Test 4 - (10/21) Cardiac Lecture 2 Flashcards
We have _____ vagus nerves that innervate the heart.
Two
The right vagus nerve innervates _____, the tips of the left vagus nerve innervate _____
R - SA node
L - AV node
The majority of the parasympathetic innervation will be at what area of the heart?
The pacemaker areas of the heart
What is happening with parasympathetic innervation from the vagus nerve?
Main emphasis of the parasympathetic innervation is the suppression of the activity of pacemaker cells in the nodal areas
There is a small amount of innervation from the branches of the vagus nerve that extend past the nodal area.
Does the vagus nerve extend past the AV and SA node?
Yes, branches of the vagus nerve do extend past the nodal area
How does sympathetic innervation differ from parasympathetic innervation?
Sympathetic is more widespread in the heart.
Describe the innervation from the sympathetic chain.
Has some innervation at the nodal areas.
Has thick connections with the atrial muscle tissue as well as the ventricular muscle tissue
What is the primary catecholamine that is released from the sympathetic nerves at the heart? What receptor will this interact with?
Norepi.
Beta
Acetylcholine will primarily bind to what receptor
mACh-R
What has the most innervation at the nodal area of the heart?
Parasympathetic nervous system
What kind of AP would this be?
ventricular muscle cell/ventricular conduction system
What are the phases for the following?
Blue:
Pink:
Green:
Orange:
Yellow:
Purple:
Blue: 4
Pink: 0
Green: 1
Orange: 2
Yellow: 3
Purple: 4
Hot pink
Sympathetic chain
Blue
sympathetic nerves
Green
Left vagus nerve
Orange
AV node
Purple
SA node
Red
Right vagus nerve
Why do we call these fast AP?
Because phase 0 is very steep. Once it starts it shoots up
What is the resting membrane potential in a ventricular myocyte?
-80
What is a ventricular myocyte
Ventricular muscle cell
If our resting membrane potential is -80mV and the peak is +20mV. What is the amount of depolarization we get?
100mV
What does an EKG show us?
A sum of all the current between a electrodes placed on the body.
Measure the current that is flowing as our heart beats.
The magnitude of deflection in an EKG is _____
about 1.5mV
The magnitude of deflection in an EKG is _____ and in a ventricular muscle cell AP it is ______.
1.5mV
100mV
The subendocardium is the deepest part of the ______ muscle wall. mainly _______
Ventricular
left ventricle
Compared to the left ventricular wall, the right ventricular wall is _____
Much more narrow
What part of the heart is most prone to infarction or ischemia?
Subendocardium (L ventricle)
The _____ to the surface you are in terms of the heart layers, the less likely you are to have ischemia
Closer
What is different about K channels in the heart vs other cells in regards to AP?
Typically K channels open in response to depolarization but in the heart they actually close in response to incoming cations.
The K channels that close in the heart during an AP are called what? What causes them to close?
Inward rectifying K channels
The inward movement of cations
The amplitude of the QRS complex is
1.5mV
Why is the magnitude of deflection in the ventricular AP so much bigger than that of the EKG
We lose a lot of the voltage in our tissue because of the high resistance in the tissue, not all of our body conducts electricity very well
Someone with COPD will have a much _____ QRS complex
Lower
During depolarization, the inside of the cell is more _____ and the outside is more ____
positive
negative
Negative electrons on the outside of a cell will want to go to ____
areas that are positively charged
Lead one is a _____ electrode that is placed on _____. It is measuring a depolarization wave that is moving ______ the ______ electrode that is placed on _____
positive
left chest.
Towards.
positive.
left chest
If we see electrons moving towards the positive lead that shows a _____ deflection in the meter. If electrons are moving away from that positive lead that would show up as ______ deflection
positive
negative
The conduction system is very ____ in the heart wall
deep
Depolarization in the heart happen from ______ to _____
Inside (deep) to outside (superficial)
Repolarization in ventricular muscle starts in more ______ structures and then goes to ______
Superficial
deep
Repolarization in the heart moves the _____ way of depolarization
opposite
P wave is ____
Depolarization of the atria
QRS is
depolarization of the ventricles
T wave is
ventricular repolarization
Why does T wave show a positive deflection even though it repolarizes in the opposite direction
the epicardium repolarizes before the endocardium.
If there is an area of a heart that is ischemic what will happen in regards to AP?
It will be depolarized constantly, cant reset itself after AP.
In the pacemaker area of the heart the AP can _____
look different
Pacemaker of the heart
SA node
Why is the SA node called the pacemaker of the heart?
The tissue at the SA node goes from resting membrane potential to threshold potential in the shortest amount of time
Normal resting HR for our class?
72 BPM
What is the resting membrane potential (Vrm) for a healthy SA nodal cell?
-55mV
What is threshold potential for a healthy SA nodal cell?
-40mV
In the SA nodal cell what causes the hefty positive slope in phase 4 from Vrm to threshold?
Ca and Na leak channels as well as HCN channel
What does HCN channel stand for?
Hyperpolarization + cyclic nucleotide mediated channel
When do HCN channels open up in the SA nodal cells?
When we get back to Vrm following AP
What ions move through HCN channels?
Fairly nonspecific for positively charged ions (cations) primary is Na and secondary is Ca
In the heart when we have norepi binding to a beta receptor we have _____ (relating to HCN channels)
Increase in cAMP
cAMP is a _______. A stands for ____
Cyclic nucleotide
Adenoside
When we have a normal amount of Beta activity we should have a normal amount of _____ channels operating in phase ______ in nodal tissue
HCN
4
If we give someone a beta agonist what will it do to the heart rate? what does cAMP have to do with this?
The HR will increase because there will be an increase in cAMP and that will cause more HCN channels to open
HCN channels can open due to what?
Repolarization (hyperpolarization)
or increase in cAMP
If we have more HCN channels opening what would that do to the slope of phase 4?
make it steeper
More HCN channels would cause a _____ slope in phase 4 and cause _____ AP due to ____
steeper
earlier
reaching threshold potential faster
Beta antagonist (atenolol) given what would that do for slope and HCN channels and HR
Less HCN channels. slope isnt as steep. later AP. slower HR
If we have lots of ACh around what will that do in terms of nodal tissue AP?
will bind to mACh-R, opening up K channel, K will leave and make cell more negative and that could lower our Vrm. Slope can be the same but phase 4 will be longer so slower HR.
will also lower cAMP
if we have small amounts of K around what would that do to HR?
slightly higher Vrm, hit threshold faster. increase HR.
How can Ca slow down our HR in nodal tissue specifically?
A slight increase in Ca and actually change our threshold potential and make it more positive..making phase 4 longer and that will slow down HR
Reduced Ca levels in the blood can _____ HR by _____
Increase
lowering threshold potential
