Regulation of Heart Pacemaker Potential Flashcards
how are cardiac cells connected
gap junctions
how do impulses move in heart muscle
cell to cell not through nerves, via gap junctions
heart cells are ______ coupled
electrically
what is the RMP of SA node
-55 to -65 mV
the RMP of SA node is very ______
unstable
SA node is very leaky to
Na+ and Ca++
describe RMP of SA node
they are very leaky to Na+ and Ca++ so when it goes down to RMP the Na and Ca bring the RMP more positive so it will depol
what causes depol in SA node
voltage gated L type Ca++ channels
if current is activated at what mV
-60
when if channel opens what happens
sodium leadks into cell, this is for SA node
when SA node is -50 mv what channel opens
iCaT (transient)
what is the third channel that opens in SA node under threshold
iCaL
desribe what is happening until threshold is reached in SA node
if channels open which cause Na to enter, then iCaT open then IcaL open
what is threshold in SA node
about -30 mv
what are the phases in SA node
4, 0, 3, 4
depol of SA node is due to
calcium entering cell
what happens at peak of SA node curve
calcium channels close and potassium currents open
does the SA node contract
no
SA nodal cells fuse with:
atrial muscle cells
anterior interatrial band cells
internodal pathway cells
what is the anterior interatrial band
it passes from right atrium to left so they depol and contract together
what is the internodal pathway
brings the impulse from SA node to AV node
what is job of AV node
slow the impulses from SA
why is it important to slow down the impulses from the SA by the AV
so the atria can contract before the ventricle
describe rate of rise in AP of AV and SA node
SA much steeper, AV takes longer to get to threshold
b/w atria and ventricle is piece of fibrous tissue:
AV bundle
what is purpose of AV bundle
muscular connection b/w atrium and ventricle, prevents re-entry of cardiac impulses into atria from ventricle
what is the only muscular connection b/w atria and ventricle
AV bundle
why is there delta wave in WPW
accessory ptahway starts to depol the ventricles too soon
after AV node where does impulse go
lef tand right bundle branches then purkinje fibers
describe conduction through purkinje fibrs
very fast - allows the impulse to spread quickly through ventricles
why are impulses so fast through purkinje fibers
bigger, more gap junctions, AP spike faster
purkinje fibers spread the AP quickly and then it gets to ventricles and it
slows down a little bit
why is there delay b/w QRS wave and ventricles contracting
electrical activity has to be converted to mechanical contractility, that takes time
only thing you are measuring with ECG is
electrical activity
depol vs. repol
depol causes another to depol, but repol just happens on its own. there is inherent property within cells that tells them how long they should stay depol
AP duration in endocardial cells is shorter than
epicardial cells ( i think its actuallyosute doublencheck)
what is intrinsic rhythmical rate
70-80 times/min
what is purkinje fibers rate
15-40 timesmin
why is SA node the pacemaker
it fires faster
what is ectopic pacemaker
anther area of heart fires faster than SA node so it becomes the pacemaker
sinus arrest - what is person’s heart rate
40-60 b/c AV node will kick in
what is sinus arrest
SA node stops working
3rd degree block what will HR be
15-40 times/min (purknje fibers)
PNS originates in
medulla
vagus nerve is nerve
trunk
vagus nerve has efferent nerves going to heart and it also has
afferent sensory nerves monitoring heart
what does it mean that vagus nerve is nerve trunk
it has efferent and afferent nerves to heart to monitor and control
vagus primarily moderates (PNS)
SA and AV node
sympathetic nerves primarily innervate
SA, AV, and ventricular muscle
there is almost no PNS control of
muscle itself
Parasympathetic releases what
ACh
what is the kindo f receptor for ACh
G protein coupled muscarinic receptor
what is affect of parasympathetic onheart
inhibitory
what is released from postganglionic nerve sympathetic
NE
NE is a
catecholamine
catecholamine
dopamine, NE, EPI
dopamine is converted into
NE
what is receptor for sympathetic, NE
betaadrenergic receptor
what nerves increase rate of conraction
sympathetic nerves
activation of beta receptors inheart does what to SA node
increases firing rate, makes them more leaky to sodium and calcium
how does beta receptors in heart increase SA node
they make them more leaky to sodium and calcium
how do muscarinic receptors slow or stop heart rate
they open voltage sensitive potassium channels to cause hyperpolarization
if sympathetic is high, PNS is
low
