Heart/Cardiac cycle Flashcards
tissue perfusion
parallel circuity
-sympathetic and parasympathetic- changes shunting of blood in these areas
-100% blood leaves the aorta
-15% to brain
-5% coronaries- supply myocardial tissue (small goes to pericardium)
-25% to kidney- regulates blood pressure, filters blood, electrolyte management (pumps), removal of waste and medications*
-25% GI- absorption, peristalsis, liver
-25% skeletal- movement
-5% skin- thermoregulation, absorption, sensory
-100% blood back to lungs
area and volume of blood
-significant amount of surface area is in the capillary compared to everything else
-the majority of the blood is in the veins- storage
-blood moves from high to low pressure -> veins are low pressure -> pools in veins
-higher volume higher pressure
-arteries- high pressure low blood volume
-veins- low pressure highest blood volume
laminar flow
-blood flowing through the middle- maximal velocity
-silent
-velocity of flow at the vessel wall is 0
-parabolic
-turbulent flow- between arterial and venous (chaotic flow) - brewy turbulent flow you auscultate
-more pressure required for turbulent flow
-korotkoff sounds- BP via turbulent flow
-stenosis of blood vessels and cardiac valve disease -> turbulent flow -> murmurs
diastolic heart failure
-not moving volume bc nothing is going in
-systolic heart failure- heart stretches and has less contraction
pulmonary artery pressure
-15 MAP
-right ventricle systole- 25
-right ventricular diastole- 8
arterioles
-pressure is pretty much constant at this point and further
-no more systole and diastole pressure changes
-highest resistance -> causes altered blood flow to organs
-extensive smooth muscle -> tonically active (always contracted)
-innervated by alpha 1 adrenergic receptors -> vasoconstriction (skin and splanchnic)
-innervated by beta 2 adrenergic receptors -> dilation (skeletal)
-resistance can be changed by sympathetic/catecholamine activity
self depolarization
-involuntary
functions of cardiovascular system
-regulation of BP
-delivers regulatory hormones from endocrine glands to target tissue
-regulation of body temp
-homeostatic adjustments to altered physiologic states -> hemorrhage, exercise, changes in posture
systemic and pulmonary circulation
-systemic- left heart, arteries, veins, capillaries -> perfuses everything but lungs
-pulmonary- right heart, arteries, veins, capillaries
cardiac output
-rate of blood pumped from either ventricle
-left ventricle CO = right ventricle CO in steady state
venous return
-rate of blood returned to atria from veins
hemodynamics
-principle’s that govern blood flow
-flow, pressure, resistance, capacitance
arteries
-thick walled -> can handle high pressure
-extensive elastic tissue, smooth muscle, and connective tissue
capillaries
-thin walled, but LARGE SURFACE -AREA to do gas exchange
-single layer endothelial surrounded by basal lamina
-Lipid soluble substances cross the capillary wall by dissolving and diffusion
-Water soluble (ions) substances cross the capillary wall either through water filled clefts between the endothelial cells or through large pores (fenestrated)
-Not all capillaries have blood at all times-> selective perfusion depending on the metabolic needs of the tissues
-regulated by constriction and dilation of arterioles via sympathetic innervation
venules and veins
-much less elastic tissue than arteries-> large capacitance (capacity to hold blood)
-high capacitance (compliance)
-largest percentage of blood
-AMOUNT OF BLOOD IN THE VEINS= UNSTRESSED VOLUME BC UNDER LOW PRESSURE
-alpha 1 adrenergic receptors-> CONSTRICTION of the veins -> reduces capacitance -> reduces the unstressed volume
-Velocity of blood flow and area have an INVERSE relationship -> bigger diameter of vein -> slower blood velocity
blood flow
-2 factors- pressure different between 2 ends of vessel and resistance
-pressure difference- driving force
-resistant- impediment to flow
-greater pressure difference -> greater blood flow
-from high to low pressure
-higher resistance lower blood flow
-total peripheral resistance- resistance of entire systemic system
poiseuille equation
-the relationship between resistance, blood vessel diameter, and blood viscosity
-increase in resistance as viscosity (η) increases
-Resistance increases as length (l) of the blood vessel increases
-**Resistance to flow is INVERSELY PROPORTIONAL to the fourth power of the radius (r^4 ) of the blood vessel
-if radius of vessel decreases by 1/2 resistance does not simply increase twofold—it increases by 16-fold (2 ^4 )
sequential blood flow
-total flow is constant at each level in series
-pressure decreases as blood flows through each sequential component
-greatest decrease at arterioles bc they contribute largest resistance
-R total = R1 + R2 + R3 ….
