Muscle Cell Physiology Flashcards
(29 cards)
True or false: larger diameter muscles have limited endurance
True
What kind of skeletal muscle type is dominant in a sprinter?
fast glycolytic
What kind of skeletal muscle type is dominant in a marathon runner?
Slow-oxidative
What kind of skeletal muscle type is dominant in postural muscles?
slow-oxidative
What kind of muscle types are recruited first in recruitment?
Slow-oxidative as they fatigue slower
What size neuron innervates slow-oxidative fibers?
Small diameter motor neurons
How can we increase muscle force?
1) Recruit inactive motor units
2) Increase firing rate of active motor units (frequency modulation)
conduction velocity of small axon size muscle fiber
slower
How is glucose stored in muscle?
Glycogen
Reserve energy for muscles
Protein
Preferred source of energy for muscles
creatinine phosphate (first), then carbs / glycogen via oxidative phosphorylation, carbs via glycolysis, fatty acids through beta-oxidation
What symptom do you feel when you switch to glycolysis during exercise?
Pain in side, short of breath
Factors influencing muscle fatigue
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
age-related changes to muscle
selective atrophy of fast muscle fibers
sprouting of slow motorneurons from deinnervated motorneurons
muscle fiber changes related to diabetes
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
Isometric contraction
same length contraction; muslce develops tension but doesn’t shorten; force duration longer than isometric
isotonic contraction
same force; muscle changes length while the load on the muscle remains constant
concentric contraction
tension exceeds the load and shortening occurs; eg: bicep curl
eccentric contraction
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
relaxation of skeletal muscle largely driven by
reuptake of calcium
what stops cross-bridge in smooth muscle?
MLC phosphatase
rate of myosin-ATPase in smooth muscle
10 - 100 x slower than skeletal muscle- prevents fatigue. smooth muscle shortening is consequentially much slower
primary muscle type in smooth muscle
slow oxidative
Features of cardiac muscle
Bifurcate for form a 3D network; striations; intercalated disks; intermediate in size
