CARDIOVASCULAR Flashcards
Cardiac output from the eft side of the hear is the __________
systemic blood flow
Cardiac output from the right side of the hears is the ________________
pulmonary blood flow
Direction of blood flow
- lungs to the left atrium via the PULMONARY VEIN
- left atrium to the left ventricle through the MITRAL VALVE
- left ventricle to the aorta through the AORTIC VALVE
- from the aorta to the systemic arteries and the systemic tissues
- from tissues to the systemic veins and vena cava
- vena cava to the Right atrium
- RA to the RV through TRICUSPID VALVE
- RV to the pulmonary artery though PULMONIC VALVE
- pulmonary artery to the lungs for oxygenation
Deliver oxygenated blood to the tissues
Arteries
site of highest resistance in the cardiovascular system
arterioles
- arteriolar resistance is regulated by the ANS
________receptors are found on the arterioles of the skin, splanchnic, and renal circulations
alpha 1
____________ receptors are found on arterioles of skeletal muscle
B2 adrenergic
have te largest total cross sectional and surface area
Capillaries
Formed from merged capillaries
Venules
Under low pressure
contain the highest proporrtion of blood in the cardiovascular system
Veins
(the blood volume is called unstessed volume)
have alpha 1 adrenergic receptors
Velocity of blood flow can be expressed by this equation
v= Q/A
- v = velocity (cm/sec)
- Q = blood flow (ml/min)
- A = cross sectional area (cm2)
Velocity is directly proportional to _____________
blood flow
Velocity is inversely proportion to the ______
cross sectional area
Blood flow can be expressed by the these equations _______________
The quation for blood flow (or cardiac output) is analogous to ________
Ohm’s law
____________ equation gives factors that change the resistance of blood vessels
Poiseuille’s
Resistance is directly proportional to ____________
viscosity of blood
Resistance is directly proportional to _____________
length of vessel.
Resistance is inversely proportional to the _______________
fourth power of the vessel
____________ resistance is illustrated by the systemic circulation
Parallel
When an artery is added in parallel, the total resistance ______________
decreases
___________resistance is illustrated by the arrangement if blood vessels within a given organ
Series
straight line (streamedlined) flow
Laminar flow
predicts whether blood flow will be laminar or turbulent
Reynauld’s number
When reynauld’s number is increased, there is a greater tendency for _________
turbulence
Factors affecting Reynold’s number
Decreased viscosity
Increased velocity
consequence of the fact that the adjacent layers of blood travel at different velocities within a blood vessel
Shear
velocity of blood is __a___ at the wall and ___b____ at the center of the vessel
a= zero
b= highest
Shear is highest at the ___________
wall
Decribes the distensibility of blood vessels
inversely related to elastance or stiffness
Capacitance
Capacitance is expressed by this equation
Capacitance _________ proportional to volume
Directly
Capacitance ______proportional to pressure
inversely
Capacitance is much greater for (veins or arteries) ?
Veins
capacitane of the arteries ________with age
Decreases
As blood flows through the systemic circulation, pressure _____________ progressively because of the resistance
Decreases
Pressure is highest in the ____a_____ and lowest in the _____b______.
a= aorta
b = venae cavae
The largst decrease in pressure occurs across the ________
arterioles
Mean pressure in the aorta
100 mmHg
Mean pressure in the arterioles
50 mm Hg
Mean pressurein the capillaries
20 mm Hg
Mean pressure in the vena cava
4 mm Hg
pulsatile pressure
not constant during cardiac cycle
Arterial pressure
Highest arterial pressure during a cardic cycle
systolic pressure
Lowest arterial pressure during a cardiac cycle
Diastolic pressure
Difference between the systolic and diastolic pressures
Pulse pressure
The most important determinant of pulse pressure is ____________
Stroke volume
- as blood is ejected from the left ventricle into the arterial system, arterial pressure increases because of the relatively low capacitance of the arteries.
Is the average arterial pressure with respect to time
mean arterial pressure
Left atrial pressure is ________ than venous pressure
lower
Left atrial pressure is estmated by ______________
Pulmonary wedge pressure
ECG wave
Represents atrial depolarization
P wave
- does not include atrial repolarization
- buried in the QRS complex
interval from the beginning of the P wave to the beginning of the Q wave (initial depolarization of the ventricle)
PR interval
Depends on conduction velocity through the AV node.
