ELEMENTS OF CARDIAC FUNCTION

Question 1

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

Answer 1

SA NODE
AV NODE

Question 2

the resting membrane potential (phase 4) of the fast response cells is considerably more ________ than that of the slow-response cells

Answer 2

negative

Question 3

in slow response cardiac tissue the action potential is propagated more __________ and conduction is more likely to be ________ than fast response cells

Answer 3

slowly
blocked

Question 4

the various phases of the cardiac action potential are associated with changed in cell membrane permeability mainly by ______, _____, and ______ ions

Answer 4

sodium
potassium
calcium

Question 5

the resting cell membrane has a relatively high permeability for ______

Answer 5

potassium

Question 6

the specific potassium channel through which potassium passes during phase 4 is a voltage-regulated channel that conducts the _______________

Answer 6

inward rectifying Potassium current

Question 7

the dependence of Vm on conductance and the intracellular and extracellular concentrations of potassium, sodium and other ions are described by the ________

Answer 7

chord conductance equation

Question 8

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

Answer 8

-90 mv
-65 mv

Question 9

FAST RESPONSE ACTION POTENTIALS
(Genesis of the Upstroke Phase 0)

sodium enters myocyte through specific __________ that exist in the membrane

Answer 9

voltage activated sodium channels

Question 10

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

Answer 10

activate
inactivate

Question 11

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

Answer 11

closed

Question 12

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 ___________

Answer 12

effective refractory period

Question 13

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

Answer 13

relative refractory period

Question 14

FAST RESPONSE ACTION POTENTIALS
(Genesis of Early repolarization Phase 1)

repolarization is brief because of activation of a _______carried by Potassium.

Answer 14

transient outward current

Question 15

FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)

during the action potential plateau _____ enters myocardiial cells through calcium channels

Answer 15

calcium

Question 16

FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)

two types of calcium channels

Answer 16

L-type T-type

Question 17

FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)

L-type channels are blocked by ____________ such as amlodipine, verapamil and diltiazem

Answer 17

calcium channel antagonists

Question 18

FAST RESPONSE ACTION POTENTIALS
(Genesis of Plateau Phase 2)

the parasympathetic neurotransmitter ___________ decreases calcium conductance

Answer 18

acetylcholine

Question 19

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

Answer 19

inward rectification

Question 20

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

Answer 20

substantially less

Question 21

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 ____________

Answer 21

Na+, K+ - ATPase

Question 22

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

Answer 22

calcium
sodium

Question 23

two types of potassium channels

Answer 23

delayed rectifier potassium currents
transient outward potassium current

Question 24

property of cardiac tissue is the ability to intiate its own beat

Answer 24

automaticity

Question 25

property of cardiac tissue

Answer 25

regularity of pacemaking activity

Question 26

_____________ 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

Answer 26

tetrodoxin

Question 27

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

Answer 27

fast sodium current

Question 28

in the pacemaker cells of the SA node at least 3 ionic currents mediate slow diastolic depolarization clue outward inward inward

Answer 28

outward potassium current hyperpolarization induced inward current inward calcium current

Question 29

the hyperpolarization induced by _______ released from vagus nerve endings in the heart is achieved by the activation of specific potassium channels

Answer 29

acetylcholine

Question 30

the automaticity of pacemaker cells diminishges after these cells have been excited at a high frequency

Answer 30

overdrive suppression

Question 31

overdrive suppression results from the activity of membrane _____

Answer 31

sodoum potassium ATPase

Question 32

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

Answer 32

briefer potassium

Question 33

abnormal prolongation of the AV conduction time is called _________

Answer 33

1st degree AV block

Question 34

the conduction pattern in which only a fraction of the atrial impulses are conducted to the ventricles

Answer 34

2nd degree AV block

Question 35

conduction pattern in which none of the atrial impulses reaches the ventricles is called a ___________ or complete AV block

Answer 35

3rd degree AV block

Question 36

triggered activity is caused by _____________ of two types clue: early d

Answer 36

afterpolarization early afterpolarization delayed afterpolarization

Question 37

early afterdepolarizations are more likely to occuire when the heart rate is __________, while delayed afterdepolarizations more likely to occur when heart rate is ________

Answer 37

slow high

Question 38

delayed afterpolarizations are associated with elevated intracellular _______

Answer 38

calcium

Question 39

during the ST interval the entire myocardium is _________

Answer 39

depolarized

Question 40

when firing of the SA node is decreased the heart rate also decreases

Answer 40

bradycardia

Question 41

increased SA node firing results in elevation of the heart rate

Answer 41

tachycardia

Question 42

if this premature depolarization occurs at regular interval or at an integral multiple of that interval the distance is called _________`

Answer 42

parasystole

Question 43

_____________ tachycardias originate from ectopic focus typically begin and end abruptly

Answer 43

ectopic tachycardias

Question 44

__________ inhibits the calcium atpase of the sarcoplasmic reticulum

Answer 44

phospholamban

Question 45

contraction of cardiac muscle is influenced by both ______ and ________

Answer 45

preload and afterload

Question 46

___________ is the force that stretches the relaxed muscle fibers, thereby increasing their resting length

Answer 46

preload

Question 47

________ is the force added to the muscle against which the contracting muscle must act

Answer 47

afterload

Question 48

in the venous pulse curve recorded from the jugular vein, 3 waves are apparent

Answer 48

a wave c wave v wave

Question 49

wave that occurs in pressure caused by atrial contraction

Answer 49

a wave

Question 50

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

Answer 50

c wave

Question 51

reflects the rise in pressure associated with atrial filling

Answer 51

v wave