The Heart Flashcards
(98 cards)
1
Q
What is an excitable cell?
A
A cell that can generate an action potential (neuron, muscle, etc.)
2
Q
What does an action potential lead to in muscle cells?
A
Contraction
3
Q
What are the three kinds of muscle?
A
Smooth, skeletal, and cardiac
4
Q
What do smooth muscle cells control?
A
Involuntary movement (digestion, etc.)
5
Q
What do skeletal muscle cells control?
A
Voluntary movement (arm, etc.)
6
Q
What are the top two chambers of the heart called?
A
Atria
7
Q
What are the bottom two chambers of the heart called?
A
Ventricles
8
Q
What is the “workhorse” of the heart?
A
Left ventricle
9
Q
From the body, which chamber does the blood go intro first?
A
Right atrium
10
Q
Which chamber pumps the blood to the rest of the body?
A
Left ventricle
11
Q
What does the septum do?
A
Separate the electrical activity of the left and right ventricles
12
Q
Why is the orientation of the myocardium important?
A
A spiral shape allows for contraction of the heart
13
Q
Where is the tricuspid valve?
A
Between the right atrium and right ventricle
14
Q
Where is the pulmonary valve?
A
Between the right ventricle and the pulmonary arteries
15
Q
Where is the aortic valve?
A
Between the left ventricle and the aorta
16
Q
Why is a heart action potential longer than a neuron action potential?
A
The function. This action potential allows for a pumping action
17
Q
When does the peak force occur (in terms of excitation-contraction coupling)?
A
Absolute refractory period
18
Q
How does the heart prevent tetanus?
A
The peak force occurs before relative refractory period, so the peak force must decrease before another action potential can start
19
Q
When a muscle cell depolarizes, what direction does it occur?
A
All directions
20
Q
Why can the SA node set the pace of the heart?
A
They are self excitatory
21
Q
What is the heart rate set by the SA node?
A
70 bpm
22
Q
Where do the signals propagate after the SA node?
A
Throughout the atria
23
Q
Where is the AV node located?
A
Boundary between atria and ventricles
24
Q
Where do the signals propagate after the AV node?
A
Into the bundle of his
25
What is the heart rate set by the AV node?
50 bpm
26
What is the primary pacemaker of the heart?
SA node
27
Where do the signals propagate after the bundle of his?
Left and right bundle branches
28
Why are the left and right bundle branches needed?
Propagate signal through ventricles faster (compared to muscle cells)
29
How does depolarization propagate in the heart?
From the inside (endocardium) to the outside (epicardium)
30
How does repolarization propagate in the heart?
From the outside (epicardium) to the inside (endocardium)
31
Why does depolarization propagate from inside to outside?
The inner cells are triggered first, and the wave travels outside
32
Why does repolarization propagate from outside to inside?
The action potentials near the outside are shorter than the ones near the inside
33
Where are purkinje fibers located?
End of the left and right bundle branches
34
What is the purpose of purkinje fibers?
Allow for synchronized contraction of the ventricles
35
What happens if there is failure at the bundle of his (in terms of the pace of the heart)?
The cells will contract at the highest frequency in that area
36
What is the major assumption of the core conductor model?
Homogeneous conductors and cross section
37
What happens when a cell is depolarized (in terms of ion flow)?
Positive ions (soidum) flow into the cell
38
If an EKG signal is positive, which direction is a depolarization wave going?
Towards the electrode
39
If an EKG signal is negative, which direction is a depolarization wave going?
Away from the electrode
40
What is the relationship between the voltage outside and the transmembrane voltage (core conductor model)?
Vo = -(ro/ro+ri)Vm ~ 0.5Vm
41
What is the relationship between the current across the membrane and the transmembrane voltage (core conductor model)?
Km(z,t) = 1/(ro+ri) * (second derivative of voltage with respect to space)
42
What happens when a cell is repolarized (in terms of ion flow)?
Positive ions (potassium) flow out of the cell
43
If an EKG signal is positive, which direction is a repolarization wave going?
Away from the electrode
44
If an EKG signal is negative, which direction is a repolarization wave going?
Towards the electrode
45
Why is the repolarizing zone bigger than the depolarizing zone?
Repolarization is a slower process
46
In a normal EKG, why do the depolarization and repolarization events have the same sign?
Depolarization moves towards the electrode (start inside, move outside), while repolarization moves away from the electrode (shorter time outside, longer time inside)
47
What is the purpose of a gap junction?
Electrically link myocytes (allow for ion passage between cells)
48
What is the significance of being an aggregate measure?
All signals are recorded and summed at a particular electrode
49
What ion is responsible for the different shape in heart action potentials?
Calcium flows into the cell
50
What chemical blocks sodium channels?
TTX
51
If TTX was added to a heart cell, what would the resulting EKG signal look like?
Smaller spike at the beginning (no sodium influx)
52
What does the P wave represent?
Atrial depolarization
53
What does the PR interval represent?
Time from atrial depolarization to ventricular repolarization
54
What does the QRS complex represent?
