Exam 4 Flashcards
(388 cards)
1
Q
Define cardiovascular physiology
A
study of how the heart & blood vessels function
2
Q
What is rule #2 of the heart
A
the heart is a muscle
3
Q
If the heart is over-worked, what happens
A
it gets larger
b/c it is a muscle
4
Q
Cardiac muscle is called
A
myocardium
5
Q
What are the unique features of myocardium
A
rapid depolarization (electrical conduction) high energy needs (glycogen & mitochondria)
6
Q
What is rule #4 of the heart
A
the heart has 3 functions
7
Q
Name the 3 primary functions of the heart
A
electrical conduction
contraction during systole
relaxation during diastole
8
Q
Through the 3 primary functions of the heart, what other important functions does the CVS have
A
delivery of O2, nutrients, water, hormones, & regulatory chemicals to tissues
removes CO2 & metabolic wastes
thermoregulation
supports blood flow dependent functions
9
Q
What are some examples of blood flow dependent functions
A
urine formation in kidneys gas exchange in the lungs metabolism in working skeletal muscle digestive processes & absorption reproductive system functions
10
Q
What is another name for the RAVV
A
tricuspid valve
11
Q
Where is the RAVV/ tricuspid valve located
A
b/w RA & RV
12
Q
Where is the pulmonic valve located
A
b/w RV & pulmonary trunk
13
Q
What is another name for the LAVV
A
bicuspid or mitral valve
14
Q
Where is the LAVV/bicuspid/mitral valve located
A
b/w LA & LV
15
Q
Where is the aortic valve located
A
b/w LV & aorta
16
Q
What are the 3 layers of the heart
A
endocardium
myocardium
epicardium
17
Q
Describe the endocardium
A
inner layer
single cell layer of endothelial cells
18
Q
Describe the myocardium
A
middle layer
thicker layer of cardiac muscle (myocardial) cells
19
Q
Describe the epicardium
A
outer layer
thin layer of mesothelial cells
also called the visceral serous pericardium
20
Q
What is the contractile unit of the heart
A
sarcomere
21
Q
What controls the sarcomere
A
complex proteins
including actin, myosin, troponin, & tropomyosin
22
Q
Are arteries high or low pressure
A
high
23
Q
Are veins high or low pressure
A
low
24
Q
RBC pulmonary circulation
A
RA -> RV -> pulmonary trunk -> pulmonary arteries -> lungs -> pulmonary veins
25
RBC systemic circulation
LA -> LV -> aorta -> systemic organs -> vena cava
26
What is rule #1 of the heart
there are two circulations arranged in series
| pulmonary & systemic
27
What is rule #5 of the heart
blood is lazy
28
Blood is lazy, which means what
it moves down its pressure gradient
| from high to low pressure
29
Name the fetal shunts
ductus arteriosus
ductus venosus
foramen ovale
30
Remnant of ductus venosus
ligamentum venosum
31
Remnant of foramen ovale
fossa ovalis
32
When do the fetal shunts close
shortly after birth
| in response to bp changes & decreased PGE2
33
Function of the placenta
oxygenates blood & removes metabolic wastes
34
Placenta takes over the job of what organs
lungs & liver
35
What is the function of ductus venosus in fetal circulation
allows blood from umbilical vein to bypass the liver on the way to the caudal vena cava
36
What is the function of foramen ovale in fetal circulation
allows blood from RA to bypass the lungs & go directly into the LA
37
What is the function of ductus arteriosus in fetal circulation
allows blood from pulmonary trunk to bypass the lungs & go directly into the aorta
38
Gas exchange in fetal vs adult circulation
fetal- placenta
| adult- lungs
39
High pressure & low pressure systems in fetal vs adult circulation
fetal- pulmonary circulation is high pressure while systemic is low pressure
adult- pulmonary circulation is low pressure while systemic is high pressure
40
Circuitry in fetal vs adult circulation
fetal- parallel
| adult- series
41
Where is the patent ductus arteriosus located
b/w pulmonary trunk & aorta
42
In fetal circulation, how did blood move through the ductus arteriosus & why
from pulmonary trunk to aorta since the pulmonary trunk had a higher pressure
43
In adult circulation, how does blood move through the patent ductus arteriosus & why
from aorta to pulmonary trunk since the aorta has higher pressure
44
Why is it incorrect to describe vessels as a plumbing system
blood vessels are not passive tubes
| not rigid; able to expand & contract
45
Name the 3 blood vessel layers
tunica intima
tunica media
tunica externa
46
Describe tunica intima
intimate contact w/ lumen
| simple squamous epithelium continuous w/ the lining of the heart
47
Function of tunica intima
prevents friction
48
Describe tunica media
middle layer
| smooth muscle w/ sheets of elastin
49
Function of tunica media
blood pressure regulator the dilates/constricts in response to the autonomic nervous system
50
Describe tunica externa
overcoat
| loosely woven collagen fiber
51
Function of tunica externa
protects & reinforces blood vessels
52
What are capillary walls made of
tunica intima only
53
Thin walls of capillaries allow for what
diffusion of gas, nutrients, & waste
54
Capillary beds have what other functions besides the exchange of gas, nutrients, & wastes
regulate blood pressure & thermoregulation
55
Function of venous valves
prevent backflow of blood
56
Why are valves necessary for veins
no pressure gradient available
| must work against gravity
57
Do veins or arteries have a larger lumen
veins
58
Do veins or arteries have a thicker wall
arteries
59
Do veins and arteries have the same layers
