A&P Test 4 Flashcards
What do the 2 vagus nerves innervate?
R-SA Node
L-AV node
They can extend past these but majority of the innervation is at the SA and AV node
Majority of the parasympathetic innervation is going to be at the ________ areas of the heart
pacemaker
the sympathetic chain in the heart innervate the
atrial muscle tissue, ventricular muscle tissue, and some at the pacemaker areas of the heart
what is the primary catecholamine at the heart? What receptors do they work on?
Norepi
B receptors
what is the primary cholinergic receptors in the heart?
MACh-R
what is vrm of resting ventricular myocyte?
-80
EKGs are basically the sum of all the ________ that’s flowing between a couple of electrodes placed on the body
current
When we place electrodes on the skin it measures
current moving around the heart
The deflection that we see on a normal ekg is about how many mV
1.5mV
Scar tissue is blocked by the use of ACE inhibitors, but it isn’t enough to slow down_________
wound healing in other areas of the body
sub endocardium is usually used when talking about which part of the heart?
Left ventricle
There is a subgroup of K+ channels close at the end of phase _______ in the heart. Why do they close?
0
as a result of the Positive influx of Na+ and Ca++. It helps to extend the action potential in the heart which is important bc it helps with the contraction of the heart
What is the name of the subclass of voltage gated K+ channels that close at the end of phase 0 in the heart?
inward rectifying channels
One would assume that because the QRS complex looks larger than an individual action potential it would have more mV, however____________
Why?
this is not the case. Instead we lose a lot of the voltage that is taking place within the heart in our tissue.
Because not all of our body conducts electricity well.
each big box on an EKG accounts for a magnitude of
.5mV
Where do we lose a lot of the current that goes through the heart
in our tissues of the heart (fat, air)
why do people with COPD have a lower QRS complex?
air doesn’t conduct well
Voltage goes from the _____ electrode to the ______ electrode
negative
positive
We have a positive and negative electrode attached to a tissue.
The inside of the tissue is negative
the outside of the tissue is positive
what should the reading be on the monitor?
0
there’s no difference between the electrodes
Describe what is happening in this depolarization picture.
Describe what is happening in this depolarization picture.
Describe what is happening in this depolarization picture.
Describe what is happening in this depolarization picture.
Describe what is happening in this depolarization picture.
Describe what is happening in this depolarization picture.
Describe what is happening in this repolarization picture.
where is the positive electrode, lead one, on the body?
Left arm or left side of the chest
If electrons are moving towards the positive lead it will show a ____________ on the meter
positive deflection
If electrons are moving away from the positive lead it will show a __________ on the meter
negative deflection
Describe what is happening in this repolarization picture.
Repolarization from right to left
Describe what is happening in this repolarization picture.
Describe what is happening in this repolarization picture.
How much tissue should we expect to be depolarized when we have the most electrical current?
about half the tissue
As smaller and smaller amounts of tissue is available for electrons to go to (past the half way point), what will we see on the meter?
less and less voltage (coming back to 0)
The conduction system of the ventricles is very ___________ in the heart wall
deep
Because the conduction system is very deep in ventricular tissue, AP start on the _________ and go to the _____________
inside to outside
which part of the ventricles depolarize first?
the deep parts
when we repolarize, where does it start and end?
on the superficial tissues and goes into the deep tissues
Because we have repolarization going in the opposite direction as the depolarization, what would you expect to see on the EKG?
the portion of the EKG that corresponds to repolarization of the ventricles to be a positive deflection
P wave is the
depolarization of the atria
QRS complex is the
depolarization of the ventricles
T wave is the
ventricular repolarization
why is the T wave a positive deflection?
because it starts on the outside of the heart and moves to the inside of the heart. This makes the wave of electrons go towards the positive lead
If electrons are moving towards the positive electrode it shows up on the EKG as a
positive deflection
If the electrons are moving away from the positive electrode it shows up on the EKG as a
negative deflection
what is the first thing that completely depolarizes in the heart?
the interventricular septum
Areas of the heart that have depolarized typically transmit current to the other parts of the heart that are
repolarized/ resting
what are some instances that can cause a cell to be “sick” in the heart?
it hasn’t gotten the nutrients that it needs
there has been a blood clot
Any instance where to tissue doesn’t have enough energy and it can’t repolarize.
if you have a cell in the heart that is sick and ischemic, it will be
depolarized constantly
Chronic depolarization that can conduct a
current of injury where no current should be happening.
When there is infarct or ischemia in the heart, you have a little spot that cannot _____ while the rest of the heart still does.
reset
The 12 lead is a tool that helps us diagnose almost any _________ in the heart
electrical abnormality
Delete
Me
vrm in a healthy SA nodal cell is
-55
why is the SA node the pacemaker of the heart?
it depolarizes fastest in the heart
what is the threshold potential of the nodal tissue?
