Cardiovascular Physiology (Part 1) Flashcards
What is the primary function of the cardiovascular system?
to deliver blood to the tissues, providing essential nutrients to the cells for metabolism and removing waste products from the cells
Do arteries or veins contain the majority of the blood volume?
The veins contain the largest percentage of blood volume
Where does the exchange of nutrients, wastes, and fluid occur?
across the capillary walls
What some other functions of the cardiovascular system?
- participates in regulation of arterial BP
- delivers regulatory hormones from the endocrine glands to their sits of action in target tissues
- participates in regulation of body temperature
- involved in the homeostatic adjustments to altered physiologic states such as hemorrhage, exercise, and changes in posture
The left heart and the systemic arteries, capillaries, and veins are collectively called the _____ circulation
systemic
The right heart and the systemic arteries, capillaries, and veins are collectively called the _____ circulation
pulmonary
The ___ ventricle pumps blood to all organs of the body except the lungs
left
The ___ ventricle pumps blood to the lungs
right
The two sides of the heart operate in series, what does this mean?
Blood is pumped sequentially from the left heart to the systemic circulation, to the right heart, to the pulmonary circulation, and then back to the left heart
The rate at which blood is pumped from either ventricle is called what?
cardiac output
Are the cardiac outputs equal between the right and left ventricles? Why or why not?
The cardiac output of the left ventricle equals the cardiac output of the right ventricle in the steady state because the 2 sides of the heart operate in series
The rate at which blood is returned to the atria from the veins is called what?
venous return
Does return to the left heart equal that to the left heart? Why or why not?
Yes, because the 2 sides of the heart operate in series
In the steady state, cardiac output from the heart _____ venous return to the heart
equals
What are the functions of the blood vessels
- serve as closed system of passive conduits, delivering blood to and from the tissues where nutrients and wastes are exchanged.
- participate actively in the regulation of blood flow to the organ
Describe the steps involved in one complete circuit through the cardiovascular system
1) oxygenated blood fills the left ventricle
2) blood is ejected from the left ventricle
3) cardiac output is distributed among various organs
4) blood flow from the organs is collected in veins
5) venous return to the right atrium
6) mixed return to the right atrium
7) blood is ejected from the right ventricle into the pulmonary artery
8) blood flow from the lungs is returned to the heart via the pulmonary vein
Blood that has been oxygenated in the lungs returns to the left atrium via what?
the pulmonary vein
Blood that flows from the left atrium to the left ventricle goes through what valve?
the mitral valve
Blood leaves the left ventricle through what valve?
the aortic (semilunar) valve
What percentage of cardiac output is delivered to the brain?
15%
What percentage of cardiac output is delivered to the heart?
5%
What percentage of cardiac output is delivered to the kidneys?
25%
What percentage of cardiac output is delivered to the GI tract?
25%
What percentage of cardiac output is delivered to skeletal muscle?
25%
What percentage of cardiac output is delivered to the skin?
5%
What are the 3 major mechanisms for achieving a change in blood flow to an organ system?
- CO remains constant, but the blood flow is redistributed among the organ systems by selective alteration of arteriolar resistance
- CO increases or decreases, but the percentage distribution of blood flow among the organ systems is kept constant
- both CO and the percentage of blood flow are altered
When are both CO and the percentage of blood flow are altered?
In response to strenuous exercise: blood flow to skeletal muscle increases to meet the increase metabolic demand by a combination of increased CO and increased percentage distribution to skeletal muscle
What is the largest vein?
the vena cava
Is pressure higher in the vena cava or in the right atrium? Explain the importance of this
Pressure is higher in the vena cava which allows for blood to flow into the right atrium
In the steady state does venous return to the right atrium equal cardiac output from the left ventricle?
Yes
Mixed blood traveling from the right atrium to the right ventricle travels through what valve?
the tricuspid valve
Describe the path blood takes once it is ejected from the right ventricle
It is ejected through the pulmonic valve into the pulmonary artery, which carries blood to the lungs.
Describe the gas exchange that occurs in the lungs
Oxygen is added to the blood from alveolar gas, and carbon dioxide is removed from the blood and added to the alveolar gas
What does hemodynamics refer to?
the principles that govern blood flow in the cardiovascular system
What are blood vessels?
The conduits through which blood is carried from the heart to the tissues and from the tissues back to the heart
Describe the direction of blood flow through the vascular bed
artery –> arteriole –> capillaries –> venule –> vein
Which type of blood vessel has the largest total cross-sectional area
the capillaries
Which type of blood vessel has the largest percentage of the blood volume contained in them?
veins
What is the function of the arteries?
to deliver oxygenated blood to the organs
Are arteries thick or thin?
thick
What are arteries made of?
extensive amounts of elastic tissue, smooth muscle, and connective tissue
The volume of blood contained in the arteries is called what?
the stressed volume
What are arterioles?
the smallest branches of the arteries
Which blood vessels are the site of highest resistance to blood flow?
arterioles
What are arterioles composed of?
smooth muscle
Describe smooth muscle contraction in arterioles
it is tonically active (always contracted)
What is the smooth muscle in arterioles innervated by?
sympathetic adrenergic nerve fibers
What type of receptors are found on the arterioles of vascular beds (skin and splanchnic vasculature)?
alpha1-adrenergic receptors
What happens when alpha1-adrenergic receptors are activated?
They cause constriction of the vascular smooth muscle with produces a decrease in the diameter of the arteriole, which increases its resistance to blood flow
What type of receptors are found in the arterioles of skeletal muscle?
beta2-adrenergic receptors
What happens when beta2-adrenergic receptors are activated?
They cause relaxation of the vascular smooth muscle, which increases the diameter and decreases the resistance of these arterioles to blood flow
Describe the structure of capillaries
They are thin-walled structures lined with a single layer of endothelial cells surrounded by a basal lamina
How do lipid-soluble substances cross the capillary wall?
They dissolve in and diffuse across the endothelial cell membranes
How do water-soluble substances cross the capillary wall?
They either cross through water-filled clefts between the endothelial cells or through large pores in the walls of some capillaries
Are all capillaries perfused with blood at all times?
No, there is selective perfusion of capillary beds depending on the metabolic needs of the tissues