yes, tunica intima/media/externa
60
Do veins or arteries have more muscle & elastic fibers
arteries
61
Do veins or arteries have higher compliance
veins
62
Do veins or arteries have higher capacitance
veins
63
Define compliance
ability to stretch
64
Define capacitance
ability to hold a large volume under low pressure
65
Describe elastic arteries
large vessels w/ large lumen
| thick walls w/ a lot of elastin tissue, smooth muscle, & CT
66
Function of elastic arteries
deliver blood to organs or lungs
67
Walls of elastic arteries allow the vessels to do what
absorb high pressure blood flow as blood is pumped from the ventricles into the elastic arteries
68
Describe muscular arteries
medium sized vessels w/ medium sized lumen
| moderately thick wall w/ moderate amounts of elastin tissue, smooth muscle, & CT
69
Function of muscular arteries
deliver oxygenated blood to the organs
70
Describe arterioles
smallest branches of the arteries w/ small lumen
71
Function of arterioles
site of highest resistance to blood flow
72
Alterations in resistance of arterioles occur in response to what
sympathetic nervous system activity
alpha 1 stimulation -> vasoconstriction
beta 2 stimulation -> vasodilation
73
Where are continuous capillaries found
skin, muscle, & brain
74
Continuous capillaries allow passage of what
lipid soluble molecules (O2/CO2) via diffusion across a lipid membrane
sm molecules through intracellular clefts
75
Where are fenestrated capillaries found
sm intestines & kidneys
76
Fenestrated capillaries allow passage of what
sm molecules through fenestrations & intracellular clefts
77
Where are sinusoidal capillaries found
liver, bone, marrow, & spleen
78
Sinusoidal capillaries allow passage of what
lg molecules through lg fenestrations
| lack basement membrane, so leaky
79
Capillaries are located b/w where
blood & tissues (systemic) or alveoli (lungs)
80
Describe the compliance & resistance of the arterial system
high resistance
| low compliance
81
Describe the compliance & resistance of the venous system
low resistance
| high compliance
82
Define basal tone
partial constriction of a vessel even when all external forces are removed
83
Put the following in order of cross-sectional area:
| arterioles, capillaries, & arteries
capillaries > arterioles > arteries
84
Define laminar flow
streamlined
| layers of fluid moving in series w/ each layer having a dif velocity
85
Laminar flow is described as being parabolic, what does this mean
```
max velocity is at the center
minimum velocity (0) is towards the vessel walls
```
86
Define turbulent flow
when streamlined flow is disrupted
irregular motion
audible vibrations
87
Audible vibrations from turbulent flow result from
major changes in diameter
| such as, arterial bifurcations, stenotic vessels, & near valves
88
Eq for velocity of blood flow
V = Q/A
89
Relationship b/w cross-sectional area of vessels to the velocity of the blood
inversely proportional
90
Arteries cross-sectional area vs velocity
low A
| high V
91
Arterioles cross-sectional area vs velocity
gradually higher A
| gradually lower V
92
Capillaries cross-sectional area vs velocity
high A
| low V
93
Venules cross-sectional area vs velocity
gradually lower A
| gradually higher V
94
Veins cross-sectional area vs velocity
low A
| high V
95
Eq for Ohm's law
Q = ΔP/R
96
Relationship b/w blood flow & pressure gradient
```
directly proportional
(pressure gradient = driving force)
```
97
Relationship b/w blood flow & resistance
```
inversely proportional
(resistance = impediment to flow)
```
98
Eq for Poiseulle's law
R = 8nl/πr^4
99
Relationship b/w resistance to flow & blood viscocity
directly proportional
100
Relationship b/w resistance to flow & length
directly proportional
101
Relationship b/w resistance to flow & radius
inversely proportional
102
What is the main determinant of resistance to flow
radius
103
Eq for Reynold's number
Nr = pdv/n
104
High Nr means
turbulent blood flow
105
Low Nr means
laminar blood flow
106
Relationship b/w turbulence & velocity of flow
directly proportional
107
Relationship b/w turbulence & blood viscocity
inversely proportional
108
What are the main determinants of turbulence
velocity of blood flow & viscosity of blood
109
How could blood viscosity be increased
increased RBCs
| dehydration
110
How could blood viscosity be decreased
decreased RBCs
| IV fluids
111
Systolic definition
highest arterial blood pressure
112
Diastolic definition
lowest pressure whether in arteries or vein
113
Pulse pressure definition
dif b/w systolic & diastolic pressure
114
Units to measure blood pressure
millimeters of mercury
| mmHg
115
What is the primary parameter responsible for assuring the tissue O2 requirements are met
cardiac output
116
Compare systemic vs pulmonary circulatory systems in regards to blood pressure
systemic is higher
(BPd ~ 80 mmHg & BPs ~ 120 mmHg)
pulmonary is lower
(BPd ~ 5 mmHg & BPs ~ 20-40 mmHg)
117
Explain the contribution of the elastic properties of arteries to systolic pressure
elastic walls of aorta stretch to accommodate for the increase in blood being pumped from the LV to the aorta
thick rubber band- able to accept blood, but the pressure increases
118
Explain the contribution of the elastic properties of arteries to diastolic pressure
allow for continued movement forward of blood even as the amount of blood moving is decreased
