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Physiology > 4- Cardiac Physiology > Flashcards

4- Cardiac Physiology Flashcards

(66 cards)

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1
Q

Where does the heartbeat originate from?

A

Cardiac pacemaker cells that generate spontaneous action potentials

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2
Q

Discuss the differences between pacemaker cells and non pacemaker cells

A

Pacemaker cells
No resting potential
Spontaneous depolarization and repolarization

Non pacemaker cells
True resting potential
Prolonged depolarization

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3
Q

What is membrane potential determined by?

A

Ion concentration gradients
Ion conductances
Electrogenic pumps

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4
Q

How do the opening and closing of ion channels alter the membrane potential

A

In resting potential
K+ channels opens (Na+, Ca2+ closed)
Hyperpolarized cell

In action potential
Na+, Ca2+ channels open (K+ closed )
Depolarized cell

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5
Q

Discuss pacemaker action potential

A

Phase 4- pacemaker potential
Phase 0- depolarization
Phase 3- repolarization

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6
Q

What are the intrinsic rate of firing for the nodes?

A

SA node: 60-100/min
AV node & bundle of His: 40-60/min
Purkinje fibers: 30-40/min

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7
Q

Discuss parasympathetic activation

A

Parasympathetic (vagal) activation decreases nodal rate (negative chronotropy)
Muscarinic (M2) receptors

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8
Q

Discuss sympathetic activation

A

Sympathetic activation increases nodal rate (positive chronotropy)
Beta-1 adrenergic receptors

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9
Q

What are the vagal, intrinsic and sympathetic rates?

A

Vagal 50/min
Intrinsic rate 100-110/min
Sympathetic 200/min

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10
Q

How is pacemaker activity influenced by hormones?

A

Hyperthyroidism increases heart rate
Hypothyroidism decreases heart rate
Catecholamines increase heart rate

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11
Q

How is pacemaker activity influenced by ions?

A

An increase in K+ decreases heart rate (K+ channels open)
A decrease in K+ increases heart rate
Nodal ischemia/hypoxia decreases heart rate

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12
Q

What are the heart rate ranges?

A

During resting
Tachycardia >100/min
Bradycardia <60/min

Maximal
220/min -age of patient ~15minutes
Decreases with age, measured during stress test

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13
Q

Discuss non pacemaker action potentials

A 
Phase 4- resting potential 
Phase 0- rapid depolarization 
Phase 1- increase gK+ &amp; decrease gNa+
Phase 2- increase gCa2+
Phase 3- increase gK+
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14
Q

Which element of the cardiac electrical pathway is the fastest conductor?

A

Purkinje fibers

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15
Q

Which element of the cardiac electrical pathway is the slowest conductor?

A

AV node

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16
Q

What is the term related to the speed of conduction in a nerve fiber?

A

Dromotropy

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17
Q

Where are possible sites of conduction blocks?

A

AV blocks: AV node, Bundle of His

Bundle branch blocks: Left bundle branch, Right bundle branch

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18
Q

Which AV block is associated with ventricular bradycardia, 2 or 3 ventricular depolarization & some atrial potential that has failed to be conducted into ventricles?

A

2nd degree AV block

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19
Q

Which AV block is associated with ventricular bradycardia and complete dissociation between atrial & ventricular depolarizations and contractions?

A

3rd degree AV block

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20
Q

Which AV block is associated with delayed conduction through AV node but the presence of a sinus rhythm?

A

1st degree AV block

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21
Q

Why don’t Purkinje fibers normally take over?

A

Every time an action potential comes through, the clock is reset

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22
Q

Ectopic foci generate action potentials that don’t follow normal conduction pathways, what effect does this have?

A

Ventricles take longer to depolarize

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23
Q

What does the ECG measure?

A

Potential differences between + and - electrodes that are generated by electrical currents emanating from the heart during global depolarization and repolarization

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24
Q

The ST segment corresponds to which electrical event in the heart?

