Muscles part 2 Flashcards
IMCT
-Intramuscular connective tissue
IMCT segments (3)
-Endomysium (surrounds muscle fibers)
-Perimysium (surrounds endomysiums)
-Epimysium (surrounds perimysiums)
muscle fiber muscle forms (4)
-Isoforms are different types of muscle fibers. Depending on the isoform, these fibers will contract faster or slower. Typically, slower muscle fibers are stronger than fast ones
There are 3 types:
-Slow oxidative (slow contraction, Ca uptake, and cross-bridge cycling)
-Fast oxidative glycolic (Fast contraction, Ca uptake, and cross-bridge cycling)
-Fast glycolic (same as FOG)
VEGF (3)
-Vascular endothelial growth factor
-Increases the amount of capillaries around each muscle fiber
-Levels decrease as muscles become more trained
Endurance training
Endurance training increases the aerobic capacity of muscle fibers by increasing the amount of mitochondria and lipid droplets in each fiber
PCG-1α experiment (2)
-PCG-1α is a coactivator that interacts with transcription factors in muscle gene expression
-In a study of wildtype mice and PCG-1α inhibited mice, both ran similar distances. The WT mice capillary density had doubled at the end of the experiment, but the PCG-1α inhibited mice’s density had not changed
PCG-1α and different types of exercise (3)
-Different types of exercise induce different forms of PCG-1α leading to changes in gene expression
-Endurance exercises induce PCG-1α1, leading to oxidative muscles which have a higher capacity for oxygen to produce energy
-Resistance training induces PCG-1α4, leading to hypertrophic muscles which are much larger and stronger
Python hearts (3)
-The heart of the Burmese python undergoes hypertrophy within 48 hours of eating a meal, and remains that way for nearly a month.
-The meal adds fatty acids to the pythons blood stream stimulating mRNA for cardiac myosin production, causing the pythons heart to increase in size by nearly 40%
-These same fatty acids were added to a mouse’s blood and resulted in the same effect
Space travel
When exposed to lower gravity, the sarcomere length (distance between z-discs) hardly changes, however the diameter of the discs (and therefore thickness of the muscle fiber) becomes significantly smaller
muscle activity primes
in running events, men and women become slower in age. However different events have different primes (peaks) that are age dependent. In speed events like the 200m, performance peaks around the age of 21, then beings to steeply decline. in marathons, performance peaks around the age of 30, with a much more gradual falloff. This indicates that different muscle isoforms reach top performance at different times in a humans life.
Bear experiment
Bears were hit with an anesthetic early into their hibernating season so that their contractile ability could be tested. They hooked up electrical stimuli to one of the nerves on the bears legs, causing it to contract on command. When it contracts, the bears foot presses against a plate attached to a force transducer. The force transducer measured the force generated by the muscle
Myostatin
Myostatin regulates muscle mass by inhibiting growth hormones and stimulation of atrophy genes
IGF-1
When a muscle exerts force, it secretes IGF-1, a growth hormone that triggers amino acid uptake and protein synthesis in the muscle. This causes the muscle to grow. When the muscle is not used, IGF-1 is not produced and myostatin’s production of atrophy genes causes the muscle to shrink
