Unit II Flashcards
1
Q
why is O2 important to the heart
A
because it is less able to function by anything other than oxidative phosphorylation
2
Q
what is the firing rate range of the SA node?
AV node?
A
60-120
40
3
Q
two examples of conduction defects that would cause arrhythmias
A
heart block
bundle branch block
4
Q
functional hyperemia
A
activly increasing blood flow to metabolically active heart cell tissues
5
Q
describe the effect of G protein subunit ßy (parasympathetic)
what happens to heart rate
A
G protein subunit ßy binds to KAch channels
potassium influx increases
membrane is hyper polarized
pacemaker potential is more negative
heart rate will decrease
6
Q
what protein regulates SERCA activity
A
phosopholamban
7
Q
how can you determine ventricle wall compliance from a PV loop
A
the diastolic compliance curve (lower line) will have a steeper slope
8
Q
describe the process of calculating HR by RR interval
A
measure the interval of time between R waves
divide 60s by the RR time
9
Q
T/F changing the filling (venous) pressure of the system alters stroke volume by increase LVESV
A
false, on LVEDV will be changed with an increase in venous pressure
10
Q
what is the distance blood must move to loss 1mmHg of pressure
A
13.6 mm
11
Q
poiseuille law
A
Q = (pi x deltaP x r^4)/8nL
n is viscosity
12
Q
what are three conductive causes of arrhythmias
A
delayed after polarizations
conductions defects
circuit re-entry
13
Q
why is parasympathetic stimulation a non factor in humans
A
because very few vagal pathways reach the heart
14
Q
positive inotropic effect
what type of drugs would cause this
A
increased contractility of the heart
Beta adrenergic agonists
15
Q
why does the AV node have the lowest conduction velocity
A
small cell diameter and few gap junctions
16
Q
MAP equation
A
MAP = Cardiac output x total peripheral resistance
17
Q
how can EF% be determined using a PV loop
A
dividing the width of the loop (stroke volume) by the volume when the aortic valve closes (LVESV)
18
Q
how does digitalis (digoxin) produce greater contractility in the heart
A
it increases intracellular Na concentration, decreasing the activty of the Ca/Na exchanger and increasing the amount of intracellular calcium
19
Q
what is the limiting factor in determining how much O2 the heart gets
why
A
the amount of blood flow
because whatever oxygen is present in blood will be taken up by the cells
20
Q
MAP formula
A
diastolic pressure + 1/3 pulse pressure
or
TPR x CO
or
Ps+Pd/3
21
Q
what percent of O2 in the blood is extracted by heart muscle on the first pass
A
70-80%
22
Q
is an ECG an action potential?
elaborate
A
no
ECG reflects the cumulative effect of action potentials at skin level
23
Q
how does the maximum of the pacemaker potential effect firing rate
A
the more negative the pacemaker potential is, the slower the firing rate will be
24
Q
what is the function of leads V1-6 on ECG
A
to observe the deoplarization wave in the frontal plane from a particular area of the heart
25
what would happen to HR if the SA node were nonfunctional due to injury
the AV node would take over and produce a HR around 40bpm
26
formula for parallel resistnace
1/R = 1/R1 + 1/R2 + 1/R3
27
what three factors determine the conduction velocity of pacemaker APs
diameter of fibers (decrease viscosity)
number of gap junctions (increase conductance)
rate of slow depolarization (increased slope)
28
what causes a change in slope during phase 4 of a pacemaker AP
what will happen in each instance?
