Muscle S11 Flashcards
determinants of muscle fibre phenotype for skeletal muscle
- cell lineage
- nerve-evoked electrical activity
- mechanical conditions
- paracrine, autocrine, and hormones
cell lineage
When mammalian muscles are transplanted and made to regenerate in a different body location, SOME of the info determining fibre type is apparently derived from muscle of ORIGIN rather than new position
cell lineage theory opposition
-studies from satellite cells
show that they have the ability to transform into a muscle fibre with either fast OR slow myosin head chain isoform
nerve-evoked electrical activity
external signal can change muscle phenotype in the adult; when a nerve from a fast muscle is transplanted to a slow muscle, or vv, both the re-innervated muscled change phenotype according to new nerve supply
type I motor units receive .. amounts of impulses delivered in …. sequences.
high; long, low-frequency
type II motor units receive … of … frequency activity
short bursts; high
effect of a … amount of activity cannot be studied in innervated muscles as a control.
REDUCED
….makes it difficult to study slow-to-fast transformation.
large amount of background activity (slow muscles)
depolarization leads to ..
shortening and/or mechanical tension in muscles
The recruitment and the activity pattern of each motor unit cary with..
force output
mechanical condition
Changes in muscle usage will transform muscle phenotype
Size can be achieved by regulating what 3 major conditions
- number of nuclei
- rate of protein synthesis for each nucleus
- rate of protein degradation
myostatin
- acts as an inhibitor of muscle growth
- disruption of myostatin genes lead to development of grossly enlarged muscles
- enlargement caused by increased number of fibres and fibre size, but not increase force
insulin-like growth factor
-has been implicated as a factor promoting hypertrophy
testosterone
promotes hypertrophy