PR interval
- if AV nodal conduction decreases, the PR interval increases
- decreased by stimulation of the sympathetic
- increased by stimulation of parasympathetic
represent depolarization of the ventricles
QRS complex
interval from th beginning of the Q wave to the end of the T wave
Representss the entire period of depolarization and repolarization of the ventricles
QT interval
is the segment from the end of S wave to the beginning of the T wave
Isoelectric
represents the period when the ventricles are deoplarized
ST segment
Represents ventricular repolarization
T wave
the resting membrane potential [cardiac] is determined by _____
conductance to potassium and approaches the K equilibrium
Inward current brings positive charge into the cell and ______the membrane potential
depolarize
Outward current takes positive out of the cell and ________ the membrane potential
hyperpolarizes
Ventricles, atria and the purkinje system have stable resting membrane potentials of about ______mV.
- 90 mV
- This value approaches the K equilibrium potential
Action potentials are of long duration, especially in Purkinje fibers, where they last ____________(msec)
300
the upstoke of the action potential
- caused by transient increase in Na conductance. this increase results in an inward Na current that depolarizes the membrane
Phase 0
is a brief period of initial repolarization
- Initial repolarization is caused by an outward, in part because of the movement of K ions (favored by both chemical and electrical and electrical gradients) out of the cell and in part because of a decrease in sodium conductance
Phase 1
the pateau of the action potential.
- caused by transient increase in calcium conductance, which results in an inward calcium current, and by an increase in K conductance.
- outward and inward currents are approximately equalm so the membrane potential is stable at the plateau level
Phase 2
Repolarization
- calcium conductance decreases
- K conductance increases
- large outward K current - > hyperpolarizes the membrane
Phase 3
resting membrane potential
- period during which inward and outward currents (Ik1) are equal adn the membrane potential potential approaches the K equilibrium potential
Phase 4
Normally the pace maker of the hear
has unstable resting membrane potential
Sinoatrial node
- Exhibits phase 4 depolarization or automaticiy
- The intrinsic rate of phase 4 depolarization (nd heart rate) is fastest in the SA node and slowest n the His-purkinje system
[SA node]
upstroke of athe action potential
- caused by an increase in calcium conductance
- inward calcum current
Phase 0
[SA node]
not present in the SA node action potential
Phase 1 and Phase 2
[SA node]
repolarization
- increase in K conductance.
- increase in outward K current that cuases repolarization of the membrane potential
Phase 3
[SA node]
- Slow depoalrization
- accounts for the pacemaker activity of the SA node (automaticity)
- inward Na current call If
Phase 4
If is turned on by _________ of the membrane potential during the preceding action potential
repolarization
upstoke of the action potential in the AV node is the result of an inward ______ current
Calcium
Reflects the time required for excitation to spread throughout cardiac tissue
Conduction velocity
- depends on the size of the inward current during the upstroke of the action potential.
- The larger the inward curent the higher the conduction velocity
Conduction velocity is fastest in the ___________
Purkinje system
Conduction velocity is slowest in the _________
AV nde
- allows time for ventricular filling before ventriular contraction.
Is the ability of ardiac cells to initiate action potentials in response to inward, depolarizing current.
Reflects the recovery of channels that carry the inward currents of the upstoke of the action potential.
