Circulatory Flashcards
(276 cards)
1
Q
Name the types of Blood Vessels.
A
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
2
Q
Common Structure of Arteries & Veins: 3 vessel Wall layers (External to Internal)
A
- Tunica Externa (Adventitia)
- Tunica Media
- Tunica Interna (Intima)
3
Q
What is the Tunica Externa (Adventitia) composed of?
A
Elastic and Collagen Fibers (Connective Tissue)
4
Q
What is contained within the Tunica Externa (Adventitia)
A
- Nerves of the vessels
- Vasa Vasorum
5
Q
What is the Vasa Vasorum (found in the Tunica Externa)?
A
Small vessels that transport O2 and nutrients to cells of blood vessel walls
6
Q
This layer of the vessel helps anchor it to the surrounding tissue.
A
Tunica Externa (Adventitia)
7
Q
This layer within the Tunica Media is only found in Arteries.
A
External Elastic Lamina
8
Q
What purpose does the External Elastic Lamina serve?
A
- Separates the tunica media from tunica externa
- Thin sheet of elastic fibers
- Variable number of window-like openings (facilitate diffusion of materials through tunica externa to tunica media)
9
Q
This layer within the Tunica Media is found in Arteries and veins.
A
Smooth Muscle (some elastic fibers) Layer
10
Q
What purpose and functions does the Smooth Muscle Layer of the Tunica Media have (Blood Vessels)?
A
- Regulates diameter of vessel lumen
- Innervated by sympathetic nerve fibers
- Contracts and relaxes for blood flow regulation as needed. (Vasoconstriction and Vasodilation)
- Contracts vessel when damaged to limit blood loss
11
Q
This layer of the blood vessel has direct contact with blood as it flows through the lumen.
A
Tunica Interna (Intima)
12
Q
What are the layers of the Tunica Interna (Intima)?
A
- Internal Elastic Lamina Layer (Arterial)
- Basement Membrane Layer (Arterial, Venous)
- Endothelial Cell Layer (Arterial, Venous)
13
Q
This layer of the Tunica Interna is only found in arteries and not veins?
A
Internal Elastic Lamina Layer
14
Q
Give the characteristics of the Internal Elastic Lamina Layer?
A
- Separates tunica interna from tunica media
- Thin sheet of elastic fibers
- Variable number of window-like openings (Facilitate diffusion through tunica interna to tunica media
15
Q
The Basement Membrane of the Tunica Interna (Intima) is also called?
A
Subendothelial Layer
16
Q
Give the characteristics of the Basement Membrane.
A
- Provides physical support for epithelia layer
- Network of collagen fibers
- Anchors endothelium to underlying connective tissue
- Helps regulate molecular movement
- Guides cell movement during tissue repair of blood vessels.
17
Q
What is the purpose of the collagen fibers in the Basement Membrane of the Tunica Interna serve?
A
- Provides significant tensile strength
- Allows for some stretching and recoil
18
Q
What is the inner most layer of the Tunica Interna (Intima)?
A
Endothelium
19
Q
Name the characteristics of the Endothelium of the Tunica Interna.
A
- Lining of the lumen of the vessel
- Continuous with endocardial lining of the heart
- Reduces blood cell damage (smooth)
- Reduce Friction of blood flow (Increased efficiency)
- Secretes chemical mediators that influence contractile smooth muscle in tunica media
- Assists with capillary permeability
20
Q
Name the layers and sublayers of each for arterial vessels. External to Internal
A
Tunica Externa (Adventitia)
-1 layer- elastic and collagen fibers
Tunica Media
-External Elastic Lamina
-Smooth Muscle Layer
Tunica Interna
-Internal elastic lamina layer
-Basement Membrane Layer
-Endothelial Cell Layer
21
Q
Name the layers and the sublayers of each for venous vessels.
A
Tunica Externa (Adventitia)
-1 layer- elastic and collagen fibers
Tunica Media
-Smooth muscle and elastic fibers
Tunica Intima (Interna)
-Basement Membrane Layer
-Endothelial Cell Layer
22
Q
Characteristics of Arteries?
