Flashcards in Circulation 3: Part II Systemic Circulation Deck (45):
Define pressure, transmural pressure, pressure gradient, and hydrostatic pressure.
pressure = force per unit area (1mmg Hg = 1.36 cm water)
transmural pressure - pressure tending to distend or collapse a vessel
pressure gradient- pressure differential between inflow and outflow
hydrostatic pressure - pressure caused by the height of a fluid column (when standing up gravity causing blood to be pulled down, causes pressure at lower extremities, valves in venous side break that up. generated by gravitational forces)
(hydrostatic means water pressure so we use term generally. hydrostatic pressure in capillaries- really just bp in capillaries)
Define mean arterial pressure and provide an equation.
average pressure existing in the aorta and proximal arterial system during one cardiac cycle.
mean arterial pressure = diastolic pressure and 1/3 pulse pressure (systolic/3)
(bc in diastole more than systole)
What are physiological and physical factors that determine arterial bp?
physiological factors- CO (HR x SV), peripheral resistance
physical factors - arterial blood volume (affects CO) affects arterial compliance...
determines arterial bp
physiological and physical factors that det. bp- other factor- how fast does blood run off to peripheral system -det. by peripheral resistance (arterials) blood pumped in, how fast? how fast going out? in and out. increase CO to put more volume in, reduce outflow by increasing peripheral resistance and that pressurizes the system.
Why do you place the bp cuff at same level as heart?
remove effect of gravitational forces
How does an increase in volume of blood change arterial bp?
makes compliance char. of arterial system decrease bc stretching more components of arterial wall - getting lower compliant system as volume goes up. other way will do it is put more volume in, more venous return, heart pumps more volume into arterial system. interact w arterial compliance and w the heart.
arterial compliance-if low compliant system higher systolic and lower diastolic pressure.
Discuss how the following physiological factors affect systolic and diastolic pressures. What changes them/how are they regulated?
1. cardiac output (stroke volume x heart rate):
a) primarily affects systolic pressure.
b) regulated by autonomic nervous system, can change beat to beat.
2. peripheral resistance:
a) primarily affects diastolic pressure.
b) regulated by autonomic nervous system, relatively constant.
c) regulated by local metabolic activity – local regulation overrides nervous control.
a) Baroreceptor Reflex – acts via the autonomic nervous system to affect both cardiac output and peripheral resistance.
b) Exercise – systolic pressure increases and diastolic pressure remains constant or decreases (depending on level of exercise). Therefore, pulse pressure widens and mean arterial pressure increases.
c) Disease – congestive heart failure, infarction, bradycardia, sepsis, all decrease blood pressure. Hypertension increases blood pressure (systolic and diastolic forms of hypertension).
What determines systolic pressure?
heart, SV, beats per minute
(if you’re anxious and someone taking your bp it will be elevated v easily by sympathetic nerve activity. regulated by autonomic nervous system- thats why its v difficult to get a consistent reading.)
can change SV easily by little sympathetic surge. bp cuff over sleeve- more difficult for cuff to constrict artery so it artificially raises the pressure bc machine has to generate more pressure to get the stenosis to occur. if you roll up sleeve and its tight that cuts off blood flow which will alter the bp measurement.
Describe how to change peripheral resistance. What does it affect?
peripheral resistance not changed as easily, primarily affects or det. diastolic pressure. how fast does the blood run off. how fast blood pumped in-systolic, how fast blood runs off to capillaries and venous system-diastolic. diastolic also regulated by autonomic NS but not so easily changed, its relatively constant. also regulated by local metabolic activity- local regulation overrides nervous control. ideas is have to get blood flow to specific organ beds and they can regulate their own blood flow locally - does it by vasodilating or vasoconstriction those pre-capillary sphincters or arterioles and that alters diastolic pressure. again, cardiac O and SV and HR det. systolic and peripheral resistance det. diastolic.
If pulse pressure widens is that always bad for heart? Give an example of when it is good/bad.
no not when exercising.. increasing O consumption.. more work for heart but strengthening heart.
widened pulse pressure with low compliant system -thats years and years of continual low compliance. congestive heart failure reduces SV dramatically and reduces systolic pressure..thats the problem w congestive heart failure- have decrease in contractility which reduces SV
What occurs with sepsis?
sepsis- causes massive vasodilation and diastolic pressure drops out…and have real drop in bp. not enough blood in system to perfuse all vascular beds at same moment, if all them open up your bp drops through floor- thats what sepsis does- response to blood bacterial infection
Describe how arterial compliance and blood volume (physical factors) affect systolic/diastolic pressures.