Excitability
Changes in excitability are described by ____________
refractory periods
begins with the upstoke of the action potential and ends after the plateau
No action potential can be initiated
Absolute refractory period
Slightly longer than ARP
period during which a conducted action potential cannot be elicited
Effective refractory period
is the period immediately after the ARP when repolarization is almost complete
Period during which an action potential can be elicited, but more than the usual inward current is required
Relative refractory period
Produces changes in heart rate
Chronotropic effects
Produces changes in conduction velocity, primarily the AV node
Dromotropic
The SA node, atria and AV node have _____________ vagal innervation
pasarympathetic
The neurotransmitter is _________ which acts on the _______receptors in the SA node, AV node, and atria
Acetylcholine
Muscarinic receptors
The mechanism of the negative chronotropic effect is __________
Decreased If
- the inward Na current tht is responsible for phase 4 depolarization in the SA node
Autonomic effects on the heart and Blood Vessels
Mechanism of action of negative dromotropic effect
Decreases inward calcium current and increases outward K current
- Decreases conduction velocity through AV node
- Increases PR interval
_________ is the neurotransmitter acting at B1 receptors
Norepinephrine
Mechanism of action of positive chronotropic effects
Increased If, the inward sodium current that is responsible for phase 4 depolarization in the SA node
Increases heart rate
mechanism of action of positive dromotropic effect
increased inward calcium current
- increases conduction velocity through the AV node
Contractlie unit of the myocardial cell
Sarcomere
- runs Z line to Z line
- Similar to Skeletal muscle
Occur at the ends of the cells
maintain cell to cell cohesion
Interacalated discs
Present at the interacalted disks
low resistance paths that allow rapid electrical spread of action potential
gap junctions
accont for the observation that the hear behaves as an electrical syncytium
Gap junctions
Continuous with the cell membrane
invaginate the cells at the z lines and carry action potentials into the cell interior
form dyads with the sarcoplasmic reticulum
T tubules
T tubules are well developed in the ____a____ but poorly developed in the ____b_____
a = ventricle
b= atria
small diameter tubules in cross proximity to the contractile elements
Sarcoplasmic reticulum
site of storange and release of calcium for excitation-contraction coupling
Sarcoplasmic reticulum
Steps in excitation-contraction coupling
- AP spreads from cell membrane to T tubules
- During the plateau, Ca conductance is increase
- This ca entry triggers more calcium to be released (ryanodine)
- Intracellular calcium increases
- Calcium binds to troponin C and tropomyosin is moced out of the way, removin the inhibition of actin and myosin binding
- Actin and myosin bind
- relaxation occurs when calcium is reaccumulated by the SR
Intrinsic ability of the cardiac muscle to develop force at a given muscle length
also called inotropism
Contactibility
- related to the intracelleular calcium concentration
Contractibility is estimated by the _______
ejection faction
normal (o.55 /55%)
Factors that increase contractility
Increased heart rate
Sympathetic stmulation via B1 receptors
cardiac glycosides
Factors that decrease contractitlity
Parasympathetic atimulation (ACh) via muscarinic receptos
- decreases the force of contraction in the atria by decreasing the inward calcium current duint the plateau of the ardiac action potential
Describes the effect of ventricular muscle cell length on the force of contraction
Analogous to the relationship in skeletal muscle
Length-tension relationship
End diastolic volume
related to right atrial pressure
Preload
for the left ventricle is aortic pressure.
For the right ventricle, pulmonary artery pressure
Afterload
- Increases in aortic pressure cause an increase in afterload on the left ventricle
- increase in pulmonary artery pressure cause an increase in afterload on the right ventrile
Frank starling relationship and the effect of positive and inotropic agents
Determines the maximum number of cross bridges that can form between actin and myosin
Sarcomere lenght
- dtermines the maximum tension or force of contraction
Velocity of contraction ata fixd muscle length is maximal when_____
afterload is zero
Describes the increases in SV and cardiac output that occur in response to an increase in venous return or EDV
Frank starling relationship
Increases in EDV cause an _______ in ventricular fier length, which produces an increase in developed tension
Increase
Is the mechanism that matches cardiac output to venous return
Frank staling relationship
- The greater the venos return, the greater the cardiac output
Increase in contractily cause an _____ in cardiac output for any level of RA pressure or EDV
Increase
Constrcuted by combining systolic and diastolic pressure curves
Ventricular pressure-volume loops
- A single left ventricular cycle of contraction, ejection relaxation, and refililig can e visualized by combining the two curves into a pressure-volume loop
Steps in the ventricular-pressure loops
- isovolumetric contraction
- ventricular ejection
- isovolumetric relaxation
- ventricular filling
Isovolumetric contraction
- Point 1-2
- Cycle begins at the end of diastole at point 1
- The left ventrile is filled with blood from LA (140ml)
- End diastolic volume
- Ventricular pressure is low becausse the ventricular muscle is relaxed
- on excitation, the ventricle contracts and pressure increases.
