Cardiovascular Physiology Lecture_7 Flashcards

Cardiac electrophysiology
Terms Definitions
ventricular repolarization is represented by what on an ECG?
T-wave
what are beta blockers?
β1-adrenergic antagonists?
what does ECG stand for?
electrocardiogram
what does SR stand for?
sarcoplasmic reticulem
sympathetic nervous system activation can cause what?
sinus tachycardia
what does RMP stand for?
resting membrane potential
what does the cardioacceleratory center affect?
the sympathetic ANS
what transmits current across the heart?
intercalated discs
how is depolarization transmitted?
cell-to-cell via gap junctions
what can atrial tachycardia be classified as?
supraventricular tachycardia
what does a T-wave correspond to?
ventricular repolarizaiton
where are postganglionic parasympathetic fibers distributed in the heart?
SA node and AV node
how does the central cardioinhibitory center sends inhibitory impulese to the SA and AV nodes via what?
the vagus nerve
what do desmosomes and gap junctions form?
intercalated discs
what may cause sinus tachycardia?
excessive adrenergic influence relative to cholinergic influence
what are examples of local anesthetics?
lidocaine and procainamide
what is the average P wave duration and amplitude in the dog?
0.04sec/0.4mV
where does the impulse from the AV bundle go?
bundle branches
what is the cholinergic affect on the AV nodal function on slow conduction velocity (AV delay)?
lengthens delay
what events occur supsequent to depolarization?
calcium exits the cell
what is the normal HR range of horses?
24-60 bpm
how does hyponatrmia/hyperkalemia result in elevated intracranial pressure?
dehydration leads to additional ADH resulting in increasing pressure
what are cardiac glycosides?
inhibit cell membrane bound Na+/K+ pump because the action of pumping Na+ out of cardiac cells indirectly supplies energy to a Na+(in)/Ca++(out) exchange that transports Ca++ out of the cells so that inhibiion of the ATPase influences the RMP in a manner that helps supress ectopy and slows AV conduction
what is an electrocardiograph?
device used to produce the electrocardiogram
what is another name for the AV bundle?
Bundle of His
parasympathetic, cholinergic influences are limited to where?
the SA node, AV node, and atrial myocardium
when does muscle relaxation occur?
when the cytosolic Ca++ concentration becomes insufficient for sustained interactions with troponin
what happens to HR during ventilation?
increase during inhalation and decrease during exhalation
how do augmented unipolar electrocardigraphics leads inscribe on the ECG trace?
electrod orientation of selected lead and the convention of trace deflection based upon the location of the positive electrode one can predict how at particular ECG pattern must reflect a given activation sequence in the myocardium
what does stimulation of B1-adrenergic receptors cause?
increased number of Ca++ channels open, increasing amount of extracellular Ca++ entering the cardiac myocites
what is calcium induced calcium release?
when the extracellular Ca++ enering through DHP channeles triggers the opening of the Ry channel (in cardiac muscles)
what are the treatment options for third degree AV block?
antimuscarinic therapy or pacemaker implantation
what is a supraventricular tachycardia?
a catch-all phrase that encompasses a variety of arrhythmias distinguished by their anatomical location 'above' the ventricles
where is the SA node?
the right atrial wall at the junction of the cranial and caudal venae cavae
what do myosin and actin do?
shorten the muscle similar to skeletal muscle
what does ventricular fibrillation do to the electrical and mechanical activity of the heart?
the electrical activity is random and obliterates mechanical pumping efficiency
Mobitz type 1 or Mobitz type 2 are what type of arrhythmias?
second degree AV block
what is the direction of an impulse propagation in the heart?
right-left, cranial-caudal (toward the left leg)
where do the bundle branches carry the depolarization?
down the interventricular septum ot the right and left ventricles respectively
what happens in a fast cardiac AP after voltage-gated fast Na+ channels open?
extracellular Na+ briefly enters the cell triggering depolarization of the membrane potential until the Na channels are inactivated
what occurs during a second degree AV block?
atrial depolarizes which are not followed by ventricular depolarization
what else must be done to evaluate the P-QRS-T complex configuration?
measure intervals, amplitudes, and durations of complexes
what prevents the impulse from being sent retrograde back up into the atria once the ventricles depolarize?
differing regions of the AV node have differing refractory periods
how are second degree AV block characterized?
as Mobitz type 1 or Mobitz type 2
the trace deflection in that lead is desplayed upward if what occurs?
when the wave of depolarization is propagated toward the positive electrode of any selected lead
On the ECG trace, what does a 2nd Degree AV block look like?
some P occur w/out accompanying QRS complexes (unable to pentrate AV node), ventricular escape complese may occur after
On the ECG trace, what does a sinus arrest look like?
sudden loss of SA node function, so no P appears for a pause > 2 normal P-P intervals, and an excape comples may appear to end pause w/out P wave
do cardiac muscles undergo summation?