A
- Transport blood from the heart to the tissues of the body
- Thicker Tunica Media layer than veins
- Elastic fibers lending to high compliance (Walls stretch and expand easily in response to pressure increases/decreases)
23
Q
What are the two major types of arteries?
A
Elastic
Muscular
24
Q
What type of artery has the largest diameter lumen?
A
Elastic arteries
25
Name the elastic arteries.
Aorta, Pulmonary Trunk, Brachiocephalic, Subclavian, Common Carotids, Common Iliac
26
How thick is the vessel wall on an elastic artery?
Thin (1/10th total diameter)
27
What is within the Tunica Externa (Adventitia) of Elastic Arteries?
Fibroblasts, Nerve Fibers, and Vasa Vasorum (Blood Vessel Network)
28
What differences are found in the Tunica Media Layer of Elastic Arteries when compared to other arteries?
- More Elastic Lamellae (elastic Fibers)
- More collagen fibers
- Minimal Smooth muscle
29
What differences are found in the Tunica Intima Layer of Elastic Arteries?
Endothelial and Myointimal Cells with supporting layer of elastin rich collagen
30
Elastic Arteries are the first place this develops.
Atherosclerosis
31
What purpose do Elastic Arteries serve?
- Propel blood onward while ventricles are in diastole (Walls expand accounting for surge of blood in the Aorta)
- Elastic fibers recoil and convert stred (potential) energy into kinetic energy propelling blood forward)
32
Expansion of Elastic Arteries creates a momentary storage of mechanical energy called?
Pressure Reservoir
33
Elastic Arteries are also know as?
Conducting Arteries (Conduct blood from the heart to medium sized muscular arteries
34
Give some examples of Muscular arteries?
Brachial, Femoral, Axillary
35
Muscular arteries are also known as?
Distributing Arteries
36
Size range for muscular arteries?
Pencil size (Femoral, Axillaries) to 0.5mm diameter
37
What difference is found in the Tunica Externa layer of muscular arteries when compared to elastic arteries?
Tunica Externa is thicker
| -Contains fibroblasts, nerve fibers, some collagen and elastin
38
What differences are found in the Tunica Media Layer of Muscular Arteries?
- Contains much more smooth muscle and less elastic fibers
- Artery is capable of greater vasoconstriction and vasodilation
- Helps adjust rate of blood flow
39
The Tunica Intima consist of what in Muscular Arteries?
Basal Lamina and Endothelial Cells
40
Muscular Arteries have a reduced ability to what? Do to the reduced amount of elastic fibers
Propel Blood
41
What layer of Muscular arteries perform the majority of work?
Tunica Media- large amount of smooth muscle (maintains a state of partial contraction)
42
The state of partial contraction is called?
Vascular/Vasomotor Tone (Stiffens vessel walls and helps maintain vessel pressure and efficient blood flow)
43
Define: Anastomoses
Union of branches of two or more arteries supplying blood to the same region of body
44
What is the alternate route an anastomoses creates called?
Collateral Circulation
45
Where else might Anastomoses occur?
Veins, Arterioles, and venules
46
What are arteries that do not anastomose called?
End-Arteries
47
Obstruction of end arteries cause interruption of blood supply to tissue/organs and cause damage called?
End-Organ/Artery Damage
48
Give the characteristics of Arterioles.
- Microscopic
- Approx 400 million
- Diameters 15micron to 300micron
- Very rich in smooth muscle
- Wall thickness 1/2 of total vessel diameter
- 7.5micron to 150micron
49
In Arterioles the Tunica Externa consist of?
- Areolar Connective Tissue containing abundant unmyelinated sympathetic nerves
- Local chemical mediators
50
The unmyelinated sympathetic nerves and chemical mediators found in the Tunica Externa of Arterioles is responsible for what?
Altering the diameter of the arterioles. This will vary the blood rate and resistance through these vessels
51
Arteriole Tunica Media Layer characteristics.
Thin- 1-2 layers of muscle cells
52
Tunica Intima of Arterioles is?
Thin
53
Arterioles are also known as?
Resistance Vessels
54
Which vessels play a key role in resistance?
Arterioles
55
What causes the resistance within Arterioles?