due to the recoil properties- moves back to its original state & pushing blood into the circulatory system
119
Mean arterial pressure definition
average pressure in a complete cardiac cycle
120
Mean arterial pressure is the driving force for what
perfusion
121
Eq for mean arterial pressure
MAP = 1/3 BPs + 2/3 BPd
| or MAP = (BPs + BPd + BPd)/3
122
Eq for pulse pressure
BPs - BPd
123
Pulse pressure represents what
stroke volume
124
Define stroke volume
volume of blood pumped out of the heart w/ each beat
125
What is felt during an exam by palpating the arterial vessels
pulse pressure
126
If a pulse is normokinetic, what does this mean
syn adequate & strong
127
If a pulse is hyperkinetic, what does this mean
syn bounding or water hammer
128
A hyperkinetic pulse could be due to what (examples)
patent ductus arteriosus
| aortic regurgitation
129
If a pulse is hypokinetic, what does this mean
syn weak or thready
130
A hypokinetic pulse could be due to what (examples)
subaortic stenosis
| hypovolemia
131
High resistance of arterioles is instilled by what component of the vessel wall
high smooth muscle
132
When measuring the blood pressure in a patient, you are measuring the pressure in what type of vessel
systemic arteries
133
What valve(s) sound louder in the left base
pulmonic & aortic valves
134
What valve(s) sound louder in the right base
none
135
What valve(s) sound louder in the left apex
mitral/ bicuspid valve
136
What valve(s) sound louder in the right apex
tricuspid valve
137
Would a needle w/ a higher gauge have a smaller or larger diameter than a needle with a lower gauge
smaller
138
Sympathetic NS is associated w/ what response
fight or flight
| increased HR & BP
139
Parasympathetic NS is associated w/ what response
rest & digest
| decreased HR & BP
140
Alpha receptors have what effect on blood vessels
constrict smooth muscle
| reduce blood flow
141
Beta receptors have what effect on blood vessels
dilate smooth muscle
| increase blood flow
142
What are baroreceptors
specialized cells that monitor BP by detecting changes in the stretch of vessel walls
143
Where are baroreceptors found
aortic arch & carotid sinuses
144
What cardiovascular centers are associated w/ the sympathetic system
vasomotor & cardiac accelerator
145
What cardiovascular centers are associated w/ the parasympathetic system
cardiac decelerator
146
If BP increases, what are the steps of the arterial baroreceptor reflex
1) baroreceptors sense mechanical stretch
2) increased frequency of baroreceptor signals to the brain
3) signal travels via glossopharyngeal (CN IX) & vagus (CN X) nerves to the nucleus tractus solitarius in the medulla oblongata
4) decreases vasomotor & cardiac accelerator
increases cardiac decelerator
147
Summary of arterial baroreceptor reflex when high BP
bradycardia (slower HR), arteriolar vasodilation, & decreased contractility
148
If BP decreases, what are the steps of the arterial baroreceptor reflex
1) baroreceptors do not sense mechanical stretch
2) decreased frequency of baroreceptor signals to the brain
3) fewer signals travel via glossopharyngeal (CN IX) & vagus (CN X) nerves to the nucleus tractus solitarius in the medulla oblongata
4) increases vasomotor & cardiac accelerator
decreases cardiac decelerator
149
Summary of arterial baroreceptor reflex when low BP
tachycardia (faster HR), arteriolar vasoconstriction, & increased contractility
150
What stimulates the Renin-Angiotensin Aldosterone Systems (RAAS)
low blood pressure (juxtaglomerular cells)
increased sympathetic tone (arteriolar baroreceptors)
low renal blood flow/ low Na+ (macula densa)
151
What does renin do
converts angiotensinogen (inactive) -> angiotensin I
152
What does Angiotensin Converting Enzyme (ACE) do
converts angiotensin I -> angiotensin II
153
What does angiotensin II do
recruits ADH, aldosterone, & norepinephrine
constricts efferent > afferent in glomerulus
increases Na+ & H2O reabsorption in proximal convoluted tubule
154
Angiotensin II, ADH, & norepinephrine act as what
vasoconstrictors
155
ADH does what
increases H2O reabsorption in the distal convoluted tubule
156
Aldosterone does what
increases Na+ & H2O reabsorption & K+ secretion at distal convoluted tubule
157
Summary of RAAS
if decreased bp, then need to increase CO (by adding more volume) & increase VR (by vasoconstriction)
158
What increases CO in the RAAS
increased Na+ & H2O reabsorption throughout the kidney (ADH, aldosterone, & angiotensin II)
increased thirst/ water intake (ADH)
159
What increases VR in the RAAS
vasoconstriction (angiotensin II, ADH, & norepinephrine)
160
Which response to BP changes is faster & why
arterial baroreceptor reflex
| occurs in sec to min b/c signals are passed through the NS
161
Which response to BP changes is slower & why
RAAS
| occurs in min to hours b/c signals are passed through the CVS via hormones
162
Filtration in capillary beds occurs where
arterial end
163
Reabsorption in capillary beds occurs where
venous end
164
Define hydrostatic pressure
pressure of fluids in an enclosed space
in this case, pressure w/in capillaries
pushes fluid out
165
Define oncotic pressure
osmotic pressure generated by proteins
| pulls fluid in
166
At the arterial end, why does filtration occur
increased hydrostatic pressure
oncotic pressure is static
Pc > πc
net outward flow
167
At the venous end, why does reabsorption occur
decreased hydrostatic pressure
