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139 Cards in this Set
- Front
- Back
As heart rate increases, what happens to contractilty and why
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contractility increases, b/c inc HR means more AP's, which means more Ca influx, and more contractions.
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Why must total systemic blood flow = cardiac output
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b/c once blood leaves ventricle (CO), the organ systems are in paralell
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Which blood vessels are under the highest pressure
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arteries (b/c they receive blood directly from the heart)
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Volume of Blood which moves through a vessel per unit of time
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Blood flow V/time
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Force per unit area of blood
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Blood pressure
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continuity equation
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Flow = velocity * area
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As you move distally away from the heart, what happens to cross sectional area of vessels and blodd velocity
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Since CA increases, velocity decreases (V=F/A)
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Why is blood flow in vessels the same
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because they are in series
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Where does Vmax occur
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at the center of the blood vessel
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Where is velocity O
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near the wall of the blood vessel
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What predicts whether flow will be laminar or turbulant
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Reynolds Number
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Laminar flow
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<2000
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Turbulant flow
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NR> 3000
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Reynolds Number
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R = ρ * v * D/η
n = viscosity D = diameter v = velocity of blood |
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what does Pouseuille's eqn describe? what is it?
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Blood Flow
F = ∏ *r^4*∆P/8Lη (pies r 4 p's) |
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what is the pressure difference in the poseuille eqn attributed to
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pressure diff produced by the contraction of the heart
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According to Poseuille eqn, if delta P is zero, what is flow
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zero
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simplified Poseuille eqn
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F = delta P/R
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Mean Blood Pressure
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Right atrial pressure is close to 0, so we can use pressure in the proximal aorta. MBP = CO * TPR
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Organs are in paralell to each other...
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Pressure is the same
Flow & Resistance are not = |
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Distensibility of a vessel, formula
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Compliance = Vol/P
Higher the compliance, the more volume it can hold |
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If compliance decreases (stiffer), what happens if volume increases
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an increase in volume will produce a larger increase in pressure than it did before
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How much higher is outside [Ca] than inside
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10,000 higher outside
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Steps of Cardiac Muscle Contraction
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1) triggered by electrical signals
2)volted L type channels open 3)Ca that entered with L channels, bind to RYR receptors in the SR 4) Ca released from both bind to troponin 5)Crossbridge cycle 6) relaxation (channels close and Ca is pumped back out) |
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Is relaxation of cardiac myocytes active or passive
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active, uses ATP
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How is Ca pumped back out of cell after contraction is done
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SERCA uses ATP to pump Ca back into SR
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What normally inhibits SERCA from pumping Ca out of cell and back into SR
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protein phospholamban
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what are 2 ways Ca can leave the cell after contraction
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Active transport with SERCA and the Na-Ca exchanger(NCX)that uses
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What are 2 ways to regulate force
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1) increase length
2) vary intracellular Ca via sympathetic NS |
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Starlings Law
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Length Tension relationship (increase length, increase force)
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Calcium concentration is a major determinant of the force of cardiac contraction
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Force increases to maximum as [Ca] increases until 100% of max force is reached
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How is intracellular [Ca] regulated
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by sympathetic NS and the NT norepinephrine
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where does cardiac depolarization initiate
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SA node
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what is the order of depolarization through the heart
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SA node
Atria AV node His-Purkinje Ventricle |
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Which part of the heart has the longest refractory period (conducts AP slowest)
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AV node
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Pacemaker of the heart
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SA node
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Parasympathetic (ACh) effects on phase 4 of the AP
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Phase 4 is depolarization
ACh increases the duration of phase 4 depolarization and reduces heart rate. |
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Sympathetic (norepinephrine) effects on phase 4 of the AP
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decreases the duration of phase 4 depolarization and increases heart rate
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Helps to ensure that the electrical activation of all portions of the ventricles are synchonrous
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His Purkinje (fastest conduction velocity in the heart)
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Occurs during the P wave
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Atrial depolarization
(right atrium at front of P wave and left atrium at hte end of P wave) |
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Occurs during the PR interval
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Depolarization of Atrial, AV node, Bundle of His, and purkinje
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PR Interval
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time it takes for the AP to spread from the artia to the AV node
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QRS Complex
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depolarization of ventricles
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flat line after T line
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all cells of hte heart are resting
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Abnormalaity shown by a shakey area before QRS - no P wave
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Atrial fibrillation (complete loss of synchronous of excitation adn resting phases)
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Abnormality shown by a EKG that looks like a scribbled line
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ventricular fibrilation (ventricle quivers and heart needs shocked to reset to threshold)
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cycle length formula
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Cycle Length = 60/HR
Cycle length lasts from one AP to the next |
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Systole
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contraction and ejection of blood
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Diastole
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resting and filling of blood
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shorter part of the cardiac cycle
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systole
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Why is blood flow through left and ride side equal
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they are in series with each other
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Side of the heart where pressure is higher
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left side is 4-5 time higher; so if there is a hole blood flows left to right
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Arrangement of systemic organs
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paralell: organs receive blood of identical composition
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The flow through systemic organs can be controlled independently of other organs because...
