Chapter 15: The Cardiovascular System - Blood vessels and Hemodynamics Flashcards
1
Q
A
2
Q
What are the five main types of blood vessels?
A
Arteries, arterioles, capillaries, venules, and veins
3
Q
What is the primary function of arteries?
A
Carry blood away from the heart
4
Q
What do capillaries allow for in the body?
A
Exchange of substances between blood and body tissues
5
Q
What are venules?
A
Small veins that form from groups of capillaries
6
Q
What is the function of veins?
A
Carry blood from tissues back to the heart
7
Q
What is the endothelium?
A
Inner layer of epithelial cells in blood vessels
8
Q
What is the role of endothelial cells?
A
Influence blood flow, secrete chemical mediators, assist with capillary permeability
9
Q
What is the basement membrane?
A
Thin layer of extracellular material that supports endothelial cells
10
Q
Define vasoconstriction
A
Decrease in the diameter of the lumen of a blood vessel
11
Q
Define vasodilation
A
Increase in the diameter of the lumen of a blood vessel
12
Q
What is vascular tone?
A
State of partial contraction maintained by smooth muscle in blood vessels
13
Q
What two types of connective tissue may be present in blood vessels?
A
Elastic connective tissue and fibrous connective tissue
14
Q
What is the function of elastic connective tissue in arteries?
A
Allows arteries to stretch and return to their original shape
15
Q
What are elastic arteries?
A
Large-diameter arteries with thick walls containing a high proportion of elastic connective tissue
16
Q
What is the function of muscular arteries?
A
Distribute blood to the organs of the body
17
Q
What are arterioles?
A
Small arteries that deliver blood to capillaries
18
Q
Why are arterioles known as resistance vessels?
A
Their small diameters provide the greatest resistance to blood flow
19
Q
What is the diameter range of arterioles?
A
15 μm to 100 μm
20
Q
What is the function of capillaries?
A
Exchange of nutrients and wastes between blood and tissue cells
21
Q
What is a capillary bed?
A
Network of 10 to 100 capillaries
22
Q
What are precapillary sphincters?
A
Rings of smooth muscle fibers that control blood flow through capillaries
23
Q
What is vasomotion?
A
Intermittent contraction and relaxation of smooth muscle of precapillary sphincters
24
Q
What are the three types of capillaries?
A
Continuous capillaries, fenestrated capillaries, and sinusoids
25
What characterizes continuous capillaries?
Plasma membranes form a continuous tube with intercellular clefts
26
What are fenestrated capillaries known for?
Having cylindrical pores that increase permeability
27
What are sinusoids?
Wide, winding capillaries with large fenestrations and intercellular clefts
28
What is the function of postcapillary venules?
Drain capillary blood and begin the return of blood to the heart
29
What do larger venules contain that postcapillary venules do not?
One or two layers of smooth muscle and a thin layer of fibrous connective tissue
30
What is the primary function of valves in veins?
Prevent backflow of blood
31
What is varicose veins?
Condition caused by leaky venous valves leading to dilated and twisted veins
32
What is the skeletal muscle pump?
Mechanism that helps move venous blood back to the heart through muscle contraction
33
What is the role of the proximal and distal valves in venous blood flow?
The proximal valve is closer to the heart and the distal valve is farther from the heart. Blood flows upward toward the heart when these valves are open.
34
What action is referred to as 'milking' in venous blood flow?
Contraction of leg muscles that compresses the vein and pushes blood through the proximal valve.
35
What happens to the distal valve during muscle contraction?
The distal valve closes as some blood is pushed against it.
36
How does muscle immobilization affect venous blood return?
It slows the return of venous blood to the heart, potentially leading to circulation problems.
37
What is the respiratory pump in venous blood flow?
A phenomenon that promotes venous blood movement back to the heart due to pressure changes in the thoracic and abdominal cavities during breathing.
38
During inspiration, what happens to the diaphragm?
It moves downward, decreasing pressure in the thoracic cavity and increasing pressure in the abdominal cavity.
39
What percentage of blood volume is typically found in systemic veins and venules at rest?
About 64%.
40
What is venoconstriction?
The constriction of veins, reducing blood volume in reservoirs to increase blood flow to skeletal muscles.
41
What is the primary mission of the cardiovascular system?
To keep blood flowing through capillaries to allow capillary exchange.
42
What is the most important method of capillary exchange?
Diffusion.