1. arterial compliance: affects both systolic and diastolic pressures.
Determined by location in arterial vasculature, age, blood volume, sympathetic tone, pregnancy.
2. blood volume: affects stroke volume and arterial compliance.
only commonality between 2 variables is they both affect bp. arterial compliance affected by blood volume - if increase blood volume, increase SV, and you also can raise arterial compliance by stretching vessels too much with increased volume
For a given peripheral resistance, as compliance decreases (L to R) what happens to arterial pulse pressure?
pulse pressure widens.
increase in systolic, decrease in diastolic
Graph slide 5
For a given compliance, as peripheral resistance increases (top to bottom) how are systolic and diastolic pressures affected? Which effect is stronger?
both systolic and diastolic pressures increase (diastolic is affected more)
Describe the graph on slide 5.
In a low compliant system, what kind of pulse pressure do you have? What kind of peripheral resistance? What does this indicate about compliance?
In a low compliance system. Describe diastolic/systolic pressures. Describe how afterload, pulse pressure have changed.
When compliance is 14, what kind of peripheral resistance is there as compared to a higher compliance system? How is systolic/diastolic pressures affected?
graph showing effect of peripheral resistance and compliance- not related to e/o both just factors that can affect pulse pressure. look at one at a time.
if you had low compliant system, in a v high compliant system have v small pulse pressure… low peripheral resistance - bc compliance is v high, nice flexible system have small pulse pressure.
then compare to v low compliance, vessels stiff, diastolic pressure and systolic have both changed…
here have large afterload, large pulse pressure now bc of change in compliance at given peripheral resistance
looking at middle one. compliance at 14. low total peripheral resistance compared to high. look at diastolic pressure…at low-about 70 or 80. now, w v high peripheral resistance diastolic pressure about 130. really high. showing 2 diff variables that can affect systolic/diastolic pressure. not directly related to e/o. 2 diff things and how they both affect pressure. look at one column at a time.
Describe local (intrinsic) control of total peripheral resistance.
Factors that affect local control:
local metabolic changes (O2, CO2, metabolites), endothelium-mediated regulation (EDRF, NO, endothelin), myogenic response
local intrinsic contral then affects arteriolar radius which affects total peripheral reisistance
in general local mechanisms can override global mechanisms. 3 mech. of local control- myogenic…muscle mechanism. endothelial mediated regulation.. release tons of diff substances.. nitric oxide.. (v important) local metabolic …all of these are vasodilators released from metabolic tissue (primarily skeletal muscles)
Describe extrinsic control of total peripheral resistance. (Global regulation)
sympathetic activity (increase with general vasoconstriction, decrease with general vasodilation, get vasoconstriction by activation (alpha receptors cause vasoconstriction) withdraw of symp. activity cause passive vasodilation. withdraws stimulation.),
hormonal effects (angiotensin- prod. usually in response to low bp , epi),
baroreceptor reflex (when bp drops out get increase in sympathetic activity, that causes vasoconstriction and raises total peripheral resistance. prevents blood from running off. baroreceptors regulate by stimulating or withdrawing symp.)
extrinsic control contributes to arteriolar radius which affects total peripheral resistance
What is total peripheral resistance? Describe 2 main ways to control total peripheral resistance.
total peripheral resistance- how fast blood from from arterial system to capillaries to veins. det. by arterioles and pre-capillary sphincters. run off of blood. back to r^4… will determine the total peripheral resistance bc its v sensitive to diameter bc of large exponential. main factor is arteriolar radius- thats whats autonomically regulated. blood viscosity also helps det. total peripheral resistance bc its internal resistance but doesn't change unless pathological conditions (anemia..) affects how fast blood runs through system. main regulatory factor is arteriolar radius -2 ways to regulate…local control mechanisms and extrinsic control mechanisms…
arteriolar radius (intrinsic and extrinsic control)
How does the autonomic system regulate arterial bp? Describe sympathetic stimulation. (heart, veins, arterioles)
can see symp. NS more imp. in regulating bp than parasympathetic. (circulatory system not specifically regulated by parasympathetic)
symp.-affects veins, heart and arteries. activation of this raises bp and withdraw lowers bp. receptors.
contractility increase SV and HR increases CO directly, HR increase strength of contraction as well through positive staircase… need inflow to have pressure. affects arterial system… by vasoconstricting, increasing peripheral resistance (diastolic goes up, raises bp, prevents the run off… heart pumping blood in, vasoconstriction preventing blood from running off as quickly) venous system venoconstricted-shifts venous function curve up and to the right and that shunts more blood to heart through valves, increases preload, SV (as result of L-tension rel) increases CO. when you withdraw symp. HR does come down but activating para. will also bring HR down.