sympathetic/parasympathetic nerve stimulation
sym: slope increases and causes higher firing frequency
para: slope decreases = lower firing frequency
29
what are the assumptions of Poiseuille's Law
C L N R S H
cylindrical tubes with aconstant diameter and length longer than the radius
laminar, not turblulent flow
newtonion flow
rigid walls
steady, non-pulsatile flow
horizontal flow with no gravitational effects
30
what is the difference between hydorstatic pressure in arteries and veins in the brain
at the heart
at the legs
why are they different
80
100
100
because at the head veins are losing pressure because of gravity, and at the feet they are gaining pressure
arterial pressure makes up the difference
31
Laplace Law for a sphere
tension in the ventricular wall is equal to the pressure multiplied by the radius divided by the width of the ventricle
32
what are the two key elements of excitation-contraction coupling
structure
CICR
33
T/F the right arm is always a positive lead in ECG
false, it is always negative
34
what should a normal sinus rhythm look like on ECG
positive P waves in the leads I and II indicate rhythm from the SA node
35
what are the three phases of a pacemaker cell
Phase 4 (slow depolarization)
Phase 0 (upstroke)
Phase 3 (repolarization)
36
two intrinsic mechanisms that regulate coronary blood flow
myogenic response to arterial pressure
local metabolic control
37
how is RMP maintained
Na/K pump keeps and restores membrane to RMP
38
normal vs impaired EF%
55-65%
= 40%
39
incisura
the point on a ventricular pressure graph where the aortic valve closes, indicated by a small increase in pressure followed by a stedy decline
40
at what point on an ECG would correspond with AV node firing
halfway through the P wave into the PR segment
41
what happens to coronary blood flow to the left ventricle during systole?
why?
what happens in the right ventricle
it decreases
the pressure of the contraction increases the pressure on coronary vessels
the right coronay blood flow has less pressure so the effect is less dramatic
42
what is this?
define the variables
a pressure time graph of the left ventricle
A diastolic filling
M1 mitral valve closes
B isovolumic contraction
A1 aortic valve opens
C ejection
A2 aortic valve closes
D isovolumic relaxation
M2 mitral valve opens
43
heart block/bundle branch block
failure of the AV node to conduct from the atria to the ventricles
44
why does the AV node make the heart vulnerable
damage to the AV node will cause a loss of conduction to the ventricles
45
driving force behind absorption
plasma colloid osmotic pressure
46
what is the "LUB" sound
what is the "DUB" sound
mitral and tricupsid valve closure
aortic and pulmonic valve closure
47
what is the function of phospholamban in response to sympathetic beta receptor stimulation
phosphorylation by cAMP will disassociated phospholamband from SERCA to allow calcium to be removed from the cytoplasm
48
what would a long PR segement indicate
slow AV conduction
49
what part of the cardiac conduction system has the slow conduction velocity?
the fastest?
the AV node
purkinje fibers
50
where is V3
midway between V4 and V2
51
what would be considered right axis deviation?
what would cause this
heart axis shift to between 90 and 180 degrees
left bundle branch block, right ventricular hypertrophy
52
where is V1
4th intercostal space to the right of the sternum
53
darcys law
flow = pressure gradiant/resistance
54
lymphpatic filling pressure formula
Pressure in tissue - Pressure in lymph
55
what two parts of the ECG should be isoelectric
PR segement and ST segment
56
what are the three main parts of an ECG wave
P wave
QRS complex
T wave
57
why can't you appreciate atrial repolarization on a normal ECG
because it is masked by the QRS
58
what is the direction of aVL
from the heart towards the legs
59
T/F the heart is the only place where each muscle fiber has a capillary
true
60
what current is at work in phase 3 of a pacemaker cell
IKv1.1
61
what is the supranormal period?
when does it occur?
a period where cells can be restimulated and threshold is lower than normal
only during phase 4
62
what is different that allows contraction during relative refractory period
during the relative refractory period some Na inactivation gates are open a second AP is possible
63
what is SERCA
what does it do
sarco/endoplasmic reticulum calcium ATPase
pulls calcium from the cytoplasm at the expense of ATP while the muscle is at rest
64
what effect will sympathetic stimulation have on ions in cardiac pacemaker cells
what will be in end result
increase of Ca and Na influx
increase the rate of depolarization (faster heart rate), slope (increased contractility), cardiac output
65
three parts of diastole
isovolumic relaxation
passive ventricular filling
atrial systole
66
how much will increasing vessel radius increase flow (Q)
by x^4
67
what would be considered a left axis devation?
what would cause that
a heart vector that is from 0 to -90 degrees
left ventricular hypertropy or inferior MI
68
automaticity
the ability of cardiac pacemaker cells to produce their own APs
69
where are fenestrated capillaries found
places that need to secrete largeer particiles
GI, exocrine, renal, choroid
70
what counteracts high venous pressure in the legs when upright
the calf muscle pump
71
what determines venoconstriction
sympathetic tone
72
which part of the cardiac cycle is longer?
as HR increases, which part get shorter?
diastole
diastole
73
why does pulse pressure increase with age?