oncotic pressure is static
Pc < πc
net inward flow
168
Describe the on/off switches when exchange is allowed in the capillaries
precapillary sphincters are vasodilated
| allows blood to move through the capillaries
169
Describe the on/off switches when exchange is prevented in the capillaries
precapillary sphincters are vasoconstricted
| blood cannot move through the capillary beds
170
When blood is prevented from entering the capillary beds, where does it go
from arterioles into venule via metarterioles
171
What are some vasodilators
decreased O2 or increased CO2 in tissues
histamine
adenosine
bradykinin
172
What are some vasoconstrictors
angiotensin II
epinephrine/norepinephrine
endothelin
acute stretch in arterioles after increased bp (myogenic autoregulation)
173
Is there net movement across capillaries in the middle
no, because Pc = πc
174
Define effusion
fluid accumulation in a cavity/ space
175
Define edema
fluid accumulation in a tissue
176
Name the two ways that filtration in the interstitial space would increase, resulting in edema
increased capillary hydrostatic pressure (Pc)
| increased capillary permeability (Kf)
177
What could cause an increase in Pc
```
arteriolar dilation
venous constriction
increased venous pressure
heart failure
ECF volume expansion
```
178
What could cause increased Kf
burns
inflammation
toxins
179
Name the two ways that there would be decreased removal from the interstitial space, resulting in edema
decreased capillary oncotic pressure (πc)
| decreased lymphatic drainage
180
What could cause a decrease in πc
loss of plasma proteins (ex: via urinary or GI system)
| decreased production of proteins (ex: liver failure or malnutrition)
181
What could cause a decrease in lymphatic drainage
standing (decreased skeletal muscle compresses lymph vessels)
lymphatic obstruction
182
Summarize what edema is and what causes it
increase in interstitial fluid volume due to an increase in filtration or a decrease in absorption/ lymph drainage
183
Temporal relationship b/w mechanical & electrical events in the heart
electrical event occurs before the mechanical event
184
What is the sequence of electrical activation in the heart
1) SA node
2) atrial myocardium
3) AV node
4) Bundle of His
5) Left & right bundle branches
6) Purkinje fibers
7) Ventricular myocardium
185
What are the driving forces that dictate the flow of ions across the cardiomyocyte membrane
electrical & chemical driving forces
186
What is the electrical driving force
difference in membrane potential b/w inside & outside of cell
187
What is the chemical driving force
difference in cation conc b/w inside & outside of cell
188
What two factors create the polarized state/ resting membrane potential
Na-K ATPase activity
| Selective permeability to K+
189
Describe the Na-K ATPase & its effect on RMP
3 Na+ out for 2 K+ in
| Creates electrochemical gradient
190
Describe the selective permeability to K+ & its effect on RMP
membrane is permeable to K+, so it diffuses out of the cell down its conc gradient
large neg charged intracellular proteins attract some K+, which prevents complete equilibrium of K+ across the membrane
191
Extracellular charge & ion conc at RMP
pos charge
high Na+
low K+
192
Intracellular charge & ion conc at RMP
neg charge
low Na+
high K+
193
Depolarization involves what channels
voltage-gated Na+ channels (Na+ influx)
| phosphorylation-gated Ca2+ channels (Ca2+ influx)
194
Repolarization involves what channels
voltage-gated K+ channels (K+ efflux)
195
Describe resting potential of AP
no net movement of ions
196
Describe stimulus & response of AP
AP not generated until a certain voltage is reached
197
Describe all or none response of AP
action potential either occurs or it doesn't
198
If threshold is reached, what is the effect on the Na+ & K+ voltage-gated channels
1) activation gate of Na+ voltage-gated channel opens quickly
2) inactivation gate of Na+ voltage-gated channel opens slowly
3) voltage-gated K+ channel opens slowly
199
Describe propagation of AP
only goes in one direction
200
Describe refractory period of AP
cells are unresponsive to re-stimulation
201
Describe relative refractory period of AP
stronger than normal stimulus from an adjacent cell can prematurely excite the cells
202
Fast response conduction systems are located where
atrial & ventricular myocytes
| purkinje cells
203
Slow response conduction systems are located where
SA & AV node
204
Phases (#'s) in fast response AP
4, 0, 1, 2, 3, & back to 4
205
Phases (#'s) in slow response AP
4, 0, 3, & back to 4
206
Summary for what happens in the phases for fast response AP
```
4- K+ efflux & Na+K+ ATPase
0- Na+ influx
1- transient K+ efflux
2- K+ efflux & Ca2+ influx
3- K+ efflux
```
207
Summary of what happens in the phases for slow response AP
4- funny current
0- Ca2+ influx
3- K+ efflux
208
RMP for fast response AP
-90 mV
209
RMP for slow response AP
-60/-65 mV
210
What is the difference in phase 0 b/w fast & slow response APs
fast- rapid influx of Na+ through fast voltage-gated Na+ channels
slow- leisurely upstroke due to a slow influx of Ca2+
211
What is the difference in phase 4 b/w fast & slow response APs
fast- K+ ion partitioning is the primary determinant of RMP; no ion movement
slow- continuously drifting towards threshold of -40 mV (via funny current); allows for spontaneous depolarization of pacemaker cells in SA node