Vasoconstriction (smaller diameter lumen) increases blood rubbing against vessel wall causing an increase of friction (greater resistance)
56
Arterioles regulate blood flow to what part of the Circulatory system?
Systemic Capillary beds and thus what comes out of capillary system
57
A high rate of firing from the sympathetic nerve fibers in arteries will cause?
Vasoconstriction
58
A low rate of firing from the sympathetic nerve fibers in arteries will cause?
Vasodilation
59
What "keeps pressure in the system", by helping to stretch the walls of arteries during heart contractions?
The back pressure created by constricting arterioles
60
Vasoconstriction and Vasodilation of arterioles plays what role in regards to blood pressure?
Vasoconstriction- Increased BP
| Vasodilation- Decreased BP
61
What connects arterioles to the capillary network?
Metarterioles
62
What are the characteristics of Metarterioles?
- Do not have a true tunica Media (Metarteriole-Capillary junction, single smooth muscle cell forms a ring)
- Encircling smooth muscle acts as pre-capillary sphincter
63
What is the Metarteriole-Capillary Junctions (Precapillary Sphincter) role in blood flow?
Regulates blood flow into capillaries that branch from Metarteriole and in response to stimuli contracts reducing the size of the lumen or closes it completely
64
What are the smallest blood vessels found in the body?
Capillaries
65
What diameter will capillaries have?
5-10 microns
66
The size of a capillary will force blood cells to do what?
- Blood cells are often 8microns, may fold over and pass "single file" through capillaries
- Allows time for nutrient exchange
67
How extensive is the capillary network within the body?
- Approx.. 20 billion
| - Forms enormous surface area to make contact with cells of the body
68
Capillaries are the union between?
Arterial and Venous Blood
69
What do Capillaries consist of?
Single endothelial cell layer and basement membrane
70
This single endothelial cell layer and basement membrane in capillaries allows for what?
Nutrient, gas, and waste diffusion to and from tissue interstitial fluid/tissue cells
71
Capillaries lack what components typically found within blood vessels?
Tunica Media and Tunica Externa
72
What is Microcirculation?
Flow of blood from Metarteriole through capillaries and into postcapillary venules
73
Capillaries are also know as?
Exchange Vessels
74
These are found near almost every cell in the body?
Capillaries
75
What is significant about Muscles, The Brain, Liver, Kidneys, Nervous System in regards to capillaries?
The higher metabolic demand increase the capillary network
76
Where are capillaries absent?
Avascular Substances
- Cornea
- Lens of eye
- Cartilage
77
Define: Capillary Beds
Network of 10-100 capillaries that arise from a single metarteriole
78
What occurs in the Capillary Bed when tissues are at rest and when tissues are active?
- At Rest- small portion of capillary network receives blood because need for metabolic exchange is low
- Active- whole capillary bed opens in order to increase efficiency of metabolic exchange
79
What is Vasomotion?
Contraction and relaxation of pre-capillary sphincters
80
Contraction and relaxation of pre-capillary sphincters (Vasomotion) occurs how many times a minute?
5-10 times per minute
81
What importance does Vasomotion serve for the capillary beds?
- Regulates blood flow through capillary beds insuring all capillary beds receive blood flow during rest
- prevents tissue from becoming ischemic without vasomotion
82
Vasomotion is mostly due to release of what from where?
Chemicals released by endothelial cells such as nitric oxide
83
Metabolic Theory of Auto-regulation refers to?
Metarteriole Sphincters constrict to all capillaries except one creating a Thoroughfare Channel directly from arteriole to venule, bypassing majority of capillary bed.
84
Thoroughfare Channel of arterioles to venules due to metarteriole sphincter constriction may occur due to?
- Hemorrhage
| - Increase Stroke Volume (Exercise)
85
Name the types of Capillaries.
- Continuous
- Fenestrated
- Sinusoids
86
Most capillaries are of which type?
Continuous
87
Characteristics of continuous capillary.
Plasma membranes of endothelial cells form continuous tube interrupted only by intercellular clefts (gaps between neighboring endothelial cells)
88
Continuous capillaries are found where in the body?
CNS, Lungs, Skin, Muscle Tissue
89
Characteristics of Fenestrated Capillaries.
