Final Exam Review Flashcards
What are the 2 pumps of the heart?
RV & LV
Right ventricle = ___ circulation
Pulmonary circulation
Left ventricle = ___ circulation
Systemic circulation
___ causes unidirectional flow in the heart
Valves
What part of the systemic circulation has the greatest resistance to blood flow?
Arterioles
What is the primary function of the veins?
Capacitance function (has the greatest percentage of blood volume)
___ of the aorta and its branches during systole
Distention
___ of the large arteries with ___ of blood during ventricular relaxation during diastole
Elastic recoil of the large arteries; forward propulsion of blood
Blood flow is essentially ___ at the capillary level
Non-pulsatile
Velocity of blood flow is ___ related to the cross-sectional area of the vascular system
Inversely
I.e.: blood flow velocity is very slow in the capillaries (large cross-sectional area), which makes conditions ideal for exchange of diffusible substances
The blood flow to each tissue of the body is almost always precisely controlled in relation to ___
Tissue needs
Cardiac output is controlled mainly by the sum of ___
All the local tissue flows
Sympathetic innervation of the heart
T1-T4 “cardiac accelerators”
Distributed throughout the heart
Parasympathetic innervation of the heart originates in the ___
Medulla oblongata, vagus nerves
Parasympathetic provides much innervation to ___ and little innervation to ___
Much innervation to SA/AV nodes; little innervation to ventricles
What is the conduction system of the heart?
SA node —> AV node —> Bundle of His —> Bundle Branches (right and left)
Interatrial conduction pathways
SA to LA
Internodal conduction pathways
SA to AV
Where is the AV node located?
On the RIGHT side of the interatrial septum, near the ostium of the coronary sinus
Where does venous drainage of the heart occur?
Coronary sinus
What are the coronary arteries (identify 2 main ones and their branches)?
- Right coronary
- Left coronary—branches = left anterior descending (LAD); left circumflex; Ramos intermedius
What is right coronary dominance?
In 85% of individuals, the RCA supplies the posterior descending artery
Branch of LAD
Diagonal
Branch of left circumflex
Obtuse marginal
What is Ramus intermedius?
A tri-furcation of the left coronary artery; found in 37% of people
What is the normal resting membrane potential?
-90 mV
Which electrolyte is high INSIDE a cardiac cell?
K+
Which electrolyte is high OUTSIDE a cardiac cell?
Na+
What is the chemical driving force?
K+ moving down it’s concentration gradient (from inside of the cell to outside of the cell)
What is the electrical driving force?
As K+ leaves the cell, negativity increases on the inside of the cell membrane and electrostatically attracts K+; this electrostatic force prevents K+ from leaving cell
What is the major determinant of the resting membrane potential?
Potassium
What is the Nernst equation? Balance of ___ + ___ = ___
Balance of chemical driving force + electrical driving force = no further net movement of K+
Na+, K+ - ATPase pump pumps Na+/K+ in what ratio?
3 Na+ out : 2 K+ in
The Na+, K+ - ATPase pump is partially inhibited by ___
Digitalis (digoxin)
What 3 things result in the resting membrane potential?
- Potassium diffusion
- Sodium diffusion
- Na+, K+ - ATPase
What type of cells (3) have the FAST RESPONSE action potential?
Myocardial muscle cells—atrial, ventricular, and purkinje myocardial fibers
What are the (5) phases of the fast response action potential?
- Phase 0
- Phase 1
- Phase 2
- Phase 3
- Phase 4
Phase 0 fast response action potential
Depolarization—Na+ into cell
Phase 1 fast response action potential
Partial repolarization—small amount of K+ out
Phase 2 fast response action potential
Plateau—slow influx of Ca+ through L-type calcium channels; stimulates the C-ICR (explained on separate flash card); some K+ moves out of the cell to counterbalance the large influx of calcium into the cell
Phase 3 fast response action potential
Repolarization—K+ moves out of the cell
Phase 4 fast response action potential
Resting membrane potential—ionic concentrations restored
What does C-ICR stand for/what does it involve/what phase does it occur during?
Calcium-induced calcium release
The slow influx of Ca++ into the cell (during phase 2 of the fast response action potential) stimulates a large amount of calcium to be released from the sarcoplasmic reticulum
ERP =
Effective refractory period—cannot regenerate another action potential
RRP =
Relative refractory period—can begin to generate another action potential
During what phases does ERP occur in the fast response action potential?
Between phases 1-2
During what phase(s) does RRP occur in the fast response action potential?
Phase 3
The characteristics of the upstroke of the action potential (depolarization, phase 0) depend almost entirely on inward movement of ___
Na+
There is a small inward ___ current during phase 0 depolarization (important for contraction)
Ca++
What produces the plateau phase (phase 2)?
Slow inward movement of Ca++ through L-type calcium channels; counterbalanced by outward K+ currents
Ventricular contraction persists throughout the action potential, so the ___ produces a long action potential to ensure forceful contraction of substantial duration
Long plateau = long action potential
___ is mainly responsible for repolarization (phase 3)
Outward K+ current
What 3 pumps are involved in the restoration of ionic concentrations (resting membrane potential, phase 4)?
- Na+,K+-ATPase
- Na+-Ca++ exchanger—driven by gradients, not electrical
- ATP-driven Ca++ pump
What type of cells have SLOW response action potentials?
Pacemaker cells—SA node, AV node
What are the 4 phases of the SLOW response action potential?
- Phase 0
- Phase 2
- Phase 3
- Phase 4
What phase is absent in the SLOW response action potential?
