Cardiac Physiology Flashcards
1
Q
Heart
A
Organ that pumps blood, supplies oxygen and nutrients to tissues, and removes CO2 and other wastes; pumped in parallel
2
Q
Composition of circulatory system
A
- Heart - pump that provides pressure to drive blood throughout the circulation
- Blood Vessels - passageways in which the blood is directed to organs and tissues
- Blood - transport medium, allows materials to be transported over body (ex: O2, CO2, nutrients, waste, electrolytes, hormones)
3
Q
Composition of blood
A
- Separated into formed elements and plasma
- RBCs - carry O2, hemoglobin
- WBCs - defense
- Platelets - clotting; low platelets results in hemophilia (bleeding out)
4
Q
Types of Circulatory Pathways
A
- Pulmonary Circulation
- Systemic Circulation
5
Q
Pulmonary Circulation
A
Pumps blood between heart and lungs; shorter circuit with less pressure
6
Q
Systemic Circulation
A
Pumps blood to all other body systems, tissues, etc.; longer circuit with more pressure; parallel pathway with portions of the blood going to several different regions of body, this means that blood flow is not in series and doesn’t go from one organ to next
7
Q
Where will oxygenated and deoxygenated blood mix?
A
Womb
8
Q
Pericardium
A
Coverings of the heart
- Fibrous pericardium = outermost
- Parietal pericardium
- Visceral pericardium = innermost
9
Q
Serous Pericardium
A
Consists of visceral and parietal, separated by cavity filled with pericardial fluid
10
Q
What happens when there is too much pericardial fluid?
A
Cardiac tamponade
11
Q
Walls of the heart
A
- Epicardium (same layer as visceral pericardium) = outermost
- Myocardium = excited cells, myocytes (muscle cells), thick layer
- Endocardium = innermost, smooth, continues with inner layer of blood vessels
12
Q
What separates the right and left ventricles?
A
Interventricular septum
13
Q
Chambers of the heart
A
- Right atrium
- Right ventricle
- Left atrium
- Left ventricle
14
Q
Valves of the heart
A
- Tricuspid/right atrioventricular valve
- Pulmonary semilunar valve
- Bicuspid/left atrioventricular valve
- Aortic semilunar valve
15
Q
Heart valves in ventricular contraction
A
Both AV valves remain closed to prevent flow backwards into the atria, and the semilunar valves are open
16
Q
Heart valves in ventricular relaxation
A
Both AV valves are open, and the semilunar valves close to prevent blood that has entered the arteries from flowing back into the ventricles
17
Q
When do valves open?
A
When pressure is greater behind the valve
18
Q
When do valves close?
A
When pressure is greater in front of the valve, it doesn’t open in the opposite direction/one-way valve
19
Q
Laminar Flow
A
Straight, doesn’t create sound
20
Q
Turbulent Flow
A
Jumbled, can be heard
21
Q
Diastole
A
Relaxation
22
Q
Systole
A
Contract
23
Q
Late Diastole
A
Both sets of chambers are relaxed an ventricles fill passively, start, already has 80% of ventricles filled
24
Q
Atrial Systole
A
Atrial contraction forces small amount of additional blood into ventricles (20% active, atria push 20% into ventricles during contraction)
25
When is lub noise heard?
At the end of atrial systole, S1
26
Isovolumic Ventricular Contraction
Firs phase of ventricular contraction that pushes AV valves closed but doesn't create pressure to open semilunar valves
27
Ventricular Ejection
Semilunar valves open and blood is ejected due to pressure in ventricles rising and exceeding pressure in arteries
28
When is dub noise heard?
At the end of ventricular ejection, S2
29
Midventricular Diastole
Blood flows from venous side into atrium and into ventricles
30
Isovolumic Ventricular Relaxation
Pressure in ventricles falls, blood flows back into cusps of semilunar valves and causes them to close
31
When is heart murmur heard?
Between dub and lub, means there is blood leaking back through the valves
32
What is the correlation between dilation and EDV?
Increased dilation = increased EDV
33
Autorhythmicity
Heart beats due to action potentials it creates on its own
34
Types of cardiac muscle cells
1. Contractile cells
2. Autorhythmic cells
35
Contractile Cells
99% of cells on heart; don't initiate their own action potential; myocytes; don't regenerate
36
Autorhythmic Cells
Do not contract, initiate action potentials for working contractile cells; pacemaker cells
37
What is Na+ responsible for?
Depolarization
38
What is K+ responsible for?
Repolarization
39
What is Ca2+ responsible for?
Depolarization and firing of action potential
40
What changes in ionic movement cause the pacemaker potential?
- Increased inward Na+ current and decreased K+ current
- Increased inward Ca2+ current
- Increased K+ outward current
41
What kind of channels are funny channels?
Sodium channels that hand off to transient Ca channels in order to reach threshold
42
What are the types of Ca channels?
1. Transient
2. Long-lasting
43
Transient Ca Channels
Propagate pacemaker potential to threshold
44
Long-lasting Ca Channels
Propel action potential to overshoot where K+ permeability increases and it exits cell
45
Pacemaker Potentials
- Ca rising phase differs from nervous and skeletal muscle cells where Na influx causes positive potential direction instead of Ca
- Falling phase is result of K efflux out of cell via activation of voltage gate K channels which are coupled with closure of long Ca channels
46
Electrical Conduction Pathway
SA node to atria via interatrial pathway
SA node on internodal pathway to AV node, which breaks off into Bundle of His --> Purkinje fibers
47
What will take over if SA node stops working?
