1. SKELETAL MUSCLE: STRUCTURE AND FUNCTION

Question 1

name the 3 types of muscular tissue

Answer 1

1. skeletal muscle
2. cardiac muscle
3. visceral muscle (smooth)

Question 2

what are the contractile proteins?

Answer 2

1. myosin

2. actin

Question 3

what are the regulatory proteins?

Answer 3

1. troponin

2. myosin light chain

Question 4

what are the structural proteins?

Answer 4

1. nebulin (structure for actin)

2. titin (structure for myosin and elasticity)

Question 5

what is the sliding-filament model?

Answer 5

muscles shorten or lengthen because thick and thin filaments slide past each other without changing length

Question 6

what are the steps in the sliding-filament model?

Answer 6

1. myosin crossbridges attach, rotate, and detach from actin filaments with energy from ATP hydrolysis
2. produces change in relative size within sarcomere’s zones and bands; produces a force at Z bands
3. I band decreases as the Z bands are pulled toward centre of sarcomere

Question 7

what are the steps of cross-bridging

Answer 7

1. activation
2. binding
3. power stroke
4. dissociation

Question 8

what are the purposes of deactivation?

Answer 8

1. prevent mechanical link between myosin crossbridges and actin filaments
2. inhibits myosin ATPase activity to reduce ATP splitting

Question 9

dissociation (equation)

Answer 9

actomyosin + ATP = actin + myosin-ATP

Question 10

what kind of fibers do endurance athletes have?

Answer 10

Type I (slow twitch)

Question 11

describe Type I muscle fibers

Answer 11

1. fatigue resistant
2. slow-oxidative fibers
3. contribute during near-maximum aerobic and anaerobic exercise

Question 12

What fiber type do speed and power athletes have?

Answer 12

type II (fast twitch)

Question 13

what energy system do Type I fibers use?

Answer 13

generate energy for ATP resynthesis through aerobic system

Question 14

what are 4 characteristics of Type I fibers?

Answer 14

1. low myosin ATPase activity
2. slow calcium handling ability and shortening speed
3. less well-developed glycolytic capacity than fast-twitch fibers
4. large and numerous mitochondria

Question 15

what are the 3 subtypes of type II fibers?

Answer 15

1. Type IIa: FOG (fast-oxidative-glyolytic fibers)
2. Type IIx
3. Type IIb (greatest anaerobic potential and most rapid shortening velocity)

Question 16

what are 4 characteristics of type II fibers?

Answer 16

1. high capability for electrochemical transmission of AP
2. high myosin ATPase activity
3. rapid calcium release and uptake by efficient sarcoplasmic reticulum
4. high rate of crossbridge turnover

Question 17

what energy system do type II fibers rely on for energy transfer?

Answer 17

short-term glycolytic system

Question 18

what are 4 genes that define skeletal muscle phenotype?

Answer 18

1. MAPK: ras/mitogen-activated protein kinase
2. calcineurin
3. calcium/calmodulin-dependent kinase IV
4. PGC-1: coactivator peroxisome proferator g coactivator 1