Phase 1
Phase 0–slow response action potential
Depolarization—caused by Ca++ influx
Phase 2–slow response action potential
Very brief
Phase 3–slow response action potential
- Not separated clearly from phase 2
- K+ efflux causes repolarization
Phase 4–slow response action potential
Resting membrane potential
What does diastolic depolarization involve? — Inward ___ and ___; outward ___
Inward Na+ (not via typical Na+ channels) / Ca++
Outward K+ (opposes effects of other ions)
What phase of the slow response action potential does diastolic depolarization occur?
Phase 4
Slow depolarization of cell in phase ___ until activated in phase 0
4
Shorter diastolic depolarization = ___ pacer
FASTER
Longer diastolic depolarization = ___ pacer
SLOWER
What is the heart’s dominant pacemaker?
SA node
The ability of a focal area of the heart to generate pacemaking stimuli is known as ___
Automaticity
What term best describes this?—the SA node rate of firing is faster than any other node, so it will suppress other nodes from firing.
Overdrive suppression
At higher heart rates, more Na+ is extruded than K+ enters the cell. This tends to ___ the cells.
Hyperpolarize
Slow diastolic depolarization requires more time to reach ___
Threshold
What is the process by which an electrical stimulus triggers the release of calcium by the SR, initiating the mechanism of muscle contraction by sarcomere shortening?
Excitation-contraction coupling
What structure within the L-type calcium channels allows for communication between extra/intracellular?
T-tubules
What structure is responsible for calcium storage in the cell?
Sarcoplasmic reticulum
Cardiac action potentials are transmitted rapidly from cell-to-cell via ___
Gap junctions
The influx of Ca++ from the interstitial fluid during the action potential triggers the release of ___ from the ___; the free cytosolic ___ level increases; this is known as ___
Ca++ from the sarcoplasmic reticulum; the free cytosolic Ca++ level increases; this is known as calcium-induced calcium release (C-ICR)
Because the T-tubules are continuous with the extracellular fluid, ___ concentration of calcium becomes important for adequate heart contraction
Extracellular concentration of calcium
During muscle contraction—calcium binds to ___, which causes a conformational change in the ___ system
Calcium binds to troponin; causes a conformational change in the troponin-tropomyosin system
After calcium binds to troponin, this releases inhibition on ___, and the muscle ___ by the ___ mechanism
Releases inhibition on the actin and myosin interaction; the muscle shortens by the sliding filament mechanism
Sliding filament mechanism = ___ bind to ___, leading to ___ movement and reduction in ___, which causes muscle contraction
Myosin heads bind to actin, leading to cross-bridge movement and reduction in sarcomere length, which causes muscle contraction
Muscle contraction requires ___
ATP
ATP is required for muscle contraction to ___
Unbind myosin from actin—this allows the sarcomere to return to its original, relaxed length so another muscle contraction can occur
Normal PR interval
0.12-0.20 sec
Normal QRS
0.06-0.10 sec
AV node is situated on the ___ side of the interatrial septum, near the ostium of the ___
Right side of the interatrial septum; near ostium of the coronary sinus
How many phases are in the cardiac cycle?
Phases 1-7
What phases are in ventricular systole?
Phase 2
Phase 3
Phase 4
What phases are in ventricular diastole?
Phase 5
Phase 6
Phase 7
Phase 1
Phase 1
Atrial systole
Phase 2
Isovolumic contraction (all valves closed)
Phase 3
Rapid ejection (70% of ventricular volume is ejected)
Phase 4
Reduced ejection
Phase 5
Isovolumic relaxation (all valves closed)
Phase 6
Rapid ventricular filling—most LV filling occurs here
Phase 7
Diastasis (reduced ventricular filling)
Closure of what 2 valves generates the first audible heart sounds (S1)? What phase is this sound heard?
Tricuspid and mitral valves, close during phase 2–isovolumic contraction
___% of blood volume is ejected during phase 3, rapid ejection
70%
Closure of what valve generates the second audible heart sound (S2)? What phase is this sound heard?
Closure of the aortic valve, phase 5–isovolumic relaxation
All valves are closed during what 2 phases of the cardiac cycle?
Phase 2: isovolumic contraction
Phase 5: isovolumic relaxation
S1 =
Closure of tricuspid/mitral valves
S2 =
Closure of aortic valve
Normal healthy heart valves are only audible when ___
Closing
An S3 heart sound is ___ and is associated with ___
Abnormal, associated with heart failure
S4 may be heard during what phase? What does it sound like?
Phase 1–atrial systole, sounds like a gallop
Very common to hear all 4 heart sounds in a person with ___
Heart failure
Phase 1 (atrial systole) contributes to ___ filling but is not essential
Ventricular filling
Contributes more to ventricular filling in a stiff heart
Dicrotic notch = ___ closure, marks end of ___
Aortic valve closure, marks end of ventricular systole
Atrial kick—at normal HR, contributes to ___% of ventricular filling
10% — insignificant
Atrial kick—at higher heart rates (i.e.: during exercise), can contribute up to ___% of ventricular filling
40%
There can be a loss of atrial kick in patients with ___
Atrial fibrillation
What are the 5 CVP waves?
A wave C wave V wave X descent Y descent
A wave =
Right atrial contraction; right after P wave/atrial depolarization
C wave =
Right ventricular contraction; just after QRS complex/ventricular depolarization
V wave =
Passive filling of right atrium; just after T wave begins/ventricular repolarization
Normal CO = ___ L/min
6 L/min
Strenuous exercise can kick CO up to ___ x normal
4-7 x normal
Cardiac output is the ___
Quantity of blood pumped into the aorta each minute
How do you calculate cardiac output?