Plasma membranes have many fenestrations allowing for easier diffusion
90
Fenestrated Capillaries are found where in the body?
Kidneys, Villi of Small Intestine, Choroid Plexuses of Ventricles of Brain, Ciliary Processes of the eyes, most Endocrine Glands
91
Characteristics of Sinusoids Capillaries.
- Wider and more winding than others
- Incomplete or absent basement membranes
- May have unusually large fenestrations
- Very Large intercellular clefts allowing some proteins and even blood cells to pass from tissue into blood
- Specialized lining cells adapted to function of the tissue
92
Give an example of Sinusoids Capillaries that allow blood cells to pass from tissue into blood.
New formed blood cells pass from bone marrow into blood stream
93
Give an example of Sinusoids Capillary that contain specialized lining cells.
Liver Sinusoids capillary contain phagocytes cells that remove bacteria and other debris
94
Sinusoids Capillaries can be found where in the body?
Spleen, Anterior Pituitary, Parathyroid, Bone Marrow, Adrenal Glands
95
When blood passes from one capillary network to another capillary network this is called?
Portal System
96
Give examples of where Portal Systems exist in the body?
- Hepatic Portal Circulation (liver)
| - Hypophyseal Portal System (Pituitary)
97
What purpose does the Portal System serve?
- Transports products of one region into another in high concentrations
- Bypasses the heart and therefore systemic circulation
98
Give an example of the Portal System.
Hepatic Portal System- allows liver to filter blood from the stomach, spleen, pancreas, gallbladder, and the mesenteric systems without sending that to the rest of the body
99
What are Venules?
Small veins that receive blood flow directly from capillary beds. (Post-capillary Venules)
100
What size are venules?
10-50 microns
101
What characteristics do the walls of the venules have?
- Smallest venules are very porous allowing phagocytic WBCs to pass through to inflamed or infected tissue
- Significant sites of exchange of nutrients and waste (last site of metabolic exchange)
102
At what site of the circulatory system does the immune response with WBC's occur?
Venules
103
Post Capillary the venules transition into?
Muscular Venules
104
What differences are seen in Muscular Venules compared to Post-capillary venules?
- Gain 1-2 layers of smooth muscle
- 50-200 micron thickness
- no metabolic exchange
105
What element/s of the vascular system is most distensible?
Postcapillary and Muscular Venules
106
These serve as reservoirs for large amounts of blood if needed?
Postcapillary and Muscular Venules
107
Blood volume increase have been measured in postcapillary and muscular venules up to what amount?
360%
108
What is the average thickness of venous walls?
1/10th of vessel diameter
109
Venous wall diameter will range from?
5 micron (small venules) to 30mm (Venae Cavae)
110
Tunica Externa of the venous system consists of?
Thickest Layer, Collagen and elastic fibers
111
Tunica Media of the venous system difference when compared to arteries?
Much thinner, much less smooth muscle and elastic fibers
112
Tunica Interna (Intima) of venous system when compared to arteries?
Much thinner
113
What sublayers are lacking within veins?
- Internal Elastic Laminae of the Tunica Intima
| - External Elastic Laminae of the Tunica Media
114
The lumen of veins tend to be what compared to arteries?
Larger
115
Many veins contain what? This is especially true in limbs.
Valves
116
Characteristics of Valves found in veins?
- Tunica Interna form cusps
- Cusps project into the lumen with "cups" towards the heart
- Valves prevent backflow of blood
117
What is the Vascular Sinus?
- Thin endothelial wall, no smooth muscle
| - Surrounding dense connective tissue replaces Tunica Media and Tunica Externa in providing support.
118
Give examples of where a Vascular Sinus is found?
Dural Venous Sinuses and Coronary Sinus
119
What are Anastomotic Veins?
- Veins are paired and accompany medium-to-small sized muscular arteries
- Paired veins escort arteries and connect with one another (veins) via these anastomotic veins
120
Where are Anastomotic Veins found?
- Greatest number in limbs
| - Superior Anastomotic Vein (Large one in Brain)
121
These veins are located within the subcutaneous layer of the skin and are unaccompanied (no arteries).
Superficial Veins
122
These travel between skeletal muscles and have small connections to superficial veins.
