block 4 review deck Flashcards
what results from the stimulation of phospholipase C?
in Gaq pathway
stimulation of phospholipase C results in increased IP3 and DAG
results in contraction
what is inhibited in striated mm at low calcium concentrations?
Pi dissociation is inhibited at low Ca concentrations
what structural protein is ONLY found in skeletal mm?
nebulin
what are the actions of caldesmon and calponin?
both participate in thin filament regulation in smooth mm, caldesmon (like TnT) and calponin (like TnI)
familial hypertrophic cardiomyopathy
defect in myosin HEAVY chain
when does “amplification” occur?
between signal reception and transduction
what is the action of cAMP in smooth muscle
cAMP activates protein kinase A
protein kinase A phosphorylates MLCK to inactivate it and causes relaxation
which G protein pathways are used in sympathetic vs. parasympathetic
parasympathetic- Gq - contraction
sympathetic- GaS- relaxation
what does cGMP regulate?
neurotransmission and smooth mm contraction
what does phospholamban regulate?
SERCA pumps
phosphorylated PLB- active SERCA
unphosphorylated PLB- inhibit SERCA
what activates eNOs?
increased ca concentration
what NT/receptor in Gq?
norepinephrine and a-adrenergic
what NT/receptor in GaS?
epinephrine and b-adrenergic
what NT/receptor in skeletal mm?
Ach and nicotinic receptors
what NT and receptor in cardiac mm?
norepinephrine and b-adrenergic
what is the action of protein kinase A?
activated by increased cAMP, promotes relaxation in smooth mm by inactivating MLCK
what is the action of protein kinase C?
activated by increased DAG, promotes contraction in smooth mm cells
what does elevated cAMP stimulate?
protein kinase a (relaxation)
what does elevated cGMP stimulate?
MLCP (relaxation)
what is a graded potential?
end plate potential thats amplitude will vary based on amount of neurotransmitter released
what synthesize Ach?
choline acetyltransferases (CAT)
why can skeletal mm cells generate AP with every release of ACh?
because of the arrangement of synaptic vesicles in active zones on pre-synaptic neuron and arrangement of post junctional folds in post-synaptic mm cells
myasthenia gravis
autoimmune condition that destroys ACh receptors and will decrease end plate potential
what is the effect of botulinum and tetanus toxins
decrease release of ACh from vesicles
what is the effect of tubocarare?
inhibits ACh-receptors
will decrease end plate potential
what are multi-unit vs. single unit smooth muscles?
multi-unit- more innervation for finer control
single unit- less innervation, coarse movements
what is the parasympathetic NT and receptor?
ACh, muscarinic receptor
what is the sympathetic NT and receptor?
norepinephrine and b-adrengeric receptor
rho-A kinase
ca-independent stimulation of smooth mm contraction through inhibition of MLCP
which ion is most responsible for the upstroke in smooth mm contraction?
Ca
which ion is responsible for the plateau in cardiac mm action potential?
Ca
what is the action of AChE?
deactivates ACh to prevent multiple reactivations of ACh receptors
calmodulin
calcium binding protein that activates MLCK and promotes contraction of smooth mm
mechanism underlying steroid hormone action
depends upon specific intracellular receptor that, in turn, binds to DNA and affects transcription
diphtheria toxin
inactivates the inhibitor of adenylyl cyclase to increase cAMP levels, which will promote relaxation of smooth mm and also affect protein synthesis
what is the “power stroke” in mm contraction
dissociation of Pi from actomyosin-ADP-Pi
what type of filaments are associated with desmosomes?
intermediate filaments
what is the effect of increasing nerve impulses to a single skeletal mm motor unit?
will increase the tension of the mm fibers so long as Ach is released
what is the length constant and what affects it?
length constant is how far the end plate potential is propagated, directly proportional to axon width and membrane resistance
what is the effect of myelination on the length constant
myelin increases resistance of the membrane and increases the length constant
what is the effect of axon width on the length constant
wider axon, increased length constant
EPSP
excitatory
(+) in or (-) out
leads to depolarization
IPSP
inhibitory
(+) out or (-) in
leads to hyper polarization
what is multi-unit smooth mm composed of?
smooth mm cells that are NOT electrically coupled
what type of mm exhibits slow wave changes in electrical and mechanical activity?
smooth mm
what could be used to treat myasthenia gravis?
K channel blockers to prolong depol and increase the ACh present in synapse
what accounts for the increased resting-length tension of cardiac mm compared to skeletal mm?
titin is shorter in cardiac mm than skeletal mm
what occurs during striated mm contraction?
thick and thin filaments slide past each other
what is the effect of increased calcium on force of contraction?
increase Ca, increase force of contraction
why does an end plate potential occur?
because Na permeability becomes greater than K permeability
what are the 2 proteins found on the membranes of NT vesicles in motor neurons?
H+/Ach exchanger (secondary AT)
H+ ATPase (primary ATP)
which 2 substances provide passive-length tension in striated mm?
collagen and titin
which protein is found on z-disc and dense bodies?
a-actinin
what is active force proportional to?
the number of active cross bridges
sequence for transmission of force from contractile proteins to extracellular space in cardiac mm
motor proteins z-line proteins cytoskeletal actin focal contact proteins connector proteins extracellular matrix proteins
what stabilizes actin in skeletal mm and is not found in smooth or cardiac mm?
nebulin
why can smooth mm produce greater active force than cardiac mm?
side-polar arrangement of actiomyosin cross bridges
what is the major components of the z-line?
a-actinin
what is permitted when Ca binds to the thin filament in striated mm?
binding of Ca allows for phosphate to dissociate from actomyosin-ADP-Pi
ca also changes the position of tropomyosin to expose myosin binding sites on actin
what forms latch bridges in smooth mm?
thought to be due to the slow rate of ADP dissociation from cross bridges after the power stroke
spatial summation
summation of EPSPs from many presynaptic sources
temporal summation
summation of EPSPs from one presynaptic source
which type of skeletal mm is most fatiguable?
fast twitch type IIB/IIX
