Heart/Cardiac cycle Flashcards by Steph Nicolette

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

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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

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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

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diastolic heart failure

-not moving volume bc nothing is going in
-systolic heart failure- heart stretches and has less contraction

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pulmonary artery pressure

-15 MAP
-right ventricle systole- 25
-right ventricular diastole- 8

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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

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self depolarization

-involuntary

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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

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systemic and pulmonary circulation

-systemic- left heart, arteries, veins, capillaries -> perfuses everything but lungs
-pulmonary- right heart, arteries, veins, capillaries

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cardiac output

-rate of blood pumped from either ventricle
-left ventricle CO = right ventricle CO in steady state

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venous return

-rate of blood returned to atria from veins

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hemodynamics

-principle’s that govern blood flow
-flow, pressure, resistance, capacitance

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arteries

-thick walled -> can handle high pressure
-extensive elastic tissue, smooth muscle, and connective tissue

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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

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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

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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