CO = HR x SV
How do you calculate SV?
SV = EDV - ESV
EDV = how much is in the ventricle when you start to squeeze
ESV = how much is left after the squeeze
Venous return is the quantity of blood flowing from ___ into the ___ each minute
Veins into the right atrium each minute
Cardiac output and venous return should match—T/F
True
What are the 4 major determinants of cardiac output?
- Preload
- Afterload
- Contractility
- Heart rate
What has more of an effect on cardiac output—change in heart rate or change in stroke volume?
Change in heart rate
If HR increases, you have (more/less) time to fill, so you will have (increased/decreased) SV/CO
If HR increases, you have less time to fill, so you will have decreased SV/CO
Bowditch (Treppe) Effect—an increase in heart rate will also cause ___ inotropy d/t an increase in intracellular ___ with a higher heart rate
Positive inotropy d/t an increase in intracellular calcium
The Bowditch (Treppe) Effect is also known as…
“Staircase” phenomenon
The increase in intracellular calcium causes more ___ per minute
Depolarizations
Why is there more calcium lingering in the cell—the ___ pump doesn’t function as well (Bowditch/Treppe Effect)?
The Na+/Ca++ exchange pump doesn’t function as well because the Na+/K+-ATPase pump can’t keep up with the influx of Na+
Increased stroke volume = ___ end diastolic volume, ___ end systolic volume
Increased end diastolic volume, decreased end systolic volume
___ preload = increased end diastolic volume (and vice versa)
Increased preload = increased end diastolic volume
___ contractility = decreased end systolic volume (and vice versa)
Increased contractility = decreased end systolic volume
___ afterload = decreased end systolic volume (and vice versa)
Decreased afterload = decreased end systolic volume
___ is the initial stretching of the cardiac myocytes prior to contraction
Preload
Preload is related to the ___ length at the end of diastole
Sarcomere
Can we measure sarcomere length (aka preload) directly?
No—so we must use indirect indices of preload
What are 4 indirect indices of preload?
- LVEDV
- LVEDP
- PCWP
- CVP
Determinants of preload—how do venous return/total blood volume affect preload?
Increase in venous return/total blood volume = increase in preload
Determinants of preload—how does respiration (i.e.: mechanical ventilation) affect preload?
Mechanical ventilation = positive pressure ventilation, which will decrease venous return d/t increased intrathoracic pressures, which in turn will decrease preload
Determinants of preload—how does filling time (heart rate) affect preload?
Higher heart rate = less time for ventricular filling, decreased preload
Determinants of preload—how does ventricular compliance affect preload?
Increased compliance = increased preload
Determinants of preload—how does inflow/outflow resistance affect preload?
Less resistance = increased preload
“The heart pumps the blood that is returned to it” refers to what?
Frank-Starling Mechanism
The Frank-Starling Mechanism plays an important role in balancing ___
The output of the 2 ventricles
Frank-Starling—increasing ___ and ___ leads to an increase in stroke volume
Increasing venous return and ventricular preload
What is afterload?
The “load” that the heart must eject blood against
Afterload is closely related to the ___ pressure
Aortic
LaPlace’s Law refers to ___
Wall stress
Increased ventricular pressure = ___ wall stress
Increased wall stress
Increased ventricular radius = ___ wall stress
Increased wall stress
Increased wall thickness = ___ wall stress
DECREASED wall stress
Thick, hypertrophied ventricle = less wall stress
Thinner wall = increased wall stress
Frank-Starling looks at changes in ___
Volume
___ (increased/decreased) aortic pressure increases afterload
Increased
___ (increased/decreased) systemic vascular resistance increases afterload
Increased
Aortic valve ___ increases afterload
Stenosis—can’t get blood out of stenotic or stiff aorticle valve
Ventricular dilation ___ afterload
Increases—ventricle itself increases in size, but the surrounding wall is thin
What is the inherent capacity of the myocardium to contract independently of changes in afterload or preload?
Contractility
What is an alternate name for contractility?
Inotropy
Increased inotropy = ___ stroke volume, ___ end-diastolic volume
Increased stroke volume, decreased end-diastolic volume
Decreased inotropy = ___ stroke volume, ___ end-diastolic volume
Decreased stroke volume, increased end-diastolic volume
Sympathetic activation/catecholamines ___ inotropy
Increase
Heart rate ___ inotropy
Increases
Afterload ___ inotropy
Increases
Systolic failure and parasympathetic activation ___ inotropy
DECREASE
Venous pooling may significantly ___ cardiac output
Reduce
Spontaneous respiration—___ (increased/decreased) intrathoracic pressure results in a ___ (increased/decreased) right atrial pressure, which ___ venous return
Decreased intrathoracic pressure results in a decreased right atrial pressure, which enhances venous return
Mechanical ventilation— ___ (increased/decreased) intrathoracic pressure during positive-pressure lung inflation causes ___ (increased/decreased) right atrial pressure, which ___ (increases/decreases) venous return
Increased intrathoracic pressure during positive-pressure lung inflation causes increased right atrial pressure, which decreases venous return
Valsalva maneuver causes a large ___ (increase/decrease) in intrathoracic pressure, which ___ venous return to the right atrium (to the point of passing out)
Large increase; impedes venous return
Heart rate has a ___ (positive/negative) effect on end-diastolic volume—the faster the heart is going, the ___ (more/less) filling time you have, so the ___ (more/less) volume you have
Heart rate has a negative effect; the less filling time; less volume
Increased afterload = ___ end-systolic volume
Increased (less is squeezed out)
Cardiac function curve = ____ curve
Frank-Starling curve
Increase in right atrial pressure = ___ in cardiac output
Increase
___ afterload = increased cardiac output
Decreased
___ inotropy = increased cardiac output
Increased
Mean circulatory filling pressure = pressure at ___
Zero flow (~ 7 mm Hg)
Changes in ___ and ___ change the hinge point (mean circulatory filling pressure)—shift it left or right
Blood volume and venous compliance
Changes in ___ = same mean circulatory filling pressure, but will shift curve up or down
Systemic vascular resistance
X-axis of venous return curve =
Right atrial pressure
Y-axis of venous return curve =
Cardiac output
Why is there a plateau in the venous return curve?