Mean BP?
atherosclerosis of large vessels
high vascular resistnace
74
two systolic murmurs
aortic valve stenosis
mitral or tricuspid valve incompetance
75
shear rate
what will this cause
increase the force running parallel to the vessel wall
the synthesis and release of NO2
76
how long does the absolute refractory period last in a cardiac myocyte AP
what are three advantages of this
almost as long as the twitch does
1. no summation of APs
2. no tetanus
3. allows for filling
77
what is the effect of digitalis on the heart
it increases contractility
78
compliance formula
compliance = (deltaV)/delta P
79
what are two common causes of heart block
ischemic heart disease
valve fibrosis
80
what is the difference in duration of AP between cardiac myocytes and pacemaker cells
cardiac myocytes are fast, pacemaker cells are slow
81
what reynold number would indicate turbulent flow?
laminar flow?
\>3000, turbulent
\<2000, laminar
82
what is the standard paper speed of an ECG
25mm/sec
83
what is stroke volume
how do you calculate it
the volume of blood ejected each beat
SV = EDV-ESV
84
reflectivity coefficient
relevant fnumbers associated
the probability that particlesin blood will reflect off vessel walls
theta = 1, the vesselis not permeable
theta \< 1, the vessel wall is freely passing
85
what determines the shape of veins
what is the result of venosconstrition
th pressure and level of vessel constriction
decrease blood reserve, send blood back to the heart
86
what happens when calcium is released from the sarcoplasmic reticulum in cardiac myocytes
BE SPECIFIC
calcium enters the L type calcium channel
it binds with ryanodine receptors on the SR
calcium induces calcium release from the SR
calcium binds to troponin C on tropomyson
87
what features of the heart allow for high O2 extraction rate in the heart
low PO2 and high myoglobin content aloow for rapid uptake
88
T/F a larger muscle will produce greater voltage and larger ECG waveform
true
89
what structures are depolarizing during the PR segment
AV node
Bundle of His
Bundle branches
Purkinje fibers
90
what currents are at work in Phase 4 of a pacemaker cell
IF
ICaT
IKv1.1
91
T/F coronary blood flow is directly correlated to blood pressure
false, coronary blood flow is largely independent of blood pressure flucuations
92
filtration
movement of solute out of blood via hydrostatic pressure
93
myocardial stunning
the loss of function due to an ischemia that can be reversible if reperfused
94
trigger calcium
calcium that enters the cell through a calcium channel that bings to ryanodine receptors and triggers CICR
95
which is more susceptible to ischemia during systole, epicardium or endocardium
why
endo
because the coronary vessels in this area are compressed almost to zero in this area
96
how should HR be calculated of ECG when the heart rate is constant
R-R distance
97
what is the relationship between turbulence and viscosity
increasing viscosity will increas turbulence
98
how can stroke volume be evaluated from a PV loop
SV = the width of the loop
99
what generates a myogenic reponse to regulate coronary blood flow
stretch receptors in smooth muscle
100
what are the functions of cAMP in regards to contractility of the heart
it stimulates L type calcium channels to increase Ca influx
phosphorylation of phospholamban to increase SERCA activilty
101
what is the function of desmosomes in intercalated discs
they hold the cells together
102
laminar flow
flow that is linear down the vessel, with the fluid near the center moving fastest and that near the edge of the lumen moving slower
103
what would a steeper diastolic compliance curve on a PV loop indicate
a decreased level of compliance indicated by less volume filling at a given pressure and preload
104
what is ejection fraction indicative of
the effectiveness of ventricular ejection
105
describe the path of blood through the heart
vena cava
right atrium
tricuspid valve
right ventricle
pulmonary semilunar valve
pulmonary artery
lungs
pulmonary vein
left atria
mitral valve
left ventricle
aortic valve
aorta
106
how long after cardiac ischemia will cells begin to die
20-40mins
107
what happens to velocity when the cross sectional area of a vessel is increased
decreased?
