Lec 15 Muscle Flashcards
What surrounds entire muscle?
epymysium
What surrounds myofiber?
endomysium
What is type 1 muscle?
red; slow twitch
sustained action
lots of mitochondria and myoglobin
oxidative phosphorylation
What is type 2 muscle?
white; fast twitch
less mitochondria/myoglobin
anaerobic glycolysis
What is a motor unit?
anterior horn motor neuron axon terminating in motor end plate muscle fibers that the nerve innervates
How is AP propagated for muscle contraction?
via T-tubules –> AP produces Ca efflux from SR causing muscle contraction
What do you see histologically with acute dennervation?
angular myofibers
What is myofiber type grouping?
due to partial chronic dennervation from collateral
What happens to muscle in stroke?
you are taking out the upper motor neruon but anterior horn cell still intact –> selective atrophy of type 2 fibers due to disabuse
When do you get type 2 myofiber atrophy?
when muscle isnt used [not same as dennervation]
What does proximal muscle disorder suggest?
intrinsic muscle process problem
What does distal muscle disorder suggest?
usually neurogenic
What do you see in Duchennes muscular dystrophy?
steadily progressive; onset first 5 years
X recessive
gowers sign = difficulty rising from floor
often have cardiomyopathy
lordotic posture
hypertrophy of calf muscles
What is pathogenesis of duchenne’s?
no dystrophin gene –> replace myofiber with connect tissue
What is beckers?
less severe form of duchenne
onset mid childhood; uncommon to have cardiac involvement; do have calf hypertrophy + weakness