As the right atrial pressure starts to fall below 0, CO begins to level off because the vena cava collapses, thus limiting venous return to the heart
Increase in blood volume shifts venous return curve/mean circulatory filling pressure ___
Up and to the right
Increase in venous compliance shifts venous return curve/mean circulatory filling pressure ___
Down and to the left
Decrease in blood volume shifts venous return curve/mean circulatory filling pressure ___
Down and to the left
Decrease in venous compliance shifts venous return curve/mean circulatory filling pressure ___
Up and to the right
Increased systemic vascular resistance shifts the venous return curve ___; how does it affect mean circulatory filling pressure?
Down and to the left; same mean circulatory filling pressure
Decreased systemic vascular resistance shifts the venous return curve ___; how does it affect mean circulatory filling pressure?
Up and to the right; same mean circulatory filling pressure
Mean circulatory pressure is the pressure in the circulatory system when there is ___ flow, CO = ___
NO flow; CO = 0
Mean circulatory pressure reflects ___ and ___
- Total blood volume
- Compliance of the entire system
Cardiac output must equal venous return—T/F?
True!
The width of the pressure-volume loop represents ___
Stroke volume—the difference between EDV and ESV
How does afterload affect the pressure-volume loop? A change in afterload = a change in ___
Change in position on line of same slope
Increased afterload = lower point on line of same slope
Decreased afterload = higher point on line of same slope
How does contractility/inotropic state affect the pressure-volume loop? A change in contractility = a change in ___
Change in the slope of the line
Increased contractility = line with steeper slope
Decreased contractility = line with less slope
Change in slope of the ESPVR (end-systolic pressure volume relationship) = ___ issue
Contractility issue
Change in slope of the EDPVR (end-diastolic pressure volume relationship) = ___ issue
Compliance issue
X-axis of pressure volume loop =
LV volume (ml)
Y-axis of pressure volume loop =
LV pressure (mm Hg)
What is not a factor in pressure-volume loops?
Time
A pressure volume loop represents one ___
Cardiac cycle
Pressure volume loop moves in what direction?
Counterclockwise
If pressure volume loop gets wider, that means there is an increase in ___
Stroke volume/preload
Velocity is ___ related to cross-sectional area
INVERSELY
I.e.: capillaries
What is flow?
Volume per unit time
What is velocity?
Distance per unit time
What is the force exerted by the blood against any unit area of the vessel wall?
Blood pressure
One mm Hg of pressure = ___ cm of H2O pressure
1.36
Blood flow is driven by a ___ pressure
Perfusion pressure aka pressure gradient—normally represented by the difference between the arterial and venous pressures across the organ
Cerebral perfusion pressure (formula) =
CPP = MAP - CVP or ICP (whichever is higher)
Coronary perfusion pressure (formula) =
Coronary perfusion pressure = diastolic pressure - LVEDP
Poiseuille’s Law—flow is directly proportional to the ___
Pressure gradient
Poiseuille’s Law—flow varies directly as the ___ power of the radius
Fourth power
What is the most important factor for flow, according to Poiseuille’s Law?
RADIUS!
Poiseuille’s Law—doubling the radius of a tube causes a ___ increase in flow
16-fold (2^4)
Flow is inversely proportional to the ___ of the fluid
Viscosity
I.e.: polycythemia—blood is more viscous, results in less flow
Flow is inversely proportional to the ___ of the tube
Length
Longer tube = less flow
What is the impediment to blood flow in a vessel that cannot be measured by any direct means?
Resistance
What are the greatest resistance vessels in the circulation?
Arterioles
SVR formula
SVR = ( (MAP-CVP) / CO ) x 80
Because CVP is normally near 0 mm Hg, the calculation is sometimes simplified to:
SVR = MAP / CO
Normal SVR = ___ - ___
700-1600
Resistance in series is ___
Additive
RT = R1+ R2 + R3
Resistance in parallel has a ___ (increased/decreased) resistance by ___ (increasing/decreasing) the overall radius
Decreased resistance by increasing the overall radius
What is the measure of the tendency for turbulence to occur?
Reynold’s number
If R > 2,000…
Turbulence is likely to occur, even in a straight, smooth vessel!
Reynold’s number is directly proportional to what 3 things?