Slide 7 chart.
Describe how parasympathetic stimulation affects bp.
symp. NS more imp. in regulating bp than parasympathetic. (circulatory system not specifically regulated by parasympathetic) … peripheral circulatory regulated not spec. innervated by parasympathetic (specific organ beds are para. innervated that do alter local blood flow through those systems but generally speaking peripheral vascular system not innervated spec. by para.
heart- decrease HR, decrease CO, decrease bp,
What affects mean arterial bp?
mainly CO (HR and SV) and total peripheral resistance (arteriolar radius and blood viscosity)
See diagram slide 8.
What affects venous return?
blood volume, respiratory pump, skeletal muscle activity
(venous return then affects SV...which affects CO)
How would number of RBC affect mean arterial bp?
#RBC affects hematocrit, viscosity, total peripheral resistance which affects MAP.
How does blood flow change during exercise?
as you continue to exercise amount of blood change dramatically bc local regulation overriding global by shifting blood from one place to another. want lots of blood flow to skeletal muscle… tremendous amount of blood flow to skeletal muscle. happens bc viscera are decreasing blood flow. shut down. when you run marathon, you don't have to pee that often, bc vasoconstricitng, not getting blood flow to kidney, not filtering, usually no flow to splanchnic region either (so don't have to poop)… blood flow shunted to skeletal muscle. brain and heart need blood flow. small increase is blood to heart. cutaneous blood flow small then gets large during exercise. cutaneous circulation gets rid of heat..main function. causing vasodilation and allowing more blood flow to skin to dissipate heat.
What happens at really high work loads? (exercise)
tends to vasoconstrict and shunt blood back to skel. muscles thats bad… at extreme levels go into shock if overextending amount of exercise.. w/o hydration you cant get rid of heat, overheat and get (hyperthermic?)
How are HR and SV affected during exercise?
HR goes up linearly as you increase in exercise. increase HR…SV shouldn't be dropping that quickly..doesn't drop till 160 170 beats per minute. does drop off when get to higher HR bc even with compensations to increase venous return, if you get short enough cycle length you just don't have time to fill. but in graph is SV was going down that much the CO wouldn’t be going up.
Describe how exercise affects pulse pressure.
What happens to diastolic pressure? When/why?
as you increase work, exercise systolic pressure goes up but diastolic doesn't go up much (graph wrong), should start coming down a bit at high work loads bc of local metabolic vasodilation… diastolic doesn't go up significantly.. imp. is that it doesn't go up and systolic does so you have much wider pulse pressure. mean prob does goes up bc in systole more than diastole at high HR. Important: total peripheral resistance coming down during exercise. (this diastolic in graph should be flat and coming down w total peripheral resistance bc total peripheral resistance does control diastolic pressure to large extent) so this decrease in total peripheral resistance is bc of massive vasodilation of skel. muscles
Describe the arteriovenous oxygen difference during exercise.
AV O diff… diff between O in arterial and venous system with increases in exercise, how well body taking in O and how well CV system absorbing it.. measure of lung and muscle function to some extent. under normal conditions the AV O diff should go up -larger diff between arterial and venous O bc venous lower bc arterial being pulled out of system bc using for muscles. so diff gets larger and larger, venous going down. local metabolic dilation of skel. muscles.- lots of blood flow at sacrifice of blood to splanchin region to large extent.
On a graph with work on x axis, draw how exercise affects
-Arteriovenous oxygen difference (mL/dL)
-oxygen consumption (mL/min)
-total peripheral resistance (mmHg/ml.min)
-arterial pressure (mmHg)
-stroke volume (mL)
See slide 9.
How does anticipation of exercise affect body?
a. decrease parasympathetic nerve activity.
b. increase sympathetic nerve activity.
c. increased heart rate and myocardial contractility.
d. continues throughout exercise.