212
What is a surface electrocardiogram (ECG)
summation of all APs over time
213
What characteristics of electrical waveforms is captured by ECGs
amplitude & direction
214
Define arrhythmia
electrical activity that has an irregular rhythm and/or abnormal heart rate
215
What does a waveform correlate w/
de/repolarization of a specific area of a heart
216
What do the pos & neg poles of an ECG serve as
point of reference to code the wave's amplitude & direction
217
What is the amplitude of deflection dictated by
tissue being depolarized & orientation of the waveform relative to the lead
218
What does Einhoven's triangle describe
orientation of a standard 6-lead ECG
219
P wave is what de/repolarization
atrial depolarization
220
QRS complex is what de/repolarization
ventricular depolarization
221
T wave is what de/repolarization
ventricular repolarization
222
Would a waveform that is parallel to an electrode have a higher or lower amplitude compared to one that is angled
higher
223
Would a waveform going through a thicker muscle have a higher or lower amplitude compared to one that is thinner
higher
224
What are ECGs great at determining
heart rate, arrhythmias, & conduction abnormalities
225
What are ECGs good at determining
chamber enlargement (specific but not sensitive)
226
What are ECGs bad at determining
mechanical activity of the heart
227
1st + deflection is what
P wave
228
1st - deflection is what
Q wave
229
2nd +, 1st + after 1st -, or 1st large + deflection is what
R wave
230
- deflection after R is what
S wave
231
+ or - deflection after QRS complex
T wave
232
Do all (normal) patients have every waveform
no, many do not have all of the waveforms in the QRS complex
| but must have a P & T wave
233
Effect of hyperkalemia on slow response AP
mimics effect of PS tone on nodal cells
leads to a reduced slope of phase 4 spontaneous depolarization
ECG shows bradycardia
234
Effect of hyperkalemia on RMP of fast response AP
les neg RMP so more Na+ channels are in an inactivated state
leads to reduced or absent excitability & a slower rate of phase 0 depolarization to the ventricles
ECG shows low amplitude/ absent P wave & a wide QRS complex
235
Order of sensitivity to hyperkalemia
atrial > ventricular > nodal
236
Effect of hyperkalemia on de/repolarization of fast response AP
faster repolarization
leads to shorted AP duration
ECG shows tented T wave
237
Heart rate calculation on ECG for a 25 mm/sec printer
```
#QRS in 15 big boxes (3 sec) * 20
#QRS in 1 BIC pen (6 sec) * 10
```
238
Heart rate calculation on ECG for a 50 mm/sec printer
```
#QRS in 30 big boxes (3 sec) * 20
#QRS in 1 BIC pen (3 sec) * 20
```
239
How big is a BIC pen
150 mm
240
What is considered a regular rhythm
beats evenly spaced
241
What is considered an irregular rhythm
beats not evenly spaced
242
Describe a regularly irregular rhythm
clear pattern to the irregularity
243
Describe an irregular rhythm
no clear pattern or lack of pattern to irregularity
244
Describe an irregularly irregular rhythm
no pattern to the irregularity
245
For a paper speed of 50 mm/sec and a calibration of 10 mm/1mV, what are the measurements for a small box
.1 mV by .02 sec
246
How does a P wave vary for QRS origin from sinus, supraventricular, & ventricular
```
sinus= wider P wave
supraventricular= +/- P prime waves; narrower
ventricular= P wave may be absent
```
247
How does a QRS complex vary for QRS origin from sinus, supraventricular, & ventricular
sinus & supraventricular= narrow QRS
| ventricular= wide QRS
248
Describe the association b/w P waves & QRS complexes for when a QRS originates from sinus, supraventricular, or ventricular
```
sinus= associated
supraventricular= may be associated or dissociated
ventricular= dissociated
```
249
Pos deflection goes towards what pole
pos pole
250
Neg deflection goes towards what pole
neg pole
251
Isoelectric describes what
electrical activity moving perpendicular to a lead
252
What does MEA stand for
mean electrical axis
253
What does MEA describe
average path of electrical activity during ventricular polarization
254
Normally, what direction do the ventricles depolarize
cranial-caudal & right-left
255
An abnormal path of depolarization indicates what
a side of the heart is diseased
256
A right axis shift is brought about by
RV enlargement or R bundle branch block
257
A left axis shift is brought about by
LV enlargement or L bundle branch block
258
Steps for finding MEA using the largest QRS method
1) circle QRS in all 6 leads
2) compare QRS's to find the one w/ the largest deflection
3) determine if the QRS from the lead w/ the largest deflection is going towards the pos or neg pole
4) assign the degree that is associated w/ that lead & electrode
259
Normal MEA
Dogs: +40 to +100
Cats: 0 to +150
260
Molecule that links excitation (electrical events) & contraction (mechanical events) of the heart
calcium
261
Where is calcium stored
longitudinal tubules & terminal cisternae of the sarcoplasmic reticulum
262
Cell membrane of cardiomyocytes
sarcolemma
263
Endoplasmic reticulum of cardiomyocytes
sarcoplasmic reticulum
264
Cytoplasm of cardiomyocytes
sarcoplasm
265
Contractile unit of cardiomyocytes
sarcomere
266
During excitation-contraction coupling, how does Ca enter the cell sarcoplasm
through voltage-gated long acting Ca channels during phase II of ventricular (fast response) action potential
267
