CV SYSTEM Flashcards
(255 cards)
1
Q
CV system delivers sufficient _______ to the tissues to meet metabolic demand.
A
Oxygen
2
Q
CV transports metabolic waste products (carbon dioxide) from the _________ and delivery to the ________ for elimination
A
From the tissues
Delivery to lungs
3
Q
CV system transports metabolic waste products to the kidneys for elimination. TRUE/FALSE.
A
TRUE
4
Q
CV system supplies nutrients by absorption from ________ and delivers to the body
A
GI tract
5
Q
How does the CVS regulate body temperature?
A
Vasodilation
Vasoconstriction
6
Q
How does the CVS help to regulate cellular function?
A
Transport of hormones and other substances (NT, drugs etc)
7
Q
The heart is an endocrine organ; what hormone does the heart secrete?
A
Natriuretic peptide
8
Q
Sits directly posterior to the sternum, inbetween the lungs and anterior to the vertebral column; heart located here.
A
Mediastinum
9
Q
From an anterior perspective, which side of the heart can be seen better?
A
RIGHT side
10
Q
_______ side of the heart seen much better from a posterior perspective
A
Left
11
Q
Great vessels are located also in the ________
A
Mediastinum
12
Q
Brings venous deoxygenated blood from the upper part of the body to the right atrium
A
Superior vena cava
13
Q
Brings deoxygenated venous blood from lower body to RA
A
IVC
14
Q
Descending thoracic aorta runs along posterior aspect of heart and pierces the __________, then becomes the abdominal aorta.
A
Diaphragm
15
Q
Esophagus and trachea also pass through the mediastinum. TRUE/FALSE
A
TRUE
16
Q
The heart is surrounded by pericardial __________
A
Membranes
17
Q
Most inner pericardial membrane
A
Visceral pericardium
18
Q
Outer pericardial membrane
A
Parietal pericardium
19
Q
Most inner pleural membrane; directly attached to the lungs
A
Visceral pleura
20
Q
Outer most pleural membrane
A
Parietal pleura
21
Q
Small band of tissue that separates the most outer pericardial and pleural membranes
A
Fibrous pericardium
22
Q
Can have CV implications when we do this to pts, bc the layer between the heart/lungs is so thin
A
PPV
23
Q
Branches right off aorta as emerges from LV, runs down coronary sulcus between RA and RV.
A
RCA
24
Q
Left Main coronary artery Branches off of the aorta and quickly divides into what two coronary arteries?
A
Left anterior descending (LAD)
Left circumflex
25
Where is the LAD located on the heart?
In sulcus between LV and RV on anterior surface of heart
26
Pulmonary carries what type of blood?
Venous deoxygenated blood
27
Arteries carry blood to the heart. TRUE/FALSE.
FALSE
Arteries carry blood away from the heart
28
Veins carry blood to the heart. TRUE/FALSE
TRUE
29
Freshly oxygenated blood is returned to the heart after pulmonary circulation via ___________
Pulmonary veins
30
In most people the _______ becomes the posterior descending artery (PDA)
RCA
31
PDA descends posteriorly between what two structures of the heart?
RV and LV
32
In about _____% of people the PDA is a branch of the RCA
80%
33
In about 20% if people the PDA is a branch of what artery
Left circumflex
34
All coronary veins join together to form what vein?
Great Cardiac Vein
35
The great cardiac vein empties into the _______ that empties into the RA
Coronary Sinus
36
Tiny, microscopic veins that permeate walls of the heart and empty deoxygenated blood into all 4 chambers of the heart
Thebesian veins
37
Two reasons why PaO2 is less in the Left side of the heart than the blood at the pulmonary capillaries after gas exchange occurs.
Thebesian veins
Bronchial circulation (need blood but do not participate in gas exchange)
38
Two types of circulations in the lungs
Pulmonary (fresh blood back to LA)
Bronchial (tracheobronchial tree)
39
Outer most layer of the heart; directly attached and cannot be separated from the heart.
Visceral pericardium (epicardium)
40
Visceral pericardium composed of what?
Squamous epithelial cells
| Loose connective tissue/fat
41
Thickest layer of the heart; muscle fibers.
Myocardium
42
What determines the thickness of the myocardium of the different chambers?
Workload on the heart
43
Order of chambers from largest myocardium to the least
LV
RV
LA
RA
44
Inner most layer of the heart, faces chambers in folds.