How does sympathetic activity to the heart affect body during exercise?
a. increase heart rate.
b. increase contractility (stroke volume).
c. increases cardiac output (HR x SV = CO).
d. as heart rate reaches maximum, stroke volume declines (reduced filling time).
neural activation of symp. NS-activates all aspects. HR through sinus node, contractility by bringing in more L type Ca current, loading sR w Ca which increases contractility so greater SV (contractility curve shifts to L, get greater amount and velocity shortening and smaller ESV) …so SV goes up, HR goes up, cardiac output goes up.
need increase in contractility to increase SV. then mech. to increase venous return to compensate for increase in HR which shortens filling time
SV declines as HR hits 160, 170 bc of lack of filling time, CO drops, feel fatigue, cant continue. fastest can go is 200 beats/min. sinus node can go faster but limiting factor is CO.
How does sympathetic vasoconstriction affect body during exercise?
a. increases vascular resistance.
b. diverts blood away from skin, kidneys, splanchnic regions and inactive muscle.
c. cerebral, pulmonary and cardiac vasculature unaffected.
global vasoconstriction- everything starts to vasoconstrict. when you start to exercise so really 3 tissues that do not vasoconstrict- no alpha in cerebral circulation, no alpha on pulmonary, little to no on cardiac- so these tissues are unaffected w global stimulation. affected locally but not from global symp. neural point of view ..kidneys spanchnic, skin and inactive muscles are symp. vasoconstricted. vasculature to skel. muscles do have alpha receptors and vasoconstriction. local regulation vasodilates needed muscles and others are vasoconstricted. not using some skel. muscles-those will get less blood during exercise. for ex. bikers long distance- use leg muscles but not upper body much. bikers can get muscle spasms in back bc not getting much blood there. upper body can go into spasm bc of lack of blood flow. locally vasodilators overcome global vasoconstriction.
How does metabolic vasodilation affect the body during exercise?
What are metabolic vasodilators?
Which muscles are affected?
What is this change dependent upon?
What limits metabolic vasodilation to some extent?
a. K+, adenosine, CO2, H+
b. lowers vascular resistance and increases blood flow (15 - 20 fold).
c. active skeletal muscle and heart.
d. change in total peripheral resistance is dependent on level of exercise and mass of active muscle.
e. sympathetic vasoconstriction slightly limits metabolic vasodilation.
vasodilation. to legs …metabolic activity overcomes global vasoconstriction… its not inhibiting it or stopping, its just overcoming, we know this bc if you cut sympathetic nerves to those muscles, they’ll vasodilate. even more.. so theres a competition going on. what are metabolic vasodilators? metabolic generated by cells- K, adenosine (bi-product of ATP), Co2, H, muscles more acidic when exercise. CO2 and H ions concentrations changes local environment of pH changes … changes binding of hemoglobin to O and changes transport of O across the muscles. adenosine powerful vasodilator. normal metabolite in body. used clinically
muscle and heart vasodilate. in response to this locally and overcome symp. vasoconstriction in skel. muscle (no vasoconstriction of heart in normal conditions
What do stress tests look for? What if you need to do a stress test on someone who can't walk?
purpose of stress test is to see if coronaries vasodilate. normally to match demand by exercising, adequate blood flow to heart? getting normal blood flow to heart? - stress test. adenosine used clinically to vasodilate, pt who cant get on treadmill-parapalegics or handicap person who can’t exercise heart. eject adenosine to coronaries and look at w scan to see if coronaries dilating
What are 2 clinical uses for adenosine?
adenosine used clinically to vasodilate, pt who cant get on treadmill-parapalegics or handicap person who can’t exercise heart. eject adenosine to coronaries and look at w scan to see if coronaries dilating. adenosine has v short half life. used to vasodilate. vascular bed to look at coronaries. adenosine also used clinically bc activates same channels that Ach. activates and can break arrhythmias causes by atrial activity. as result of that it lowers vascular resistance in that tissue and increases blood flow up to 15-20 fold.
How does the muscle in heart vasodilate?
vasodilates, immediately in response to work. work directly related to HR, contractility, and afterload- 3 things that increase work of heart and increase O consumption by increasing metabolic vasodilation.
What if someone's diastolic pressure started to rise during exercise? What would this signify?
whole body exercise at moderate level-lower of total peripheral resistance (controls diastolic pressure) so diastolic pressure will go down a bit. tell hypertensive patients bc diastolic pressure brought down by exercise. diastolic pressure starts to rise when exercise then stop test, big problem, means not vasodilating, and body not responding normally and its dangerous bc increasing afterload. so sign of pathology of don't maintain diastolic pressure at normal level during exercise
How does capillary recruitment affect the body in exercise?
a. active muscle capillaries all open for maximum blood flow.
when exercise open up additional capillaries in pulmonary sys-lowers pulmonary resistance to allow more blood flow into capillaries. not due to metabolic activity, just increase in flow into lungs bc CO greater and pops open capillaries not being used
increase capillaries in skel. muscles- IS metabolic activity …vasodilation. opens up. in resting about 75 percent of capillaries in muscles closed down. in exercise metabolic vasodil. pops them open and contributes to reduction in resistance - better blood flow
How does enhanced O2 extraction affect the body in exercise?