43
Which substances typically enter and leave capillaries by simple diffusion?
* Oxygen (O2) * Carbon dioxide (CO2) * Glucose * Amino acids * Hormones
44
How do lipid-soluble substances cross capillary walls?
They pass directly through the lipid bilayer of endothelial cell plasma membranes.
45
What are intercellular clefts?
Spaces between endothelial cells that allow small water-soluble substances to pass across capillary walls.
46
What cannot pass through the walls of continuous or fenestrated capillaries?
Erythrocytes and plasma proteins.
47
What is transcytosis?
A process where substances in blood are enclosed in vesicles and transported across endothelial cells.
48
What is bulk flow?
A passive process where large numbers of ions, molecules, or particles move together in the same direction.
49
What is filtration in the context of capillary exchange?
Pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid.
50
What is reabsorption in capillary exchange?
Pressure-driven movement from interstitial fluid into blood capillaries.
51
What are Starling forces?
Four pressures that determine fluid movement across capillary walls.
52
What is capillary hydrostatic pressure (PC)?
The pressure that water in blood exerts against the inner surface of capillary walls, promoting filtration.
53
What is plasma colloid osmotic pressure (πP)?
The pressure due to the colloidal suspension of plasma proteins in blood, promoting reabsorption.
54
What is the net filtration pressure (NFP) formula?
NFP = (PC + πIF) - (πP + PIF).
55
What is the fate of excess filtered fluid that does not return to capillaries?
It enters the lymphatic system.
56
What are the primary functions of the lymphatic system?
* Drains excess interstitial fluid * Returns filtered plasma proteins * Carries out immune responses * Transports dietary lipids
57
What structure begins the lymphatic vessels?
Lymphatic capillaries.
58
What mechanism helps maintain the flow of lymph?
* Smooth muscle contractions * Skeletal muscle pump * Respiratory pump
59
What is hemodynamics?
The factors that affect blood flow through blood vessels.
60
What two major factors determine blood flow?
* Pressure gradient * Resistance to blood flow
61
Blood flow (F) is directly proportional to _______ and inversely proportional to _______.
Pressure gradient (ΔP), Resistance (R).
62
What does a high resistance in blood vessels imply for blood flow?
It results in smaller blood flow.
63
What drives blood flow through a tissue?
The pressure gradient and resistance to blood flow
## Footnote
Blood flow is influenced by the difference in pressure and the resistance encountered in blood vessels.
64
How is blood flow (F) related to the pressure gradient (ΔP) and resistance (R)?
F is directly proportional to ΔP and inversely proportional to R
## Footnote
This relationship is fundamental in understanding hemodynamics.
65
What are the three factors that determine resistance to blood flow?
* Blood viscosity
* Blood vessel length
* Blood vessel radius
## Footnote
Each of these factors plays a significant role in how easily blood flows through the circulatory system.
66
How does blood viscosity affect resistance?
Resistance is directly proportional to blood viscosity
## Footnote
Higher viscosity leads to greater resistance, influenced by factors like erythrocyte ratio and plasma protein concentration.
67
What effect does blood vessel length have on resistance?
Resistance is directly proportional to blood vessel length
## Footnote
Longer vessels increase resistance; however, vessel length is typically constant in adults.
68
How does blood vessel radius relate to resistance?
Resistance is inversely proportional to the fourth power of the radius
## Footnote
Small changes in radius can lead to large changes in resistance.
69
What is total peripheral resistance (TPR)?
TPR refers to all vascular resistances offered by systemic blood vessels
## Footnote
TPR is crucial for regulating blood pressure and blood flow.
70
What is laminar flow?
Blood flow in a smooth, streamlined manner parallel to the vessel axis
## Footnote
Laminar flow is characterized by layers of fluid sliding past one another.
71
What happens to laminar flow under certain conditions?
It becomes turbulent
## Footnote
Turbulent flow occurs with constricted areas, rough surfaces, or high velocities.
72
What is blood pressure (BP)?
The hydrostatic pressure exerted by blood on vessel walls
## Footnote
BP is influenced by cardiac output, blood volume, and vascular resistance.
73
What are systolic and diastolic pressures?
* Systolic pressure (SP): highest blood pressure during ventricular contraction
* Diastolic pressure (DP): lowest blood pressure during ventricular relaxation
## Footnote
These pressures are critical for assessing cardiovascular health.
74
What is pulse pressure (PP)?