During excitation-contraction coupling, what does the small influx of Ca into the cell sarcoplasm trigger
Ca release from the sarcoplasmic reticulum by binding to the calcium release receptor
268
What is the name of the calcium release receptor
ryanodine receptor
269
During excitation-contraction coupling, what does calcium bind to & what effect does this have on the contractile proteins
Ca binds to troponin C in the sarcoplasm
| troponin complex undergoes a morphologic change that pulls tropomyosin away to expose the myosin binding site on actin
270
After the myosin binding site is exposed on actin, what happens
myosin binds to actin
| myosin releases a phosphate, creating a power stroke that results in myocardial contraction
271
During excitation-contraction coupling, for ventricular relaxation to occur, what has to happen
Ca must be removed from the sarcolemma
272
How is Ca removed from the sarcolemma
re-sequestration of Ca into the sarcoplasmic reticulum by the sarco(endo)plasmic reticulum Ca ATPase & its gatekeeper phospholamban
elimination of Ca from the cell by a Na-Ca exchanger & Ca-ATPase pump
273
What must happen for phospholamban to open the gate for resequestration
must be phosphorylated
274
What are the effects of autonomic tone during systole on contractility of the heart
sympathetic stimulation-> increases contractility
| parasympathetic stimulation-> decreases contractility
275
Drugs that increase/decrease contractility of the heart are called what
increase contractility-> positive isotropes
| decrease contractility-> negative isotropes
276
What are the effects of autonomic tone during diastole on relaxation of the heart
sympathetic stimulation-> increases relaxation
| parasympathetic stimulation-> decreases relaxation
277
Drugs that increase/decrease relaxation of the heart are called what
increase relaxation-> positive lusitropes
| decrease relaxation-> negative lusitropes
278
What happens during mechanical systole
ventricles contract
279
What happens during mechanical diastole
ventricles relax
280
What is rule #6 of the heart
blood pressure is the product of cardiac output & vascular resistance
281
Two phases of systole
isovolumic contraction & ejection
282
Position of valves during isovolumic contraction
atrioventricular & semiulnar are closed
283
Chambers contracting/relaxing during isovolumic contraction
atria relaxing
| ventricles contracting
284
Blood flow during isovolumic contraction
no blood flow since valves are closed
285
Position of valves during ejection
atrioventricular are closed
| semiulnar are open
286
Chambers contracting/relaxing during ejection
atria relaxing
| ventricles contracting
287
Blood flow during ejection
from ventricles to aorta/pulmonary trunk
| atria filling from vena cava
288
Describe S1 heart sound
lub
occurs at time of mitral valve closure
marks start of systole
289
Describe S2 heart sound
dub
occurs at time of aortic valve closure
marks end of systole
290
What occurs between S1 & S2
systole
291
Describe coronary circulation
provides oxygenated blood to cardiac muscle
292
Describe path of coronary vessels
branch from aorta, travel on the epicardial surface, & enter into the myocardium
293
Define isovolumic
volume of blood does not change b/c the valves are closed
294
Define diastasis
period of slower/ reduced filling
295
Four phases of diastole
isovolumic relaxation, early rapid filling, diastasis, & atrial contraction
296
Position of valves during isovolumic relaxation
atrioventricular & semiulnar are closed
297
Chambers contracting/relaxing during isovolumic relaxation
atria & ventricles relaxing
298
Blood flow during isovolumic relaxation
no blood flow b/c valves are closed
| but atria are filling w/ blood
299
Position of valves during early rapid filling
atrioventricular are open
| semiulnar are closed
300
Chambers contracting/relaxing during early rapid filling
atria & ventricle relaxed
301
Blood flow during early rapid filling
LA -> LV
| RA -> RV
302
Why do the ventricles fill quickly during early rapid filling
large pressure gradient b/w atria & ventricles
303
Position of valves during diastasis
atrioventricular are open
| semiulnar are closed
304
Chambers contracting/relaxing during diastasis
atria & ventricle relaxed
305
Blood flow during diastasis
LA -> LV
| RA -> RV
306
Why do the ventricles fill slowly during diastasis
pressure b/w atria & ventricles are almost the same
307
Position of valves during atrial contraction
atrioventricular are open
| semiulnar are closed
308
Chambers contracting/relaxing during atrial contraction
atria contracting
| ventricles relaxing
309
Blood flow during atrial contraction
LA -> LV
| RA -> RV
310
P wave corresponds w/ what phase of the cardiac cycle
atrial contraction during diastole
311
QRS complex corresponds w/ what phase of the cardiac cycle
isovolumic contraction during systole
312
T wave corresponds w/ what phase of the cardiac cycle
ejection during systole
313
Describe S3 heart sound
ah
| occurs at the time of early rapid filling (mid-diastole) in patients w/ dilated hearts
314
S3 sound is caused by what
oscillation of hemodynamic structures when a dilated ventricle w/ poor compliance fills
315
In small animals, an S3 gallop indicates what
dilated cardiomyopathy (DCM)
316
Describe S4 heart sound
bah
| occurs at the time of atrial contraction (late diastole) in patients w/ hypertrophied ventricles.
