Exam 4 - Lecture 2 Flashcards
Right vagus nerve hangs out in
SA node
Tips of left vagus nerve tend to sit more
AV node
Majority of parasympathetic innervation is at the ________ areas of the heart
Pacemaker
Branches of the vagus nerves tend to ________ the nodal areas
Extend past
Main emphasis of the parasympathetic innervation is ________ of activity of __________ cells of _________ areas in heart (most commonly this area) May affect REST of heart too.
suppression; pacemaker; nodal areas
Sympathetic innervation
widespread in heart, may go to nodal areas, but has thick connections with atrial muscle tissue as well as ventricular muscle tissue.
What does the sympathetic innervation have thick connections with?
Atrial and ventricular muscle tissue.
primary catecholamine that is released from sympathetic nerves of heart and its receptor
Norepi; beta receptors
Acetlycholine will primarily affect ________ receptors.
mACh-r
Predominant innervation of nodal areas (has greater effect, greater stimulus)
Parasympathetic innervation.
Predominant innervation of rest of heart including ventricles
Sympathetic innervation
VRm of a ventricular myocyte
-80mV
What is a ventricular myocyte
ventricle muscle cell
Peak of action potential in ventricular myocyte (mV)
+20mV
Total change of resting mV and peak of action potential. What is this essentially? (Total ______)
100mV; total depolarization.
EKGs are essentially the
sum of all the current that’s flowing between electrodes placed on the body
A normal deflection we see on EKG should be somewhere around ______ mV which equates to ______ boxes.
1.5mV; 3 boxes
A graph of total action potential is _______ mV
100mV total
Typically a QRS complex is in between _______ big boxes
3 and 4
Each big box on EKG is worth _______ mV
0.5mV
Why does the EKG have so much less mV than action potentials?
We lose alot of the voltage that takes place within tissues. Not all of our body conducts electricity very well
What parts of our bodies dont conduct electricity very well?
Fat tissue, air (COPD pt will have much lower QRS complex)
What kind of patient would have a much smaller QRS complex?
A fat person with COPD
At rest, you have tissue that is _____ charged on the inside, and _________ charged on the outside.
Negatively; Positively
If we have two electrodes that are attached to a voltage meter, and monitoring the tissue, it will read ______ when the tissue is at rest.
No charge (No deflection)
If we were to stimulate tissue on the left side of the cylinder, and thats also the side where the negative electrode is, and ONLY the first bit of tissue is stimulated, the voltage meter will read
Slightly positive deflection
The depolarized part of the tissue is the result of _____ coming in, and results in ______ on the inside and ________ on the outside.
Cations; making that side of the cell positive; making it positive in that spot
The negative charge on the outside of the cell during depolarization is considered to be
an electron
Where do electrons want to go?
Areas that are positively charged
When the electrons are moving toward the positive electrode, the voltage meter reads
positive
When half of the tissue is depolarized, and the other half is still resting but about to be depolarized, the voltage meter is reading _________. Why?
Very very positive deflection, because there is a ton of electron movement.
The entire tissue is now involved, as now there is more electron current, and still a lot of area of tissue to accept the electrons.
when is there MOST electron movement during depolarization?
when half the tissue is depolarized
When almost the entire cell is depolarized, the voltage meter will read _________. Why?
only slightly positively deflected; because there is only a small area for the electrons to go to
Drawing out the voltage on a graph, what would the peak of the electron current indicate as far as the tissue?
Most tissue involvement, highest membrane polarity, and the cell is halfway depolarized.
when is there highest membrane polarity in regards to depolarization of tissue?
When the cell is halfway depolarized.
What are the two instances when the voltage meter reads zero current? (No deflection)
Resting state and complete depolarization
on the graph of mV current that we drew out, it was shaped like a ________. When its going down towards zero after its peak, is this a negative or positive deflection?
Half-moon; still a positive deflection, just isnt as positive as it previously was. It is positive because it is still above zero, even though its heading downward.
With lead 1, you have a __________ electrode to left arm, and it is measuring _________
positive; depolarization wave that is moving toward the positive electrode on left arm.
If we repolarize in the same order that we depolarize, it would start where?
Same spot it first depolarized, not backwards.
During complete depolarization, what is the charge state of each inside and outside the tissue?
Completely positive inside, negative outside.
Where are the electrons hanging out, and where are they going to go during repolarization? What kind of deflection does this make?
They are on the negative charges outside the cell, and they are going to go towards the positive tissue that just started repolarizing. This creates a negative deflection.
The most negative reading on the voltage meter will be when
half the cell is repolarized, and there is a ton of electron current repolarizing the cell.
A fully depolarized tissue, and the repolarization starts on the right side of the cylinder, where is the electron current flowing?
Electron current is flowing to the right, cause the outside charge at the beginning of repolarization becomes positive, and the electrons move towards it, in the direction of positive electrode.
The conduction signals in the ventricles are very
Deep
when we repolarize ventricular muscle, it starts and ends where?
Starts in superficial, ends in deeper layers.
The action potentials start in the ____ part of the ventricles, before the ____ layers are depolarized.
inside, outside.
So, what is the order of depolarization and repolarization for ventricular muscle?
Depolarization starts in deep parts of ventricles and ends in outside. Repolarization starts in superficial (epicardium) and ends in deep (endocardium/subendocardium).
This would be left to right on drawn example, then right to left for repolarization.
If we have repolarization in opposite direction in ventricles, this what show up as what deflection?
positive deflection, T-wave
P-wave is _________ of _______
depolarization of atria
QRS is depolarization of
ventricles
T-wave is __________
ventricular repolarization
The _____ will repolarize before the endocardium.
