Muscle Contraction 3

Question 1

What are the two main types of muscle contraction?

Answer 1

-Static (isometric)
-Dynamic (isotonic)

Question 2

Static/ isometric contraction:

Answer 2

-muscle produces force but does not change length
–joint angle does not change

-myosin cross-bridges form and recycle, no sliding (external force too great)

-ex: trying to lift an object that is heavier than the force generated by the muscle

Question 3

Dynamic/ isotonic contraction:

Answer 3

Concentric contraction:
-muscle shortens while producing force
-most familiar type of contraction
-sarcomere shortens, filaments slide toward center

Eccentric contraction:
-muscle lengthens while producing force
-cross-bridges form but sarcomere lengthens, filaments pulled away from the center
-ex: lowering a heavy weight

Question 4

How can muscle fibers by classified?

Answer 4

-how fast they can contract
–dependent on how quickly ATPase hydrolyzes ATP to produce cross-bridges

-how they produce ATP:
oxidative fibers produce through aerobic pathways
glycolytic fibers produce through anaerobic pathways

Question 5

3 main types of muscle fibers:

Answer 5

-slow oxidative
-fast oxidative
-fast glycolytic

Question 6

Slow fibers:

Answer 6

-large number of mitochondria and extensive blood supply
-store O2 in myoglobin (gives red color)
-can contract for longer because of the amount of ATP they produce (useful for muscles that maintain posture, stabilize joints, and make frequent small movements)
-small diameter=less tension

Question 7

Fast fibers:
Fast oxidative
Fast glycolytic

Answer 7

Fast oxidative:
-can produce more tension than slow fibers
-do not have much myoglobin (light in color)
-used primarily for movements such as walking that require a moderate amount of energy

Fast glycolytic:
-large diameter=high tension
-high amounts of glycogen
-not much myoglobin or mitochondria (white color)
-fatigue quickly
-used to produce quick, powerful contractions

Question 8

Hypertrophy vs atrophy:

Answer 8

-new muscle cells are not added when muscles grow

-hypertrophy: enlargement of muscles
caused by the addition of myofibrils which increases thickness of muscle fibers

-atrophy: loss of muscle mass
sarcopenia= age related atrophy

Question 9

Endurance exercise:

Answer 9

-modifies slow fibers
more mitochondria and myoglobin -> more efficient aerobic respiration
-can trigger formation of more capillary networks around fibers
(angiogenesis)

Question 10

resistance exercise:

Answer 10

-increases formation of myofibrils
–increases thickness of muscle fibers
–results in hypertrophy
–requires large amounts of proteins

-connective tissues become more developed to counter increased forces

Question 11

PEDs:

Answer 11

anabolic steroids:
stimulate muscle growth

EPO:
triggers formation of red blood cells

hGH:
facilities building muscles and speeds recovery

Creatine phosphate:
may increase power in initial stages of contraction