(hemoglobic, AV O difference, O consumption.. cardiac muscle vs skeletal muscle)
a. rightward shift in oxyhemoglobin dissociation curve.
b. less O2 held by hemoglobin; more O2 available for skeletal muscle tissue.
c. increase in arteriovenous oxygen difference.
d. oxygen consumption increases.
e. NOTE: the heart does not increase O2 extraction during exercise.
skel. muscles can enhance extraction of O. changes in pH locally and CO2 shifts rel. of O and hemoglobin so skel. muscles can extract, can take more O during exercise. more O off hemoglobin. benefit. less O held by hemoglobin, more O available for skeletal muscle specifically. increases AV O diff. by pulling more O out of arterial blood, lowers concentration of O in venous blood and diff is increased and allows for more O consumption in skeletal muscles. heart unable to increase extraction of O during exercise. VERY important. this mech. that occurs in skel. muscle doesn't occur in heart. so heart considered flow limited organ -aerobic exercise vasodilates. and brings blood flow to lots of tissue that lowers total peripheral resistance (diastolic pressure held down) means arterial pressure not going up quite as much even tho systolic can go up to 200 (normal) diastolic not changing much. pulse pressure widens dramatically but mean arterial pressure not elevated too much w aerobic exercise
How is venous return changed during exercise? How does the venous return curve change?
a. sympathetic venoconstriction decreases venous compliance and shunts blood back to heart, i.e. increases venous return.
b. muscle pump – working skeletal muscles compress veins and shunt blood back to the heart through one-way venous valves to increase venous return.
c. respiratory pump – during deep inspiration, negative intra-thoracic pressure and positive intra-abdominal pressure create a pressure gradient for increased venous return.
venous return curve shifting up and to right, happens during exercises, increases CO. causes cardiac function curve shift up and to L. changes CO w/o changing central venous pressure v much
How does arterial pressure change during exercise? Discuss systolic, diastolic, and pulse pressure.
-systolic pressure is increased primarily by the increase in stroke volume. However, sympathetic vasoconstriction also contributes to maintaining and raising mean arterial pressure during exercise.
-diastolic pressure is determined primarily by changes in total peripheral resistance. Depending on the level of exercise and mass of active tissue, the diastolic pressure can rise slightly, remain unchanged or even decrease slightly.
-pulse pressure widens.
What is similar between body's response during hemorrhage and exercise?
same response as in hemorrhage- if bleeding baroreceptor response that closes blood flow to kidney, skin, splanchnic region, everything except your brain, heart and lungs, shunts blood to vital organs. if thats strong vasoconstriction goes on for hour or 2 makes kidney and bowels ischemic (following isovolumic shock could have permanent damage…) these vasoconstrictions cant go on for v long. blood has to be distributed to one place to another based upon changes in arteriolar radius.
Would would happen if you had coronary disease and started to exercise?
can only get additional O during exercise though vasodilation. and increase in blood flow not extraction, to tissue. to contrast, skel. muscle increase blood flow but also O extraction. heart can only increase O delivery by increasing flow. if coronary disease and go exercise could have heart attack bc cant vasodilate, can’t open up those lesions and therefore you’re flow limited. mismatch between demand and supply. dep. on kind of exercise
How is peripheral resistance and mean arterial pressure and afterload affected when just lifting weights, not aerobic exercise?
but weight limiting-limited muscle use, symp. activity up dramatically but not lowering total peripheral resistance so using small amount of muscle. tremendous increase to symp. to heart. total per. resistance not down bc not vasodilating. as a result your mean arterial pressure goes up a LOT. and after load (mean arterial pressure) so need lots more O lots of vasodilation. of heart.
Why might an older man around 60 have a heart attack when shoveling snow?
when someone has heart attack usually 60-ish. sometimes shoveling snow, lifting weight… symp. activity raises mean arterial pressure bc total peripheral resistance is not going down, and have little coronary disease so have mismatch- heart demanding more blood flow and you can’t supply it. thats a heart attack.