-40
which has a bigger slope, ventricular tissue or nodal tissue?
nodal tissue
What are the ions that come through a HCN channel?
Which is the primary, secondary, and third ion that comes through?
Na+ primarily
Ca++ secondary
K+ a little bit
What does HCN stand for?
Hyperpolarization and Cyclic Nucleotide Channel
a channel that opens d/t hyperpolarization (VRM in the heart) and is controlled by a cyclic nucleotide (cAMP)
*also opens in response to cAMP
HCN channels open up in response to
repolarization or hyperpolarization
what is cAMP? (a&p)
adenosine in a circular form
when you have a normal amount of beta activity you should have a normal amount of
HCN channel operating during phase 4 in the nodal tissue
beta agonist speed up the HR by
increasing cAMP which causes more HCN open.
more HCN channels opening makes the phase 4
steeper.
Less time in phase 4= faster HR
If you give atenolol (or any other beta antagonist) you would expect to see less involvement of ________ which would give us a decreased slope of phase 4 therefore decreasing the HR
HCN channels
Less HCN channels =
slower heart rate
changes in resting membrane potential in the nodal tissue can be controlled by
mACHr
More ACh around in the heart would reduce our __________
(not HR)
VRM
-60 instead of -55
if the slope of phase 4 is the same, but our VRM is more negative, it will take us a longer period of time to reach
threshold potential.
This slows down the HR
There is ____________ between muscarinic and catecholamine receptors in the heart
antagonism
VRM is determined by how many _________ we have __________
K+ channels
open
If VRM is more positive than -55 and threshold is still at -40, we would expect to reach threshold
faster, within reason.
If you have a little hyperkalemia you would expect to see a_____________.
Why?
faster heart rate
This increases vRM
what is the concentration gradient of potassium in the heart?
30:1
what are the 3 ways that the heart controls HR?
- Change the slope of phase 4
- change the starting points of VRM
- Ca++ changing the threshold potential
a reasonable increase in blood Ca++ can change the threshold potential in the ____________
heart. Only the heart
If we increase the threshold potential in the heart you would expect to see a
decreased hr.
If we have a low Ca++ you would expect a
increased HR
We don’t know how
what part of the heart produces fast action potentials?
ventricular muscle cells
what on a graph tell us if the action potential is a fast action potential?
if the phase 0 slope is very steep
If we look at an individual action potential, we see much bigger numbers than is shown on an ______ because _____
EKG
because an EKG is looking at all the millivolts that are making their way around the heart.
Describe what is happening in this repolarization picture.
Describe what is happening in this repolarization picture.
Describe what is happening in this repolarization picture.
Entire tissue is depolarized
Meter is reading zero
Describe what is happening in this repolarization picture.
A little bit of the tissue is repolarized at the right of the tube
The rest of the tissue is still depolarized
We have a lot of electrons on the left side of the tube
We would expect to see a few electrons moving from the left side to the right
Not too much current because hardly any of the tissue is reset.
A small amount of current is moving toward the positive electrode on our meter.
The arrow on the meter is pointed slightly to the right (positive deflection or reading)
A little positive
Describe what is happening in this repolarization picture.
Half of the tissue is repolarized and half is still depolarized
We would expect to see the most electrical current at this point
Electrons are moving from the left to the right
Meter would point towards the positive readout (pointed to the right)
Very positive
Describe what is happening in this repolarization picture.
As we continue to repolarize from right to left, there will be a few electrons on the left side of the tube.
We will still expect the electrons to move from left to right. HOWEVER, there will not be too many of them moving at this point.
We would see a little bit of a positive deflection on the meter
This is because the electrons are still moving from left to right on the outside of the tissue.
Describe what is happening in this repolarization picture.
Entire tissue is repolarized
We would expect to see no electrical current.
This is because there is no difference in the charge state of the tissue.
Would read as zero on your meter.
what is an HCN channel?
A NON SPECIFIC channel for Positively charged ions (Na+, Ca++, K+)
Why is phase 4 at a slope in the nodal tissue?
It is leaky to Ca++ and Na++
d/t more and more HCN channel opening
what is the healthy normal human heart rate
72BPM
Describe what is happening in this repolarization picture.
what is the difference between the resting membrane potential and the highest point on the Phase 1 slope in a normal cardiac action potential?
about 100mV
what number are we making up to use to measure the peak of the AP charge on a ventricular myocyte?
+20
which has the strongest stimulus on the broad tissue (considering the atria and ventricles) in the heart? sympathetic or parasympathetic?
sympathetic
which has the strongest stimulus on the nodal tissue? sympathetic or parasympathetic?
parasympathetic