- Velocity (how fast it’s flowing)
- Density
- Diameter
Reynold’s number is INVERSELY proportional to ___
Viscosity
Viscosity is related to ___ flow
Laminar
Density is related to ___ flow
Turbulent
Relationship of hematocrit to blood viscosity—increased hematocrit = ___ (increased/decreased) viscosity, so ___ (more/less) flow
Increased hematocrit = increased viscosity, so less flow
Dicrotic notch = closure of ___
Aortic valve
Normal RA pressure
2-3 mm Hg
Normal RV pressure
25 mm Hg
Normal PA pressure
20-30 [systolic] / 8-12 [diastolic] (mean 25 mm Hg)
Normal PCWP
4-12 mm Hg
The best transducer placement is at a vertical height approximately 5 cm BELOW the left sternal border at the fourth intercostal space—T/F
True
Normal SV =
70 ml/min
Normal EF =
> 55%
Calculating cardiac output with thermodilution technique—cardiac output is ___ proportional to the area under the curve (AUC)
INVERSELY proportional
CO thermodilution technique—greater area under the curve, ___ (higher/lower) cardiac output
LOWER
Function of the ___ system is to distribute blood to the capillary systems in the body
Arterial system
The ___ regulate the distribution of flow of blood to the various capillary beds
Arterioles
Arterioles are AKA the “___” of the vascular system
Stopcocks
The ___ are the greatest resistance vessels
Arterioles
Pulse pressure =
Systolic BP - diastolic BP
How do you calculate MAP?
([2 * diastolic] + systolic ) / 3
Does MAP increase or decrease as blood is pumped out of LV and goes through the arteries»_space; arterioles»_space; capillaries»_space; venules?
MAP decreases
Where does pulse pressure disappear?
In the capillaries
Does the venous system contain a pulse pressure?
No
Pressures are very ___ (high/low) in the veins just before reentry into the heart
Low
The arterial system converts pulsatile blood flow to ___ blood flow
Continuous
Arterioles are the “___” of the circulation
“Stopcocks”
Veins are the ___ for the CV system
Reservoir
___% of blood volume may be stored in the veins
70%
Venous pump helps propel blood ___
Forward—enhances venous return
___ (increased/decreased) cardiac output increases CVP
Decreased CO (less blood leaving the heart)
___ (increase/decrease) in total blood volume increases CVP
Increase in total blood volume (increases preload)
Venous ___ (dilation/constriction) increases CVP
Venous constriction (more blood returns to the heart)
If you go from standing to supine position, does CVP increase or decrease?
CVP increases—blood pooled in legs returns to the heart
Arterial ___ (dilation/constriction) increases CVP
Dilation
How does respiratory activity increase CVP?
Increased respiratory rate promotes venous return (normal breathing is negative-pressure respiration…decreased intrathoracic pressure = more venous return)
Does exercise increase or decrease CVP?
Increases—promotes venous return to the heart
Arterioles contain ___ (thick/thin) smooth muscle
Thick smooth muscle
Arterioles give rise to ___, then to capillaries
Metarterioles
Metarterioles contain ___, which regulate flow into the capillaries
Precapillary sphincters
What regulates the opening/closing of the precapillary sphincters?
Local conditions in the tissues
Capillaries are ___-walled (thick/thin)
Thin-walled
Capillaries are the ___ vessels in the circulation
Smallest
Capillaries have the greatest ___ because they are so numerous
Cross-sectional area
Capillaries have the greatest ___ for exchange
Surface area
True capillaries are devoid of ___ and are incapable of ___
Devoid of smooth muscle and are incapable of active constriction
Capillary distribution varies from tissue to tissue—T/F
True
Why can capillaries withstand high intravascular pressures?
Because small capillaries have less wall stress—LaPlace’s law
What is the difference in pressure in cylindrical vessels vs. spherical vessels?
Cylindrical vessels have > pressure than spherical vessels—spherical vessel you divide by 2
How do O2, CO2, and lipid-soluble substances move through the capillary membrane?
Diffusion
How do H2O, electrolytes, and small molecules move through the capillary membrane?
Bulk flow
How do macromolecules move through the capillary membrane?
Via vesicles
How do ions and small molecules move through the capillary membrane?
Active transport
The permeability of the capillary endothelial membrane is the same in all body tissues—T/F
FALSE—permeability of the capillary endothelial membrane is NOT the same in all body tissues!!!
Body fluid compartments—ICF = ___%
40%
ECF = ___%
20%
ICF = ___ L
28 L
ECF = ___ L
14 L
ECF—interstitial fluid = ___ L
11 L
ECF—plasma = ___ L
3 L
Colloid goes into what body fluid compartment(s)?
Intravascular space (plasma)
0.9% NS/LR go into what body fluid compartment(s)?
ECF—both plasma and interstitial fluid compartments
0.9% NS and LR are ___ fluids
Isotonic
5% dextrose goes into what body fluid compartment(s)?
ICF and ECF—goes into ALL compartments
5% dextrose is what kind of fluid?
Isotonic until entering body; once it enters the body, the glucose gets metabolized and it becomes hypotonic
Capillary hydrostatic pressure, interstitial fluid hydrostatic pressure, and interstitial fluid osmotic pressure all move fluids ___
OUTWARD from the capillary
Plasma colloid osmotic pressure moves fluid ___
INTO the capillary
Lymphatics are lacking in ___ junctions
Tight junctions
Pumping by the lymphatic system is the basic cause of ___ pressure in the interstitial fluid space
Negative pressure
Plasma filtrate from the lymphatics is returned to the circulation by what 4 things?
- Tissue pressure
- Intermittent skeletal muscle activity
- Lymphatic vessel contraction
- System of one-way valves
Lymphatics return what 4 things to the circulation?
- Protein (albumin)
- Bacteria
- Fat
- Excess fluid
What are 4 things that cause edema?
