Cardiovascular Anatomy and Physiology Flashcards
1
Q
Ability to generate an action potential spontaneously
A
Automaticity
2
Q
Ability to respond to an electrical stimulus by depolarizing and firing an action potential
A
Excitability
3
Q
Difference in electrical potential between the inside and outside of the cell
A
Resting membrane potential (RMP)
4
Q
Movement of a cell’s membrane potential to a more postitive value
A
Depolarization
5
Q
Voltage change that must occur to initiate depolarization
A
Threshold potential
6
Q
The return of a cell’s membrane potential towards a more negative value after depolarization
A
Repolarization
7
Q
The movement of a cell’s membrane potential to a more negative value beyond the baseline RMP
A
Hyperpolarization
8
Q
What features are unique to cardiac myocytes?
A
Intercalated discs form gap junctions that facilitate the spread of action potentials
They contain more mitochondria than skeletal muscle cells (consume O2 at ~8-10mL O2/100g/min at rest)
9
Q
The ability to transmit electrical current
A
Conductance
10
Q
Inotropy
A
The force of myocardial contraction during systole
11
Q
Chronotropy
A
Heart rate
12
Q
Dromotropy
A
Conduction velocity through the heart (V= D/T)
13
Q
Lusitropy
A
The rate of myocardial relaxation during diastole
14
Q
What three factors determine RMP?
A
Chemical force (concentration gradient)
Electrostatic counterforce
Sodium/ potassium ATPase
15
Q
The primary determinant of RMP
A
Serum potassium
16
Q
How does decreased serum potassium affect the RMP
A
It decreases the RMP (becomes more negative)
17
Q
How does increased serum potassium affect the RMP
A
It increases the RMP (becomes more positive)
18
Q
What is the primary determinant of threshold potential?
A
Serum calcium
19
Q
How does decreased serum calcium affect threshold potential?
A
It decreases the threshold potential (becomes more negative)
20
Q
How does increased serum calcium affect threshold potential?
A
It increases the threshold potential (becomes more positive)
21
Q
How do cells depolarize?
A
Sodium or calcium enter the cell
22
Q
What is the all or none phenomenon of depolarization?
A
Once depolarization starts, it cannot be stopped
23
Q
What determines the cell’s ability to depolarize?
A
The difference between RMP and TP
When the two are closer, the cell is more easily depolarizes
When the two are further away, it is more difficult for the cell to depolarize
24
Q
How does repolarization take place? (electrolytes)
A
Either potassium leaves the cell or chloride enters the cell
25
The cell's resistance to subsequent depolarization
Refractory period
26
What functions does the Na/K-ATPase pump serve?
In excitable tissue, it restores the ionic balance towards RMP
Removes the Na+ that enters the cell during depolarization
Returns K+ that has left the cell during repolaraization
27
What is the ratio of Na+ to K+ that the Na/K ATPase pump moves?
3 Na+ ions out
2 K+ ions in
28
What positive inotrope inhibits the Na/K ATPase pump?
Digoxin
29
How does severe hyperkalemia affect Na+ channels?
Na+ channels are inactivated
30
Why is calcium given to hyperkalemic patients?
Reduces the risk of dysrhythmias by increasing the gap between RMP and threshold potential
31
What two parts of the cardiac electrical system do not have a plateau phase?
SA node
AV node
32
What is the normal RMP of the myocyte?
-90mV
33
What is the normal threshold potential of the myocyte?
-70mV
34
Phase of myocyte action potential characterized by activation of fast Na+ channels
Phase 0, depolarization
35
Phase of myocyte action potential characterized by inactivation of Na+ channels; Cl- and K+ channels open
Phase 1, initial repolarization
36
Phase of myocyte action potential characterized by activation of slow Ca++ channels--> delays repolarization --> fast Na+ channels remain inactivated--> refractory period prolonged
Phase 2, Plateau phase
37
Phase of myocyte action potential characterized by K+ leaving the cell faster than Ca++ enters; slow Ca++ channels deactivate--> RMP restored
Phase 3, final repolarization
38
Phase of myocyte action potential characterized by K+ leak channels opening and Na+/K+ ATPase pump maintaining RMP
Phase 4, resting phase
39
What are the phases of the SA node action potential?
Phases 4, 0, and 3 (there is no phase 1 or 2)
40
What phase of the SA node action potential includes:
leaky Na+ channels leading to progressive positivity (funny channels)
T-type Ca++ channels open --> further depolarization
Phase 4
41
What phase of the SA node is characterized by:
Ca++ entry via L-type channels
Depolarization
Na+ channels close
Ca++ T-type close
Phase 0
42
How are T-type and L-type Ca++ channels different?
