Nueromuscular system Part 2 Flashcards
Can motor units be converted?
Motor units cannot completely convert in humans with normal training
there is some shift of the contractile properties and metabolic profile can occur
Can fiber type be converted?
Can modify their expression of myosin heavy chain content
Can co-express types of MHC of the same fiber type (after intense exercise training)
What is shifting?
Shifting is when the fiber type moves up to the next position
Type I moves to Type IC but cannot move to type II
Type IIX is fastest in humans and type II b occurs only in animals
What happens to the muscle during immobilization?
The muscle atrophies
Fiber type profile shifts from ST to FT
Muscle oxidative capacity reduces
General weakness
When stressors on muscle are taken off
fibers will convert to type II
What happens to muscle when we age?
Motor neuron apoptosis(natural death) = muscle fiber necrosis especially FT(not natural death)
40% loss of FT
Loss of muscle mass
Decrease MF size
Increase muscle connectivity tissue content
Increase grouping due to reduced number of MU
Decrease in overall metabolic activity
How does muscle increase in size?
Hypertrophy = increase size of fibers Hyperplasia = increase number of fibers
Does muscle increase through hypertrophy, hyperplasia or both?
MacDougall - showed same number of fibers in bicep muscle of body builders and the untrained (hypertrophy)
Sjostrom- showed that dominant tibialis anterior had greater muscle fiber compared to non-dominant (hyperplasia or genetic?)
What is the possible hyperplasia mechanism?
Muscle fiber splitting
Muscle satellite cell incorporation
(replicate cells to create a new muscle fiber)
What are the effects of training on the neuromuscular system?
1) Change in neural properties
2) Change in muscle fiber properties
1)Changes in neural properties
Increase CNS drive Increase the synchronization of MU Increase MU recruitment Decrease less inhibition due to resetting of neural tension limiting mechanisms) Increase in size and number of NMJ
What is asynchronous MU firing?
Allows for some MU to fire while other “relax” which increase all MU efficiency
What is asynchronous MU firing?
Allows for some MU to fire while other “relax” which increase all MU efficiency
2) changes in muscle fiber properties
2A) Increase size of muscle fiber with strength trainigng
2B) Angle of pennation is less in vastus lateralis and gastroc of sprinters then endurance
2C) Increase anaerobic potential/aerobic potential of FT and ST (Type I become more like type II)
What causes pain and soreness?
When nociceptors are stimulated by:
1) Mechanical damage to muscle or connective tissue
2) Stretch due to swelling
3) Muscle spasm
4) Inflammatory chemical
5) Ion accumulation
(Brain mediates the peripheral neural stimulation)
What is short term pain?
Immediate during or after exercise usually a dull ache, burn or throb the subsides with recovery
What causes short term pain?
Ionic imbalance within the muscle Muscle edema (fluid in the muscle) that causes stretch during high intensity
How long doe short term pain last?
Subsides relatively quickly during recovery
pH in muscle restored within 20min
What is long term pain?
Muscle soreness ecperienced over several hrs/day
Delayed Onset Muscle Soreness (DOMS)
What causes long term pain?
Actual muscle damage caused by mechanical stress
What are the results of DOMS?
Tearing of the sarcomere and muscle tendon
Release of chemicals that continue to stimulate nerve ending that results in prolonged sensation
Swelling/muscle edema
Disruption of Ca2+ regulation
Inflammation
What types of exercises cause DOMS?
1) Eccentric forms of muscular contractions and training
2) Unaccustomed forms of exercise
How long does DOMS last?
2-3 days
Peaks at 48hrs
Severs can last several days
What can you do about DOMS?
Training will reduce it by:
Increase connective tissue
Increase muscle fiber size
Increase suppleness and flexibility through greater ROM
Others Warm up/cool down Stretch Antioxidant supplements Pharmaceuticals