- the mitral valve closes when the LV pressure is greater than the LA pressure
- no blood can be ejected from the ventricle
Ventricular ejection
- point 2-3
- Aortic valve open at point 2 whenpressure in the LV exceed pressure in the aorta
- Blood is ejected to the aorta
- ventricular volume decreases
- The volume that is ejected = stroke volume
- width of he pressure volume loop
- the volume remaining in theleft ventricle at point 3 is End systolic volume
Isovolumetric relaxation
- point 3-4
- at point 3, the ventricle relaxes
- When ventricular pressure decreases to less than aortic pressure = aortic valve closes
- ventricular volume is constant
- isovolumetric
- ventricular volume is constant
Ventricular filling
- Point 4-1
- once LV pressure decreases to less than aortic pressure
- mitral valve opens = filling of the ventricle begins
- ventricular volume increases to about 140 ml (EDV)
Changes in ventricular pressure volume loop
simultaneous plots of cardiac output and venous return as a function of right atrial pressure or end diastolic volume
Cardiac and vascular function curves
Depicts the Frank starling relationship for the ventricle
Shows the cardiac output is a function of EDV
The cardiac function (cardiac output) curve
Depicts the relationship between the blood flow through the vascular system (or venous return) and right atrial pressure
Vascular function (venous return) curve
the point at which the vascular function curve intersects the x axis
equals right atrial pressure when there is “no flow” in the cardiovascular system
Mean systemic pressure
Mean systemic pressure is inreaased by an _______ in boodv volume
Increase
mean systemic pressure is increased by ________ in venous capacitance
decrease
Slope of the venous return curve is determined by ______________
resistance of the arterioles
A clockwise rotation of the venous return curve indicates a ____________ in total peripheral resistance
decrease
A counterclockwise rotation of the venous return indicates an ______________ in TPR
increase
Effect of a positive inotropic agent on the cardiac function curve, cardiac outpu, and RA pressure
Inceases in blood volume or decrease in venous capacitance _________ the Mean systemic pressure
Increase
Decrease in blood volume or increase in venous capaciance _________ mean systemic pressure
Decrease
Increasing TRP causes a ______ in both cardiac output and venous return
decrease
Decreasing TPR causes an _________ in both cardiac output and venous return
Increase
The volume ejected from the ventricle on each beat
Stroke volume
SV = EDV -ESV
Formula for cardiac output
SV x HR
the fraction of the end diastolic volume ejected in each stroke volume
Relate to contractility
Ejection fraction
EF = SV/EDV
is the work the heart performs on each eat
equal to pressure x volume
Stroke work
(aortic pressure x stroke volume)
the primary energy source for stroke work
Fatty acids
Directly related to the amount of tension developed by the ventriles
Cardiac oxygen consumption
Fick Principle fir measuring cardiac output
Preceded by the P wave
Contributes to, but is not essential for ventricular filling
Atrial systole
The increase in atrial pressure (venous pressure) caused by the atrial systole is the ______ wave on venous pulse wave
a wave
In ventricular hypertrophy, filling of the ventricle by atrial systole causes the _______
4th heart sound
begins during the QRS complex
Isocolumetric ventricular contraction
ventricular pressure reaches its maximum value during __________
Rapid ventricular ejection
________ wave on venous pulse curve occurs because because of the bulging of tricuspid valve into the RA during right ventricular contraction
C wave
The onset of T wave, which represent repolarization of the ventricles, marks the end of both ventricular contraction and reapid ventricular ejection
Rapid ventricular ejection
Ejection of blood from the ventricles continues, but slower
Venricular pressure begins to decrease
Aortic pressure also decreases because of the runoff of blood from large arteries into smaller arteries
Reuced Ventricular ejection
Cardiac cycle
_____wave on venous pulse curve represents blood flow into the RA (rising phase of wave) and from RA into RV
V wave
Repolarization of the ventricles (end of T wave)
The AV valves remain closed during most of this phase
Isoviumetric ventricular relaxation
The blip in the aortic pressure tracing occurs after closure of the aortic valve and is called the_______
dicrotic notch or incisura
When ventricular pressure, becomes less than atrial pressure, the mital valcve opens
Rapid ventricular filling
Rapid flow of blood from the atria into the ventricles causes the _________
third heart sounds
The longest phase of the cardiac cycle
ventricular filling continues, but at a slower rate
The time required for diastasis and ventricular filling depends on heart rate
Reduced ventricular filling (diastasis)
The most important mechanisms for regulating arterial pressure a fast, neurally mediated _______a_____ and a slower, hormonally regulated __________b_______mechanism
a = baroreceptor
b = renin-angiotensin aldosterone mechanism
Includes fast, neural mechanisms
negative feedback system that is responsible for the minute to minute regulation of arterial blood pressure
baroreceptor reflex
______are stretch receptors located within the walls of the carotid sines near the bifurcation of the common carotid arteries
baroreceptors
Steps in the baroreceptor reflex
- A decrease in arterial pressure decreases stretch on the walls of the carotid sinus
- Decreased stretch decreases the firing rate of the carotid sinus nerve. [Herring’s nerve, cranial nerve], which carries information to the vasomotor center in the brain stem
- The set point for mean arterial pressure is the vasomotor center is about 100 mmHg.