A

Isoelectric depolarized state of the ventricles

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25
Heart rate is based on which electrocardiogram tracing interval?
RR interval
26
The P wave corresponds to which electrical event in the heart?
Atrial depolarization
27
The PR intervals corresponds to which electrical event in the heart?
Atrial depolarization, AV nodd delay, bundle of His and branches
28
The QRS complex corresponds to which electrical event in the heart?
Ventricular depolarization
29
What is usually the cause of a widened QRS complex?
A premature ventricular complex
30
The QT interval corresponds to which electrical event in the heart?
Ventricular action potential duration
31
The T wave corresponds to which electrical event in the heart?
Ventricular repolarization
32
In resting conditions when the membrane potential is around -90 mV, which channel is most likely open in a cardiac myocyte?
Potassium channels
33
What is the primary current responsible for phase 0 of a nodal cell action potential?
I Ca (L)
34
Which mechanism does the sympathetic nervous system use to increase the heart rate?
Positive chronotropy, norepinephrine releases from presynaptic yterminal and binds to Beta 1 adrenergic receptors to speed up heart rate. Increase in rate of phase 4 depolarization.
35
Which element of the cardiac electrical pathway is the primary pacemaker?
The SA node
36
Non pacemaker cells are usually found in which cardiac elements?
Ventricular myocytes
37
What is the usual resting membrane potential for ventricular myocytes?
-90 mV
38
Which phase is the depolarization phase of the action potential
Phase 0
39
The SA node normally beats in between?
60-100 bpm
40
Acetylcholine binds to which muscarinic receptors on the SA node?
M2 receptors
41
Norepinephrine binds to which adrenergic receptors to speed up the heart?
Beta 1 adrenergic receptors
42
The conductance of which ion results in phase 2 characteristics in a ventricular myocyte action potential?
Calcium
43
Which cell junctions connect heart cells together?
Gap junctions
44
Based on the concentration gradient of sodium, potassium and calcium in cardiac myocytes, what occurs to the process of depolarization?
Sodium and calcium move into the cell
45
Which phase occurs if there is a signal through the gap junctions that travels through and stimulates fast sodium channels?
Phase 0
46
The small downward deflection in the QRS complex of the ECG is most likely related to which electrical event?
Septal depolarization
47
A depolarization traveling toward a negative electrode will give what ECG change?
Negative (downward) deflection
48
The normal period of PR interval is between?
0.12 and 0.2 seconds
49
In which phase of the cardiac cycle does the a-wave occur in left atrial pressure
Phase 1-2
50
During transmural ischemia what changes are seen on an ECG?
Normal P wave, ST segment elevation, normal T wave
51
Which phases of the cardiac cycle are seen during both systole and diastole?
Active relaxation
52
Ventricular volume curve drops sharply during which stage of the cardiac cycle?
Ejection
53
Which location has the absolute lowest diastolic pressure in a normal healthy individual?
Right ventricle
54
Which heart sound is associated with early diastolic filling and could be an indicator of pathology
S3
55
Atrial systole accounts for up to what percentage of ventricular filling during exercise conditions?
40%
56
Stroke volume is calculated by?
End diastolic volume-End systolic volume
57
Atrio-ventricular valve open during which stage of the cardiac cycle?
Ventricular filling
58
What contributes to 2nd heart sound?
Closure of aortic and pulmonary valves
59
What contributes to 1st heart sound dying systole?
Closure of AV valves
60
Cardiac output is calculated through which formula?
Stroke volume x heart rate
61
Which parameter increases ventricular preload?
Increased atrial inotropy
62
Velocity of myocardial contraction depends on which factor?
Ease of valvular opening
63
A decrease in inotropy does what to stroke volume of all other cardiac variables are held constant?
Decrease stroke volume
64
Which cardiac change will increase stroke volume?
Increased preload
65
Greater atrial contraction occurs in which physiological condition?
Increase in venous return
66
Which parameter decreases ventricular preload?
Decreased atrial inotropy

Physiology (8 decks)

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