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107 Cards in this Set

  • Front
  • Back
The binding of norephinephrine/epinephrine to a B1 receptor on a cardiac cell activates
adenylyl cyclase which makes cAMP which phosphorylates PKA.
PKA-p increases [Ca] i by what methods?
Phosphorylates Ca channel in sarcolemma increasing flow of Ca
PKA-p decreases [Ca]i by what methods?
Phosphorylates phospholamban decreasing its inhibitory effect on SR Ca ATPase, decreasing [Ca] i
Preload of cardiac muscle
force that stretches the relaxed muscle fibers - force against ventricle during filling
Afterload if cardiac muscle
force against which the contracting muscle must act - pressure in the aorta that must be overcome to open aortic valve
How can you increase pre-load?
greater filling of ventricle during diastole
Increasing pre-load has what effect on systolic pressure?
increases systolic pressure to max and then it decreases if further increases in pre-load occur
Changes in afterload effect systolic pressure how?
Increases in afterload (increased aortic pressure) increases systolic pressure
The ventricle is effected how during maximal afterload increase?
Ventricle stretched to where it cannot create enough force to open aortic valve. - isovolumic contraction
The first heart sound is the closure of the ?
AV valves (tricuspid - Rt AV, mitral - L AV)
The second heart sound is the closure of ?
pulmonic and aortic valves
Thin filament regulation
The actin filament is blocked at low [Ca] and exposed during high [Ca].
The long action potential in cardiac muslce is due to
VG L-type Ca channel characteristics:long refractory period - prevents tetany.
Altering the VG L-type Ca channel changes
[Ca]i, thus changes contractility, force of contraction
The increase in size of [Ca]i transient, and thus force of contraction is due to what type of stimulation
B-adrenergic - norepi/epi
positive inotropy
increase in force of contraction
positive lusitrophy
increase in rate of muscle relaxation
positive chronotrophy
increase in contraction of heart - B-adrenergic
What is a dipole?
a separation of charge in space; orientation and magnitude of an electrical field
What does an ECG detect?
dipole created by depolarization of myocardium
The dipole of the myocardium has what 2 characteristics?
it changes over time
can be detected on the body surface
The dipole can be described as _____ having a
magnitude and direction
The ECG represents the ____ of the ___ ____ of the ___.
electrical activity of the myocardium
The ECG does or does not detect activation of the specialzed conduction system
does not
The ECG does or does not provide information about mechanical activity
does not
The ECG can or cannot see the AV node depolarization
Lead I of an ECG is set up how
Right arm (-) to Left arm (+)
Lead II of an ECG is set up how?
Right arm (-) to Left leg (-)
Lead III of an ECG is set up how?
Left arm (-) to Left leg (-)
AVR unipolar lead is set up how?
RA as sensing electrode
AVL unipolar lead is set up how?
LA is sensing electrode
AVF unipolar lead is set up how?
LL is sensing electrod.
automaticity of the heart is what?
the ability to initiate its own beat
the regularity of pacemaking activity
The region of heart that initiates impulses at the greatest frequency is the
SA node
4 unique characteristics of the SA node depolarization
RMP is less neg, upstroke less steep, plateau not sustained, repolarization is more gradual
The SA node depolarization is not facilitated by
fast sodium channels
No effect from fast Na channel blockers
Both AV and SA node RMP is less negative than myocytes because
they both lack iK channels
The SA and AV node MP varies more from ______ than myocytes
Equilibrium potential of K
Pacemaker cells have a unique characteristic of phase 4
a slow steady diastolic depolarization
Pacemaker cell frequency can be varied by ______
rate of phase 4 depolarization, the max neg during phase 4, or threshold potential
To slow nodal firing
increase threshold, make phase 4 MP more negative,
The slow diastolic nodal depolarization is caused by what 3 things
outward K current
inward current from hyperpolarizaiton, and inward Ca current
The slow diastolic depolarization of the nodes is because
K current out slows, funny channel Na current, and Ca current in.
Ca channel antagonists do what in the nodes?
diminish the amplitude of the action potential, and slop of the slow diastolic depolarization
funny channels are triggered by
hyperpolarization and are different Na channels than fast channels
Ectopic pacemakers become pacemakers when
their own rhythmicity is enhanced, higher order pacemakers are depressed, or conduction pathways between the higher order and ectopic are blocked
adrenergic transmitters effect what channels
all 3 - 1) outward K, 2) Na funny 3) Ca inward
The bundles of His are what
the upper portion of the specialized conduction system for the ventricles
The AV nodal delay (time between P and QRS) allows for what
ventricular filling
Blocking fast Na channels effects the AV node how?
no effect
Ca channel antagonists have what effect on the AV node?
decreases the amplitude and duration of the AP and depresses AV conduction
The AV node relative refractory period ends
well beyond complete repolarization
1st degree AV block is what?
abnormal prolongation of the AV conduction time.