PP = SP − DP
## Footnote
Pulse pressure provides insight into cardiovascular conditions.
75
How is mean arterial pressure (MAP) calculated?
MAP = DP + ⅓(PP)
## Footnote
MAP represents the average blood pressure in arteries over one cardiac cycle.
76
What is the relationship between cardiac output (CO) and mean arterial pressure (MAP)?
MAP = CO × TPR
## Footnote
Changes in CO or TPR will affect MAP.
77
What is compliance in the context of blood vessels?
The ability of a hollow object to stretch
## Footnote
Compliance is defined as the change in volume per unit change of transmural pressure.
78
How do veins and arteries differ in compliance?
* Veins: high compliance, easily stretch
* Arteries: low compliance, less ability to stretch
## Footnote
This difference affects how blood volume changes impact blood pressure.
79
What is the significance of venous return?
Volume of blood flowing back to the heart through systemic veins
## Footnote
Venous return is crucial for maintaining adequate cardiac output.
80
What factors enhance venous return?
* Venous pressure gradient
* Valves in veins
* Skeletal muscle contractions (skeletal muscle pump)
* Pressure changes during respiration (respiratory pump)
* Venoconstriction
## Footnote
These mechanisms help counteract the effects of gravity on blood return.
81
What is the normal circulation time for blood in a resting person?
About 1 minute
## Footnote
This is the time taken for blood to complete a full circuit through the body.
82
How does the velocity of blood flow change as it moves through the circulatory system?
Velocity decreases as blood moves from arteries to capillaries and increases as it returns to veins
## Footnote
This change is related to cross-sectional area.
83
What is the average blood volume in an adult?
About 5 liters
## Footnote
Changes in blood volume can significantly affect blood pressure.
84
What is venoconstriction?
Increases venous return by reducing the volume of blood in reservoirs, allowing greater blood volume to flow back to the heart
85
How is the velocity of blood flow related to blood flow and vessel cross-sectional area?
Directly proportional to blood flow and inversely proportional to the cross-sectional area of the blood vessel
86
What percentage of cardiac output do the digestive tract and liver receive at rest?
27%
87
What percentage of cardiac output do the kidneys receive at rest?
20%
88
What is vascular tone?
A state of partial contraction in arteriolar smooth muscle that establishes a baseline level for contraction
89
What happens during vasoconstriction?
Increases vessel resistance and decreases blood flow
90
What is the effect of vasodilation?
Increases vessel radius, decreases resistance, and increases blood flow
91
What are the two methods of controlling arteriolar radii?
* Intrinsic control
* Extrinsic control
92
What is autoregulation?
The ability of a tissue to maintain relatively constant blood flow despite changes in mean arterial pressure
93
What physical change promotes vasodilation?
Warming
94
What is myogenic response?
Smooth muscle contracts more forcefully when stretched and relaxes when stretching lessens
95
What triggers vasodilation during increased arterial pressure?
Stretch of arteriolar smooth muscle causing mechanically-gated channels to open, allowing Ca2+ to enter
96
What are examples of local chemical mediators that can cause vasodilation?
* CO2
* K+
* H+
* Adenosine
* Nitric oxide
97
What is the difference between active hyperemia and reactive hyperemia?
Active hyperemia occurs due to increased metabolic activity; reactive hyperemia occurs due to a temporary blockage of blood supply
98
What are the two types of extrinsic control of arteriolar radius?
* Nerves
* Hormones
99
What type of receptors do most arterioles have?
α1-adrenergic receptors
100
What is the effect of norepinephrine on α1-adrenergic receptors?
Causes vasoconstriction
101
What is the average mean arterial pressure (MAP)?
About 83 mmHg
102
What is the formula for mean arterial pressure (MAP)?
MAP = CO × TPR
103
What does TPR stand for?
Total peripheral resistance
104
What regulates mean arterial pressure through negative feedback?
The nervous system via baroreceptor reflexes and chemoreceptor reflexes
105
What is the role of the cardiovascular center?
Regulates mean arterial blood pressure by altering heart rate, contractility, and blood vessel radius
106
What inputs does the cardiovascular center receive?
* Higher brain regions
* Sensory receptors
107
What do baroreceptors monitor?
Changes in pressure and stretch in the walls of blood vessels
108
Where are baroreceptors located?
