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Physio > Systemic Circulaion > Flashcards

Systemic Circulaion Flashcards

1
Q

. Elastic (Windkessel) vessels

A

. Contain abundant elastic fibers, smooth muscle, and collagen

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2
Q

Resistance vessels

A

. Arterioles and precapillary sphincter
. High thickness/lumen ration
. Have greatest ability to control blood flow

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3
Q

Exchange vessels

A

. Capillaries formed by single layer endothelial cells

. Allows efficient diffusion of substrates

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4
Q

Capacitance vessels

A

. Veins
. Contain abundant collagen fibers and some smooth muscle
. Have small wall thickness/lumen diameter ratio and therefore regulates volume more than pressure

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5
Q

. Velocity of blood flow vs cross sectional area of vascular bed

A

. Inverse relationship btw velocity of blood flow and the total cross-sectional area of the entire cardiovascular system
. Cross-sectional area in capillaries is greatest and velocity is slowest

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6
Q

Factors controlling arterial pressure

A

. Physical: arterial blood volume, arterial compliance

. Physiological: CO, peripheral resistance

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7
Q

Pulse pressure (PP)

A

. Systolic pressure - diastolic pressure
. Aortic bp is pulsatile due to oscillating output of pumping heart
. Arterial pressure rises during ventricular systole and falls during ventricular diastole

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8
Q

Peripheral runoff

A

. Transfer blood from arterial circulation into capillaries and veins during diastole

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9
Q

Systolic pressure

A

Peak aortic pressure

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10
Q

Diastolic pressure

A

. Lowest aortic pressure just prior to ventricular ejection

. Determined by the arterial compliance and residual arterial volume immediately before next cardiac ejection

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11
Q

Mean arterial pressure

A

. Average pressure of blood perfusing the capillaries during cardiac cycle
.results from area under the pulse curve divided by a time interval
. Approximated by adding 1/3 of the PP to the DP
.

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12
Q

Why does capillary flow continue during diastole even though heart output is cyclic?

A

. Part fo the energy of cardiac contraction is stored as potential energy by distensibility walls of the aorta and arteries during systole

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13
Q

Windkessel effect

A

. Elastic recoil of the arterial walls that converts the potential energy into capillary blood flow

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14
Q

What is responsible for generating a large diastolic pressure

A

. Aortic compliance
. Allows aorta to store as much as 50% of the SV during systole
. Elastic recoil of aorta propels this volume to the periphery generating continuous peripheral blood flow,, reduces ventricular afterload

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15
Q

Distortion of arterial pressure pulse

A

. Propagation of pressure pulse wave depends on elastic stiffness, radius, and thickness of vessel and density of the blood
. Arterial pulse changes shape and amplitude as it travels down the arterial tree
. Sharp incisura is lost, pulse pressure becomes larger, diastolic waves become apparent, mean pressure falls as pressure wave travels from aortic arch to femoral a.
. Changes result from heterogeneities in geometry and distensibility/elasticity of aa. And partial reflection of pressure waves occurring at any sharp discontinuity in arterial tree
. Reflecting waves interfere w/ upcoming pulse enhancing and dampening different components of pressure wave

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16
Q

Arterial pressure wave travels down aorta at ____ while blood flow wave travels at ____

A

.pressure: 5 m/s
. Blood: 1 m/s
. Explains why you can feel the peripheral pulse shortly after hearing the 1st heart sound in the precordial region

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17
Q

Measurement of arterial pressure

A

. Bp measured anywhere in circulation
. Most accurate w/ saline-filled catheter connects to a pressure transducer
. Both systolic and diastolic bp measured using sphygmomanometer
. High velocity blood flow is turbulent and produces korotkoff sounds

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18
Q

Determinants of arterial blood pressure

A

MAP = (HR X SV) TPR
. CO and total peripheral resistance are major determinants of MAP
. MAP and CO are measured, TPR is estimated

19
Q

Peripheral runoff

A

. Qr
. Inversely determined by TPR
. Determines the change in arterial pressure as a direct result from changes in arterial blood volume
. Qh&raquo_space; Qr = inc. arterial pressure
. Qh &laquo_space;Qr = dec. arterial pressure
. These relationships are transient, in steady state Qh (CO) always equals to Qr

20
Q

Determinants of pulse pressure and systolic pressure

A

. Determined by SV and aortic compliance and ventricular ejection velocity to a lesser degree
. DeltaP = DeltaV/C
.

21
Q

Relationship between arterial pressure, TPR, and arterial compliance

A

. For given TPR, as compliance dec., the arterial pulse pressure widens (inc. in systolic, dec. in diastolic)

22
Q

Relationship between pressure on SV and compliance

A

. When SV is dec. (hypovolemia, HF) the systolic pressure becomes smaller and pulse pressure is reduced
. Opposite when SV inc. (adrenergic stimulation, exercise)
. Dec. in arterial compliance causes an inc. in pulse pressure

23
Q

Determinants of diastolic pressure

A

. Diastolic pressure is mainly influenced by HR and TPR
. HE determines interval for blood transfer from arterial system to venous system
. TPR determines rate of peripheral run-off
. Both affect volume of blood remaining in arterial system at the end of the diastolic period affecting diastolic pressure

24
Q

Venus pressure

A

. Up to 65% of total blood volume is in venous system at one time
. High compliance, low resistance. Low pressure (0-6 mmHg)
. As veins fill, the cross-sectional area of veins inc. even though the perimeter measurement stays the same

25
Q

Venous return

A

. Venous blood flow from peripheral veins to the RA
. Equal CO at steady-state
. Pressure gradient for venous return is determined by different btw peripheral venous pressure(pressure form flow of blood from capillaries to veins) and right atrial pressure (central venous pressure)