Trabeculae corneae
45
2 functions of the folds of the trabeculae corneae
Provides structure so when undergo contraction, do not collapse
Creates turbulence of blood flow; prevents blood clots
46
The visceral pericardium completely surrounds the heart, when it gets to the _________ it turns out on itself and becomes the parietal pericardium.
Great vessels
47
Space between visceral and parietal pericardium
Pericardial space (potential space)
48
Parietal and visceral pericardium combines are the ___________ pericardium; secretes fluid into pericardial space.
Serous pericardium
49
Under normal conditions there is ~______mL of fluid in the pericardial cavity
20mL
50
Purpose of pericardial fluid
Allows visceral/parietal pericardium to glide over smoothly during systole/diastole
51
Right outside the parietal pericardium and heaps anchor the heart in place and to adjacent structures
Fibrous pericardium
52
When pericardial membranes become inflamed; can be from infection, virus, etc.
Pericarditis
53
Classic auscultated sign of pericarditis
Friction rub
54
Pericarditis can be caused from something infectious or non-infectious. TRUE/FALSE
TRUE
55
Example of non-infectious cause of pericarditis
Nephrogenic toxins
| Trauma to chest
56
Where is a friction rub best heard?
Apex of heart; 5th intercostal space midclavicular line
57
Increased capillary permeability in the pericardial membranes, allowing excess pericardial fluid to accumulate
Pericardial effusion
58
Pericardial effusion can lead to _________
Cardiac tamponade
59
Difference in pericardial effusion and cardiac tamponade
With cardiac tamponade, you will have CV manifestations
60
What usually is the determinant factor in whether a pericardial effusion/tamponade causes manifestations?
Length of time fluid is accumulated
The more quickly fluid accumulates, the more quickly can decompensate
61
How do we manage anesthesia with cardiac tamponade?
FULL, FAST, FORWARD
Keep them full, HR up, and blood moving forward
62
Pts with CT have a fixed _________ and cannot adjust their contractility; so CO is dependent on________ primarily. So you should avoid __________.
Fixed SV
CO dependent on HR
Avoid bradycardia
63
With CT, you want to avoid ________, because you take a risk of decreasing venous return and preload
Vasodilators
64
With CT, we need to optimize __________ to maximize LV filling
Volume status
65
With CT, maintain _________ tone, but do not overly constrict them.
Sympathetic
66
Why should we maintain spontaneous ventilation with CT?
PPV can result in CV collapse bc of decreased venous return
67
There are no valves between the IVC/SVC and the RA. TRUE/FALSE
TRUE
68
There should be constant flow of blood into RA, with a pressure gradient. What should the pressure gradient be between CVP and RA to allow this to happen?
CVP should be a little higher than pressure in the RA to allow blood to flow forward.
69
When RA pressure is greater than RV pressure, _________ opens and blood flows passively from RA to RV
Tricuspid leaflets
70
At some point the RA goes into systole and injects more blood into RV. TRUE/FALSE.
TRUE
71
When do the tricuspid leaflets close?
When RV pressure is > RA
72
RV goes into systole and chamber gets smaller, increasing RV pressure; when RV pressure is > pulmonary artery pressure, the ________ valve opens and blood ejected into pulm art circuit to lungs.
Pulmonary valve
73
"Heart strings"
Chordae tendineae
74
Chordae tendineae are attached to __________ muscles that are continuous with the myocardium
Papillary
75
During systole chordae tendineae are pulled tight and hold _______ in place. Preventing _________ bloodflow and favoring forward flow of blood into pulm circuit.
Tricuspid leaflets
Retrograde
76
Just like the vena cava, there are no _______ between the pulmonary veins and the LA.
Valves
77
When LA pressure is > LV pressure, then ________ leaflets open and there is initial passive blood flow into LV.
Mitral
78
When does mitral valve close
When LV pressure is > LA
79
LV goes into systole, and when LV pressure exceeds aortic pressure, then _________ valve opens to eject blood into aorta
Aortic
80
When does aortic valve close
When aortic pressure is > LV pressure
81
What opens and closes valve leaflets
Pressure Gradients
82
Which valves are associated with chordae tendineae and papillary muscles?
Atrioventricular valves
Tricuspid and mitral
83
Passive flow of blood from atrium to ventricle accounts for about ____% of ventricular preload.
~75%
84
When atria goes into systole, ~___% of blood is ejected into ventricle = atrial kick.
25%
85
What type of arrhythmia would cause atria to contract against closed atrioventricular valve, losing atrial kick.
