L14: Cardiac Output & Blood Flow to Muscle Tissues Flashcards
cardiac output definition
quantity of blood pumped into the aorta each minute by the heart
other CO definitions
- quantity of blood that flows thru the circulation
2. sum of all blood flow to all tissues of body
cardiac index
CO per square meter of body surface
calculating CI
normal human = 70kg
body surface = 1.7
CO = 5 L/min
CI = 5/1.7 == 3 L/min/meter squared
cardiac index by age
decreases with age
CO and O2 consumption w/ exercise
both increase w/ exercise
used to calculate blood flow thru an organ
flick principle of blood flow
also for blood flow thru entire body
CO = O2 consumption / (O2pul vein - O2pul art)
how to measure pulmonary vein [O2]
in systemic arterial blood
how to measure pulmonary artery [O2]
in systemic mixed venous blood
using flick principle to calculate CO
= rest O2/ (art - venous)
using flick principle to calculate SV
= CO / HR
what is the determining factor that controls how much blood the heart pumps out?
–the amount of blood that is returned to the heart is what gets pumped out
–the heart pumps out whatever blood it gets
the heart is a _____ pump
demand
pumps out what the tissues demands
the cardiovascular system consists of two ____ and two ____ connected in ____.
2 pumps
2 circuits
connected in series
pumps of the cardiovascular system
left and right ventricles
circuits of the cardiovascular system
pulmonary and systemic circuits connected in series
relate flow in both circuits
- flow is equal in both circuits
relate CO in both circuits
CO is equal
relate pressures of both circuits
systemic is always higher
relate chemical composition of both circuits
pulmonary venous composition = systemic arterial blood
systemic veins = pulmonary arterial blood
factors that directly affect cardiac output
- basic metabolism rate
- exercise?
- age
- size
normal values of CO
young = 5.6
women = 4.9
resting adult = 5.0 L/min
are peripheral or internal factors more important in controlling CO?
peripheral factors
frank-starling law of CO
heart automatically pumps whatever amount of blood that flows into the right atrium
stretching of heart causes…..
heart to pump faster and initiates Bainbridge reflex
ohm’s law of CO
any time the long-term level of total peripheral resistance changes, the CO will change in opposite direction
Bainbridge reflex
atrial stretch reflex
it responds to changes in blood vol. as detected by stretch receptors in right atrium
can control HR
baroreceptors
respond to changes in arterial pressure
for HR control
baroreceptors and Bainbridge reflex importance
not very important in humans
ex. of Bainbridge reflex in humans
after giving birth
large amount of blood from placenta returning to mother’s circulation
resulting in tachycardia
relate CO to arterial pressure and TPR
CO - art. press
directly related
CO - TPR
inversely related
effect of anemia on CO and arterial pressure
increases both
factors that cause of hypereffective heart
- nervous stim
- hypertrophy of heart
- exercise via nervous sys.
factors that cause a hypoeffective heart
- increased art. press.
- inhibition of heart’s excitability
- pathological abnormal rhythms or HR
- art. blockages
- valve disease
- congenital heart disease
- cardiac hypoxia
ventricular function curve
right atrial pressure vs. CO
can demonstrate frank-starling mechanism
define hypereffective heart
a heart that puts out more blood than normal/ necessary
define a hypoeffective heart
a heart that puts out less blood than normal/ less than what is needed
DNP
metabolic stimulant
venous return pressure range
-2 - +7
if right atrial pressure = -2
venous return reaches a plateau
caused by collapse of veins entering chest
mean systemic filling pressure
when venous return = 0 mmhg, right atrial pressure = +7
mean circulatory filling pressure
–pressures everywhere in the body become equal
when 4L blood vol - it = 0
when 5L blood vol - it = 7 mmhg
the greater the difference between the mean systemic filling pressure and the right atrial pressure …….
the greater the venous return
the difference between the mean systemic filling pressure and the right atrial pressure = ?
the pressure gradient for venous return
resistance to venous return
2/3 from venous resistance
1/3 from arteriolar/small artery resistance
venous return = ?
(mean systemic filling - right atrial pressure) / resistance to venous return
numerator = venous gradient
normal VR values
5L/min = (7 - 0) / 1.4 mmhg/L/min
factors that affect venous return
- right atrial pressure
- mean systemic filling pressure
- blood flow resistance between peripheral vessels and right atrium
right atrial pressure number
0
mean systemic filling pressure
= +7
when R atrial pressure = mean systemic filling pressure
venous return = ?
0
plateau on venous return curve
–caused by collapse of large veins entering chest when r atrial press. < atmospheric press.
how does sympathic stimulation/inhibition effect mean circulatory filling pressure
stim = decreased (green)
inhibit = increased (blue)
a decrease in resistance allows more blood to flow which = ?
while an increase in resistance has the _____ effect.
more venous return
opposite
the highest level to which the right atrial pressure can rise is equal to ______ ?
the mean systemic filling pressure
venous return curve does not include
cardiac output
as right atrial pressure increases, venous return _____ .
decreases
mean systemic filling pressure is measured when ?
the heart is stopped experimentally
an increase in blood volume will _____ CO and an ________ in mean systemic pressure.
increase
increase
if cardiac output is decreased, right atrial pressure is ______ .
decreased
decreased venous compliance = _______ blood stored in veins
less blood stored
positive iontropic effect
increases CO equilibrium
and lowers right atrial pressure
negative iontropic effect
decreases CO equilibrium and raises right atrial pressure
local control of blood flow to muscles
concentration changes in chemicals/ions
nervous control of blood flow to muscles
sympathetic nerves and adrenal medulla secrete vasoconstrictors
mass discharge of sympathetic nervous system: blood flow to muscles
HR increases
peripheral arteries strongly contracted except those in heart, brain, active muscles
veins contracted
exercise and blood flow to muscles: results
vasoconstriction
increased pumping activity
increased arterial pressure and CO
base of ascending aorta gives off ?
2 coronary arteries
a right and left
supply the heart muscle itself
during systole, coronary blood flow in the left ventricle …..?
falls to a low value
opposite to flow in vascular beds of the body
during diastole, the cardiac muscle _____ and no longer _______ blood flow throughout the left ventricular ________. results in ?
relaxes
obstructs
capillaries
=increased blood flow to heart
primary controller of coronary flow
local muscle metabolism
coronary flow ______ in ______ proportion to additional metabolic consumption of _____ by heart.
increases
direct
oxygen
coronary occlusion can result in death
- decreased CO
- pulmonary edema
- fibrillation
- rupture of heart