Deep Veins
123
Describe Superficial Veins of the Upper Limbs.
- Larger than deep veins
| - Serve as pathways from capillaries of upper limb back to heart
124
Describe Deep veins of Lower Limbs.
- Larger than Superficial veins
- Principle return pathway to heart
- One-way valves in small anastomosing vessels allow blood to pass from superficial to deep veins, prevent reverse flow
125
A leaky venous valve can cause veins to become dilated and twisted causing?
Varicose
126
Varicose are most common in?
- Esophagus
- Anal Canal
- Superficial veins of lower limbs
127
What are some of the cause of Varicose?
Congenital issues or mechanical stress (prolonged standing/pregnancy) or aging
128
Treatment for Varicose Veins?
- Elastic Stocking
- Sclerotherapy
- Laser Occlusion
- Stripping
129
What is the blood distribution within the body at rest?
```
64% systemic veins and venules
13% systemic arteries and arterioles
9% pulmonary blood vessels
7% systemic capillaries
7% in the heart
```
130
What are considered the Blood Reservoirs of the body?
Systemic Veins and Venules
131
What is the mission of the cardiovascular system?
Keep blood flowing through capillaries to allow for capillary exchange
132
What percentage of blood is continually exchanging materials with interstitial fluid?
7%
133
What are the three basic mechanisms that allow for exchange of substances in capillaries?
- Diffusion
- Transcytosis
- Bulk Flow
134
Which of the three basic mechanisms of exchange is most important?
Diffusion
135
What is Diffusion?
Movement down the concentration gradient
136
Name some of the substances that diffuse?
- O2
- CO2
- Glucose
- Amino Acids
- Hormones
137
Which way will O2 and nutrients move in the concentration gradient?
O2 and nutrients typically have higher concentration in blood and will move across (down concentration gradient) capillary bed into tissue/interstitial fluid
138
Which way will CO2 and waste move in the concentration gradient?
CO2 and waste typically have higher concentration in tissue/interstitial fluid and will move across (down concentration gradient) capillary bed into vessels
139
What substances diffuse through intercellular clefts/fenestrations?
- Glucose
| - Amino Acids
140
What substances diffuse through Endothelial cell lipid bilayer?
- Lipid soluble substances
| - O2,CO2, Steroid Hormones
141
Define Blood Pressure.
Hydrostatic pressure exerted by blood on the walls of a blood vessel
142
Blood Pressure is determined by what?
- Cardiac Output
- Blood Volume
- Vascular Resistance
143
Define Mean Arterial Pressure (MAP).
Average blood pressure in arteries
144
What is the formula used to calculate Mean ArteriaI Pressure?
MAP= diastolic BP+ 1/3 (systolic BP - diastolic BP)
145
What is the normal range of MAP?
70-100 mmHg
146
This is considered to be a more accurate measure of perfusion pressure.
Mean Atrial Pressure (MAP)
147
Control of Blood Pressure by several negative feed back systems is accomplished by making adjustments in...
- Heart Rate
- Stroke Volume
- Systemic Vascular Resistance
- Blood Volume
148
Most RBC's and Plasma proteins can only pass through this type of capillary?
Sinusoids
149
What type of capillary is found in most areas of the brain?
Continuous Capillaries
150
Continuous Capillaries in the Brain are surrounded by what? And this creates what within the Brain?
Astrocyte Processes and creates the Blood Brain Barrier
151
Due to the "tight" junctions of the BBB few substances are able to diffuse. What other way are substances able to cross the BBB and give some examples of substances?
Carrier Mediated
- Glucose
- Amino Acids
152
What areas of the Brain lack the Blood Brain Barrier?
Hypothalamus, Pineal Gland, Pituitary Gland
153
Describe the process of Transcytosis in capillaries.
Substances in blood plasma become enclosed in tiny pinocytic vesicles and cross via Endocytosis and Exocytosis
154
Transcytosis allows what kind of material to cross the capillary walls?
Large, lipid-insoluble molecules
-Insulin (enters blood stream)
-Certain Antibodies (Proteins) pass from maternal
circulation into fetal circulation
155
What is the passive process by which large number of ions, molecules, or particles in a fluid move together in the same direction?