* Aorta
* Internal carotid arteries
* Other large arteries in the neck and chest
109
What happens to heart rate when the CV center increases parasympathetic nerve action potentials?
Heart rate decreases.
## Footnote
This is due to increased parasympathetic stimulation of the heart.
110
What is the effect on heart rate and contractility when the CV center increases sympathetic nerve action potentials?
Heart rate and contractility increase.
## Footnote
This also results in vasoconstriction.
111
Where are baroreceptors located?
In the aorta, internal carotid arteries, and other large arteries in the neck and chest.
## Footnote
They are pressure-sensitive sensory receptors.
112
What are the two most important baroreceptor reflexes?
* Carotid sinus reflex
* Aortic reflex
## Footnote
These help regulate blood pressure.
113
What initiates the carotid sinus reflex?
Baroreceptors in the wall of the carotid sinuses.
## Footnote
This reflex helps regulate blood pressure in the brain.
114
What initiates the aortic reflex?
Baroreceptors in the wall of the arch of the aorta.
## Footnote
This reflex regulates systemic blood pressure.
115
How do baroreceptors respond when blood pressure falls?
They send action potentials at a slower rate to the CV center.
## Footnote
This leads to decreased parasympathetic stimulation and increased sympathetic stimulation.
116
What is the result of increased sympathetic stimulation from the CV center?
Increased heart rate, contractility, and vasoconstriction.
## Footnote
This raises blood pressure to normal levels.
117
What is orthostatic hypotension?
Excessive lowering of systemic blood pressure when assuming an erect posture.
## Footnote
It can be caused by fluid loss, certain drugs, and cardiovascular or neurogenic factors.
118
What do chemoreceptors monitor?
The chemical composition of blood, including levels of O2, CO2, and H+.
## Footnote
They are located near baroreceptors.
119
What stimulates chemoreceptors to send input to the cardiovascular center?
Hypoxia, acidosis, or hypercapnia.
## Footnote
These conditions indicate changes in blood chemistry.
120
What does the renin–angiotensin–aldosterone (RAA) system do?
Raises blood pressure by vasoconstriction and increasing blood volume.
## Footnote
It is activated when blood volume falls or blood flow to kidneys decreases.
121
What is the effect of epinephrine and norepinephrine on cardiac output?
They increase cardiac output by increasing the rate and force of heart contractions.
## Footnote
Norepinephrine causes vasoconstriction while epinephrine causes vasodilation in some areas.
122
What is the role of antidiuretic hormone (ADH) in blood pressure regulation?
Causes vasoconstriction and increases water reabsorption, raising blood pressure.
## Footnote
ADH is also called vasopressin.
123
How does atrial natriuretic peptide (ANP) affect blood pressure?
Lowers blood pressure by causing vasodilation and promoting salt and water loss in urine.
## Footnote
ANP is released by cells in the heart's atria.
124
What are the types of shock?
* Hypovolemic shock
* Cardiogenic shock
* Vascular shock
* Obstructive shock
## Footnote
Each type has different causes related to blood flow and pressure.
125
What is a common cause of hypovolemic shock?
Acute hemorrhage.
## Footnote
This can be due to trauma or internal bleeding.
126
What happens to the heart in cardiogenic shock?
The heart fails to pump adequately.
## Footnote
This is often due to a myocardial infarction.
127
What is vascular shock?
Shock due to inappropriate vasodilation.
## Footnote
It can occur even with normal blood volume.
128
What is obstructive shock caused by?
Obstruction of blood flow.
## Footnote
A common cause is pulmonary embolism.
129
What are the major compensatory mechanisms in shock?
* Activation of the RAA system
* Secretion of ADH
* Activation of the sympathetic division of the ANS
* Release of local vasodilators
## Footnote
These mechanisms work to restore blood pressure and flow.
130
What is the effect of decreased blood flow to the kidneys during shock?
The kidneys secrete renin, activating the RAA system.
## Footnote
This helps increase blood volume and blood pressure.
131
What happens to the skin during shock?
It becomes cool, pale, and clammy.
## Footnote
This is due to sympathetic constriction of skin blood vessels.
132
What are some signs and symptoms of shock?
* Systolic BP < 90 mmHg
* Rapid resting heart rate
* Weak and rapid pulse
* Altered mental state
* Reduced urine formation
* Thirst
* Low blood pH (acidosis)
* Nausea
## Footnote
These symptoms arise from inadequate oxygen delivery and compensatory mechanisms.