increased area will cause a decrease in velocty
decreased area increases velocity
108
what determines MAP
cardiac output
total peripheral resistance
109
what is a condition that would cause decreased compliance in the left ventricle?
the aorta?
what would cause an increase?
myocardial infarction
HTN
nothing
110
what intrinsic factors control function hyperemia of the coronar vessels
local metabolic control
111
T/F the resistance to blood flow can be measured directly
false, it is measured by R = (deltaP)/Q
112
how do velocity, diameter, and density relate to turbulence
increasing any of these factors will increase turbulence
113
what happens to flow when it reaches critical velosity
it becomes turbulent and it takes significantly more force to increase flow
114
increased vascular tone will result in what
a constriction of coronary vessels to increase resistance and decrease blood flow
115
why does intracellular calcium increased contractility
more calcium means there are more Ca bound to troponin which will allow for more myosin binding sites
116
what is quick way to estimate HR on ECG if the rate is regular
1 space between R waves is 300bpm
2 = 150
3 = 100
4 = 75
5 = 60
117
what are the four areas of auscultation over the heart
aortic
pulmonic
tricuspid
mitral
118
what limbs are used in lead III?
what is the direction of the wave
left arm and lower limb
down and to the right
119
two special structure found in intercalated disks
desmosomes and gap junctions
120
how is flow related to the length of the tube
longer tube = less flow
121
two locations of nodal cells in the heart
BE SPECIFIC
SA node (right atria)
AV node (inferior posterior section of the intratrial septum)
122
what will be the effect of increasing afterload on a PV Loop
what is the result
it will move the point of aortic valve closing to the right due to higher pressure required with less volume ejected
decreased stroke volume
123
PR interval
the length between the begining of the P wave to the Q wave
124
what is the pattern of heart damage when the coronary arterial pressure falls below 40mmHg
the epicardium is less injured, the endocardium is more widespread and severely injured
125
what causes ventricular fibrillation to persist
re-entry of AP into the circuit, causing repeating circus pathways
126
how are cardiac pacemaker cells able to produce a slow depolarization
they have an unstable resting membrane potential
127
what is the physiological and clinical significance of delayed AV conduction
optimal ventricalr filling during atrial contraction
128
where are discontinous capillaries found
places that need to get rid of or absorb large particles
liver, spleen, bone marrow
129
basal tone
the amount of vasoconstriction at rest
130
how long is an AP delayed at the AV node
0.1 second
131
what is the difference between contractility and Frank-Starlings law
contractility is intrinsic and Ca dependant
Frank-Starling is dependent on preload, not calcium
132
what are the four phases of the **ventricular cycle**
filling
isovolumic contraction
ejection
isovolumic relatxation
133
PR segement
isoelectric portion of the ECG between the end of the P wave and the start of the QRS
134
what would happen if the purkinje fibers began to fire at a rate of 140bpm even with a functional SA and AV node
the whole heart will be driven by the faster rate
135
what is the function of the bundle of his, bundle branches, and purkinje fibers
ventricular excitation
136
how can Laplace Law be manipulated to find pressure
P = (w/r)(T)
137
at what point will increasing blood pressure stop increasing coronary blood flow
150 mmHg
138
what current is at work in phase 0 of a pacemaker cell
ICaL
139
what is this?
define the variables
a pressure volume loop
## Footnote
A diastolic filling
M1 mitral valve closes
B isovolumic contraction
A1 aortic valve opens
C ejection
A2 aortic valve closes
D isovolumic relaxation
M2 mitral valve opens
140
what is the effect of neural control on coronary blood flow
what is the secondary effect of this
sympathetic stimulation causes a transient, weak, alpha constriction
metabolic demand is increased, which causes vasodilation and increase in blood flow
141
what recordings are included on a 12 lead ECG
I, II, III
aVR, aVL, aVF
V1-6
142
Frank-Starlings law
increased ventricular filling (preload) will increase tension in the heart muscle and increase contraction force
143
two causes of incresaed pulse pressure
exercise
decreased compliance
144
two examples of delayed after polarization
ectopic beats
PVCs
145
describe the process that produces Phase 2 (plateau)
L type calcium channels open at threshold (-50mV)
calcium enters the cell
creates a slow inward current
146
when the heart is stimulated by a metabolic and neural factor, which wins out
metabolic
147
EDV vs ESV
EDV: the amount of blood in heart during ventricular filling
ESV: the amount of blood remaining in the heart after a contraction
148
what causes the absolute refractory period
the closing of Na inactivation gates
149
what percent of ATP used in the heart is for contraction?