L-type: voltage gated channels, long lasting
T-type: transient, not long lasting
43
What phase of the SA node action potential is characterized by:
K+ channels opening > K+ efflux > repolarization > decreased Ca++ conductance by closing L-type Ca++ channels
Phase 3
44
What determines heart rate?
Intrinsic firing rate
Autonomic tone
45
What is the intrinsic firing rate of the SA node?
70-80 bpm (faster in the denervated heart)
46
What is the intrinsic firing rate of the AV node?
40-60 bpm
47
What is the intrinsic firing rate of the Purkinje fibers?
15-40 bpm
48
How do volatile anesthetics affect the SA node?
SA node depression = may lead to junctional rhythm
49
What role does the autonomic nervous system play on the heart rate at rest?
Parasympathetic tone dominates
Vagus nerve (CN 10)
R vagus nerve innervates the SA node, and the L vagus innervates the AV node
50
Where does the sympathetic nervous system exert its effect on the heart rate?
Via the cardiac accelerator fibers (T1-T4)
51
What are the SNS effects on heart rate?
Norepinephrine stimulates beta-1 receptor > increases Na+ and Ca++ conductance > increases heart rate
52
How does the SNS effect on HR affect the SA node action potential slope?
Phase 4 depolarization slope is steeper
53
What are the PNS effects on heart rate?
Acetylcholine stimulates the muscarinic-2 receptor > increases K+ conductance > hyperpolarization in the SA node > HR decreases
54
How does the PNS effect on HR affect the SA node action potential slope?
Resting membrane potential and reduce the slope of phase 4 depolarization- slope is less steep
55
What is the equation for oxygen delivery (DO2)?
DO2 = cardiac output x [(hgb x SaO2 x 1.34) + (PaO2 x 0.003)] x 10
56
The amount of gas dissolved in a solution follows what law?
Henry's Law
57
What is the formula for oxygen content (CaO2)?
CaO2 = (Hgb x SaO2 x 1.34) + (PaO2 x 0.003)
58
What is normal cardiac output?
5-6 L/min
59
What is normal stroke volume?
50-100 mL/ beat
60
What is normal ejection fraction?
60-70%
61
What is normal mean arterial blood pressure?
70-105 mmHg
62
What is normal systemic vascular resistance?
800-1,500 dynes sec cm-5
63
What is normal pulmonary vascular resistance?
150-250 dynes sec cm-5
64
Formula for cardiac output
HR x SV
65
Formula for cardiac index
CO/ BSA
66
Formulas for stroke volume
EDF- ESV
CO x (1,000/ HR)
67
Formula for stroke volume index
SV/ BSA
68
Normal cardiac index
2.8-4.2 L/min per m2
69
Normal stroke volume index
30-65 mL/ beat per m2
70
Formulas for ejection fraction
[(EDV-ESV)/ EDV] x 100
(SV/EDV) x 100
71
Formulas for mean arterial blood pressure
(1/3 x SBP) + (2/3 x DBP)
[(CO x SVR)/ 80)] + CVP
72
Formulas for pulse pressure
SBP- DBP
Stroke volume output/ Arterial tree compliance
73
Normal pulse pressure
40 mmHg
74
Formula for systemic vascular resistance
[(MAP - CVP)/ CO] x 80
75
What is the normal systemic vascular resistance index
1,500 - 2,400 dynes sec cm-5 per m-5
76
Formula for systemic vascular resistance index
[(MAP - CVP)/ CI] x 80
77
Formula for pulmonary vascular resistance
[(MPAP - PAOP)/ CO] x 80
78
What is normal pulmonary vascular resistance index?
250 - 400 dynes se cm-5 per m2
79
Formula for pulmonary vascular resistance index
[(MPAP - PAOP)/ CI] x 80
80
What is the functional unit of the contractile tissue in the heart?
Sarcomere
81
What is preload?
Ventricular wall tension at the end of diastole just prior to contraction
Volume that returns to the heart during diastole
82
What factors influence preload?
Blood volume
Atrial kick
Venous tone
Intrapericardial pressure
Intrathoracic pressure
Body position
Valvular regurgitation (increases)
83
The relationship between volume and pressure can be changed by what?
Anything that alters compliance (ie ischemia, hypertrophy)
84
What is contractility (inotropy)?
The ability of the myocardial sarcomeres to perform work (shorten and produce force)
85
What percentage of left ventricular end diastolic volume is from atrial kick?
20-30%
86
What conditions are associated with reduced myocardial compliance?
Myocardial hypertrophy
Heart failure with preserved EF (diastolic failure)
Fibrosis
Aging
87
How does reduce compliance affect ventricular filling?
It is more dependent on atrial kick to fill the ventricle and generate a sufficient stroke volume
88
How do preload and after load affect contractility (inotropy)?
