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77 Cards in this Set
- Front
- Back
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functions of cardiovascular system
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* provide essential nutrients to tissues & remove wastes
* hormone transport * thermoregulation |
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contain largest % of blood
low pressure system |
veins
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Right heart pumps into ___________
Left heart pumps into ___________ |
R - pulmonary circulation
L - systemic circulation (more muscular) |
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heart valves function to ensure
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one-way blood flow
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blood flow to an organ system can be altered by:
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* changes in arteriolar tone (resistance)
* changes in CO |
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Artery composition to function with high pressure blood flow - allow for expanding and recoil to reduce oscillations
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* Thick walled
* elastic tissue * smooth muscle * CT |
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Arterioles composition to provide highest resistance
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* HIGHER PROPORTION OF SMOOTH MUSCLE
* elastic tissue * CT |
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Arterioles in splanchnic & skin circulation contain what receptors?
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alpha1 that are stimulated by norepinephrine from SANS
vasoconstriction |
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Arterioles in skeletal muscle contain what receptors?
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Beta2 stimulated by epinephrine by SANS
vasodilation |
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Perfusion of the capillaries is based on...
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The metabolic needs of surrounding tissue
this is not constant |
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These can pass directly through capillary endothelial cells
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lipid-soluble substances
O2 and CO2 |
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These pass between or through pores (fenestrations) running through capillary endothelial cells
Can also pass membrane via specific transporters |
Water-soluble substances
- determined by the degree of dilation or constriction of arterioles or precapillary sphinctors |
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venules and vein composition to be compliant and able to distend
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* elastic
* smooth muscle * CT * IN SMALLER PORTIONS * valves |
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smooth muscle in the walls of the veins contain these receptors for?
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Alpha1
SANS - norepinephrine venoconstriction |
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the greatest cross-sectional area is within the ________ system
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capillary
reduces blood flow to increase exchange |
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equation for velocity of blood flow
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V = Q/A
Q is constant for all blood vessels in a system |
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velocity of blood flow is greatest in ____
slowest in ______ |
aorta
capillaries |
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Blood flow equation
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Q = (P2 - P1) / R
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TPR equation by rearranging flow equation
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TPR = (Paorta - Pvena cava) / CO
most TPR is result of the arterioles |
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Magnitude of blood flow is proportional to ________
Direction of blood flow is determined by the _______ |
Magnitude - pressure difference
Direction - pressure gradient |
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equation for resistance in regard to diameter and viscosity
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R = 8nl/pir^4
n - blood viscosity l - blood vessel length |
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A SERIES of resistances illustrates blood flow ...
and equation |
through a system
R = R1 + R2 + R3 .... |
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In a series of resistances, blood flow remains constant through the vessels, but ____________ decreases
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blood pressure
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Where is the greatest decrease in BP in a series of resistances?
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arterioles - due to resistance being highest
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PARALLEL resistances illustrate ....
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arterial distribution of blood flow
- resistances from each system |
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Total resistance in a parallel system is what compared to the individual resistances?
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total resistance in a parallel system is less than any individual resistance
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how does adding a resistance circuit affect total resistance?
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adding a resistance to parallel DECREASES total resistance
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how does increasing an individual resistance affect the total resistance?
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INCREASES total resistance
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Laminar blood flow has _______ velocities; and shear force break up RBC aggregates at vessel wall
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parabolic
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turbulent blood flow is made up of streams that mix radially and axially causing loss of energy; where more pressure is need to drive blood flow
Where is this seen? |
* Valves - normal
* Thrombus * Anemia - low viscosity and increased velocity * heard as murmurs |
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volume of blood a vessel holds at a given pressure
equation |
compliance
C = V/P |
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low value of oscillating arterial pressure
occurs during left ventricular relaxation |
diastolic pressure
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highest arterial pressure
occurs during left ventricular contraction |
systolic pressure
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what is the pulse pressure?
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PP = SP - DP
directly proportional to stroke volume fraction of the blood pushed into aorta |
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what is Mean Arterial Pressure?
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DP + 1/3PP
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dip in pressure when aortic valve closes
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dicotic notch
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what drives blood flow?
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blood pressure
differences in mean arterial pressure |
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where are the highest pulsations in the pressure profile of systemic circulation?
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large arteries
-elastic recoil prevents loss of energy and maintains pressure |
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where does the largest pressure drop occur in the pressure profile of systemic circulation
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in arterioles due to largest increase in resistance
-pressure drops continue |
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how are systolic, diastolic, mean and pulse pressures altered in arteriosclerosis?