- The responses of the vasomotor center to a decrease in mean arterial bp are coordinated to increase the arterial pressure back
- Decreased parasympathetic (vagal) outflow to the heart
- Increased sympathetic outflow
Four effects that increase the arterial pressure back to normal
- Increase heart rate
- decreased parasympathetic tone
- increased sympathetic tone
- Increase contractility and stroke volume
- increased sympathetic tone to the heart
- Increase vasoconstriction of arterioles
- increased sympathetic outflow
- Increase vasoconstriction of veins
- increased sympathetic outflow
Renin angiotensin aldosterone system
enzyme that catalyze the conversion of the angiotensinogen to angiotensin I in plasma
Renin
catalyzes the conversion of angiotensin I to angiotensin II, primarily in the lungs
Angiotensin converting enzyme
Four effects of angiotensin II
- Stimulates the synthesis and secretion of aldosterone by the adrenal cortex
- Increases Na-H exchange
- It increases thirst and therefore water intake
- causes vasoconstriction of the arterioles, thereby increasing TPR and arterial pressure
When the brain is ischemic, the partial pressure of ___________ in brain tissue increases
carbon dioxide
Chemoreceptors in the vasomotor center and respond by __________ sympathetic outflow to the heart and blood vessels
Increasing
example of the response to cerebral ischemia.
Increases in intracranial pressure cause compression of the cerebral blood vessels, leading to cerebral ischemia and increased cerebral PCO2
Cushing reaction
Are located near the bifurcation of the common carotid arteries and along the aortic arch.
have very high rates of Oxygen consumption and are very sensitive to decrease in the partial pressure of oxygen
Chemoreceptors in the carotid and aortic bodies
_____in PO2 activate vasomotor centers that produce vasoconstriciton, an increase in TPR and an increase in arterial pressure
Decrease
involved in the regulation of blood pressure in response to hemorrhage, but not in minute to minute regulation of normal blood pressure
Vasopressin (ADH)
Vasopressin is a potent vasoconstrictior that increases TPR by activating ___________ on the arterioles
V1 receptors
Vasopressin increases water reabsorption by the renal distal tubule and collecting ducts by activating _____________receptors
V2
released from the atria in response to an increase in blood volume and atrial pressure
causes relaxation of vascular smooth muscle
causes increased excretion of sodium and water by the kidney which reduces blood volume and attemps to bring arterial pressure down to normal
Atrial natriuretic peptide (ANP)
Atrial natriuretic peptide inhibits _________ secretin
renin
At the junction of the arterioles and capillaries is asmooth muscle band called the __________
Precapillary sphincter
true capillaries do not have smooth muscle; they consist of a single layer of _______________ surrounded by a basement membrane
Enothelial cells
In the liver and intestine, theclefts are exceptionally wide and allow passage of protein. These capilalries called
sinusoids
large water soluble substances can cross by ___________
pinocytosis
The starling equation
Fluid flow
when Jv is positive, there is net fluid movement out of the capillary (filtration)
when Jv is negative, there is net fluid movement into the capilalry (absorption)
_______is the filtration coefficient
the hydraulic conductance (water permeability) of the capillary wall
Kf
determined by arterial and venous pressures and resistances
capillary hydrostatic pressure
- an increase in Pc favors filtration out of the capillary
- an increase in either arterial or venous pressure produces an increase in Pc; increases in venous pressure have a greater effect on Pc
- Higher at the arteriolar end of the capilalry than at the venous end (except in glomerular capilalries, where it is nearly constant)
Interstitial fluid hydrostatic pressure
opposes filtration
normally close to 0 mm Hg
Factors that increase filtration
- Increase in capilalry hydrostatic pressure
- caused byincreased arterial pressure, increased venous pressure, arteriolar dilation and venous constriction