317
S4 sound is caused by what
oscillation of hemodynamic structures when the atrium tries to fill a hypertrophied ventricle w/ poor compliancee
318
In small animals, an S4 gallop indicates what
hypertrophic cardiomyopathy (HCM)
319
How do S3 & S4 sounds differ in large vs small animals
normal in large animals
| abnormal in small animals (indicate heart disease)
320
Determinants of stroke volume
preload, afterload, & contractility
321
Preload definition
volume filling the ventricle (~end diastolic volume)
322
Afterload definition
pressure needed to pump blood out of the ventricle (~arterial bp)
323
Contractility definition
strength of contraction (modulated by drugs or autonomic tone) for a given preload
324
Volume overload disease affects preload or afterload
preload
325
Volume overload disease results in concentric or eccentric hypertrophy
eccentric
326
Eccentric hypertrophy means what
normal wall thickness w/ a dilated chamber
327
What could increase preload
IV fluids & mitral/tricuspid valve regurgitation
328
What could decrease preload
dehydration & atrial fibrillation
329
Pressure overload disease affects preload or afterload
afterload
330
Pressure overload disease results in concentric or eccentric hypertrophy
concentric
331
Concentric hypertrophy means what
increased wall thickness w/ a small chamber
332
What would increase afterload
arterial hypertension, stenosis of aortic or pulmonary valves, & arterial vasoconstriction
333
What could decrease afterload
arterial vasodilator
334
Describe the Frank-Starling mechanism
when preload increases, the force of contraction is increased by increasing cTn-C affinity for Ca & increasing actin-myosin interaction when stretched
335
What is rule #3 of the heart
the heart's response to disease is predictable
336
What is the equation for tension of the heart
tension = [pressure (P)*radius (R)]/wall thickness (h)
337
Why does ventricular hypertrophy occur
to reduce ventricular wall tension (compensatory mechanism)
338
When does the mitral valve open
when LA P > LV P
339
When does the mitral valve close
when LA P < LV P
340
When does the aortic valve open
when LV P > Ao P
341
When does the aortic valve close
when LV P < Ao P
342
What wave/complex, electrical event, & mechanical event are associated w/ S4
P
atrial depolarization
atrial contraction
343
What wave/complex, electrical event, & mechanical event are associated w/ S1
QRS
ventricular depolarization
ventricle contraction
344
What wave/complex, electrical event, & mechanical event are associated w/ S2
T
ventricular repolarization
ventricle relaxation
345
What wave/complex, electrical event, & mechanical event are associated w/ S3
no associated wave/complex or electrical event
| early rapid filling
346
Fluid accumulation on the left side is associated w/ what
pulmonary edema
347
Fluid accumulation on the right side is associated w/ what
ascites, cavitary effusions (pleural, peritoneal, or pericardial), hepatomegaly (enlarged liver), peripheral edema
348
Synonym to forwards heart failure
low output
349
Synonym to backwards heart failure
congestive
350
Forwards heart failure results from the failure of the heart to do what
pump an adequate volume of blood to meet oxygen demands of tissues
351
Backwards heart failure results from the failure of the heart to do what
prevent fluid accumulation in tissues
352
Clinical signs of forwards heart failure
exercise intolerance, reduced systolic bp & pumping function, syncope (fainting), azotemia, pallor (pale gumbs), cyanosis (blue gums), hypokinetic pulse, pulmonary edema
353
Clinical signs for backwards heart failure-> specifically, left sided congestive heart failure
pulmonary edema
354
Clinical signs for backwards heart failure-> specifically, right sided congestive heart failure
subcutaneous brisket edema, moderate fluid accumulation in the abdomen (peritoneal effusion), other cavitary effusions (pleural or pericardial), hepatomegaly, ascites, peripheral edema
355
How does the RAAS system work to alter the BP equation to increase BP
Retains Na/H2O -> increases preload
Vasoconstriction -> increases preload & afterload
These factors increase SV, which increases CO, which subsequently increases BP
356
Function of the stethoscope bell
listening to low frequency sounds
| heart sounds & gallops
357
Function of the stethoscope diaphragm
listening to high frequency sounds
| murmurs
358
How does a flexible (tunable) diaphragm work
w/ gentle pressure, behaves like a bell
| w/ firm pressure, behaves like a diaphragm
359
How do you conduct a venous assessment
view jugular vein on a standing patient
360
Describe jugular pulsation
wave-like motion in the jugular vein that moves up the neck