Afib
86
What causes a transient increase in atrial pressure during ventricular systole?
Valve leaflets ballooning into the atrium
87
What causes heart sounds
Turbulence of bloodflow with opening and closing of valves
88
Location of pulmonic auscultatory area
2nd intercostal space, Left sternal border
89
How do you find the 2nd intercostal space?
Start at sternal notch, below notch is manubrium, bump where the manubrium meets the sternum is the angle of Louis; directly over should be 2nd intercostal space
90
Location of aortic auscultatory area
2nd intercostal space, Right sternal border
91
Location of tricuspid auscultatory area
5th intercostal space, Left sternal border
92
Location of mitral auscultatory area
5th intercostal space, L Midclavicular line
93
Why do we not auscultate to diagnose murmurs anymore?
Echocardiography/TEE
94
During ventricular diastole, what valves should be open?
Tricuspid
| Mitral
95
If you hear a murmur during diastole at the tricuspid area, it would indicate what type of murmur?
Tricuspid stenosis
96
If you hear a murmur during diastole at the mitral area, it would indicate what type of murmur?
Mitral stenosis
97
If you hear a murmur during diastole at the aortic area, it would indicate what type of murmur?
Aortic regurgitation
98
If you hear a murmur during diastole at the pulmonic auscultatory area, it would indicate what type of murmur?
Pulmonic valve regurgitation
99
During systole, what valves should be open?
Aortic
| Pulmonic
100
If you hear a murmur during systole at the aortic auscultatory area, it would indicate what type of murmur?
Aortic stenosis
101
If you hear a murmur during systole at the pulmonic auscultatory area, it would indicate what type of murmur?
Pulmonic stenosis
102
If you hear a murmur during systole at the tricuspid auscultatory area, it would indicate what type of murmur?
Tricuspid regurgitation
103
If you hear a murmur during systole at the mitral auscultatory area, it would indicate what type of murmur?
Mitral regurgitation
104
You can have combined diastolic systolic murmurs. How?
May be very stenotic when blood flowing through and valves may not shut completely either.
105
Why is it common for pts to have murmurs after an MI?
Bc papillary muscles or muscles attached to them can be infarcted and not function correctly anymore in keeping tricuspid/mitral valves shut during systole
106
The first organ to be perfused by the heart is the______
Heart
107
During the resting state, about ___% of CO circulates through the coronary arteries.
~3%
108
Driving force against blood flowing through the coronary arteries is what?
Pressure created by the LV during systole/contraction
109
Most perfusion of the heart occurs during ventricular systole. TRUE/FALSE
FALSE
Most perfusion occurs DIASTOLE
110
Why is perfusion of the heart hindered during systole?
Small arteries, arterioles, and capillaries are compressed during systole
111
Which chamber is it most important to have adequate diastole for perfusion?
LV
112
Sympathetic stimulation with epi/NE at alpha-1 receptors causes coronary artery ________
Constriction
113
Sympathetic stimulation with epi/NE at beta-2 receptors causes coronary artery ________
Dilation
114
During sympathetic stimulation, which receptor effect normally dominates?
Beta-2
115
Possible parasympathetic/vagal stimulation that affect coronary artery blood flow, via _______ receptors, usually minimal effect and mild _________.
Acetylcholine/muscarinic
| Mild dilation
116
During the resting state, about _____% of O2 is extracted from coronary blood flow
~75%
117
Under normal conditions, in other areas of the body besides the heart, ~____% of O2 is extracted from the blood flow
~30%
118
The heart is very _______ hungry
Oxygen
119
Coronary arter blood flow and myocardial perfusion are controlled primarily by what?
Rate of myocardial O2 consumption
120
Any condition that increases myocardial O2 consumption causes reflex ________ of coronary arteries.
Dilation
121
If _______ on the heart increases, then O2 consumption increases.
Workload
122
For O2 supply to meet O2 demand, coronary arteries must __________ to increase blood flow and O2.
Dilate
123
What are some things that increase myocardial workload?
Increased strength of contraction
Increased afterload
Increased preload
Increased HR
124
What increases myocardial oxygen consumption and workload on the heart more than any other factor?
INCREASED HR
125
What would be of most benefit to a pt you were worried about perfusion of their CA?
Betablocker; decreased HR
126
What are some metabolic vasodilators; providing more bloodflow, more O2 delivery to tissues?