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decreased blood vessel diameter
decreased compliance increased systolic, mean, and pulse pressures |
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how are SP, DP, MAP, and PP altered in aortic stenosis?
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narrowing of aortic valve
decreased stroke volume decreased SP, MAP, and PP |
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These rapidly conduct AP and are capable of automaticity
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conducting cells
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majority of atrial and ventricular muscle cells made of these
AP here cause contraction and force |
contractile cell
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Pathway of conduction
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* SA node
* atrial internodal tracts * AV node * Bundle of His * bundle branches * Purkinje fibers |
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Criteria for normal sinus rhythm:
(3) |
1. SA origination
2. 60-100 impulses/min 3. myocardial activation in sequence and timing |
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why are SA and AV nodes automatic?
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unstable resting potential which slowly depolarizes these cells to threshold
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shortest duration of AP occurs where?
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SA and AV nodes
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Describe SA and AV node AP
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4. Na+ into cells, funny current, pacemaker potential
0. strong depolarization (upstroke) Ca enters (t-type) which open when threshold is met 3. repolarization - K rushes out |
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what determines the heart rate?
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depolarization (phase 4) rate
strength of current |
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longest duration of AP occur where?
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ventricular cells - 250 ms
Purkinje fibers 300 ms |
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Phases of ventricular AP
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0. strong upstroke - Na into cell via fast VNa
1. initial repolarization - Na inactivate and K leaves cell 2. plateau - Ca influx (L-type) and K out. Ca leaves SR - contraction 3. repolarization - L-type Ca channels close and K efflux 4. stable resting potential |
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which myocytes act as the cardiac pacemakers?
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fastest phase 4 depolarization
SA node AV node Bundle of His Purkinje fibers |
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when do multiple pacemakers occur?
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if pacemakers are firing but the conduction pathway is blocked such that overdrive suppression does not occur
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conduction velocity through myocardium is determined by what?
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size of the upstroke current
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where is the slowest AP conduction?
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AV node to allow pause between atrial and venticular contraction to fill ventricles with blood
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where is the fastest AP conduction?
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His-Purkinje to stimulate entire ventricular muscle so that contraction of individual areas is nearly simultaneous
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why is there no AP during absolute RP?
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Na channels are inactivated
phase 0-3 |
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why is there no AP during effective RP?
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cannot start if conducted from adjacent site
can start if it generates AP on own |
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why is there no AP during relative RP
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requires greater AP - greater current/upstroke
during phase 3 |
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How do catecholamines effect SA node?
How do catecholamines effect AV node? |
SA - Beta1 - increase HR by increasing funny current
AV - increase conduction velocity, increase upstroke phase |
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How does Ach effect SA node?
How does Ach effect AV node? |
SA - M2- decreases HR by decreasing funny current and lengthening phase 4 depolarization
AV - decreases conduction velocity of AP by increasing pause between A and V contraction, decreases upstroke phase |
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P wave
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atrial depolarization
- length correlates with conduction time through atria |
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PR interval
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time it takes AP to travel from SA to AV node
- onset of P wave to QRS - flat portion is AV node conduction |
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QRS interval
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ventricular depolarization
-atrial repolarization buried in |
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QT interval
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mechanical contraction of ventricles
- onset of QRS to beginning of T wave |
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ST segment
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plateau phase of ventricular AP
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T wave
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ventricular repolarization
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An abnormal heart rhythm or arrhythmia, may be due to .... (4)
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1. abnormal rhythmicity of SA node
2. ectopic pacemaker 3. blocks in the normal impulse conduction pathway 4. abnormal impulse conduction pathways |
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causes of tachycardia (>100 beats/min)
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- increased body temp
- SANS - weakened heart muscle - can be normal |
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causes of bradycardia (<60 beats/min)
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- normal in athletes
- aging - HTN - damage to heart muscle |
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what happens in an AV block?
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impulses from atria may not reach the ventricles
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1st degree block:
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delayed conduction through AV node
- longer PR interval -> .2 sec |
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2nd degree block:
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- even longer PR interval
> .25 sec - occasional impulse block - more P than QRS intervals |
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3rd degree block:
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complete impulse block
- slower pacemaker working - P waves dissociated form QRS complex -fanting |
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most serious arrhythmia?
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ventricular fibrillation
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characteristics of ventricular fibrillation
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1. chain reaction of increasing circus movements
2. small portions of V contract independently 3. no coordinated contraction |
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causes of ventricular fibrillation
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electrical shock
ischemia of muscle or conducting system see initial "coarse waves", low voltage, irregular waves |