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all organs are in paralell
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Organs that have blood flow in excess of what they need for basic metabolism needs
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blood conditioning organs (skin, kidneys, lungs)
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they get blood solely for their metabolic needs (not excess)
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brain, heart and muscle (these dont tolerate blood fluctuations as well as blood conditioning organs)
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Cardiac output for adequate blood supply
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5L/min
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Flow equation
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F = Change in P/Resistance
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Only ways to change blood flow through an organ
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Pressure difference and vascular resistance(most common)
F = ΔP/R |
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Why does blood flow through organs
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b/c the pressure difference exists between the arteries supplying it and the veins draining it
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Since change in pressure is the same in organs , how is cardiac output distributed amoung organs
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based on their resistances to flow
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is blood flow through organs passive or active
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passive (occurs only because venous pressure is kept lower then arterial pressure)
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Ventricle pressure drops below aorta pressure, why and what happens then?
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Ventricle contracts, inc pressue. Blood will be forced from high P to low P, out of ventricle through aorta.
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Ventricle pressure falls below atrium pressure, why and what happens then?
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ventricle relaxes, pressure falls. The Av valve can open and the ventricle can fill with blood from atrium.
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What is the purpose of gap junctions in the heart
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AP can conduct from one cell to the next via gap junctions that conecct all heart cells as one unit
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initites the AP and contains slow conducting cells
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SA node - pacemaker cell
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Assures all cells contract at the same time
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purkinje fibers
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what happens if cardiac filling increases
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volume ejected also increases (Starlings law: inc EDV inc SV)
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sympathetic nerve fibers effects (norepinephrine)
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inc HR
inc AP conduction rate inc force of contraction inc rate of contraction/relax |
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parasympathetic nerve fibers effects (acetylcholine)
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interacts with muscarinic receptors to:
dec HR dec AP conduction velocity dec contraction of atrial cells |
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what is an increase in parasymp activity usually coupled with
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sympathetic activity
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Main ions in cardiac cell membrane potential
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Ca, Na (high outside)
K (high inside) |
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When mitral and aortic valves are closed
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Since volume is not changing, Isovolumic (IVC), pressure is rising though due to contraction
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SV equation
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SV = EDV - ESV
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EDV
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volume that fills the ventricle
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ESV
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Volume that is left after ejection
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Blood pressure eqn
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BP = CO * TPR
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Ejection fraction
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EF = SV/EDV
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final closing of valves is due to what
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small retrograde of blood flow
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S1 - what does it mark
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start of systole due to the closing of AV valve, which causes vibrations of cardiac structures
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S2 - what does it mark
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closure of aortic valve, end of systole
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ventricular preload
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(resting) end diastolic volume, because it is the resting length of hte cardiac muslce fibers
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Most important regulators of SA node
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para and sympa b/c they have immediate effects
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Tension - Muscle Length relationship
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As muslce length is increased, force created is increased
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Influences on Stroke Volume (5)
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1) HR
2) Preload - EDV 3) Afterload - total arterial pressure 4) Contractility 5) Diastolic ventricular compliance |
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Compliance
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C = ΔV/ΔP
low compliance = stiff heart |
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Force or pressure that the ventricle must overcome to eject the stroke volume
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afterload
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Relationship between HR and tme for ventricular filling
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If HR is increased(arrythimia), the ventricular filling can be reduced so much that SV, CO and blood pressure decrease
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which are more distensible, veins or arteries
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veins
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where is most blood of the body
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veins of hte systemic organs
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does gravity affect venous return
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yes, b/c CV system is composed of distensible vessels not rigid tubes
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Distention of veins due to gravity can cause:
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pooling of blood in the lebs, decrease n venous return to the heart
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What assist in venous return and overcome gravity
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closing of venous valves decreases weight of fluid column, contraction of muscle funcations as a pump
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Why does average venous return equal cardiac output
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b/c the CV system is a closed circuit
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what is the realtionship between CVP (central venous pressure) and CO (cardiac output)
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CO increases, CVP decreases
(as we increase CO, we are taking blood out of the veins) CVP increases, CO increases |
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what arises when a Starling curve and a vascualar fxn curve are plotted together?