- Lymphatic obstruction (can’t filter excess fluid out)
- Change in capillary permeability
- Reduction in plasma protein (reduced albumin)
- Increased capillary hydrostatic pressure (increased outflow on arterial end)
What are two ways peripheral blood flow is regulated?
- Extrinsic control
- Intrinsic control
Extrinsic control =
- Nervous system
- Humoral control
Intrinsic control =
Locally in the tissues
What is the main factor in acute control of local blood flow?
Tissue metabolic activity
Each tissue in the body is able to control its own local blood flow in proportion to ___
Its metabolic needs
What is this describing?—any intervention that results in an inadequate oxygen (nutrient) supply for the metabolic requirements of the tissues results in the formation of vasodilator substances which increase blood flow to the tissues
Metabolic mechanism
What specific condition contributes to metabolic mechanisms?
Hypoxia
What are 4 tissue metabolites/ions that contribute to metabolic mechanisms?
- K+
- CO2
- H+
- Lactic acid
Two types of hyperemia:
- Active hyperemia
- Reactive hyperemia
Which type of hyperemia is this?—when any tissue becomes highly active, the rate of blood flow through the tissue increases. The increase in local metabolism causes the cells to devour tissue fluid and nutrients extremely rapidly and also increases large amounts of vasodilator substances (i.e.: exercise).
Active hyperemia
Which type of hyperemia is this?—when blood supply is blocked to a tissue for a few seconds to as long as an hour or more and then is unblocked, blood flow through the tissue usually increases immediately 4-7 times normal for a few seconds to many hours (i.e.: tourniquet).
Reactive hyperemia
Within limits, the peak blood flow and the duration of the reactive hyperemia are proportional to the duration of the ___
Duration of the occlusion
Autoregulation is the intrinsic ability of an organ to maintain a constant ___ despite changes in ___
Constant blood flow despite changes in perfusion pressure
The myogenic mechanism proposes that the stretch of vascular smooth muscle causes activation of ___ channels
Calcium channels
Myogenic mechanism—higher pressure ___ (increases/decreases) flow but also increases ___; vessel contracts back down to maintain increased pressure and returns to original flow
Higher pressure increases flow but also increases vessel diameter
Myogenic mechanism—when the lumen of a blood vessel is suddenly expanded, the smooth muscles respond by ___ in order to restore the vessel diameter and resistance; the converse is also true
Contracting
What are 4 vasoactive substances released from the endothelium?
- Nitric oxide (NO)
- Prostacyclin
- Endothelin
- Endothelial-derived hyperpolarizing factor (EDHF)
Nitric oxide =
Vasodilator; endothelium-derived relaxing factor
Prostacyclin =
Vasodilator
Endothelin =
Vasoconstrictor
What is the primary site in the brain for regulating sympathetic and parasympathetic (vagal) outflow to the heart and blood vessels?
The medulla
Chronotropy =
Heart rate
Inotropy =
Contractility
Dromotropy =
Conduction velocity
Lusitropy =
Relaxation
Sympathetic stimulation comes from ___ nerves and ___ gland
Sympathetic nerves and adrenal gland
Sympathetic nerves release ___
Norepinephrine
Adrenal gland releases mostly ___ and lesser amount of ___
Mostly epinephrine (80%); lesser amount of norepinephrine (20%)
Which has a longer lasting sympathetic effect, sympathetic nerves or the adrenal gland?
Adrenal gland
Adrenergic receptors (3)
- Alpha
- Beta 1
- Beta 2
Alpha receptor =
Vasoconstriction
Beta 1 =
Increased heart rate and contractility
Beta 2 =
Vasodilation
Bronchodilation
What reflex is this?—increased arterial pressure causes parasympathetic response
Baroreceptor reflex
What reflex is this?—increase in volume causes sympathetic response; AKA atrial stretch receptor reflex
Bainbridge reflex
What reflex is this?—hypotension with bradycardia/parasympathetic response; also known as ventricular receptor reflex
Bezold-Jarisch reflex
What reflex is this?—high PCO2, low PO2, and high H+ can cause sympathetic response
Chemoreceptor reflex
What reflex is this?—hypertension with bradycardia
CNS ischemic response/Cushing response
What reflex is this?—water on the face causes vasoconstriction and slowing of HR
Diving reflex
Baroreceptor reflex is responsible for rapid adjustments of ___
Blood pressure—helps with postural changes in BP
Where are the baroreceptors located?
Carotid sinus and aortic arch
Bainbridge reflex—the atrial stretch receptors are ___ pressure receptors that respond to stretch; sense CV system ___
Low pressure; sense CV system volume
Where are the atrial stretch receptors located?
Vena cava—right atrial junction
Pulmonary vein—left atrial junction
Bainbridge reflex—infusion of volume causes an ___ in heart rate d/t activation of atrial stretch receptors, which causes medullary center activation of sympathetic output to the SA node
Increase in HR—a small portion of HR increase is d/t stretch of the SA node (not mediated by atrial stretch receptors)
Bainbridge reflex—degree and direction of heart rate change depends on the prevailing heart rate; slow baseline heart rate = ___ HR with infusion; high baseline heart rate = ___ HR with infusion
Slow baseline = increased HR with infusion
High baseline = decreased HR with infusion
D/t baroreceptor reflex
How does the Bainbridge reflex affect urine output and BP? (remember, these are not technically part of the Bainbridge reflex…these are just additional effects)
- Increased urine output
- Decreased BP
What elicits the Bezold-Jarisch reflex?
