cardiac output and blood flow in muscle tissues Flashcards Preview

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Flashcards in cardiac output and blood flow in muscle tissues Deck (40):

define cardiac output

quantity of blood pumped into the aorta each minute by the heart
quantity of blood that flows through the circulation
sum of all the blood flows to all the tissues of the body


define cardiac index

cardiac output per square meter of body surface


what happens to cardiac output and oxygen consumption when you exercise

they both increase


what is the fick principle used for

used to calculate blood flow through an organ


what is the equation for the fick principle of blood flow

cardiac output= O2 consumption/ [O2]pul vein-[O2]pul art


what determines how much blood the heart pumps out

the amount of blood returning to the heart


how are the 2 circuits of the cardiovascular system connected



are pressures higher in systemic or pulmonary circuits



what factors directly affect cardiac output

basic level of body metabolism
whether the person is exercising
size of the body


what is the frank-starling law

heart automatically pumps whatever amounts of blood that flows into the right atrium


define ohm;s law

anytime the long-term level of total peripheral resistance changes the cardiac output changes quantitatively in exactly the opposite direction


what does the bainbridge reflex do

responds to changes in blood volume as detected by stretch receptors in the right atrium


what factors cause hyper effective heart

nervous stimulation
hypertrophy of heart
exercise via nervous system


what factors cause hypo effective heart

increased arterial pressure (hypertension)
inhibition of nervous excitation of the heart
pathological factors causing abnormal heart rhythm/rate
coronary artery blockage
valvular heart disease
congenital heart disease
cardiac hypoxia


cardiac factors causing decreased cardiac output

severe blood vessel blockage--> myocardial infarction
severe valvular disease
cardiac tamponade
cardiac metabolic arrangements


what is beriberi

caused by insufficient quantity of the vitamin thiamine of the tissues to use some cellular nutrients, and the local tissue blood flow mechanisms in turn cause some marked compensatory peripheral vasodilation


what is atriovenous fistula

when fistula occurs between a major artery and vein=a lot of blood flows direction from artery to vein. This greatly decreases the total peripheral resistance and increase the venous return and cardiac output


what is hypothyroidism

metabolism of most tissues of the body becomes greatly increased. oxygen usage increases and vasodilator products are released from the tissues. Total peripheral resistance decreases markedly because of the local tissue blood flow control reactions throughout the body=venous return and cardiac output often increased to 40-80% above normal


what is anemia

2 peripheral effects greatly decreased the total peripheral resistance (1st reduced viscosity of the blood result in form the decreased concentration of RBC. 2nd diminished delivery of oxygen to the tissues, which causes local vasodilation). due to both of these, the cardiac output increases greatly


non-cardiac factors that decreased cardiac output

decreased blood volume
acute venous dilation
obstruction of large veins
decreased tissue mass
decreased metabolic rate of tissues


what factors affect venous return to the heart from the systemic circulation

right atrial pressure
degree of filling of systemic circulation (when heart pumping stops, all blood flow ceases, pressure everywhere in the body become equal)
the greater the difference between the mean systemic filling pressure and the right atrial pressure, the greater the venous return
resistance to blood flow
right atrial pressure
mean systemic filling pressure
blood flow resistance between peripheral vessels and right atrium


define pressure gradient for venous return

the difference between the mean systemic filling pressure and the right atrial pressure


what is the equation to calculate venous return

(mean systemic filling pressure-right atrial pressure)/resistance to venous return


how is the resistance to blood flow determined (factors that affect venous return to the heart from the systemic circulation)

about 2/3 of the resistance to venous return is determined by venous resistance
about 1/3 of the resistance to venous return is determined by arteriolar and small artery resistance


how does right atrial pressure affect venous return

impedes flow of blood from veins into right atrium


how does the mean systemic filling pressure affect venous return

forces systemic blood toward heart
pressure when arterial and venous pressures come to equilibrium and systemic circulation flow comes to a stop


what does a decrease in resistance do to blood flow (venous return curves)

allows more blood to flow (more venous return)


what does increasing Psf do to vascular volume and venous compliance

increases vascular volume
decreases venous compliance


what does an increase in Psf do to the vascular return curve

shifts it to the right and enhances filling of the ventricles


what does decreasing Psf do to vascular volume and venous compliance

decrease vascular volume
increase venous compliance


what does decreased Psf do to the vascular return curve

shift to the left and reduces filling of the ventricles


what are the local controls of blood flow regulation to skeletal muscle

large blood flow during skeletal muscle activity is due mainly to chemicals that act directly on muscle arterioles to dilate them (reduction in oxygen, adenosine, potassium ion, ATP, lactic acid, carbon dioxide


what are the nervous controls of blood flow regulation to skeletal muscle

sympathetic vasoconstrictor nerves (secrete norepinephrine, can decrease blood flow through resting muscles to as little as one half to one third normal)
adrenal medullae (secrete norepinephrine and epinephrine, epinephrine also has a slight dilator effect)


what happens when there is a mass discharge of the sympathetic nervous system

heart rate increases
most peripheral arteries are strongly contracted except (those in active muscles, coronary arteries, cerebral arteries)
muscle walls of veins are contracted


what does the sympathetic stimulate cause when there is an increase in arterial pressure

vasoconstriction of arterioles and small arteries in most tissues
increased pumping activity of the heart
increase in mean filling pressure caused mainly by venous contraction


what happens to blood flow during contractions



what happens during systole in coronary flow

coronary blood flow in the left ventricle falls to a low value (opposite to flow in vascular beds elsewhere in the body)


what happens during diastole in coronary flow

the cardiac muscle relaxes and no longer obstructs blood flow through the left ventricular capillaries


what is the primary controller of coronary flow

local muscle metabolism


what can cause coronary occlusion and death

decreased cardiac output
damming of blood in pulmonary blood vessels and death resulting from pulmonary edema
fibrillation of heart
rupture of heart