```
Increased CO2
Increased H+ ions
Decreased pH
Lactate
Adenosine
```
127
What does it mean to be right coronary artery dominant?
PDA is a branch of the RCA
128
How is it determined whether you are right/left CA dominant?
By which CA your PDA branches off of
129
Regardless of dominance, the ___________ artery supplies the majority of blood flow to the heart in EVERYONE.
LEFT MAIN CA
130
Right atrium is perfused by what major artery?
RCA
131
Left atrium is perfused by what major artery?
Left circumflex
132
Right ventricle anterior is perfused by what major artery?
RCA
133
Right ventricle posteriorly is perfused by what major artery?
RCA (PDA)
134
LV (diaphragmatic/inferior) is perfused by what major artery?
Left circumflex and RCA(PDA)
135
LV anteriorly is perfused by what major artery?
LAD
| Left circ
136
LV laterally is perfused by what major artery?
Left circ
137
Apex is perfused by what major artery?
LAD
138
Interventricular septum anteriorly is perfused by what major artery?
LAD
139
Interventricular septum posteriorly is perfused by what major artery?
RCA (PDA)
140
LV papillary muscles anteriorly is perfused by what major artery?
LAD
| L circ
141
LV papillary muscles posteriorly is perfused by what major artery?
L circ and RCA (PDA)
142
SA node is perfused by what major artery?
RCA
143
Atrial internodal pathways are perfused by what major artery?
RCA
144
AV node is perfused by what major artery?
RCA
145
Bundle of HIS is perfused by what major artery?
RCA
146
Right bundle branch is perfused by what major artery?
LAD
147
Left bundle branch anteriorly and posteriorly is perfused by what major artery?
LAD
148
Leads V1-V4 are indicative of changes in what area of the heart?
Anterior surface
149
Leads V5-V6 are the best leads to see changes effecting what area of the heart?
Lateral surface of the heart
150
If you saw prominent Q waves in leads V1-V4, what coronary artery is most likely infarcted?
LAD
151
If ST elevation was present in V5-V6, what coronary artery is most likely infarcted?
Left circumflex
152
Two types of muscle
Striated and smooth
153
Two types of striated muscle
Skeletal
| Cardiac
154
Muscle fibers in the atria and ventricles that bring about muscle contraction
Mechanical contractile fibers
155
Form electrical conduction system throughout the heart
Electrical fibers
156
Electrical fibers initiate and conduct __________ throughout the heart and to mechanical contractile fibers.
Action potentials
157
AP's transferred to contractile fibers and are __________ with mechanical contraction
Coupled
158
This MUST precede mechanical contraction of the heart
Electrical impulses (AP)
159
Clinical scenario where we know there is not electrical/mechanical coupling.
PEA
160
Cardiac muscle is smooth muscle. TRUE/FALSE
FALSE
It is striated muscle
161
Actin:myosin ratio for cardiac muscle
2:1
162
Cardiac muscle includes tropmyosin and troponin (I,T, and C) similar to skeletal muscle fibers. TRUE/FALSE
TRUE
163
In cardiac muscle, actin is attached to _______ and forms sarcomeres.
Z-discs
164
What is actin attached to in smooth muscle
Dense bodies
165
Cardiac muscle contains intercalated discs and __________ between adjacent sarcolemma for spread of AP directly from muscle fiber to muscle fiber
Gap jxns
166
This allows for free flow of ions in cardiac muscle, and contraction as a unit.
Gap junctions
167
What are the 2 functional syncytium of the cardiac muscle?
Right and left Atria
Right and Left Ventricles
168
What's the purpose of the functional syncytium?
When one muscle fiber becomes excited in either the right/left atria/ventricle, all of the fibers in the fxnal syncytium become excited and contract at the same time
169
The atria and ventricles are separated by fibrous tissue with openings for _________ and pathway for _________ fibers so impulse can be conducted, one way, from atria to ventricles
Valves
| Electrical fibers
170
Heart requires flow of Ca+ into sarcoplasm from from what two sources?
Sarcoplasmic reticulum
| EC fluid
171
The 2 sources of Ca+ allow for sustained contraction of cardiac muscles to enhance _______ and ______.
Stroke volume
Cardiac output
172
If you gave calcium to a pt having contraction issues, it would enhance their contraction bc the heart is affected by extracellular Ca+ concentrations. TRUE/FALSE.
