L11 Skeletal Muscle II Flashcards
What is isometric contraction?
Contraction that generates force, but no appreciable shortening of muscle length
What is isotonic contraction?
Contractions that result in shortening of the muscle length against a constant load
Are most muscle contractions isometric or isotonic?
Most actually have components of both
Why can’t you stretch a muscle fiber out and have it still work?
Because the actin and myosin filaments won’t be able to interact with each other in a way that can generate a force
What is passive tension?
Tension developed by just stretching the muscle (no stimulation)
What it total tension?
tension developed when a muscle is stimulated at different muscle lengths (preloads). It is the SUM of the active and passive tensions
What is active tension?
Active=Total-Passive
Determined by the difference in tension
What does peak active tension represent
Optimum length
It is the resting length of our muscles (they are perfect length)
What is Lo (L “not”)
optimal muscle length
In the body, resting skeletal muscle is at what length?
Lo
L “not”
What causes twitch summation?
Sustained release of calcium
What is tetanus?
Maximal sustained contraction of the muscle
What is a motor unit?
A motor neuron plus its corresponding muscle fibers
Which motor units are activated first?
The smaller ones and the slower ones (type I)
Taking small steps at first and then bigger steps and faster steps
What are the 3 types of myosin found in humans?
I
IIa
IIx
True or False:
A motor unit contains more than one type of fiber
False
A motor unit only has one type of fiber. An entire muscle can have a mosaic of different types but not a single motor unit
What muscle types are fast but fatigue easily
IIx
What muscle type of metabolism do IIx fibers do
Glycolysis
What tupe of muscle fibers are fast and fatigue-resistant?
IIa
What type of muscle fibers are slow
type I
What type of metabolism do type I fibers do?
Oxidative
What type of metabolism do type IIa muscle fibers do?
Glycolytic and oxidative
What type of muscle fibers would a Long distance runner have more of
Type I
What type of muscle fibers would a sprinter have more of/
type IIx
WHat type of fibers are in Large motor units?
Fast twitch (Type IIx)
What type of muscle fivers are in small motor units?
Type I (slow)
What type of fiber has high myosin-ATPase activity?
Type IIa and IIx
What type of fiber has low myosin-ATPase activity?
Type I