Bulk Flow
156
Bulk Flow rate of movement is _________ when compared to diffusion.
Much Greater
157
Bulk Flow can occur as long as what exists?
Pressure difference- Movement from high pressure to low pressure
158
Diffusion is more important for solute exchange, where as Bulk Flow is more important for?
Regulation of relative volumes of blood and interstitial fluid
159
What is the pressure driven Bulk Flow movement of fluid and solutes from blood capillaries into interstitial fluid
Filtration
160
What two pressures promote filtration?
- Blood Hydrostatic Pressure (BHP)
| - Interstitial Fluid Osmotic Pressure (IFOP)
161
What is Blood Hydrostatic Pressure (BHP)?
Pressure blood exerts against blood vessel walls(generated by pumping action of the heart)
162
What is the pressure driven Bulk Flow movement of fluids and solutes from interstitial fluid into blood?
Reabsorption
163
What one main pressure promotes reabsorption?
Blood Colloid Osmotic Pressure (BCOP)
164
Describe Net Filtration Pressure (NFP).
- Balance of the filtration and reabsorption pressures
| - Determines whether volumes of blood and interstitial fluid remain steady or change
165
What is Starling's law of the Capillaries?
Volume of fluid and solutes reabsorbed is near the volume of fluid filtered
166
What is the equation used to calculate "Net Filtration Pressure"?
NFP= (BHP + IFOP) - (BCOP + IFHP)
167
In the NFP equation what portion accounts for pressures that promote filtration?
(BHP + IFOP)
BHP= Blood Hydrostatic Pressure
IFOP= Interstitial Fluid Osmotic Pressure
168
In the NFP equation what portion accounts for pressures that promote reabsorption?
(BCOP + IFHP)
BCOP= Blood Colloid Osmotic Pressure
IFHP= Interstitial Fluid Hydrostatic Pressure
169
What is the typical mmHg at the arterial and venous end of the capillary for BHP?
35mmHg- Arterial end of capillary
| 16mmHg- Venous end of capillary
170
What effect does BHP have on fluid in the capillary?
"Pushes" fluid out of the capillaries into interstitial space
171
What effect does IFOP have on fluid in the capillary?
"Pulls" fluid out of capillaries into interstitial fluid
172
What is the typical IFOP? This is due to what?
1mmHg due to only small amounts of protein present in interstitial fluid
173
This pressure is due to a force caused by colloidal suspension of proteins in plasma?
Blood Colloid Osmotic Pressure (BCOP)
174
What is the typical BCOP?
26mmHg
175
What effect does BCOP have on fluid in the capillary?
"Pull" fluid from interstitial spaces into capillaries
176
This is the opposing pressure to Blood Hydrostatic Pressure (BHP)?
IFHP (Interstitial Fluid Hydrostatic Pressure)
177
What is the typical IFHP?
0mmHg (Noncontributory unless pathologic)
178
On the arterial end of the capillary fluid movement out of the capillary and into interstitial spaces is called?
Filtration
179
On the Venous end of the capillary fluid movement out of interstitial fluid and into capillaries is called?
Reabsorption
180
On average how many liters per day is filtered out of capillaries into tissue?
20L/day
181
On average how many liters per day is reabsorbed into capillaries from tissue? =percentage of total?
17L/day (85%)
182
The remaining 3L (15%) not reabsorbed makes its way back into the blood via what?
Lymphatic capillaries (Lymph drains into junction of jugular and subclavian veins in upper thorax)
183
Clinical Correlation: If filtration (into Interstitial fluid) greatly exceeds reabsorption (into bloodstream), what occurs?
Edema
184
Edema is not usually visible until what percent of rise in volume occurs?
30%
185
Excess filtration or inadequate absorption can cause what?
Edema
186
Hemodynamics: What two factors contribute to how cardiac output is distributed into circulatory routes?
Flow
| Resistance
187
Flow can be explained by which law?
Poiseuille's Law
188
Poiseuille's Law: Flow is directly proportional..?