Strong contraction of an under filled ventricle
Bezold-Jarisch reflex plays a role in ___ regulation
Blood pressure regulation
Bezold-Jarisch reflex is possibly involved in what 2 things?
- Cardiac arrest during spinal anesthesia
- Vasovagal syncope
Where are the peripheral chemoreceptors located?
Aortic and carotid bodies
Remember—the baroreceptors are located in the carotid sinus and aortic arch (NOT the same thing)
The peripheral chemoreceptors in the aortic and carotid bodies are primarily concerned with regulation of ___
Respiration
___ (increased/decreased) arterial blood oxygen tension, ___ (increased/decreased) CO2, and/or ___ (increased/decreased) hydrogen ion concentration results in excitation of the vasomotor center
Decreased arterial blood oxygen tension, increased CO2, and increased H+ concentration results in excitation of the vasomotor center
The peripheral chemoreceptor reflex, aside from its role in the regulation of respiration, helps to return the blood pressure back to a normal level; it is usually not stimulated strongly until the arterial pressure falls below ___ mm Hg
Below 80 mm Hg
CNS ischemic response is the result of decreased blood flow to the vasomotor center in the ___
Medulla
CNS ischemic response—increased local concentration of ___ results in sympathetic stimulation in the medulla; results in ___ (increased/decreased) BP; very powerful activator of the sympathetic nervous system
Increased local concentration of CO2; results in increased BP
Cushing response is a special type of ___
CNS ischemic response
Cushing response is the result of increased ___
Intracranial pressure
Cushing response—increased ___ results in increased ___, until blood flows once again in the vessels of the brain
Increased ICP results in increased BP
What is Cushing’s triad?
- Increased ICP
- Increased BP (hypertension)
- Bradycardia
Diving reflex—cold water to face = ___
Reduced heart rate (which results in reduced O2 consumption)
Sinus arrhythmia—heart rate ___ with inspiration, ___ with expiration
Increases with inspiration (increased sympathetic activity with inspiration), slows with expiration (increased parasympathetic activity with expiration)
Renin-angiotensin-aldosterone system—renin is released from the ___
Kidney
Renin converts ___ to ___
Angiotensinogen to angiotensin I
Angiotensin converting enzyme (ACE) converts ___ to ___
Angiotensin I to angiotensin II
Angiotensin II causes release of aldosterone from the ___
Adrenal cortex
Aldosterone results in ___ and ___ retention; systemic ___ = ___ BP
Sodium and water retention; systemic vasoconstriction = increased BP
Vasopressin is AKA ___
Antidiuretic hormone
Vasopressin is released from the ___
Posterior pituitary
Vasopressin causes ___ and ___ BP
Vasoconstriction and increases BP
Vasopressin causes ___ of fluid at the kidney level and ___ blood volume
Reabsorption of fluid at the kidney level and increases blood volume
Atrial Natriuretic Peptide is released as a result of ___ distention; ___ stimulation; angiotensin ___; and ___
Atrial distention; sympathetic stimulation; angiotensin II; and endothelin
ANP ___ SVR; ___ BP; causes an ___ in urine output and sodium loss, leading to a ___ in blood volume
Decreases SVR; decreases BP; causes an increase in urine output and sodium loss, leading to a decrease in blood volume
What are the indirect effects of hypoxia (lesser degree)?
Sympathetic nervous system stimulation—increase HR, contractility, SVR
What are the direct effects of hypoxia? (if hypoxemia is very profound)
Decreased contractility, HR
What are indirect effects of hypercarbia?
SNS activation—increase HR, contractility, SVR
What are direct effects of hypercarbia?
Decreased contractility
Do the major epicardial arteries contribute to coronary vascular resistance?
NO—epicardial conductance vessels do NOT contribute significantly to coronary vascular resistance—only a small % of a resistance normally
What vessels contribute most to total coronary vascular resistance?
Intramyocardial vessels (Arterioles)
Is capillary density increased or decreased in the myocardium?
Increased!
What are the 3 major determinants of myocardial oxygen demand?
Heart rate
Contractility
Systolic wall tension
What are the 3 major determinants of myocardial oxygen supply?
Vascular resistance
Coronary blood flow
Oxygen-carrying capacity
Resting oxygen consumption of the heart is higher or lower relative to other organs in the body?
Higher
What is the pressure gradient that drives blood through the coronary circulation?
Coronary perfusion pressure
Formula for coronary perfusion pressure =
Diastolic BP - LVEDP (or PCWP)
What organ extracts oxygen to the greatest extent?
The heart
Why is the coronary sinus PO2 value so low (normally in range of 20-22 mm Hg; % sat = 32-38%)?
It is low because the heart extracts so much oxygen
Can the heart increase O2 extraction significantly?
No—can only minimally increase O2 extraction
Increases in O2 demand must be met by ___
Increased coronary blood flow
When does the majority of coronary blood flow occur? During systole or diastole?
During diastole in the left ventricle because ventricular myocytes collapse the coronary arterial supply vessels as they contract (extravascular compression); during diastole, the compressive forces are removed, and blood surges through the coronary musculature at peak rates
The idea that ventricular myocytes collapse the coronary arterial supply vessels as they contract is known as ___
Extravascular compression
Extravascular compressive forces are greater in the ___ layer and least near the ___ layer
Greater in the subendocardium (inner) layer; least near the subepicardial (outer) layer
Which layer of the heart is most susceptible to ischemia?
