ELEMENTS OF CARDIAC FUNCTION Flashcards
the other type of action potential, the slow response occurs in the ___________ which is the natural pacemaker region of the heart
and in the ______________ which is the specialized tissue that conducts the cardiac impulse from the atria to the ventricles
SA NODE
AV NODE
the resting membrane potential (phase 4) of the fast response cells is considerably more ________ than that of the slow-response cells
negative
in slow response cardiac tissue the action potential is propagated more __________ and conduction is more likely to be ________ than fast response cells
slowly
blocked
the various phases of the cardiac action potential are associated with changed in cell membrane permeability mainly by ______, _____, and ______ ions
sodium
potassium
calcium
the resting cell membrane has a relatively high permeability for ______
potassium
the specific potassium channel through which potassium passes during phase 4 is a voltage-regulated channel that conducts the _______________
inward rectifying Potassium current
the dependence of Vm on conductance and the intracellular and extracellular concentrations of potassium, sodium and other ions are described by the ________
chord conductance equation
FAST RESPONSE ACTION POTENTIALS
(Genesis of the Upstroke Phase 0)
when the resting membrane potential suddenly depolarized from ________ mV to the threshold level of approximately ____mV the cell membrane properties change dramatically
-90 mv
-65 mv
FAST RESPONSE ACTION POTENTIALS
(Genesis of the Upstroke Phase 0)
sodium enters myocyte through specific __________ that exist in the membrane
voltage activated sodium channels
FAST RESPONSE ACTION POTENTIALS
(Genesis of the Upstroke Phase 0)
the sodium channels open rapidly or ________ thereby resulting in an abrupt increase in sodium conductance. however once open the sodium channels _______ and sodium conductance rapidly decreases
activate
inactivate
FAST RESPONSE ACTION POTENTIALS
(Genesis of the Upstroke Phase 0)
with repolarization the channels transition to the ____ state from which it can then be reopened by another depolarization of Vm to the threshold
closed
FAST RESPONSE ACTION POTENTIALS
(Genesis of the Upstroke Phase 0)
when the sodium channels are inactivated they cannot be reopened and another action cannot be generated. the cell is said to be in its ___________
effective refractory period
FAST RESPONSE ACTION POTENTIALS
(Genesis of the Upstroke Phase 0)
during this period called the _________ another action potential can be generated but it requires a larger than normal depolarization of Vm
relative refractory period
FAST RESPONSE ACTION POTENTIALS
(Genesis of Early repolarization Phase 1)
repolarization is brief because of activation of a _______carried by Potassium.
transient outward current
FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)
during the action potential plateau _____ enters myocardiial cells through calcium channels
calcium
FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)
two types of calcium channels
L-type T-type
FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)
L-type channels are blocked by ____________ such as amlodipine, verapamil and diltiazem
calcium channel antagonists
FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)
the parasympathetic neurotransmitter ___________ decreases calcium conductance
acetylcholine
FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)
the reduction of potassium conductance at both positive and low negative values of Vm is called _____________. __________ is a characteristic of several potassium currents
inward rectification
FAST RESPONSE ACTION POTENTIALS
(Final repolarization Phase 3)
the duration of the plateau is substantially ____ in atrial myocytes than in ventricular myocytes because the magnitide of outward potassium currents are greater in atrial myocytes than in ventricular myocytes
substantially less
FAST RESPONSE ACTION POTENTIALS
(restoration of ionic concentration Phase 4)
the steady inward leak of sodium that enters the cell rapidly during the phase 0 and more slowly throughout the cardiac cycle would gradually depolarize the resting membrane voltage were it not for the ____________
Na+, K+ - ATPase
certain cells in the heart notably those in the SA and AV nodes exhibit slow response action potentials, in these cells depolarization is achieved mainly by influx of_________ through L-type calcium channels instead of influx of _______ through fast sodium channels
calcium
sodium
two types of potassium channels
delayed rectifier potassium currents
transient outward potassium current
property of cardiac tissue is the ability to intiate its own beat
automaticity
property of cardiac tissue
regularity of pacemaking activity
_____________ blocks fast sodium current has no influence on the SA nodal action potential because the action potential upstroke is not produced by an inward sodium current through fast channels
tetrodoxin
tetrodoxin blocks ____________has no influence on the SA nodal action potential because the action potential upstroke is not produced by an inward sodium current through fast channels
fast sodium current
in the pacemaker cells of the SA node at least 3 ionic currents mediate slow diastolic depolarization
clue
outward
inward
inward
outward potassium current
hyperpolarization induced inward current
inward calcium current
the hyperpolarization induced by _______ released from vagus nerve endings in the heart is achieved by the activation of specific potassium channels
acetylcholine
the automaticity of pacemaker cells diminishges after these cells have been excited at a high frequency
overdrive suppression
overdrive suppression results from the activity of membrane _____
sodoum potassium ATPase
action potential duration in atrial myocytes is ______ than in ventricular myocytes because efflux of ______ is greater during the plateau in atrial myocytes than in ventricular myocytes
briefer
potassium
abnormal prolongation of the AV conduction time is called _________
1st degree AV block
the conduction pattern in which only a fraction of the atrial impulses are conducted to the ventricles
2nd degree AV block
conduction pattern in which none of the atrial impulses reaches the ventricles is called a ___________ or complete AV block
3rd degree AV block
triggered activity is caused by _____________ of two types
clue:
early
d
afterpolarization
early afterpolarization
delayed afterpolarization
early afterdepolarizations are more likely to occuire when the heart rate is __________, while delayed afterdepolarizations more likely to occur when heart rate is ________
slow
high
delayed afterpolarizations are associated with elevated intracellular _______
calcium
during the ST interval the entire myocardium is _________
depolarized
when firing of the SA node is decreased the heart rate also decreases
bradycardia
increased SA node firing results in elevation of the heart rate
tachycardia
if this premature depolarization occurs at regular interval or at an integral multiple of that interval the distance is called _________`
parasystole
_____________ tachycardias originate from ectopic focus typically begin and end abruptly
ectopic tachycardias
__________ inhibits the calcium atpase of the sarcoplasmic reticulum
phospholamban
contraction of cardiac muscle is influenced by both ______ and ________
preload and afterload
___________ is the force that stretches the relaxed muscle fibers, thereby increasing their resting length
preload
________ is the force added to the muscle against which the contracting muscle must act
afterload
in the venous pulse curve recorded from the jugular vein, 3 waves are apparent
a wave
c wave
v wave
wave that occurs in pressure caused by atrial contraction
a wave
wave that is caused by impact of the common carotid artery with the adjacent jugular vein and to some extent by the abrupt closure of the tricuspid valve in early ventricular systole
c wave
reflects the rise in pressure associated with atrial filling
v wave
