Skeletal Muscle

Question 1

3 Troponin Subunits and Functions

Answer 1

Tn-T - binds to tropomyosin
Tn-C - binds Ca++
Tn-I - binds actin, inhibiting contraction

Question 2

Crossbridge Cycle

Answer 2

Muscle is energized w/ ADP and Pi, still retains energy from ATP
W/ Ca, binds to actin and releases ADP/Pi for power stroke/rotation, moving it like 10nm
ATP displaces actin, and ATPase activity of myosin head brings back to start

Question 3

Triad Components

Answer 3

2 SR Lateral Cisternae and a T-tubule

Question 4

SERCA

Answer 4

SR Calcium ATPase, that uses ATP to transport 2 Ca from sarcoplasm into SR lumen to clear all Ca after contraction. In high concentrations on lontidudinal cisternal membrane

Question 5

Calsequestrin

Answer 5

Sequesters calcium in SR

Question 6

2 Prots involved w/ Ca Release from SR

Answer 6

Dihydropyridine R (DHPR) is like a Vg Ca channel but doesn’t have a pore. Sits on T-tubule membrane and moves w/ depol, unplugging Ca release channel on SR membrane, allowing Ca to leave into sarcoplasm

Question 7

4 Sources of ATP in Muscle Cell (shortest to longest duration of supply)

Answer 7

Free ATP
Creatine Phosphate
Glucose/Glycolysis
Pyruvate/Krebs and OXPHOS

Question 8

5 Differences b/w Slow and Fast (Red and White) Muscle Fibers

Answer 8

Small vs. Large Fibers
High vs. Low Myoglobin Conc
Many vs. Few mt
High vs. Low Fatigue Resistance
Moderate vs. Very High Glycogen Stores

Question 9

2 Mechs to Generate More Force

Answer 9

1. Increase stimulation frequency

2. Increase recruitment of more muscle fibers

Question 10

Tetanic Frequency

Answer 10

Max stimulation frequency after which no further increases of force sustained

Question 11

Isotonic vs. Isometric Contractions

Answer 11

Muscle undergoes shortening while tension remains constant vs. experiencing max tension with no change in length

Question 12

Duchenne Muscular Dystrophy

Answer 12

Problem w/ dystrophin, one of complex of prots that links IC cytoskeleton to EC matrix so you get progressive tearing of muscles

Question 13

Nebulin

Answer 13

Finite rod-shaped protein acts as molecular ruler in striated muscle to determine actin filament length or else the globules assemble infinitely. Mutations can cause late-onset dystrophy

Question 14

Titin

Answer 14

Largest prot in genome, acts as scaffold from Z line to center for thick/thin filaments

Question 15

alpha-actinin

Answer 15

in all 3 types to anchor thin filaments (either with dense bodies or Z lines)