Module 17 - Muscle 2 Flashcards
how long is an AP compared to a muscle contraction
AP = 2ms
muscle contrac = 20-100ms, and start is slightly delayed after AP
(due to Ca2+)
result of differing APs at diff rates
single AP = twitch
intermediate rate = summation, unfused tetanus
high rates = fused tetanus (max stimulation
what is hennemans size principle
bigger the motor neuron cell body
the more muscle fibres it innervates (hence the larger contraction force)
3 types of skeletal muscle
slow-twitch oxidative
fast-twitch glycolytic
fast-twitch oxidative
what type of myosin ATPase do the 3 types of skeletal muscle have
slow oxd = low
fast oxd = high
fast glyc = high
mitochond content in ech skeletal muscl etype
slow oxd = high
fast oxd = high
fast glyc = low
general stuff with each skeletal muscle type
slow oxd = vry good blood supply, fatigue resistant, for sustained contrac, doesnt use much ATP, small
fast oxd = kinda intermediate, still resist fatigue, uses some glycogen, uses up lots of ATP,
fast glyc = fatigue prone, uses glycolytic metabolism so lactate accumulation+acidosis
duchenne muscular dystrophy
x-linked disorder
mutation in dystrophin gene
causes skeletal muscle to not be linked properly
excess Ca can enter the cells = muscle fibres die = replaced with fat or conn tissue
(25-30yrs life expec)
what causes myostatin deficiency
myostatin usually regulates
null mutation means it’s not produced
causing excess muscle, low body fat
what is the structure of cardiac muscle cells
branched syncytium, incompletely fused cells which are joined by intercalated discs, gap junctions allow electric flow
diff between normal APs and cardiac APs
much longer (200ms)
plateaus after AP fires
due to Ca2+ going in, channels inactivate slower
how does cardiac excitation contraction coupling differ from skeletal
still uses L type Ca channel
but not phsyically linked to RyR
= CALCIUM INDUCED Ca RELEASE
but other than that, same thing
(also, the Ca from outside also contributes)
what is pacemaker potential
slow depol prodcued by SA node
aka funny current
what is the only neuronal input in cardaic contraction
symp and parasymp can affect HR
and also the conc Ca2+ = force of contrac
what is frank starling law
more blood more stretch of cardiac muscle
= more forceful contraction
what metabolism does cardaic muscle use
oxididative metab
cuz needs to beat continuously
diff in smooth muscle composition compared to the others
no striations
no t tubules
no troponin
small spipndle shaped
are smooth muscle cells coupled together or act independant
both lol
coupled w/gap junction = unitary (similar to cardiac)
or independent =multiunit
2 functions of smooth muscle
propel contents of the organ it surrounds
regulate flow e.g. in blood vessels
what is smooth muscle controlled by
autonomic nervous system
how is smooth muscle diff in terms of contraction
slowly and for longer
more energy efficient
diff excitation contraction coupling mechanisms
can contract over large range of tensions
what are the 3 sources for Ca2+ in smooth muscle
- L type channel = ca induced ca release (same as cardiac
- low ca in SR signals store operated ca channel
- IP3 receptor (ligand gated ca channel in SR)
controled by phospholipase C and GPCR
(this mech means it can contract WITHOUT action potential)
if no troponin in smooth muscle, what carries the Ca
calmodulin
what does calmodulin-calcium complex activate
myosin light chain kinase
which phosphorylates the regulatory light chain
and switches on ATPase activity
