Exam 4 Flashcards
Why are Potassium channels in the heart called inward rectifying K+ channels?
The inward movement of cations (Ca++ and Na+) is what causes the potassium channels to close
Is the left or right ventricular sub endocardium more prone to ischemia or infarct and why?
Left ventricle sub endocardium
-sub endocardium is furthest from the coronary arteries the supply the epicardial area. First to suffer with decreased blood flow.
-Left ventricle has higher o2 demand pumping blood out systemically so decreased o2 causes this area to be more vulnerable
Closer to surface of the heart _____ likely ischemia will be.
least
Ventricular myocyte also considered
ventricular muscle cell/ Purkinje fiber
R Vagus innervates
SA node
L Vagus innervates
AV node
Parasympathetic innervation is mainly at the __________ areas of the heart.
pacemaker
Sympathetic innervation of the heart is more ________.
widespread
SNS primary catecholamine of the heart
Norepinephrine
What parts of our body do NOT conduct electricity very well?
Fat tissue
air, copd (lower qrs complex)
where do you see the most voltage in the depolarization of the tissue?
Half of the tissue is resting and half is depolarized, you’ll see the most voltage/ electrical current.
Arrow pointing to the left
negative deflection
Arrow pointing to the right
positive deflection
Towards the positive lead denotes a
positive deflection in the meter
Away from the positive lead denotes a
negative deflection in the meter
P wave is the depolarization of the
atria
QRS is depolarization of the
ventricles
T wave is __________ repolarization
ventricular
Why does the T wave show up as a positive deflection on the EKG? explain.
The ventricles have an opposite order of depolarization and repolarization. They depolarize one way and repolarize in the opposite way.
- Action potential starts in the deep areas of the ventricle and make their way further to the surface. inside depolarizes 1st. outside depolarizes 2nd.
The ________ repolarizes before the endocardium in the ventricles.
epicardium
Where is the conduction system of the ventricles located?
Deep in the heart wall
The ventricle is _________ isolated from the atria
electrically
___________ does not allow the resetting of cells after action potential.
Ischemia
Usually an abnormal current of injury can be located where?
In an area where we should not have any current.
Why is the SA node considered the pacemaker of the heart?
Tissue at the SA node depolarizes and reaches threshold potential faster than any other tissue in the heart
Normal HR produced at the SA node?
72 BPM
HCN channels are non specific for ________.
Cations
HCN stands for?
Hyperpolarization + Cyclic nucleotide
Explain HCN channels in the SA node and how they contribute to physiologic antagonism in this area of the heart?
HCN channels are tied to the beta adrenergic activity in the heart. when norepinephrine binds to beta adrenergic receptors they cause an increase in Cyclic Adenosine monophosphate (CAMP), which increases the amount of HCN channels during phase 4 slope of the action potential. More HCN channels helps get to threshold potential faster with the influx of cations (Na+/ Ca++) into the cell. Muscarinic Ach- R are also located at the heart and cause an increase in resting membrane potential with the Efflux of potassium out of the cell, making it harder to reach threshold potential and lowering the HR.
Beta adrenergic activity tends to _______ ________ the potassium channels tied to muscarinic Ach receptors.
shut down
How does ECF calcium affect HR and Vrm?
Hypercalemia–> increases threshold potential (more +) and slows down HR
Hypocalcemia–> decreases threshold potential (more -) and increases HR
What is the pathophysiology on how calcium affects Vrm?
It is unknown
