting potential

Question 32

Concentration of ATP in muscle fiber

Answer 32

4 mmol, enough to maintain contractions for 1-2 seconds

Question 33

Rephosphorylation: how

Answer 33

Energy derived from phosophcreatine, glycolysis, oxidative metabolism

Question 34

Muscle Contractions: two types, plus describe them

Answer 34

Isometric: occurs when tension increases but muscle length does not

Isotonic: Muscle length changes in two ways

a) eccentrically: muscle length increases
b) concentrically: muscle length shortens

Question 35

Muscle Fiber Types: White

Answer 35

Also called fast: more mitochondria, less myoglobin, primarily utilizes anaerobic respiration

Question 36

Muscle Fiber Types: RED

Answer 36

Also called slow: less mitochondria, more myoglobin, primarily utilizes aerobic respiration

Question 37

Fiber and Fibril Regeneration

Answer 37

Myofiber cannot be regenerated after birth, but myofibrils can. So mass can increase.

Question 38

“Dark fibers”

Answer 38

soleus

Question 39

“light fibers”

Answer 39

gastrocnemius

Question 40

a neuron and the myofibers it innervates constitute

Answer 40

a motor unit

Question 41

What happens when a neuron interfacing a myofiber fires a signal?

Answer 41

all the myofibers in the motor unit contract. All or none.

Question 42

Summation

Answer 42

Before calcium ions have returned to SR, an additional release of calcium can occur: total amount of Ca increases, each additional “spike” adds to the effects of the last one.

Question 43

Tetany

Answer 43

Too many spikes, not enough time. The muscle remains at maximal contraction