TRUE
173
The inward movement of Ca+ from EC fluid and SR occurs during the cardiac ______
AP
174
Where one cardiac muscle fiber adjoins to the next one; forms gap jxn
Intercalated disks
175
Cardiac muscle fibers require a lot of this organelle because of a lot of consumption of O2 needed in the heart
Mitochondria
176
Cell membrane of cardiac muscle fiber
Sarcolemma
177
T tubule along with terminal cisterna on either side of it makes up what?
Triad
178
AP travels along sarcolemma and down the T tubule; opens up _________ channel where calcium enters from __________.
v-g Ca+ channel
EC fluid
179
Ca+ enters sarcoplasm and AP is transferred from T tubule to _________ , membrane is depolarizes, and v-g _____ channels are opened
Sarcoplasmic reticulum (on either side of t tubule)
V-g Ca channels
180
Both the Ca+ from the SR and EC fluid increases Ca+ sarcoplasmic conc, this pulls troponin ___ towards the Ca+, along with troponin ___ and ______.
troponin C towards Ca+
Troponin T and tropomyosin
181
When tropomyosin is pulled away, this uncovers the binding sites on ______ and allows for ________ to crossbridge and powerstroke
Uncovers binding sites on ACTIN
Allows for MYOSIN HEADS to CB and PS
182
Muscle fibers are arranged _______ around the ventricles to allow for a more effective SV and CO.
Obliquely
183
Vasopressors are frequently utilized for intraoperative hypotension in a radical neck dissection with free flap. TRUE/FALSE.
FALSE
You CANNOT use vasopressors for intraoperative hypotension in these cases
184
This can be used to verify adequate fluid volume status intraoperatively.
Pulse Pressure Variation
185
What would the benefits be of calcium administration for your patient with intraoperative hypotension?
Increased myocardial contractility
Calcium dependent exocytosis of NT (NE)
186
Sympathetic postganglionic neurons are depending on this for release of NE.
CALCIUM dependent exocytosis
187
3 properties of electrical fibers
Automaticity
Excitability
Conductivity
188
Property: Ability to automatically generate AP
Automaticity
189
Property: Becomes excited in response to AP's
Excitability
190
Property: rapidly conducts AP's
Conductivity
191
All electrical fibers have all 3 properties, BUT some fibers have more of one than the other properties. TRUE/FALSE.
TRUE
192
Located in the roof of the RA where the SVC joins with the RA.
SA node
193
SA node
<1cm
194
SA node primarily composed of ______ cells
Pacemaker cells (P cells)
195
Primary property of P cells.
Automaticity
196
Rate P cells generate AP
~60-100
197
AP generated by the SA node are transmitted through the superior, middle and inferior ____________ pathways
Atrial internodal pathways
198
Provides input to the LA from the SA node.
Interatrial branch of the atrial internodal pathway
199
Atrial internodal pathways and interatrial branch are composed of ______ cells.
Purkinje fibers
200
Primary property of purkinje cells is _______
Conductivity
201
We hope purkinje cells are lying adjacent to atrial muscle fibers to allow what?
Electrical mechanical coupling
202
2 atrial internodal pathways join back together to form the ________.
Atrioventricular node (AV node)
203
Where is the AV node located?
Bottom of the RA, right above the tricuspid valve
204
What type of cells compose the AV node
```
P cells
T cells (transitional cells)
```
205
What are the 2 functions of the T cells in the AV node?
Slow the AP slightly so atria contract before the ventricles
Regulates # of AP's that can get through
206
At what rate does the AV node generate AP in the absence of the SA node?
~40-60
207
Where the AV node enters and becomes the Bundle of HIS.
Superior part of interventricular septum
208
Bundle of HIS divides into what 3 bundle branches?
Right bundle branch
Anterior branch of Left bundle
Posterior branch of left bundle
209
Bundle branches terminate at ____________ that are hopefully adjacent to muscle fibers.
Purkinje fibers
210
Which two bundle branches descend into the interventricular septum towards the apex?
Right bundle branch
Anterior branch of Left bundle
211
Posterior branch of Left bundle innervates the _______ aspect of the LV.
Posterior
212
Bundle branch that innervates the purkinje fibers on the anterior and lateral LV
Anterior branch of Left bundle
213
Why does the left side of the heart have 2 bundle branches, and the right side have only one branch?
More muscle mass to depolarize on the L side.
214
Which ventricle contracts first?
RV
Less muscle mass to depolarize
215
AP from a large axon or skeletal muscle fiber has a RMP of ~ _____mV and a TP of ~ ____mV.