Contractility is independent of preload and afteroad
89
What factors increase contractility?
SNS stimulaiton
Catecholamines
Calcium
Digitalis
Phosphodiesterase inhibitors
90
What factors decrease contractility?
Myocardial ischemia
Severe hypoxia
Acidosis
Hypercapnia
Hyperkalemia
Hypocalcemia
Volatile anesthetics
Propofol
Beta-blockers
Calcium channel blockers
91
How does beta-1 stimulation increase contractility?
Activates adenylate cyclase > ATP converts to cAMP > cAMP increases activation of protein kinase A (PKA) > activated PKA phosphorylates proteins = :
-L-type Ca++ channels activated (more calcium in the cell)
-Stimulates RyR2 to release more Ca++
-Stimulates SERCA2 to increase Ca++ uptake > enhanced Ca++ release
92
What is the primary substance that determines inotropy?
Calcium
93
What is afterload?
The force that the ventricle must overcome to eject its stroke volume
94
What factors decrease stroke volume?
Decreased preload
Decreased contractility
Increased afterload
95
What hemodynamic measurement is used as a surrogate for afterload?
Systemic vascular resistance
96
What does SVR measure?
Arteriolar tone
97
Why does SVR not directly measure afterload?
It does not account for blood viscosity, blood density, or ventricular wall tension
98
What conditions can set the afterload proximal to the systemic circulation?
Aortic stenosis
Coarctation of the aorta
99
What law explains how afterload affect myocardial wall stress?
Law of LaPlace
100
According to the Law of LaPlace what factors reduce wall stress?
Decreased intraventricular pressure
Decreased radius
Increased wall thickness
101
What is wall stress?
The force that holds the heart together
102
What is intraventricular pressure?
The force that pushes the heart apart
103
What is the relationship between wall stress and myocardial oxygen consumption?
Directly proportional: anything that increases wall stress increases myocardial oxygen consumption
104
Identify coronary artery A
Right coronary artery
105
Identify coronary artery B
Posterior descending artery
106
Identify coronary artery C
Left anterior descending artery
107
Identify coronary artery D
Circumflex artery
108
Identify coronary artery E
Left coronary artery
109
What are the two divisions of the left coronary artery?
Left anterior descending artery
Circumflex
110
Which portions of the heart does the left anterior descending artery perfuse?
Anterolateral and apical walls of the LV
Anterior two-thirds of the interventricular septum
111
Which portions of the heart does the circumflex artery perfuse?
Left atrium
Lateral and posterior wall of the LV
112
Which portions of the heart does the right coronary artery perfuse?
Right atrium
Right ventricle
Interatrial septum
Posterior third of the interventricular septum
113
Which portions of the heart does posterior descending artery perfuse?
Inferior wall
114
What determines coronary dominance?
The origin of the posterior descending artery
115
What is right coronary artery dominance?
The posterior descending artery originates from the right coronary artery
Present in 70-80% of patients
116
What is left coronary dominance?
The posterior descending artery originates from the circumflex
117
What is co-dominance?
The posterior descending artery originates from the circumflex and right coronary artery
118
What coronary artery supplies the sinoatrial node in MOST patients?
Right coronary artery
119
What coronary artery supplies the atrioventricular node in MOST patients?
Right coronary artery
120
What coronary artery supplies the Bundle of His in MOST patients?
Left coronary artery
121
What coronary artery supplies the left and right bundles branches?
Left coronary artery
122
What coronary vein does A represent?
Anterior cardiac vein
123
What coronary vein does B represent?
Middle cardiac vein
124
What coronary vein does C represent?
Great cardiac vein
125
What structure does D represent?
Coronary sinus
126
Where does most of the blood returning from the left ventricle drain?
Coronary sinus
127
Where does most of the blood returning from the right ventricle drain?
Empty directly into the right atrium via the anterior cardiac veins
128
What are the Thebesian veins?
They empty a small amount of deoxygenated blood into all four chambers of the heart
129
Explain the anatomic shunt caused by the Thebesian veins.
Blood that returns to the left side of the heart via the Thebesian veins dilutes the PaO2 of the blood that is returning from pulmonary circulation.
130
On a 12 lead EKG, which leads correlate with the RCA?
Inferior:
II, III, aVF
131
On a 12 lead EKG, which leads correlate with the circumflex?
Lateral:
I, aVL, V5, V6
132
On a 12 lead EKG, which leads correlate with the LAD?
Septal:
V1, V2
Anterior:
V3, V4
133
What is the best TEE view for diagnosing left ventricular ischemia?
Midpapillary muscle level in short axis
134
What law defines coronary blood flow?
Ohm's law
135
Coronary blood flow value
225-250 mL/min
136
What is the equation for coronary blood flow?