parallel blood flow
-total resistance is less than any individual resistances
-flow through each organ is a fraction of total blood flow
-no loss of pressure in major arteries
-MAP in each major artery is the same as MAP of aorta
-1/Rtotal= 1/R1 + 1/R2 + 1/R3…
anemia
-decreased Hct
-reynolds number- predictor of turbulent flow
-reynold number is high in anemia bc of low blood viscosity and high CO -> increase in velocity of flow
thrombi
-narrow vessels
-increase velocity at site of thrombus
-increases reynold number
-turbulence
shear
-occurs if layers of blood travel at different velocities
-layers travel at the same velocity-> no shear
-Shear is highest at blood vessel WALL- bc there’s a big difference between a moving RBC and a stationary one
-At walls= no movement, next to walls= blood movement: therefore the
DIFFERENCE between blood at the walls and next to the wall is highest
-In the middle, everything is moving at the same speed -> no difference in velocity= no shear
-shear breaks up clusters of RBCs next to each other= decreases blood viscosity (no more clumps)
-Therefore, at the wall which has the HIGHEST shear, RBC aggregation and viscosity are LOWEST
capacitance (compliance)
-volume of blood a vessel can hold at given pressure
-volume of blood in vessel changes for a given change in pressure
-veins high
-arteries low
-if vein capacitance decreases blood redistributes from unstressed to stressed volume
blood pressure
-not the same throughout system
-bp differences is driving force
-pulmonary wedge pressure- measures left arterial pressure-> catheter in pulmonary artery into a branch -> catheter wedges and block blood flow from that branch -> once flow stops -> catheter senses pressure in left atrium
-diastolic- lowest arterial pressure during ventricular relaxation
-systolic- highest pressure after ventricular contraction
why does pressure decrease as you move farther from heart
energy is consumed in overcoming frictional resistances
stroke volume
-volume of blood ejected from left ventricle on single beat
-pulse pressure= systolic - diastolic = SV
mean arterial pressure
-average pressure in complete cardiac cycle
-NEED TO KNOW
-why is MAP important? -> at the level of arterioles contraction pressure doesnt influence -> dependent on MAP
-we are in diastole more than we are in systole -> diastole x2
-MAP = diastolic + 1/3 pulse pressure
-MAP = (diastolic + diastolic + systolic) / 3
arteriosclerosis
-plaque deposits in arterial wall
-decrease diameter
-stiff, less compliant
-SV causes much greater change in arterial pressure
-increases systolic, pulse, and mean pressure
aortic stenosis
-aortic valve stenosis (narrow)
-opening is reduced -> less blood ejected
-decreases SV, systolic pressure, pulse pressure, mean pressure
-less blood enters aorta
aortic regurgitation
-incompetent valve
-congenital
-pressure is very low
-pulmonary pressure is much lower than systemic
-pattern of pulmonary is analogous to systemic
-By the time the blood reaches the veins, pressure is already so low and will continue to drop even more in the vena cava and the right atrium
QRS complex
-Isovolumetric contraction- contraction of ventricles that doesnt result in corresponding volume change
-begins during the QRS complex
-short moment that takes place when all the valves are closed -> electrical activation of ventricles
-When left ventricular pressure exceeds left atrial pressure, the mitral valve closes
P wave
-atria depolarize and contract
-ventricles are filling the whole time (even before atrial contraction)
-atrial contract further fills the ventricles
T wave
-ventricles eject blood into arteries
-ventricular volume reaches minimum
-aortic pressures starts to fall as blood runs off into arteries
First heart sound (S1)
-closure of the AV valves
-mitral valve closes slightly before the tricuspid
-ventricular pressure increases but volume is constant bc all valves are closed
-When ventricular pressure is greater than aortic pressure -> aortic valve opens (too much pressure= bursts open)
-blood rapidly ejects from the aorta
-atrial filling begins -> pressure increases
-End of phase -> ST segment-> beginning of T wave and the end of ventricular contraction (end of the QRS complex)
-T wave- ventricles begin to repolarize; blood is leaving the left ventricle bc the aortic valve is still open -> LV pressure decreases
Second heart sound (S2)
-aortic valve closing
-closes slightly before pulmonic valve (AP)
-Aortic valve closes when left ventricle pressure falls below aortic pressure
-aortic valve closes -> aortic pressure curve shows a “blip” called the dicrotic notch or incisura
-All valves are closed -> no blood is getting ejected or filling -> this phase is called the isovolumetric phase since it is constant (no change in volume)
Third heart sound (S3)
-rapid flow of blood from atria to the ventricles
-sound is normal to hear in children, but not adults
-In adults- suggests volume overload, as in congestive heart failure
-ADULTS: IF YOU HEAR A THIRD HEART SOUND (BLOOD FROM ATRIA → VENTRICLES)= BAD = CHF / REGURGITATION
diastasis
-aka reduced ventricular filling
-longest phase in the cardiac cycle
-final portion of ventricular filling
-occurs at a SLOWER RATE than in the previous phase
-If diastasis is reduced by increase in heart rate -> ventricular filling will be compromised -> end diastolic volume will be reduced -> stroke volume will also be reduced (frank starling relationship)
CO VENTRICLES
ARE EQUAL
-what comes in must come out
-right ventricle lower pressure- ~25