RMP ~ -85mV
TP ~ 60mV
216
In an AP of a large axon or skeletal muscle fiber, the depolarization/repolarization phase is SLOW/RAPID?
RAPID
217
Repolarization in cardiac AP is __________
Slow, prolonged
218
Why does the heart need slow, prolonged repolarization?
Allows for sustained AP and sustained contraction (CO and SV)
219
Cardiac AP takes about ________ msec.
~500msec
220
RMP for cardiac AP
~ -85mV
221
what are the 4 contributors to RMP at this time?
Potassium leak channels
Sodium leak channels
Na-K pump
(-) charged proteins that line cell membrane
222
If stimulus applied to cell membrane, causes initial influx of _____ ions and moves RMP upward in less negative fashion.
Sodium
223
At TP (~ ____ mV), there is opening of ___________ Channels and more influx of + charges into the cardiac cell
~ -60mV
V-g Na channels
224
Early Phase 0 of depolarization begins at -____mV and continues to about -____mV.
-90mV to ~ -40mV
225
What initiates early phase 0 of depolarization?
Initial stimulus causing initial Na influx
226
During early phase 0, cell membrane becomes impermeable to _______
Potassium
227
Early phase 0, -40mV, opening of v-g ________ channels.
Voltage gated Ca-Na channels
228
LATE phase 0 of depolarization begins at -___mV and continues to about +_______ mV.
-40mV - +20-30mV
229
Peak amplitude of depolarization in cardiac fiber is ~____mV
~ +20mV
230
At peak amplitude of depolarization, +20mV, the v-g ______ channels snap shut; ending __________ and beginning ____________.
At the same time, v-g _____ channels start to open up; initiating phase 1 of repolarization.
V-g Na channels shut
Ends depolarization
Begins repolarization
V-g K channels open
231
Phase 1 of repolarization begins at +_____mV and continues to _____ mV.
+20-30mV - 0mV
232
Longest phase of repolarization of cardiac muscle fiber.
Phase 2
233
Phase 2 of repolarization, the MP remains at about ______mV
0mV
234
Why does the MP remain at ~0mV during all of phase 2 of repolarization?
Equal influx/efflux of cations
Inward movement of Ca+ through slow Ca-Na channels; K channels are open = outward K+.
235
V-g Ca/Na channels shut at the end of phase ____ of repolarization; no more influx of + charges; beginning phase ____.
Phase 2
Begin phase 3
236
During phase 3, the only channels open for ion movement are?
K channels
237
During phase 3, K channels are fully open and MP SLOWLY/RAPIDLY returns to RMP.
Rapidly
238
The phase in between AP's is phase ______; RMP.
Phase 4
239
Cell cannot depolarization again regardless of stimulus during this period
Absolute RP
240
ARP starts and ends at what phases of repolarization?
Starts Early phase 0, late phase 0, phase 1, 2 and most of 3.
Lasts until reaches TP in phase 3 (~60mV)
241
If an extra strong stimulus is applied, depolarization might occur in this period.
Relative refractory period RRP
242
RRP lasts from ~____mV down to ~_____mV.
-60mV down to ~ -85mV
243
Is depolarization happens during RRP, what abnormality might you see on the EKG?
QRS sitting right on top of the T wave
244
Only a mild stimulus applied can cause depolarization during this period
Supranormal refractory period. SNP.
245
SNP is form __mV to __mV.
~-85mV down to -90mV, RMP.
246
If depolarization occurs during SNP, what EKG change would you see?
QRS on downslope of T wave
247
In pacemaker cell AP's, these channels are inactivated.
V-g Na channels
248
RMP in pacemaker cell starts at ~-_____mV
~ -55mV
249
When MP of P cell gets to -40mV, there is opening of v-g ________ channels (depolarization)
Ca-Na channels
250
Pacemaker cells are VERY leaky to _____ ions; we don't have to have a stimulus applied to generate AP bc of this!
Sodium
251
In P cells, after opening of v-g Ca-Na channels, MP gets to peak amplitude, _____mV, _____ channels close, and ______ channels open (repolarization); MP moves back down to RMP
~+20mV
V-g Ca-Na channels close
K channels open
252
Rate of AP generation: 60-100/min
Overrides lower, slower potential pacemakers
SA node (normal pm)
253
Inherent rate 40-60/min
AV node/jxn
254
Inherent rate 15-40/min
Ventricular purkinje fibers
255
_________ pacemakers can occur anywhere in the conduction system.
Ectopic