2nd degree AV block is what?
Only a fraction of atrial impulses are conducted to ventricle
2nd degree AV block may protect the heart how?
protects the vetricles from excessive contraction frequencies to allow sufficient filling times
Weak vagal activity does what to the AV node?
prolong the AV conduction time. Atrium to His, A to V conduction time will be prolonged.
Strong vagal tone does what to the AV node?
blocks some or all of the atrial impulses
3rd degree or complete AV block?
none of the atrial impulses reach the ventricles
vagal stimulation of the heart is carried out by
the action of acetylcholine to hyperpolarize the RMP of conducting fibers in the AV node
Sympathetic nerves ______ AV conduction
by decreasing AV conduction time,
Sympathetic release of ________ on the __ ____ the amplitude and slope of upstroke of AV node
postganglionic sympathetic nerve terminals
The bundle of His is located _____ and then divides into
right side of interventricular septum, R & L bundle branches
Bundle branches eventually branch into
Purkinje fibers
Purkinje fibers have a ____ refractory period that _____ some _____ impulses.
The refractory period of Purkinje fibers is ______ during slow heart rates
The PR interval is the time between the
onset of atrial depolarization and the onset of vetricular depolarization
A long QRS complex indicates a
block in the normal conduction pathways through the ventricles (L/R bundle branches
ST represents the
entire ventricular depolarization and is isoelectric
The duration of the myocardial cell AP varies ______ with the heart rate
T waves can be __ or ____ but must be ________
positive or negative
The unipolar leads take two leads and _____ their values
averages, not take the difference
If P to R interval is longer it means what?
AV node slow to depolarize, not that depolarization takes longer
If the QRS complex is wide and bizarre it means
depolarization started elsewhere from AV node, conduction system not working
R waves are always
positive or not present
cholinergic stimulation of the heart (ACh) causes
Inc K perm, hyperpol SA node, depress fun and Ca currents, slows spontaneous depolarization
Vagal stimulation of the SA node causes the net effect of
decreasing HR by lowering RMP and slowing diastolic depolarization
Vagal stimulation of the AV node has the effect of
shortening the plateau phase - weakend A contraction - not impt
Vagal stimulation of the AV node
increases K perm, decreases excitability, slows or stops impulse trnsimission
Vagal stimulation of the AV nodes has the net effect of
increasing AV nodal delay or inducing 3rd degree block
Vagal stimulation of the ventricles causes
not much effect
Vagal stimulation of the heart overall effects
HR and AV nodal delay
Sympathetic stimulation of the SA node causes
increase in f, and Ca > K currents,
Sympathetic stimulation of the SA node has the net effect of
increase spontaneous depolarization, increased HR
Sympathetic stimulation of the AV node
increases conduction velocity - decreased AV node delay
Sympathetic stimulation of the AV node has the net effect of
Increased HR and increased conduction velocity
Sympathetic stimulation of the Atrial and ventricular contractile cells causes
calcium load the cells
Calcium loading of myocytes includes
phosphorylation of Ca channels and phospholambam increasing Ca in cell and SR
Sympathetic stimulation of the myocytes causes the net effect of
increased strength of contraction, and rate of relaxation
Sympathetic stimulation of myocytes increases the rate of relaxation by
increasing CA uptake into SR, decreasing calcium sensitivity, phosphorylating troponin I
sympathetic stimulation of the myocytes is carried out by
postive lusitropic
increased rate of relaxation
positive inotrophic
increased strength of contraction
Sinus rhythm means
SA nod starts depolarization and upright P leads to QRS
sinus arrhythmia
sinus rhythm with irregular R-R interval caused by changes in symp/vagal tone during respiration
Sinus arrhythmia can't happen in animals with
fast HR
Sinus arrhythmia occurs in dogs with
high vagal tone
Baroreflex is coordination of
vagal/sympathetic tone.
S1 of heart auscultation associated with
closure of AV valvem onset of systole, present in all species
S2 of heart auscultation associated with
closure of aortic and pulmonic valves, signals end of systole, present in all species
S3 is during diastole and associated with
rapid ventricular filling, not in normal dogs/cats, with heart failure, increased venous return in preg mares
S4 is associated with
atrial contraction, immediately precedes S1, present in horses
Murmurs are
abnormal sounds induced by turbulent blood flow
Murmurs can originate from
stenosis, relative stenosis, incompetent valve, anemia, septal defects
Anemia causes a murmur because
decreased PVC, decreases viscosity, causes turbulent flow
Systolic murmurs are from
incompetent AV valves, stenosis of pulmonic or aortic valve, sub-aortic stenosis, relative pulmonic stenosis
diastolic murmurs are from
incompetent pulmonic/aortic valves