SR pumps?
60-70%
30-40%
150
which part of the autonomic nervous system dominates HR variability
parasympathetic
151
a patient presents with an HR +200bpm
why would this need to be treated immediately
because over 180bpm increasing HR causes a decrease, not an increase in CO
152
what current is at work in Phase 1 of a cardiac myocyte AP
Ito (IKv1.4)
153
what is the function of a ryanodine receptor
binds with calcium to allow for the release of calcium from the SR
154
describe the pathway of sympathetic stimulation on pacemaker cells up to PKA
Norepinephrine is release from the adrenal medulla
NE binds to beta 2 adrenergic receptor
B2 receptor releases G protein
alpha subunit activates adenylate cyclase
adenylate cyclase releases protein kinase A
155
how is resistance effected by size of the artery
large arteries have little resistance, small arteries have a lot of resistance
156
what current is at work in Phase 3 of a cardiac myocyte AP
IKv1.1
157
what are three conditions related to turbulence
anemia (low viscosity)
atherosclerosis (turbid flow is more difficult to move)
aneurysms (larger diameter causes turbid flow)
158
ejection fraction
the amount of blood ejected from the left ventricle each beat
159
where is V2
fourth intercostal space at the left sternal border
160
what is the effect of norepinephrine on the coronary vessels
it increases intracellular calcium to increase tension
161
what starts a ventricular fibrillation
R on T firing
162
what is the effect of hypoxia on the coronary vessels
vasodilation
163
what determine the total energy of a vessel
how does this relate to the amount of pressure
the pressure + the kinetic energy
a larger veseel will have a lower velocity and high pressure
a smaller vessel will have a high velocity but produce low pressure
164
what substances provide local metabolic control to coronary blood flow
K A N A C O
K+
ATP
NO
Adenosine
CO2
O2
165
compensatory pause
what is the function
a prolonged isoelectric period following an ectopic beat and the resumption of sinus
allows the heart to reset
166
T/F compliance always goes up in the heart
false it always go down
167
water flux
Jv = LpS[Pc-Pi] - theta(pic - pii)
Lp = hydrostatic pressure
S = surface area
Pc = hydrostatic pressure in capillaries
Pi = hydrostatic pressure in interstitium
Theta: reflection coefficient
pic and pii =oncotic pressure in side and outside capillaries
168
T/F there is no parasympathetic innervation to the heart vessels
true
169
reactive hyperemia
a significant increase in blood flow into a tissue after ischemia has been relieved
170
how is flow related to pressure gradient
greater pressure, greater flow
171
what current is at work in Phase 4 of a cardiac myocyte AP
IKir
172
the movement of what two ions is balanced during phase 2
potassium intitally decreases in conductance, then increases as the AP transitions to phase 3
calcium increases in conductance then slowly decreases
173
three CNS symptoms caused by tetrotoxin
muscle weakness
numbness
coma
174
three examples of conditions that might cause a murmur
high blood flow through a valve in pregnancy
systemic disease such as anemia
valvular heart disease
175
what happens to blood flow through vessels with progressively smaller radii
the resistance to flow for the whole segment is the sum off all the resitances, so increased resistance at the end of the vessel increases resistance for the whole
176
what are three general symptoms of tetrotoxin poisoning
GI distress
CNS
Cardiovascular
177
what is the RMP of a cardiac myocyte
-90mV
178
what is the relationship between MAP and pulse pressure
as MAP increases, pulse pressure increases
179
what are the 5 phases of a cardiac myocyte AP
Phase 4 (resting)
Phase 0 (upstroke)
Phase 1 (Early Repolarization)
Phase 2 (Plateau)
Phase 3 (final repolarization)
180
explain the hydraulic filter of the arterial blood flow
the aorta expands to hold blood from the left ventricle so that blood flows at a constant pressure, not in pulses
181
contractility
the intrinisic contractile force of the heart a given preload and afterload
182
what forms ECG recordings
the electrical signals formed by action potentials in the heart
183
why can turbulence be good?
