Hemodynamics Flashcards
the study of the movement of blood throughout the circulatory system along with the regulatory mechanisms and driving forces involved
it studies the factors that govern blood flow
hemodynamics
Two major divisions of the circulatory system
Pulmonary- delivers blood to the lungs
Systemic (Peripheral) - delivers blood to all other organs and tissues
Arteries transport blood under ___________ pressure to tissues
Arterioles are ______________ valves that regulate local blood flow
high; control
Veins serve as a major _____________ of blood
reservoir
Arteries are very muscular and hence are not very ________________. As a result increases in arterial pressure (AP) causes only small increases in arterial ________
distensible; diameter
Veins are highly _____________. As a result, small increases in venous pressure cause large increases in venous diameter`
distensible
The adult circulatory system contains __________ liters of blood, 64% of which is in the systemic ___________-
5; veins
What makes blood flow ?
Blood moves through vessels because the force that drives blood flow is greater than the resistance to flow
Blood moves through vessels because the force that drives blood flow is greater than the __________________ to blood flow
resistance
The force that drives blood flow is the _____________ gradient between two points in a vessel
pressure
Blood will flow from the point where pressure is higher toward the point where pressure is lower
Resistance to blood flow is determined by ………..
the diameter and length of the vessel and by blood viscosity,
From a pharmacological viewpoint, the most important determinant of resistance is:
vessel diameter; the larger the vessel, the smaller the resistance
When vessels dilate, ____________ declines, causing blood flow to ____________
resistance; increase
When vessels constrict, ___________ rises, causing blood flow to ____________–
resistance; decline
To maintain adequate flow when resistance rises, ______________ must rise as well
blood pressure
In addition to the small pressure head in the venules, three mechanisms help ensure venous return to the heart:
1) negative pressure in the right atrium sucks blood toward the heart
2) constriction of veins increases venous pressure and thereby drives blood toward the heart
3) contraction of skeletal muscles, in conjunction with one-way venous valves, pumps blood toward the heart
Every minute the heart pumps the equivalent of all the blood in the body. TRUE OR FALSE
TRUE
cardiac output is about 5 L/minute in the average adult
CO=
HR X SV
Heart rate is increased by the sympathetic branch of the autonomic nervous system acting through ____________________ receptors in the SA node
beta 1 adrenergic receptors
Heart rate is decreased by the parasympathetic branch acting through _________________ in the SA node. These impulses reach the heart via the ____________ nerve
muscarinic; vagus
What are the 3 factors stroke volume is determined by ?
Contractility, Preload, Afterload
defined as the amount of tension (stretch) applied to a muscle before contraction
preload
defined as the load against which a muscle exerts its force
afterload
for the heart, _______________ is the Arterial pressure that the left ventricle must overcome to eject blood
afterload
the force with which the ventricles contract
myocardial contractility
Cardiac afterload is determined primarily by peripheral resistance, which in turn is determined by the degree of ____________ in arterioles
constriction
_________________ law states that the force of ventricular contraction is proportional to myocardial fiber length. Because of this relationship, when more blood enters the heart, more is pumped out. As a result the healthy heart is able to precisely match output with venous return.
Starling’s
basically states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction, when all other factors remain constant
this is the force that returns blood to the heart
systemic filling pressure
_____________ is the primary determinant of stroke volume
venous return
_________ volume and venous ___________ can both be altered with drugs
Blood; tone
This can effect the systemic filling pressure and hence the stroke volume and hence the Cardiac output
The most important determinant of venous return is _____________ filling pressure, which can be raised by _____________________
systemic; constricting veins and increasing blood volume
Because cardiac muscle operates under Starling’s law, the right and left ventricles always pump exactly the same amount of blood (assuming the heart is healthy). Hence, balance between the ______________ and ____________ circulations is maintained.
pulmonary; systemic
Arterial pressure is regulated by the _____________, the RAAS, the __________, and natriuretic peptides
Autonomic nervous system; kidneys
The ANS regulates arterial pressure through 2 things
1) tonic control of heart rate and peripheral resistance
2) through the baroreceptor reflex
The __________________ reflex is useful only for short term control of AP. When pressure remains elevated or lowered, the system resets to the new pressure within 1-2 days, and hence ceases to respond
baroreceptor
Drugs that lower AP trigger the ____________________ reflex, and thereby _________ tachycardia. Hence, the _______________ reflex can temporarily negate efforts to lower AP with drugs.
baroreceptor; reflex; baroreceptor
The RAAS supports AP by causing
1) constriction of arterioles and veins
2) retention of water by the kidneys
vasoconstriction is mediated by angiotensin II; water retention is mediated in part by aldosterone
The _______ provide long term control of blood pressure by regulating ______________ volume
kidneys; blood
Postural (orthostatic) hypotension is caused by decreased ___________return secondary to pooling of blood in veins, which can occur when we assume an ____________ posture.
venous; erect
Drugs that ____ veins intensify and prolong ________________. As with other drugs that reduce AP, venodilators trigger the ______________ reflex and can thereby cause reflex tachycardia
dilate; postural hypotension; baroceptor
Natriuretic peptides defend the cardiovascular system from _________________ overload- primarily by reducing blood volume and promoting ____________
volume; vasodilation