361
Is a jugular pulsation normal
only in large animals at the lower 1/3rd of the neck
362
Describe jugular distension
jugular vein remains full
363
What causes jugular pulsation/distension
right heart pressure/volume overload
pericardial effusion
obstruction by a mass/thrombus
364
How do you conduct an arterial assessment for small animals
palpate femoral artery in femoral triangle where it is the largest
365
How do you conduct an arterial assessment for large animals
palpate facial artery on the medial aspect of the ramus of the mandible
366
What are some ex of what causes a hypokinetic pulse
subaortic stenosis
hypovolemia (dehydration/blood loss)
arrhythmias that result in less filling of the ventricle
367
What are some ex of what causes a hyperkinetic pulse
```
patent ductus arteriosus
severe aortic regurgitation
bradycardia
decreased vascular resistance (anemia)
high sympathetic tone
```
368
Define point of maximal intensity
location on the chest where the murmur is the loudest
369
SA node ECG correlate
none
370
Atrial myocardium ECG correlate
P wave
371
AV node ECG correlate
PQ interval
372
Bundle of His, left & right bundle branches, & Purkinje fibers ECG correlate
QRS interval
373
Ventricular myocardium ECG correlate
still QRS interval, there is not anything with the T wave
374
Why are sinus arrhythmias a normal finding in dogs
healthy dogs have a predominance of parasympathetic tone
375
Pathological vagal tone (increased parasympathetic tone) may be in response to what
disease in the GI, ocular, CNS, or respiratory system
376
Describe the changes of the heart rate during a sinus arrhythmia
cyclic changes vary w/ respiratory phase
inspiration = faster hr
expiration = slower hr
377
Explain why ventricular ectopic depolarization take longer than the sinus node depolarization
since ventricular ectopic depolarization starts in the ventricular myocardium, the depolarization events do not depolarize the atria or use the His-Purkinje “superhighway” system. As a result, the ventricular ectopic complexes depolarize the ventricular myocardium slowly by travelling from cell to cell
378
Describe the two different kinds of ventricular ectopic beats
ventricular premature beats: occur before the next expected sinus beat
ventricular escape beats: occur after the next expected sinus beat (aptly named because the patient escapes from certain death)
379
Why do the QRS complexes in Sinus rhythm with supraventricular premature complexes have a normal width
all supraventricular origin beats travel through the AV node & ventricles using the normal conducting system
380
What might cause a sinus rhythm with supraventricular premature complexes
atrial enlargement, inflammation/infection of the atrial myocardium, atrial masses, or pressure from masses in the thorax pressing on the myocardium
381
Name for P wave originating from a supraventricular premature complexes
P' waves (just means they have a different morphology than a normal P wave)
382
What is the main feature of 3rd degree AV block
dissociated P wave
383
During 3rd degree AV block, the atrial & ventricular depolarization events are unrelated to one another (termed “dissociated”). How does this appear on an ECG
two independent rhythms are superimposed over one another on the ECG
sinus/atrial rhythm is usually faster than the ventricular rhythm
384
What are the causes of AV block
disease of the AV node (e.g. fibrosis, neoplasia, inflammation/infection most notably Chagas disease or Lyme disease).
385
How is AV block fixed
pacemaker implant
386
What are causes of ventricular arrhythmias (think HEADS)
Heart disease (ventricular chamber enlargement, fibrosis, ischemia)
Electrolyte imbalances & Endocrine diseases (hyperthyroidism, pheochromocytoma)
Altered Autonomic tone (high sympathetic tone can worsen ventricular arrhythmias), intra-Abdominal disease
Drugs and toxicities (e.g digoxin toxicity)
S*&% surgeons see (gastric dilation and volvulus, splenic disease, sepsis, etc.)
387
What happens when the enlarged & fibrotic atria are too large to maintain the organized atrial depolarization wave
disorganized electrical activity (fibrillation) leads to f waves that reach the atrioventricular node at irregular time intervals. Sometimes the AV node is in the refractory period & cannot conduct the impulse. Sometimes it can conduct the impulses very quickly. Impulse is erratically passed to the ventricles in rapid, irregular fashion with no pattern to the irregularity. Following depolarization of the atrioventricular node, the impulse is propagated along the normal path of conduction to the ventricles.
388
What part of the conduction system goes through the cardiac skeleton
Bundle of His