AV node can take over and compensate because 80% of heart fills based on pressure difference alone
48
Atrial Excitation
Actional potential from SA node spreads through the atria
49
Pathways that speed up conduction in the atria
1. Interatrial Pathway
2. Internodal Pathway
50
Interatrial Pathway
From SA node in right atrium to left atrium
- Rapidly transmits AP from right to left atrium and ensures that both atria become depolarized and contract simultaneously
51
Internodal Pathway
SA node to AV node
- Only way that an electrical signal can pass to the ventricles (via AV node)
52
How long and why is conduction slow through AV node?
Delayed for about 100 msec (AV nodal delay); happens so ventricles can fill
53
Where does impulse go after AV nodal delay?
Bundle of His and then to Purkinje fibers
54
Conduction System of Heart
1. SA node depolarizes
2. Electrical activity goes rapidly to AV node via internodal pathways
3. Depolarization spreads more slowly across atria and conduction slows through AV node
4. Depolarization moves rapidly through ventricular conducting system to apex of heart
5. Depolarization wave spreads up from apex
55
AP of Contractile Cells
Induced by pacemaker cells; contain different electrophysiological characteristics than pacemaker cells
56
What is the resting membrane potential of cardiac contractile cells (myocytes)?
Around 90 mV
57
Phases of AP for contractile cells
1. Cell at resting potential
2. Na+ channels open and depolarize
3. Na+ channels close and K channels open transiently to cause small repolarization
4. Long Ca channels open and fast K channels close (decreasing permeability), causing plateau and halts repolarization
5. Ca channels close and K channels open causing repolarization
58
What is the area under the curve known as?
Absolute refractory period
59
Why does tetanus not occur with these contractile cells/myocytes?
The absolute refractory period overlaps with myocyte contraction and relaxation. This means another AP cannot fire until the cell is completely relaxed
60
Excitation Contraction Coupling
1. AP enters from adjacent cell
2. Voltage-gated Ca channels open and Ca enters cell
3. Ca induces Ca release through ryanodine receptor-channels (RyR)
4. Local release causes Ca spark
5. Summed sparks create Ca signal
6. Ca ions bind to troponin and initiate contraction
7. Relaxation occurs when Ca unbinds from troponin
8. Ca pumped back into sarcoplasmic reticulum for storage
9. Ca exchanged with Na by NCX antiporter
10. Na gradient maintained by Na-K-ATPase
61
Process of Ca release
- Ca influx causes opening of ryanodine receptors on lateral sacs of sarcoplasmic reticulum = Ca induced Ca release
- Incoming Ca sparks SR to release Ca
62
Muscle Contraction w/ Excitation Contraction Coupling
1. AP in contractile cell
2. AP travels down T-tubules
3. Entry of small amount of Ca from ECF through long Ca channels causes Ca induced Ca release
4. Increased cytosolic Ca
5. Troponin-tropomyosin complex in then filaments pulled aside
6. Cross-bridge cycling between thick and thin filaments
7. Thin filaments slide inward between thick filaments
8. Contraction
63
When would tetanus occur in cardiac muscle?
If the refractory period did not align with the muscle twitch
64
Electrocardiogram (ECG)
Record of overall spread of electrical activity through heart
- 6 leads to chest and 6 to legs
65
What is ECG recording of?
Recording of activity present in body fluids from cardiac impulse that reaches the body surface, not a direct recording of activity from heart
66
What does ECG show?
Shows overall activity and not APs; at any one time it represents sum of activity. Also shows voltage comparison of two points of body surface --> exact pattern of activity depends on orientation of electrodes
67
Waveforms of ECG
1. P wave
2. QRS complex
3. T wave
68
P Wave
Represents atrial depolarization/contraction; SA node fires
69
QRS Complex
Represents ventricular depolarization/contraction while atria repolarize/relax
70
T Wave
Represents ventricular repolarization/relaxation
71
Why is the QRS complex so big?
The ventricles have more myocytes and electrical activity
72
Where is the atrial relaxation on ECG?
It's covered up by QRS complex
73
How do mechanical events of heart correspond to electrical events?
They slightly lag behind them
74
PR Segment
AV nodal delay
75
ST Segment
Time when ventricles are contracting and emptying
76
TP Interval
Time when ventricles are relaxing and filling
77
What are the types of cardiac abnormalities?
1. Rate
2. Rhythm
3. Cardiac Myopathies
78
Rate Abnormalities
1. Tachycardia
2. Bradycardia
79
Tachycardia
Heart rate of more than 100 bpm
80
Bradycardia
Heart rate of less than 60 bpm
81
Rhythm Abnormalities
Arrhythmia
- Atrial flutter
-Atrial fibrillation
- Ventricular fibrillation
- Heart block
82
Atrial Fibrillation
Atrium contracts while other relaxes; less dangerous than V-fib because 80% of flow still occurs
83
Ventricular Fibrillation
Ventricle contracts while other relaxes
84
How are A-fib and V-fib treated?
Treated with defibrillation, but there must be some current to work
85
Cardiac Myopathy
Damage of heart muscle
- Myocardial ischemia
- Necrosis
- Acute MI
86
Myocardial ischemia
Inadequate delivery of oxygenated blood to heart tissue
87
Necrosis
Death of heart muscle cells
88
Acute MI
Heart attack; blood vessel supplying area of heart has been blocked or ruptured
89
Second-degree block
Half of P waves aren't followed by QRS complex and T wave while other half is; SA node works(contracts?) but ventricle doesn't contract
90
A-fib ECG
Abnormal pattern prior to QRS complexes and increased frequencies between QRS complexes
91
Ventricular Tachycardia ECG
QRS complex has strange shape --> S dips down
92
V-fib ECG
No normal electrical activity; very dangerous and can be lethal
93
Third-degree block
Some impulses initiated by SA node don't reach AV node while others do; P waves not followed by QRS complex; very rare, death occurs with no treatment