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intersection point is an equillibrium point, the CVP
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what flows are equal at the intersection point of a cardiac adn vascular function curve
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total arterial flow, total venous flow, total system capillary flow
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List the arterial system in order of decreasing pressure
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heart pump, arteries, arterioles, capillaries, venules, veins
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Pulse pressure
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PP = Ps-Pd
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Mean Arterial(Blood) Pressure
Formula and definition |
pressure in the large arteries over a cardiac cycle
MBP = Pd + 1/3 (PP) |
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How is BP controlled
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Baroreceptor reflex
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Effects of the baroreceptor reflex
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the increases in arterial pressure lead to an immediate decrease in sympathetic nerve activity and a simultaneous increase in parasympathetic nerve activity (vice versa)
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What initiates the baroreceptor reflex
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pressure sensing by stretch sensitive baroreceptor nerve endings in the walls of arteries
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After initiating pressure sensitive receptors what happesn
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neural centers in the brain adjust autonomic nerve activty in response to info received from baroreceptors
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Components of the baroreceptor reflex
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1) sensory receptors (arterial baroreceptor)
2) Afferent pathways (to CNS) 3) CNS - sends signals to para or sympa |
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Where are the afferent pathways of hte baroreceptor reflex found
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walls of the aortic arch (aortic receptors)
carotid sinus (either side of the neck) |
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what does increased stretch cause
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increased AP generation by arterial baroreceptors (sent to parasympathetic in this case; GABA inhibits the sending of AP to the sympathetic)
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What can pass through microvessels, what cant
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can: small molecules and water (K, Na, Cl); lipids
cant: proteins |
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Why are microvessels efficient exchange sites
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thin walls and large surface area
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Name 4 mechanisms of blood flow
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neural, humoral, metabollic, myogenic
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Neural mechanism of blood flow
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sympathetic vasoconstrictor nerves release norepinephrine, which increases tone
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Humoral mechanism of blood flow
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histamine and bradykinin cause dilation of arterioles and constriction of venules
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Metabolic (local) blood flow control
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oxygen delivery to a tissue can be matched to oxygen consumption by altering the resistance of the arterioles, which in turn alters blood flow
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Myogenic mechanism of blood flow control
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when vascular smooth muscle is stretched, it contracts. So when arterial pressure is increased, the walls are stretched and then contract to maintain constant flow in teh face of increased pressure.
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Fluid Movement ini microvessels eqn
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FM = k[(Pc + ∏i)-(Pi + ∏p)]
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If Fluid movement in microvessel is 0
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no net flow
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Fluid movement is positive
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favors filtration
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Fluid movement is negative
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Favors absorption
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What is diffusion across microvessels calcualted by
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Ficks law
J = -P*A*(Cin-Cout) P is the permeability |
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What happens if large particles get into interstitial space
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filtration forces will exceed reabsorption (edema results)
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Function of plasma proteins (albumin)
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osmotic pressure rises b/c plasma has a higher protein concentration than does interstitial fluid
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why does the left coronary artery have higher flow
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left ventricle has more tissue mass
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Why is capillary density higher in the heart than skeletal muscle
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b/c cardiac cells are smaller in diameter (more room for capillaries)
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Why are myocardial capillaries more effective than skeletal muscle cells
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the distance hte molecules must diffuse is smaller
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Coronary Blood flow
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CBF = BP/CVR
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What determines coronary blood flow
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Blood pressure, CVR and mainly myocardial compression, metabolic control, mass
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metabolic control of coronary blood flow
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exercise and adenosine (product of metabolism that results in vasodilation and inc blood flow)
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Myocardial ischemia
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oxygen supply does not meet demand
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What does hypoxia increase the production of
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adenosine (vasodilator)
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what change does ischemia cause in the EKG
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change in ST segment
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Signs of ischemia
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change in ST segement and angina
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Treatment of ischemia
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to increase blood flow (thrombolytic agents, baloon angioplasty) or by decreasing myocardial energy consumption(dec HR, Dec work or inc efficiency)
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most imp vasodilator that controls cerebral vascular resistance
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CO2, adn inc in CO2 causes vasodilation of cerebral arteries, which results in inc blood flow to remove excess CO2
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Why dont many circulating vasoactive substances affect cerebral circulation
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b/c their large molecule size cant cross the blood brain barrier
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Cushing response
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-intercranial pressure inc
-compression of arteries - CO2 inc b/s it is not adeequately removed - medulla chemoreceptors respond and cause intense vasoconstriction (inc BP, dec HR) |
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2 types of exercise
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dynamic (aerobic)
static (anerobic) |
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why is it important to warm up
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to give CV and respiratory system to catch up to Oxygen demand (O2 debt)
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what is payback
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O2 consumption stays high until your body temp goes back down
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normal O2 consumption
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3.5 mL O2/min/kg
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