Cardiovascular Physiology - Exam 1 Flashcards
Atrial and ventricular syncytium can be attributed to each side having _ _
gap junctions
Which side of the heart has lower pressures?
right
-hence PE, clots, etc
What anatomical structure allows the atria to fully contract before the ventricles?
fibrous insulator
What helps keep the blood flow in the heart unidirectional?
valves
Cardiac muscle is comprised of _ and _ filaments
myosin and actin
-much lower resistance to conduction than cell membranes
RMP of cardiac muscle is _-_mV, and the action potential is _ mV
-85 to -95mV
105mV
-plateau lasts longer than skeletal musc ~0.2-0.3sec
Action potential of cardiac muscle results in _
depolarization
Ventricular Muscle Action Potential
-phases
0-Fast Na+ channels open, slow Ca++ channels open too
1-K+ channels open
2-Ca ++ channels open more
3- K+ channels open more
4-resting membrane potential
-K+ channels opening is pretty transient bc Ca++ channels open wider and offsets K+ leaving cell
-the latter K+ is vent repolarization occurring
-biggest diff from skeletal musc is in phase 2 with Ca++ channels opening wider
T/F Vent conduction AP is the same process as pacemaker cells
false
The _ refractory period does not allow the ventricle’s cardiac muscle to be re-excited again
absolute
-an AP is currently occurring
The _ refractory period can allow the ventricle’s cardiac muscle to be re-excited again
relative
The absolute refractory period of ventricular AP is - sec and _ sec in atria
0.25-0.3sec
0.15sec
On an EKG, the P wave represents conduction prior to _ _
atria contracting
On an EKG, the QRS complex represents conduction prior to _ _
ventricular depolarization
-this is SYSTOLE!
-this also is masking the atria repolarizing
On an EKG, the T wave represents electrical conduction of _ _
ventricular repolarization
-vent diastole
-vents stay contracted a few milliseconds after T wave
S1 heart sound is heard when the _ valves close
AV
-@ START of vent systole
During atrial systole, which valves are open?
Tricuspid and Mitral
During ventricular systole, which valves are open?
Pulmonic and Aortic
In the vent pressure/volume curve, isovolumetric relaxation occurs:
AFTER T wave
S1 heart sound is heard when the _ valves close
AV (tricuspid and mitral)
-@ START of vent systole
In the vent pressure/volume curve, isovolumetric contraction occurs:
DURING QRS complex
S2 heart sound is heard when the _ and _ valves close
aortic and pulmonic
-@ END of vent systole
On a vent pressure/volume curve, an “a” wave represents:
atrial cx
On a vent pressure/volume curve, a “c” wave represents:
vent cx (AV valves bulge)
On a vent pressure/volume curve, a “v” wave represents:
blood flowing back into atria
What does a dicrotic notch(incisura) represent?
sudden stop of back flow toward L vent
Aortic pressure must overcome _ pressure to allow blood forward
systemic (SVR)
_ _ accounts for 25% of filling in the ventricle during diastole
atrial systole
-“atrial kick”
Normal Values
End diastolic volume (EDV)
120mL
-max volume at end-diastole
-directly proportional to SV and CVP
-higher CVP increases EDV which increases SV ; (good; more volume on the receiving end, so SV is more forceful and more blood is readily replenishing chambers)
Normal Values
End systolic volume (ESV)
50mL
-directly proportional to afterload (SVR) and INversely proportional to SV
-increased SVR increases ESV which decreases SV ; (heart is pushing against too strong of a force and it’s leaving volume behind and making the stroke weaker)
Normal values
Ejection volume (SV)
SV= EDV - ESV
~70mL
Normal values
Ejection fraction
EF= SV / EDV
normally ~60%
EDV-ESV =
SV
_ is the total volume of blood going thru the heart in 1 min
CO
If HR increases, SV will _
decrease
-helps maintain CO, compensatory
Normal values
CO
~5L/min
Chordae tendinae are attached to which valves?
AV
Resting cardiac muscle stretch is _ than skeletal muscle
less
T/F Afterload should be > LV pressure
false
_, or venous return, is important to the Frank-Starling curve because it causes the optimal stretch for maximum contraction.
preload/CVP
Preload is synonymous with _ and _ _ _
CVP and end diastolic pressure (EDP)
T/F High afterload is from HTN coming from the heart
false,
this is systemic~SVR
CO will only increase when HR is elevated if _ also increases
SV
Sympathetic activity would _ CO
increase
-increased HR and contractility
Vagal fibers mainly go to the _
atria
PNS stimulation would cause CO to _
decrease
-slows HR and slightly decreases SV
During a normal cardiac cycle, the impulse is delayed in the _ _
AV bundle
-lets atria fully contract
Which structure brings the cardiac impulse into the ventricular area?
AV bundle
Which structure brings the cardiac impulse to each part of the ventricles?