- decrease interstitial hydrostatic pressure
- increase capillary oncotic pressure
- caused by decreased protein concentration in the blood
- increase in interstitial oncotic pressure
- inadequate lymphatic function
Excess filtered fluid is returned to the circulation via the ___________
lymph
__________permits interstitial fluid to enter, but notleave, the lymph vessels.
flow through larger lymphatic vessels is also unidirectional
one-way flap valves
oCcurs when the volume of interstital fluid exceeds the capacity of the lymphathics to return it to the circulation
can be caused by excess filtration or bloccked lymphatics
Edema
causes both arteriolar dilation and venous constriction, which together produces a large increase in Pc and local edema
Histamine
produced in the endothelial cells
causes local relaxation of vascular smooth muscle
Nitric oxide
Causes and examples of edema
The mechanism of action
activation of guanylate cyclase and production of cyclic guanosine monophosphate (cGMP)
Blood flow to an organ remains constant over a wide range of perfusion pressures
Autoregulation
- Organs that exhibit autoregulation are the
- heart
- brain
- kidney
- if perfusion pressure to the heart is suddenly decreased, compensatory vasodilation of the arterioles will occur to maintain a cconstant flow
Summary of control of special circulations
is an increase in blood flow to an organ that occurs after a period of occlusion of flow.
the longer the period of occlusion is, the greater the increase in blood flow is above the peocclusion levels
Reactive hyperemia
Mechanism tat explain local control of blood flow
Myogenic hypotheis
Metabolic hypothesis
Explains autoregulation but not active or reactive hyepremia
based on the observaton that vascular smooth muscle contracts when it is stretched
Myogenic hypotheis
based on the observation that te tissue supply of oxygen is matched to the tissue demand of oxygen.
vasodilator metabolites are produced as a result of metabolic activity in tissue.
metabolic hypothesis
- Vasodilators”
- CO2
- H
- K
- lactate
- adenosine
Increae in sympathetic tone cause__________
vasoconstriction
causes arteeriolar dilaion and venous constriction
produces increaed filtraion out of the capilalries and causes local edema
Bradykinin
causes arteriolar constriction and is released in response to blood vessel damae to help prevent blood loss
implicaed in the vascular spasms of migraine headaches
Serotonin
E series prostaglandings are ___________
vasodialtors
F series prostaglandins are ________
vasoconstrictors
Thromboxane A2 is a ________
vasoconstrictor
Coronary circulation is controlled almost entirely by____________
local metabolic factors
- exhibits autoregulation
- exhibits active and reactive hyperemia
The most important metabolic factors are ___________________
hypoxia and adenosine
Cerebral circultion is almost entirely controlled by ___________
local metabolic factors
- Exhibits autoregulation
- exhibits active and reactive hyperemia
The most important local vasodialtor for the cerebral circualtion is ________
CO2
Primary regulato of blood flow to the skeletal muscle at rest
Sympathetic innervation
Stimulation of alpha 1 receptors cause_______
vasoconstriction
stimulation of B2 receptors causes ____________
vasodialtion
During exercise, when demand is high these _______________are dominant
local metabolic mechanisms
is the principal fucntion of cutaneous sympathetic nerves.
Temperature regulation
Changes occur when an individual moves from a supine to a standing position
- significant volume of blood pools in the lower extremities because of high compliance of the veins
- Increased local venous pressure. - > edema
- venous return decreases - > SV and cardiac output decreases
- Arterial pressure decreases
- Compensatory mechanis will attempt to increase BP
- carotid sinus baroreceptors - > decrease the firing rate of the carotid sinus nerves
Summary of responses to standing
Summary of Effects of exercise
Cardiovascular response to exercise
Summary of compensatory response to Hemorrhage
cardiovascular response to hemorrhage