Subendocardium > midmyocardium > subepicardium
Changes in ___ affect myocardial oxygen consumption LESS than do changes in other factors
Preload (less effect than increased heart rate, inotropy, or afterload)
Coronary vessels have to be at least ___% occluded before interventional measures are taken (i.e.: balloon angioplasty, stent placement, arterial bypass surgery)
75%
What is the final intracellular ion disturbance that leads to impaired myocardial contraction and cell death?
Increased intracellular calcium
What best describes the following?—single or multiple brief periods of ischemia can be protective against a subsequent prolonged ischemic insult. The brief periods of ischemia appear to “precondition” myocardium against reversible or irreversible tissue injury, including stunning, infarction, and the development of malignant ventricular arrhythmias.
Ischemic preconditioning (IPC)
What agents have effects that mimic IPC?
Inhaled anesthetic agents—SEVO!
What channels play an important role in IPC?
K+ ATP channels
What are 3 major factors that affect flow across any valvular lesion?
- Valve area (more area = better flow; less area = less flow)
- Square root of the hydrostatic pressure gradient across the valve (higher pressure gradient = more flow and vice versa)
- The time duration of transvalvular flow (less time = less flow and vice versa)
Increasing any of these major factors increases transvalvular flow; conversely, decreasing any of these major factors decreases transvalvular flow
It is desirable to INCREASE transvalvular flow with ___ lesions
Stenotic lesions
It is undesirable to increase flow with ___ lesions
Regurgitant
Goal for regurgitant lesions is to ___ flow
Reduce flow
How can you reduce flow in regurgitant lesions?
Increase HR—there will be less time for regurgitant flow to occur across a valve
Goal for stenotic lesions is to ___ flow
Maximize flow
How can you maximize flow for stenotic lesions?
Slow HR down—you will have a longer period of time for flow to occur across that stenotic valve
The valve area in regurgitant or stenotic lesions can respond to changes in loading conditions (preload, afterload)?
Regurgitant lesions—the valve area will respond to changes in preload, afterload
The valve area in stenotic lesions is generally ___
Fixed—so they are NOT affected by changes in preload or afterload
What kind of murmur (systolic/diastolic) is heard with aortic stenosis?
Systolic murmur
What kind of murmur (systolic/diastolic) is heard with aortic regurgitation?
Diastolic murmur
What kind of murmur (systolic/diastolic) is heard with mitral stenosis?
Diastolic murmur
What kind of murmur (systolic/diastolic) is heard with mitral regurgitation?
Systolic murmur
Aortic stenosis usually has a long ___ period
Asymptomatic
Aortic stenosis presenting with angina (with no planned surgical intervention) typically has life span of ___
5 years
Aortic stenosis presenting with syncope (with no planned surgical intervention) typically has life span of ___
3 years
Aortic stenosis presenting with CHF (with no planned surgical intervention) typically has life span of ___
2 years
Aortic stenosis is considered an independent risk factor for perioperative ___
Perioperative morbidity
Aortic stenosis—want ___ preload
Increased preload—to fill non compliant LV
Aortic stenosis—HR goals
Want to avoid extremes of HR, maintain sinus rhythm
Aortic stenosis—SVR goals
Increased; AVOID hypotension
Aortic regurgitation is AKA ___
Aortic insufficiency
Aortic regurgitation has a long ___ period, during which the LV undergoes progressive ___ hypertrophy
Asymptomatic period; eccentric hypertrophy
What is eccentric hypertrophy?
LV chamber size is normal, but the LV wall is very thick—occurs with pressure overloading
Two main symptoms of aortic regurgitation:
- CHF (fatigue, exercise intolerance, ankle swelling)
- Angina
Patients with aortic regurgitation develop pressure or volume overloading?
VOLUME overloading
___ (increased/decreased) coronary perfusion pressure with aortic regurgitation because you have ___ (increased/decreased) diastolic pressure in the LV, ___ (increased/decreased) diastolic pressure in the aorta
Decreased coronary perfusion pressure
Increased diastolic pressure in the LV
Decreased diastolic pressure in the aorta
Aortic regurgitation—want ___ preload
Increased preload to maintain forward flow (avoid hypovolemia)
Aortic regurgitation—___ heart rate
Increased HR—reduces diastolic time and reduces regurgitant fraction
Aortic regurgitation—___ SVR
Decreased SVR—afterload reduction is helpful in improving forward flow
Mitral stenosis—maintain ___ heart rate
Decreased—slow to allow time for ventricular filling
Mitral stenosis—maintain ___ PVR because these patients have elevated ___ pressures
Decreased PVR d/t elevated PA pressures
Mitral stenosis—avoid what 3 things so we don’t further elevate PA pressures?
Avoid acidosis, hypercarbia, and hypoxemia
Mitral regurgitation—___ HR; leads to a ___ in LV volume, ___ forward flow, and ___ regurgitant fraction
Increased HR; leads to a decrease in LV volume, increased forward flow, and decreased regurgitant fraction
Mitral regurgitation—___ contractility tends to ___ forward flow and ___ regurgitant fraction by constricting mitral annulus
Increase contractility tends to increase forward flow and reduce regurgitant fraction
Mitral regurgitation—___ SVR
Decreased SVR—afterload reduction is helpful in improving forward flow
Hypertrophic cardiomyopathy goals—___ preload; ___ SVR; ___ HR; ___ inotropy
Increase preload (reduces gradient across LVOT); increase SVR (reduces gradient across LVOT); decrease HR (reduces oxygen demand of thickened myocardium); decrease inotropy (reduces gradient across LVOT)