Epicardium
What is the first part of the ventricles to completely depolarize?
Interventricular septum
are the ventricles electrically isolated from the atria?
yes
What happens if there is ischemia in the cells? what can’t happen?
Constantly depolarized, so repolarization can’t occur.
If the rest of the heart can reset but one patch that can’t due to ischemia, a __________ will result.
Current of injury.
The constantly depolarized cells will cause an
abnormal current.
Think about the ONE part of the cylinder has a positive charge while everything else is negative. It is sending AP in both directions of cylinder, causing an abnormal current.
The main pacemaker of the heart is ____. Why?
SA node. It depolarizes and reaches threshold potential faster than any other tissue in the heart. Therefore, it sets the heart rate cause nothing is pacing it faster than that.
Heart rate in a completely healthy heart in this class
72 BPM
VRm of healthy SA node
-55 mV
Action potential shape of SA node?
__/^\__
relatively uniformed curve with an upslope at rest.. There is not a plateau.
Threshold potential of SA node cell
-40 mV
To generate an action potential in SA node, you’ll need the cell to reach
-40 mV
SA node heart rate
72 BPM
Why is there an upslope for membrane potential in SA node phase 4
caused by Ca++ and Na++ leakiness, and HCN channel
Slope of phase 4 in SA node
hefty slope, happens really quick, much faster than purkinje fibers
When is HCN channel in SA nodal tissue activated? Do they all open together?
When the cell resets after AP, we go back to VRm, which opens up HCN channels. Some open right away as we hit VRm, some take awhile to open up.
More HCN channels open with more cAMP
HCN channels in SA nodal tissue are non-specific to
cations such as sodium (primarily) and calcium (secondarily), very little potassium.
What is the slope in phase 4 of SA nodal tissue due to?
It’s the “change” happening in permeability of cell to ions, more HCN channels opening.
Primary ion for HCN channels in SA nodal tissue
Sodium
Secondary ion for HCN channels in SA nodal tissue
Calcium
What does HCN stand for?
Hyperpolarization + Cyclic Nucleotide
What does the hyperpolarization part of HCN name mean?
Refers to fact of HCN channel opening during VRm after cell is reset and a little bit of hyperpolarization is occurring.
CN part of HCN name is referred to
What is the result of?
controlled by cyclic nucleotide
Cholinergic vs beta adrenergic signaling in heart
When you have norepi binding to beta receptor in heart, what happens? (2 things) (in SA node)
Adenylyl cyclase increases and cAMP increases
cAMP is a _________ and it stands for?
cyclic nucleotide
c - cyclic
A - adenosine
MP - monophosphate
Adenosine is a
nucleotide
Adenosine in its cyclic form is a
cyclic nucleotide
When we have a normal amount of beta receptor activity, we should have a normal amount of _______ operating during ______ of SA nodal tissue
HCN channels; phase 4
If we have a beta agonist, it speeds up heart rate by increasing cAMP levels in nodal tissue, which will open ______, which will make ________. (in SA node)
more HCN channels; phase 4 steeper
More HCN channels open, means more _______, thus _______ of phase 4. Overall, this equals a _________ action potential. End result is ________. (in SA node)
inward sodium/calcium current; shortens time; earlier; elevated heart rate.
If you open up HCN channels, the slope of phase _ will _______. (in SA node)
4; steepen
If you have beta-antagonist such as _________, there will be _____ involvement of HCN channels. (in SA node)
atenolol; less
Less HCN channel involvement will affect the slope of phase 4 how? (in SA node)
Reduce the slope, causing a longer time to fire AP, lower heart rate.
Do mACh-r affect VRm or threshold potential? (in SA node)
VRm
mACh-r provide a conduit for ________. (in SA node)
K+ to leave the cell, reducing VRm
mACH-r activity may ____ VRm from -55 to ____. (in SA node)
reduce; -60
During mACH-r activity in SA node, VRm will be _____ and phase 4 will take a ________ amount of time. (in SA node)
more negative; longer
Is the slope of phase 4 in SA node affected by mACh-r?
Yes, secondarily to reducing adenylyl Cyclase activity.
Reduced AC, reduces cAMP, reducing HCN channel activity, lowering slope.
The more mACh-r you have in SA node, the more
inhibitory alpha subunit effect there is on adenylyl cyclase, reducing it.
Beta-adrenergic activity can have what effect on mACh-r in SA node?
shut the K+ channels down
VRm is directly tied to amount of ________, which is directly tied to _______ activity. (in SA node)
K+ we have open; acetlycholine we have at nodal tissue.
Reducing K+ permeability will result in what to the VRm? Overall effect on body in small and major instances?
more positive, small increase HR in small elevated amounts of serum K+, but when it becomes too positive, causes major problems in electrical activity.
By increasing VRm with higher level of serum K+ outside heart cells, the ________
less of a gradient they have to move down, resulting in less K+ movement, more positive VRm.
Beta-receptors control HR by ____, and mACh-r control HR by ______
increasing phase 4 slope (elevated HR); lowering VRm (lowering HR)
3rd way you can manipulate HR is by ____. How?
serum calcium levels; change threshold potential
How does does calcium change threshold potential? does this occur anywhere else in body other than the heart?
No one knows. No.
Reasonable increase in serum calcium will _______. Resulting in what?
increase threshold potential; longer period of time in phase 4 to reach threshold and slow down HR
If we have a serum calcium deficiency, it may result in
a lower threshold potential (more negative), and a faster HR
What are the electrodes actually looking at?
all this current that is coming from depolarized areas of the heart and heading to areas that are repolarized or resting.