Ventricular depolarization
55
What does the ST segment represent?
Beginning of ventricular repolarization
56
What does the QT interval represent?
Total ventricular activity (depolarization to repolarization)
57
What does the T wave represent?
Ventricular repolarization
58
What does the U wave represent?
Repolarization of purkinje fibers
59
What does a galvanometer do?
Measure current flow by utilizing magnetic fields
60
What are the leads of Einthoven's triangle?
RA (right arm), LA (left arm), LL (left leg)
61
How can you determine a positive lead in Einthoven's triangle?
An L is a positive lead
62
What do we measure on a lead in Einthoven's triangle?
The projection of the heart vector onto that lead
63
How is a projection onto a lead calculated?
The dot product (magnitudes times cos(angle))
64
What is the relationship between leads I, II, and III in Einthoven's triangle?
I + III = II (voltages)
65
Why is it better to use multiple leads?
Get a better idea of different events along different leads
66
What modification is done to convert Einthoven's triangle into Wilson Central Terminal?
Connect all the leads at a central point
67
What is the advantage of the Wilson Central Terminal (compared to Einthoven's triangle)?
Have a central terminal voltage as a reference node (average of three voltages)
68
What modification is done to convert Einthoven's triangle into Goldberger Augmented leads?
Add three leads that bisect the leads in Einthoven's triangle
69
How is the voltage of an augmented lead calculated?
Corner potential minus the average potential across the lead
70
What is the advantage of Goldberger Augmented leads (compared to Wilson Central Terminal)?
Larger signal (~50%)
71
Why is lead II a good indicator of heart activity?
Heart lies on a tilt that closely aligns with lead II
72
For EKG paper, what is the scale for the x axis?
5 large boxes is 1 sec
73
For EKG paper, what is the scale for the y axis?
2 large boxes is 1 mV
74
What happens in acute coronary syndrome (ACS)?
Clot formation in the heart
75
What is infarction?
Tissue dies due to lack of blood
76
How is an infarction measured in an EKG signal?
Acts as a "window", so other signals can be seen
77
In an EKG signal measured near the left ventricle, there is a large negative spike at the QRS complex. What could be the underlying reason?
Infarction at left ventricle, thus being able to see the biological activity at the right ventricle
78
In an EKG signal, the T wave is inverted. What could be the underlying reason?
Partial loss of tissue, returning blood flow
79
In an EKG signal, the ST wave is elevated. What could be the underlying reason?
Myocardial infarction
80
In an EKG signal, the QRS complex is normal, but the ST segment is lower than normal. What could be the underlying reason?
Partial occlusion in the heart
81
In an EKG signal, two complexes are very close together, followed by a long pause. What could be the underlying reason?
Atrial ectopic heartbeat
82
In an EKG signal, there is a very large negative spike, followed by a positive bump. The rest of the signal is normal. What could be the underlying reason?
Ventricular ectopic heartbeat
83
Why does a ventricular ectopic heartbeat have a large negative spike?
Depolarization in wrong direction compared to normal (depolarization going from outside to inside)
84
In an EKG signal, the QRS complex is normal, but the P wave is inverted. What could be the underlying reason?
Atrial ectopic heartbeat, close to AV node (traveling up the atria instead of down)
85
In what situation could a P wave and a T wave fuse together?
Atrial ectopic heartbeat happening too early, fusing with the repolarization of the ventricles
86
What is tachycardia?
Heart rate greater than 100 BPM
87
In an EKG signal, the QRS complexes are all negative, and fairly rapid. What could be the underlying reason?
Ventricular tachycardia
88
In ventricular tachycardia, what direction are the QRS complexes?
Negative (depolarize away from electrode)
89
In an EKG signal, the signals are normal, but at a rapid rate. What could be the underlying reason?
Supraventricular tachycaridia
90
In supraventricular tachycardia, what directions are the QRS complexes?
Positive (still go through AV node)
91
In an EKG signal, the P waves are upright and PR intervals is normal, but the beat is rapid. What could be the underlying reason?
Sinus tachycardia (SA node misfiring)
92
In an EKG signal, the P waves are inverted, and the PR interval is short, with the beat being rapid. What could be the underlying reason?
Junctional tachycardia (AV node misfiring)
93
In an EKG signal, some leads are reading a positive P wave, while other leads are reading a negative P wave, with a rapid beat. What could be the underlying reason?
Atrial ectopic heart beat (outside SA and AV node, close to the left)
94
In an EKG signal, the signal is irregularly irregular. What could be the underlying reason?
Atrial fibrillation
95
What biological condition could underly atrial fibrillation?
Multiple depolarizations in the atria
96
What information does a Fourier transform reveal?
Different frequencies in a signal
97
What samples can you trust in a Fourier transform?
Up to half of the signaling frequency
98
If we want to remove frequencies between 55 and 60 Hz, and the sampling rate is 1000 Hz, what range of frequencies would we delete in the Fourier transform?
55-60 Hz and 935-940 Hz