it ensures mixing of blood
provides heart sounds
184
three types of capillaries
continous
fenestrated
discontinuous
185
what properties allow veins to store blood
thin
collapsable
high compliance
186
where is 2/3 of blood kept in the body
what is the clincial significance
in the veins as a blood reserve
blood in veins can refill arteries if there is a hemorrhage
187
describe the pathway of parasympathetic stimulation on HR (up to G protein release)
acetylcholine binds to muscarinic receptors
M receptors release G protein
G protein subunits beta and gamma induce intracellular response
188
if you hear systolic murmur over the 5th intercostal space at the midclavicular line, what would be the expected cause
what if it were at the 5th sternal intercostal space
mitral valve incompetance
tricuspid valve incompetence
189
two phases of the cardiac cycle
systole
diastole
190
afterload
the force that opposes ventricular shortening against aortic pressure
191
on a standard ECG what are the units on the x axis? y axis?
x axis = .04seconds per division
y axis = .1mV per division
192
what six things can be evaluated looking at a PV loop
* stroke volume
* cardiac output
* ejection fraction
* contracility
* ventricular wall compliance
* ventricular preload an afterload
193
T/F the slowest functional pacemaker dominates the heart
fast, the fastest pacemaker does
194
what does SERCA do
uses ATP to pump calcium back into the SR afer a contraction to allow the muscle to relax
195
why do the purkinje fibers have the highest conduction velocity
large diameter and many gap junctions
196
what is necessary for cardiac muscle relaxation
a decrease in intracellular calcium concentration
197
what part of an ECG would correspond with SA node firing
the isoelectric period prior to the P wave
198
define the phrase "the heart is a syncytium"
it works as a unit
199
what is the driving force behind the movement of blood during the cardiac cycle
pressure
200
what would happen if the AV node were knocked out but the SA was still firing
the SA node AP would not be able to reach the purkinje fibers so the fibers would produce a HR of around 30
201
R on T firing
ectopic APs that occur during the "vulnerable period" of the late T wave
202
what is the function of phospholamban at rest
describe the sympathetic interaction between phospholamban and SERCA
at rest phospholamban inhibits SERCA
stimulation of beta adrenergic receptors releases cAMP
cAMP phosphorylates phospholamban
phosphorylation allows SERCA to function
203
which pacemaker node in the heart produces impulses at the highest frequency
the SA node
204
three cardiovascular symptoms caused by tetrotoxin
decreased cardiac output
hypotension
bradycardia
205
what happens during circuit re-entry that causes arrhythmia
conduction from the ventricle is looped around to cause an abnormal conduction and stimulation pattern
206
what is the systemic resistance to blood flow
20mmhg/L/min
207
T/F contractility is dependent on preload and afterload
false, it is an intrinsic capability of the heart dependent on calcium
208
how should HR be calculated if the HR varies
count the number of RR intervals in 10 seconds and multiply by 6
209
what type of murmur would be heard with aortic valve incompetance
diastolic murmur over the 2nd right intercostal space
210
where is V6
at the midaxillary line at the 5th intercostal space
211
Laplace Law formula
T = (P x r)/w
212
what are two factors that determine the fire frequency of pacemaker cells
the rate of depolarization in phase 4
the maxium pacemaker potential
213
hydrostatic pressure
formula
the pressure exerted by a fluid on its container
Hp = height x density x gravity
214
what is an example of atissue with parallel vessels
lungs
215
what effect would increased contractility have on a PV loop
what would be the result
the systolic pressure curve would sift to the upper left, indicating a higher pressure per volume
increasing stroke volume
216
negative inotropic effect
what would cause this
decreased contractility
beta blockers
217
turbulent flow
flow that creates whirls due movement faster than critical velocity
218
what current is at work in Phase 0 of a cardiac myocyte AP
INa
219
how does tonic stimulation apply to pacemaker cells
the parasympathetic nervous system displays tonicity by constantly having a inhibitory effect on heartrate
220
when is pressure the highest in the ventricles and aorta
during ventricular systole
221
what is effect of compliance on end systolic volume?