CBF = coronary perfusion pressure / coronary vascular resistance
137
What is the equation for coronary perfusion pressure?
Coronary perfusion pressure = Aortic DBP - LVEDP
138
What is coronary reserve?
The difference between coronary blood flow at rest and maximal dilation.
139
What is autoregulation of coronary blood flow?
Constant coronary blood flow over a range of perfusion pressures between a MAP of ~60 - 140 mmHg.
140
How does coronary blood flow change outside of autoregulation range?
It becomes dependent on coronary perfusion pressure
141
How is coronary autoregulation different in atherosclerotic vessels?
Maximum dilation may be present at rest = in the setting of increased O2 demand the vessels cannot dilate further > decreased coronary reserve
142
What three factors contribute to autoregulation of coronary blood flow?
Local metabolism
Myogenic response
Autonomic nervous system
143
What is the most important determinant of coronary vessel diameter?
Local metabolism
144
As myocardial volume oxygen consumption increases, the endothelium releases what vasodilators?
Nitric oxide
Prostaglandins
Hydrogen
Potassium
Carbon dioxide
145
What benefits does vasodilation have for the heart during increased myocardial volume oxygen consumption?
Decreases vascular resistance
Increases coronary perfusion
Flushes out products of metabolism
146
When does the autonomic nervous system prevail over local metabolism in control of coronary vessel diameter?
Vasospastic myocardial ischemia (variant angina)- overactive coronary alpha receptors >intense vasoconstriction> chest pain (always at rest)
147
Coronary artery vasodilation or Constriction:
Histamine- 1
Vasoconstriction
148
Coronary artery vasodilation or constriction:
Muscarinic stimulation
Vasodilation (d/t nitric oxide)
149
Coronary artery vasodilation or constriction:
Beta-2 (endocardial)
Vasodilation
150
Coronary artery vasodilation or constriction:
Alpha (epicardial)
Vasoconstriction
151
Coronary artery vasodilation or constriction:
Histamine-2
Vasodilation
152
Which waveform correlates with right coronary artery flow?
C
153
Which waveform correlates with aortic pressure?
A
154
Which waveform correlates with left coronary artery flow?
B
155
Why does right coronary artery flow remain constant relative to left coronary artery flow?
The right ventricle does not generate enough pressure to occlude blood flow during systole
156
Which myocardial arterial bed is most susceptible to ischemia?
Endocardial blood vessels
157
When do most perioperative myocardial infarctions occur?
Between 24-48 hours following surgery
158
What conditions both increase oxygen demand and decrease oxygen supply?
Tachycardia
Increased preload
159
At rest, what percentage of delivered oxygen does the myocardium consume?
70%
160
What is normal coronary sinus oxygen saturation?
30%
161
Regulation of vascular smooth muscle tone is dependent on what factors?
Autonomic nervous system
Renin- angiotensin- aldosterone system
Local metabolism
Myogenic response
162
What cellular pathways affect intracellular calcium concentration?
G-protein cAMP pathway
Nitric oxide cGMP pathway
Phospholipase C pathway
163
What cellular pathway(s) result(s) in vasodilation?
G-protein cAMP pathway
Nitric oxide cGMP pathway
164
What cellular pathway(s) result(s) in vasoconstriction?
Phospholipase C pathway
165
In the vascular muscle cell, how does increased protein kinase A affect intracellular calcium concentration?
Decreases
166
In the cardiac myocyte, how does increased protein kinase A affect intracellular calcium concentration?
Increases
167
In what ways does protein kinase-A affect excitation-contraction coupling in the vascular smooth muscle?
Inhibition of voltage-gated Ca++ channel in the sarcolemma
Inhibition of Ca++ release from the sarcoplasmic reticulum
Reduced sensitivity of the myofilaments to Ca++
Facilitation of Ca++ reuptake into the sarcoplasmic reticulum via the SERCA 2 pump
168
What factors/ substances increase the production of nitric oxide?
Acetylcholine
Substance P
Bradykinin
Serotonin
Vasoactive intestinal peptide
Shear stress
169
What enzyme catalyzes the conversion of L-arginine to nitric oxide in the first step of the nitric oxide cGMP pathway?
Nitric oxide synthetase (NOS)
170
What activates the phospholipase C pathway?
Phenylephrine
Angiotensin 2
Endothelin-1
171
The phospholipase C pathway increases the production of what second messengers?
Inositol triphosphate (IP3)
Diacylglycerol (DAG)
172
Normal DO2 value
1,000 mL O2/min
173
Solution coefficient for dissolved oxygen
0.003
174
Normal CaO2 value
20 mL/dL
175
Venous oxygen content equation
CvO2 = (Hgb x SvO2 x 1.34) + (PvO2 x 0.003)
176
Normal CvO2
15 mL/dL