No!
trauma, inflammation, and infection can cause what?
ectopy
what does SA stand for?
sinoatrial node
can tetanus occur with repeated stimulation in cardiac muscles?
No!
what is ischemia?
restriction in blood supply
what is the resting membrane potential of pacing cells?
-60mV
what type of receptors are stimulated by postganglionic parasympathetic fibers?
cholinergic
what type of muscle is cardiac muscle?
striated
what does PVC stand for?
premature ventricular contractions
what does VPC stand for?
ventricular premature complex
which autorhythmic cells have the most rapid intrinsic rate of spontaneous depolarization?
SA node
what is the means of stimulation of skeletal muscle?
nerves
during ventricular repolarization, what states might individuals cells be in?
fully repolarized, relative refactory period, absolutely refractory
what is an example of a β1-adrenergic antagonists?
atenolol
which lead has negative = RA, positive LL?
II
what is the standard means by which the composite electrical activity of the heart is assessed from the surface of the body?
electrocardiography
how does ventricular contraction occur?
it follows ventricular depolarization in a wave-like manner that 'wrings' the heart from the apex toward the atria, ejecting blood intothe pulmonary and systemic vasculature
how does the secondary increase in cytoplasmic Ca++ occur in myocardial cells?
ryanodine (Ry) receptors
what is the normal HR range of cats?
120-220 bpm
what are some supraventricular tachycardia?
sinus tachycardia, atrial tachycardia, and junctional tachycardia
lidocaine is an exampled of what type of drug?
local anesthetics
what is electrocardiography?
standard means by which the composite electrical activity of the heart is assessed from the surface of the body
in pacing cells, what occurs after repolarization and K+ channels close?
funny' Na+ channels open
what modulates the activity of the intrinsic conduction system?
the autonomic nervous system
what is the only nervous system input that influences cardiac function?
autonomic nervous system
what does Ca++ ATPase do?
pumps Ca++ back into the SR
what is sick sinus syndrome?
organic heart disease characterized by extremely slow sinus node discharge rate, often with abnormal sinus bradycardia at rest and inappropriate slow rate during exercise (ie failure of appropriate response to epinephrine)
where does the AV node send an impulse?
to the AV bundle
any disruption of normal sinus rhythm (NSR) renders the heart what?
as a less efficient pump
how does cardiac muscle differ from skeletal muscle?
has intercalated discs with desmosomes, gap junctions, has functional syncytium, huge mitochondria, extensive branching & variations in diameter that alter the arrangement of sarcomeres
when a sinus impulse is transmitted to the AV node, but is never propagated to the ventricles, it is called what?
third degree AV block
what are examples of causes of PVC?
etiologies that cause ventricular ectopy and hyperthyroidism
what is the major clinical relevance of any arrhythmia?
the negative impace upon cardiac output, a hemodynamic consideration
what is necessary to initiate interactions between myosin and actin?
a Ca++ signal that establishes an intracellular Ca++ concentration that binds troponin
a disruption of normal sinus rhythm does what to the heart?
renders it a less efficient pump
what is an AV nodal block?
an arrhythmia that is an abnormality of impulse conduction
what are augmented unipolar electrocardigraphic leads?
leads aVR, aVL, and aVF utilize same limb lead positions but the ECG machine connects them in different combinationsthat percieves the electrical potential at one of the limb locations compared to the voltage between the others
what causes the falling phase of the action potential is pacing cells?
increasing K+ permeability and efflux when K+ channels open
what is different in the calcium ion delivery system in cardiac muscle vs skeletal muscle?
T-tubules are wider and fewer, entering the cell only once per sarcomere at the Z-discs, the SR is simpler and lacks terminal cisternae, resulting in no triads
what is first degree AV block associated with?
high vagal tone, which slows AV conduction velocity
on the ECG trace, what does an atrial fibrillation look like?
rapid, irregular rhythm w/out identifiable P waves (irregular baseline) w/normal looking QRS, minor variability in QRS morphology, sign of generally serious atrial stretch disease
what is the adrenergic affect on the AV nodal function on long refractory period?
shortens - ventricles keep pace at increased sinus HR
what occurs during a third degree AV block?
the sinus node and atria continue depolarizing at the sinus rate,and the ventricles begin depolarizing and contracting at a slower rate corresponding to the spontaneous rate of depolarization of ventricular pacing cells
when the wave of depolarization is propagated toward the positive electrode of any selected lead, where is the trace deflection?
the trace deflection in that lead is desplayed upward
What happens if a complex get to near an edge?
they will appear clipped and voltage measurements will be inaccurate
On the ECG trace, what does a sinus arrhythmia look like?
like a normal sinus rhythm but with a cyclic irregularity to the P-P & R-R intervals, usually at a normal or slow (bradycardia) heart rate
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