Muscle Cell Physiology

Question 1

True or false: larger diameter muscles have limited endurance

Answer 1

True

Question 2

What kind of skeletal muscle type is dominant in a sprinter?

Answer 2

fast glycolytic

Question 3

What kind of skeletal muscle type is dominant in a marathon runner?

Answer 3

Slow-oxidative

Question 4

What kind of skeletal muscle type is dominant in postural muscles?

Answer 4

slow-oxidative

Question 5

What kind of muscle types are recruited first in recruitment?

Answer 5

Slow-oxidative as they fatigue slower

Question 6

What size neuron innervates slow-oxidative fibers?

Answer 6

Small diameter motor neurons

Question 7

How can we increase muscle force?

Answer 7

1) Recruit inactive motor units

2) Increase firing rate of active motor units (frequency modulation)

Question 8

conduction velocity of small axon size muscle fiber

Answer 8

slower

Question 9

How is glucose stored in muscle?

Answer 9

Glycogen

Question 10

Reserve energy for muscles

Answer 10

Protein

Question 11

Preferred source of energy for muscles

Answer 11

creatinine phosphate (first), then carbs / glycogen via oxidative phosphorylation, carbs via glycolysis, fatty acids through beta-oxidation

Question 12

What symptom do you feel when you switch to glycolysis during exercise?

Answer 12

Pain in side, short of breath

Question 13

Factors influencing muscle fatigue

Answer 13

1) Delivery o fO2 to exercising muscle
2) Elevation of intracellular K+
3) Generation of free radicals
4) Accumulation of inorganic phosphate, not pH
5) Glycogen depletion from select compartments

Question 14

age-related changes to muscle

Answer 14

selective atrophy of fast muscle fibers

sprouting of slow motorneurons from deinnervated motorneurons

Question 15

muscle fiber changes related to diabetes

Answer 15

FG prevalence associated w/ obesity / lack of exercise may contribute to insulin resistance;
SO fibers are more active than FG fibers in removing glucose from blood

Question 16

Isometric contraction

Answer 16

same length contraction; muslce develops tension but doesn’t shorten; force duration longer than isometric

Question 17

isotonic contraction

Answer 17

same force; muscle changes length while the load on the muscle remains constant

Question 18

concentric contraction

Answer 18

tension exceeds the load and shortening occurs; eg: bicep curl

Question 19

eccentric contraction

Answer 19

unsupported load is greater than tension generated by cross bridges and load pulls muscle to longer length in spite of opposing forces; eg: thigh eccentric when site back down in a chair

Question 20

relaxation of skeletal muscle largely driven by

Answer 20

reuptake of calcium

Question 21

what stops cross-bridge in smooth muscle?

Answer 21

MLC phosphatase

Question 22

rate of myosin-ATPase in smooth muscle

Answer 22

10 - 100 x slower than skeletal muscle- prevents fatigue. smooth muscle shortening is consequentially much slower

Question 23

primary muscle type in smooth muscle

Answer 23

slow oxidative

Question 24

Features of cardiac muscle

Answer 24

Bifurcate for form a 3D network; striations; intercalated disks; intermediate in size

Question 25

What triggers the opening of the ryanodine receptor in skeletal muscle?

Answer 25

depolarization causing confirmation change of DHP receptor

Question 26

What triggers the opening of the ryanodine receptor in smooth muscle?

Answer 26

binding of Ca2+ to the ryanodine receptor directly on the SR

Question 27

can a cardiac muscle be tetanized?

Answer 27

No

Question 28

What is stage 4 of SA node called?

Answer 28

pacemaker potential

Question 29

What determines maximum HR?

Answer 29

Duration of relative refractory period

Intrinsic rhythm of SA node also inputs