R and L Purkinje bundles
Normal rate of discharge
-sinus node
70-80bpm
Normal rate of discharge
-AV node
40-60bpm
Normal rate of discharge
-purkinje fibers
15-40bpm
-think about a heart block pt and how low their rates can be. Their conduction doesn’t work thru the SA and AV node so Purkinje takes over and old man Purkinje is slow
Valve areas
-aortic
2.5-3.5cm^2 -same as mitral!
crit=0.7cm^2
Valve areas
-pulmonic
4-6cm^2
Valve areas
-mitral
2.5-3.5cm^2-same as aortic
crit=<1cm^2
Valve areas
-tricuspid
8-10cm^2
Normal chamber pressures
-RA
0-6mmHg
very similar to CVP…
Normal chamber pressures
-RV
15-30 Systole
0-6mmHg Diastole
“Quarter over a nickel”
Normal chamber pressures
-LA
6-12mmHg
Normal chamber pressures
-LV
100-140mmHg Systole
6-12mmHg Diastole
LV works hard and doesn’t like to relax
Normal chamber pressures
aorta
100-140 mmHg Systole
60-80mmHg Diastole
kinda like a normal BP….
Normal chamber pressures
PA
15-30 mmHg Systole
6-12mmHg Diastole
“A quarter over a dime”
Normal PR interval
0.16sec
Normal QT interval
0.4sec
If alterations in the _ _ pump occur, could change EKG
Na/K+ ATPase pump
-I’m looking at you, Digoxin (rate control, inc contractility)
T/F No potential is recorded when vent muscle is either depolarized or repolarized
true
T/F QRS complex has positive deflections only
false, has both
-deflection depends on which lead you are looking at
Lead II and _ have opposite QRS deflections
V2
HR counting methods
-high
if 2 R-R waves are seperated by one box =300bpm
if 2 boxes = 150bpm, etc.
HR counting methods
-low
count R waves in 6 sec, x by 10
HR counting methods
-irregular/high
if strip is 10 sec, count R waves and x 6
if strip is not 10sec, count how many R waves in 6 sec and x10
T/F Repolarization of atria occurs rapidly follows depolarization and occurs during PT segment
true
T/F Depolarization of vents = QRS and repolarization is T wave
true
When a depolarization wave spreads towards the electrode, the deflection will be _ and when if depolarizes away from the electrode it will be _
positive
negative
-when current flows obliquely towards the lead it will deflect up a little less (occurs with bipolar impulses)
The cardiac cycle is coordination of 5 things:
-electrical changes
-ions
-pressure changes in LA, LV, and aorta
-ventricular volume changes
-cardiac valves
Which lead is best to look at for ischemia?
II
12 lead ekg
-3 bipolar limb leads
I, II, and III
12 lead
-3 augmented voltage leads
aVR, aVL, aVF
12 lead
-precordial leads
V1-V6
Frank Starling mechanism
-heart will pump blood that comes to it without damming veins TO A CERTAIN POINT…
-extra stretch on cardiac myocytes makes actin and myosin interdigitate to more optimal degree of force generation
(actin and myosin adjust to accommodate stretch to allow for forceful contraction)
-think about yourself (volume) jumping on a trampoline (contractility). If your trampoline is a perfect size and is working well, you can get a good bounce off it. Your older brother joins and you can bounce higher on it bc he’s bigger (adding more volume to same system).
Systolic issue: At a certain point, too many people (too much volume) on the trampoline will break it and you wear it out and you all can’t bounce as high.
Diastolic issue: Similarly, if you have a small trampoline or if it’s too stiff (less contractility) you won’t bounce as well either
ABV
-premies
95mL/kg
ABV
-full term neonate
85mL/kg
ABV
-infants
80mL/kg
ABV
-men
75mL/kg
ABV
-women
65mL/kg
Pulse pressure is _ - _ and normal value is _mmHg
SBP - DBP
40mmHg
Factors affecting pulse pressure
-SV
Direct relationship
increased SV = increased PP
decreased SV = decreased PP
Factors affecting pulse pressure
-arterial compliance
inverse relationship
higher compliance = lower PP
lower compliance = higher PP
Factors affecting pulse pressure
-arteriosclerosis
decreases compliance = increases PP
Factors affecting pulse pressure
-PDA
-low diastolic and high systolic pressures = net INCREASE in PP
Factors affecting pulse pressure
-aortic regurg
backflow causes low diastolic and high systolic pressures = INCREASE in PP
Factors affecting pulse pressure
-aortic stenosis
low BF thru aortic valve causing low systolic pressure = decreased PP
RAP correlates with which hemodynamic measurement?
CVP
Normal value
CVP
0mmHg
-can be as high as 20-30mmHg
Factors that increase RAP/CVP
-increased blood volume
-increased venous tone
-dilation of arterioles
-decreased cardiac function
Increased SNS activity would _ CVP
increase
Increased CVP can be useful to increase _ but detrimental if too high and cause _ edema
SV
peripheral
Local blood flow in the heart is controlled via _
autoregulation
-via catecholamines and hyperemia from increased tissue demand
Resistance equation
R= change in P (pressure difference in 2 points in vessel) mmHg / Q (mL/min-flow)