26
Q

Effect of posture of venous pressure

A

. Supine: hydrostatic force form gravity insignificant
. Standing: hydrostatic force prominent and superimposes to other vascular pressures, inc. pressure below reference point
. Perfusion pressure does not change from head to toe or from supine to upright

27
Q

Effect of posture on venous return

A

. Supine to standing there is rapid translocation of blood from thorax to lower extremities
. Blood pools in dependent peripheral veins and capillary hydrostatic pressure inc.
. Translocation followed by capillary transduction moving fluid into interstitium of lower extremities
. Blood pools in lower extremities and venous return dec. so CO and MAP transiently dec.
. Mechanism then activated to return levels to normal

28
Q

Skeletal muscle pump

A

. Upon standing, leg muscles begin rhythmic cycles of contraction/relaxation causing swaying motion of body’s
. Reflex initiated by stimulation of plantar surface of foot
. Mm. Contractions squeeze veins w/in mm. And drive blood centrally towards the heart
. Veins refill w/ blood during rhythmic relaxation of muscles
. Activity potentiated w/ walking/running
. Pump augments venous return that facilitates ventricular filling and inc. SV
. Pump enhances perfusion of m. Capillary bed by inc. arterial-venous pressure gradient in leg mm.
. Occurs c venous pressure falls during muscular contraction while arterial pressure remains constant

29
Q

Respiratory pump

A

. During forced inspiration, intrathoracic pressure is more neg. and intra-abdominal pressure inc. from diaphragm contraction
. The more neg. the intrathoracic pressure causes inc. in venous transmural pressure so central vv. Dilate and central venous pressure dec. while pressure in intra-abdominal vv. Inc.
. Inc. the pressure gradient to favor venous return from peripheral vv.
. Inc. in venous return inc. ventricular filling and inc. SV
Enhanced w/ exercise

30
Q

Mean circulatory pressure

A

. Equilibrium pressure when pressure in aa. And vv. Equilibrate during cardiac arrest
. Function of both blood volume and vessel compliance
. Normal is approx. 7 mmHg

31
Q

Vascular function curve

A

. Defines the changes in CVP that are caused by changes in CO
. At a constant TPR, an inc. inc CO will dec. CVP, occurs bc of transfer of blood from venous circulation to arterial circulation

32
Q

How CO affects vascular function curve

A

. Changes in CO changes arterial pressure and venous pressure
. Acute HF occurs occurs as result of an astute MI and is accompanied by dec. in arterial bp and an inc. in venous bp

33
Q

How blood volume affects vascular function curve

A

. MCP will inc. as blood volume is expended

. MCP dec. as blood volume dec.

34
Q

Venomotor tone affect on vascular function curve

A

. MCP will inc. as tension exerted by vascular smooth mm. Surrounding veins inc.
. MCP will dec. as tension exerted by smooth muscle surround the vv. Dec.

35
Q

Affect of peripheral resistance on vascular function curve

A

. Gradual changes in contractile state of arterioles don’t significantly alter MCP
. Sudden inc. in TPR causes greater blood volume to be retained in arterial system
. Inc. in arterial blood volume is accompanied by equivalent dec. in venous blood volume
. At any CO, an inc. in TPR will dec. venous pressure w/ no change in MCP, the curve is rotated counter clockwise
. A dec. in TPR at any CO will inc. venous pressure and rotate the vascular function

36
Q

Contractility affect on cardiac function curve

A

. Inc. in ventricular contractility shifts cardiac function curve upward
. Dec. in contractility will shift the curve downward

37
Q

How afterload affects cardiac function curve

A

. Inc. in ventricular afterload (inc. TPR) shifts curve down
. Dec. in afterload shifts curve upward
.

38
Q

Equilibrium point

A

. Intersection between vascular function curve and cardiac function curve
. Represent values of CO and CVP at which a system operates
. Only transient deviations possible

39
Q

How myocardial contractility affects cardiovascular function curve

A

. Inc. in myocardial contractility shifts curve upward w/ no effect on vascular function curve
. During periods of inc. contractility CO will inc. slightly and CVP will dec. slightly
. Dec. in contractility will shift functions urve down, w/ no effects on function curve
. During periods of inc. contractility CO will dec. slightly and CVP will inc. slightly

40
Q

How blood volume affects cardiovascular function curve

A

. Inc. in blood volume shifts function curve right w/ no direct effect on curve, inc. CO and CVP
. Dec. in blood volume shifts curve left w/ no direct effect on curve, dec. CO and CVP

41
Q

Venootor tone effect on cardiovascular function curve

A

. Inc. in tone will shift curve right, inc. CO and CVP w/ no direct effect on curve
. Dec. in tone will shif curve left w/ no direct effect on curve, dec. CO and CVP

42
Q

Peripheral resistance effect on cardiovascular function curve

A

. Inc. in resistance rotates vascular curve counterclockwise and shift CO curve downward dec. CO w/ no changes in CVP
. Dec. in resistance rotates vascular curve clockwise and shifts cardiac curve upward, inc. CO w/ no major changes in CVP

43
Q

Heart failure affects on cardiovascular curve

A

. Pumping capability of heart is impaired and myocardial contractility is dec.
When acute: cardiac curve shifts down, blood volume changes do not occur immediately
. When chronic: cardiac curve shifts down and vascular curve is shifted right indicating inc. in blood volume
. Moderate degrees of Hf, CVP is inc. but CO may be normal
. Severe HF, CVP is inc. and CO is decreased

Physio (62 decks)

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