end diastolic volume?
no effect
decreased volume
222
what is a normal ejection fraction
what would it mean if EF were low
+50%
lower values indicate heart failure
223
scalar ECG
a recording of the potential differences between two points on the body surface
224
what two limbs are used in lead II?
what is the direction of the wave
right arm and a leg
from the right arm down to the leg
225
what is the general process of calcium induced calcium release CICR
Calcium enters the the cell during phase two, triggering the release of calcium from the SR and producing a contraction
226
what is this and what is it used for
the nerst equation used to determine the Ex for a particular ion
227
at what pressure will blood flow to the endocardium be attenuated
40mmHg
228
what are the leads that should be placed for an ECG
right/left arm and leg
V1-6
229
what is the average presure in arterial blood flow
venous
flow rate
100mmhg
0
5L/min
230
what two limbs are used in lead I?
what is the direction of the force?
right and left arms
from right to left
231
what electrical event does the QRS complex represent
ventricular depolarization
232
if you hear a systolic murmur over the 2nd right sternal intercostal space, what would this most likely be
aortic vale stenosis
233
what are the two advantages of the plateau period for cardiac function
maintenance of force generation (long contraction)
creation of a long absolute refractory period (allows for filling)
234
what two structures are most important to EC coupling
T tubules
sarcoplasmic reticulum
235
what electrical event does the P wave represent
atrial depolarization
236
what are the functions of protein kinase A in pacemaker cells
what is the result
increasing Na conductance to allow If
phosphorylation of T-type calcium channels to increase Ca conductance and allow ICat
increase pacemaker potential
237
define the variables
1. mitral valve opens
2. diastolic filling
3. mitral valve closes
4. isovolumic contraction
5. aortic valve opens
6. ejection
7. aortic valve closes
8. isovolumic relaxation
9. stroke volume
238
what are the Dipolar leads in ECG?
why are they called that
Leads I-III
because there will always be two leads, one will be more negative to reflect the passing of an AP wave
239
where is V4
the midclavicular line at the 5th intercostal space
240
two parts of systole
isovolumic contraction
ejection
241
where is the aortic area of ausculation?
pulmonic?
mitral?
tricuspid?
2nd right intercostal space
2nd left intercostal space
5th intercostal space at the sternm
5th intercostal space at the mid clavicle
242
what electrical event does the T wave represent
ventricular repolarization
243
what is pulse pressure dependant on
stroke volume and arterial compliance
244
in general, what is measured by a pressure/volume loop
the efficiency and work performed by the heart
245
what is the function of the AV node
delays ventricular excitiation to ensure filling
246
a standard paper speed, what are the x and y axes
x is time
y is voltage
247
four large cardiac vessels
right coronary
left coronary
left circumflex
left anterior descending
248
Describe the calcium signalling process
Ca enters the cell
trigger calcium binds to ryanodine triggering CICR
depolarization and muscle contraction
repolarization through calcium sequestering by SERCA
249
transmural pressure
the difference in pressure placed on the intraventricular septum by the ventricles
250
what is cardiac output
how do you calculate it
the total volume of blood ejected from the heart each minute
CO = SV x HR
251
einthovens triangle
an imaginary triangle formed by the upper and lower limbs along with the pelvis used to measure the amplitude and direction of cardiac APs at the skin
252
reynolds number equation
Re = VDp/n
253
how can you determine the contractility of the heart from a PV loop
the systolic pressure (upper) line will have an increased slope with increased contractility
254
what happens during diastole to compensate for compression of coronary vessels to the endocardium during systole
blood flow is greater than average, so that the average amount of blood flow ist he same
255
pulse pressure formula
pulse pressure = systolic - diastolic
or
pp = stoke volume/arterila compliance
256
velocity equation for a blood vessle
Velocity = Flow(Q)/vessel cross section(A)
257
where is V5
at the anterior axillary line in the 5th intercostal space
258
describe the process of calculating heart rate using R-R interval
measure the distance in mm between consecutive R waves
divide the paper length in 60s (1500mm) by the RR length
259
what is the direction of aVL
