cardiac output and blood flow in muscle tissues Flashcards
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
series
are pressures higher in systemic or pulmonary circuits
systemic
what factors directly affect cardiac output
basic level of body metabolism
whether the person is exercising
age
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 myocarditis 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
decreases
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
