Lecture 8 Flashcards
what are the effects of the presence, quantity and pattern of neural input (innervation) into a developing or mature fiber?
it can alter growth factor, trophic factor synthesis or transcription
what is muscle fiber type specification a result of
the sum of genetic, chemical and activity factors
what do clonal analysis studies show
there is genetic influence on what type of muscle cell/ fiber type a cell will become
What does the migration of myogenic precursor cells depend on?
genetic signals, cell to cell contact, and environmental cues
what is the S-type of cells
most superficial layer as body wall and limbs develop
what are F-type cells
closer to bone/ deep
what do slow fibers rely on
neural input
do fast fibers rely on neural input
not really
what happens to fibers if innervation type switches
twitch fiber type switches
why do fiber types switch when innervation type switches?
the pattern of activity of APs varies the amount of trophic substances at the NMJ and concentration of calcium in the muscle fiber which could lead to downstream alterations in protein synthesis and new isoforms related to force production
what happens with disuse of muscle
a decrease in quantity of activation could result in other changes such as conversion to more fast type fibers overall
what is a satellite cell
the muscle stem cell that resides outside the muscle fiber sitting between the sarcolemma and basal lamina
why are satellite cells important
after birth myonuclei lose ability to divide so when satellite cells divide they donate a nucleus to the muscle fiber enhancing the fibers ability to synthesize or manage a greater volume of sarcoplasm and contractile proteins
what are some stimuli for satellite cells to divide
injury stretch or exercise
What does HGF do
acts as a chemical signal to initiate proliferation of satellite cells in response to injury stretch or exercise