from the heart to the left arm
260
what would be the effect of increased preload on a PV loop
what would be the result
it would increase the LVEDV, increasing the amount of tension in the wall and increasing contraction force
increased stroke volume
261
what are two factors that generate RMP
unequal distribution of ions (Gibbs donnan)
relative permeability of ions (conductance)
262
why do cardiac myocytes have a lot of mitochondira
they function mainly on aerobic metabolism
263
what is the function of phospholamban at rest
inhibition of SERCA
264
heart cells are particularly vulnerable to arrhythmias at what point in the cardiac cycle
the phase 4 supranormal period
265
how do SNS and PsNS differ in terms of onset of effect after stimulus and decay of effect when the stimulus is with drawn
SNS: slow onset, slow decay
PsNS: fast onset, fast decay
266
what are the two extrinsic regulators of coronary blood flow
sympathetic control
hormone regulation
267
describe the effect of G protein subunit Gαi on pacemaker cells
cAMP is decreased, causing a decrease in PKA
If, ICaL, IKv1.1 all decrease
slope/rate of depolarization are decreased
268
what would be effect of decreased compliance on a PV loop
what is the result
decreased compliance would require more pressure with less filling, resulting in a steeper diastolic loop
decreased stroke volume
269
three GI symptoms caused by tetrotoxin
nausea, vomitting, cramping
270
what is the benefit of parallel vessels rather than vessels in series
one vessel with high resistance does not compromise blood flow through the rest of the vessels
271
what is the direction of aVR
from the heart toward the right arm
272
what is the clinical relevance of having a high number of capillaries in the heart
it allows for the minimum possible distance to intracellular mitochondria
273
how can cardiac output be evaulated on a PV loop
CO = SV x HR
274
ST segment
the isoelectric portion between the end of QRS and the start of the T wave
275
what will an ECG look like with heart block
normally firing P waves from the SA node with missing QRS complexes
276
whatis ST segment depression/T wave inversion indicative of
signs of previous ischemia
277
four arterial pressures
systolic
diastolic
pulse
MAP
278
where are continous capillaries found
cells with relatively or variable metabolic need
CNS, Lung, Skin, msucle
279
what are the three augmented unipolar leads
aVL, aVR, aVF
280
how can a cardiac AP be considred a wave
there is a wavefront of depolarized cells followed by hyperpolarizing cellls
281
how does coronary blood flow regulate heart function
sympathetic stimulation of the coronary vessels can increase cardiac metabolic rate
removing the stimulus will decrease metabolism
282
what is the end result of parasympathetic stimulation on pacemaker cells
decreased pacemaker potential and rate of depolarization, leading to a slower HR
283
myogenic reponse
increasing transmural pressure will cause constriction of coronary vessels
decreasing will cause dilation
284
what is ficks principle used for?
what is the equation
to determine CO by the amount of O2 consumed divided by the difference of arterial and venous PO2
CO = (VO2)/(Cpv - Cpa) \*high minus low
285
compliance formula
change in volume/change in pressure
286
describe the path of an action potential through the heart
SA node
internodal pathways
AV node
bundle of His
bundle branches
purkinje fibers
287
tetradotoxin
a volrage gated channel blocker derived from the venom of a puffer fish
288
how does SERCA allow for enhanced contractility
increased SERCA activation will increase the amount of Ca in the SR and allow for a greater release, whch will trigger a stronger contraction
289
what is the function of gap junctions in an intercalated disc
allow direct transport between cells
290
what would a high slope on a pressure/time graph indicate
increased contractility
291
what current is at work in Phase 2 of a cardiac myocyte AP
ICaL
IKv1.4
IKv1.1
292
T/F increasing contractility would affect LVEDV
false
293
oncotic pressure
the pressure driving fluid into blood due to protein content
294
what is the formula for EF
SV/EDV
295
what point on a pressure/volume loop indicate LVEDV and LVESV
mitral valve closing
aortic valve close
296
what is the primary determinant of coronary blood flow
intrinsic mechanisms
297
ryanodine receptors
receptors on the SR of muscle cells that are triggered by calcium to release calcium into the cytoplasm
298
what intrinsic factors control flow autoregulation and reactive hyperemia in coronary vessels
myogenic response and local metabolic control