- Longitudinal Pressure Gradient (Higher gradient=Higher Flow)
- Radius of the tube (raised to the fourth power)- (Increased radius=Increased Flow)
189
Poiseuille's Law: Flow is inversely proportional..?
- Length of the tube (Increased Length=Decrease Flow)
| - Viscosity of the fluid (Increased Viscosity=Decrease in Flow)
190
Define: Resistance regarding blood flow.
Opposition to blood flow due to friction between blood and walls of blood vessels
191
A higher resistance of blood flow means what in regards to amount and speed of blood flow?
- Less amount of flow
| - Lower speed
192
Resistance is directly proportional..?
- Viscosity (Increased Viscosity=Increased Resistance)
| - Length of the tube (Increased Length=Increased Resistance)
193
Resistance is inversely proportional..?
-Radius (Increased radius=Decreased Resistance)
194
What three factors does Vascular Resistance (VR) depend on?
- Size of the Lumen (Radius)
- Blood Viscosity
- Total Blood Vessel Length
195
What is Systemic Vascular Resistance (SVR)?
All the vascular resistance offered by systemic blood vessels
196
Systemic Vascular Resistance (SVR) is also know as?
Total Peripheral Resistance (TPR)
197
What portion of the circulatory vessels contribute most to resistance?
Arterioles, Capillaries, and Venules
198
These need only to change their diameter slightly to have a large effect on SVR (Systemic Vascular Resistance)?
Arterioles
199
The major function of these is to control SVR (BP)?
Arterioles
200
Define: Syncope
Fainting, sudden temporary loss of consciousness that is not due to head trauma, followed by spontaneous recovery
201
What causes Vasodepressor Syncope?
Sudden emotional stress or real threat
202
What causes Situational Syncope?
Antihypertensive, diuretics, vasodilators
203
What causes Orthostatic Syncope?
Excessive decrease in BP when one stands from seated position
204
What affect do capillaries have on velocity and in-turn has what effect on the cross-sectional area?
Velocity of blood flow is slowest
| -Greatest aggregate of cross-sectional area
205
What affect do large vessels (aorta) have on velocity and in-turn has what effect on the cross-sectional area?
Velocity of blood flow is fastest
| -Smallest aggregate cross-sectional area
206
What has an inverse relationship to the cross sectional area?
Velocity (cm/sec)- Increase Cross Section=Decrease Velocity
207
What is the Cross Sectional area and velocity of the Aorta?
3-5cm^2 (smallest cross section)
| 40cm/sec (fastest velocity)
208
What is the Cross Sectional area and velocity of the Venae Cavae?
14cm^2 (Larger Cross section compared to aorta)
| 15cm/sec (slower velocity compared to aorta)
209
What is the Cross Sectional area and velocity of Capillaries?
4500-6000cm^2 (Largest Cross section compared to aorta)
| 0.1cm/sec (slowest velocity compared to aorta
210
What is meant by Laminar Flow?
Greatest velocity is in center of vessel
| Lowest velocity is near vascular wall
211
What is Streamlining?
Caused by shear stress produced as blood flows past stationary wall
212
What is Turbulent Flow?
irregularities in flow pattern
213
What are some of the patterns in turbulent flow?
Whorls
Vortices
Eddies
214
What is meant by Circulation Time?
Time required for 1 drop of blood to pass from right atrium through pulmonary circulation, back to left atrium, through systemic circulation, down to a foot and back to right atrium.
215
Typical Circulation Time in a resting healthy adult?
1 minute
216
What is Venous Return?
Volume of blood flowing back to the heart through systemic veins
217
Describe what is occurring in the Skeletal Pump of venous return when standing at rest?
Venous valves (distal and proximal) are open allowing blood to flow towards the heart
218
Describe what is occurring in the Skeletal Pump when the leg muscles contract such as standing on tiptoes?
Blood pushes open Proximal Valve (Milking) and at the same time Distal Valve closes due to blood pushing against it from contraction of muscle
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Describe what is occurring in the Skeletal Pump when the leg muscle is then relaxed after contraction?
Proximal Valve closes and distal valve opens (higher pressure at distal end since it was closed)
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Describe what is occurring in the Respiratory Pump during Inhalation?
Diaphragm moves downward causing decreased pressure in thoracic cavity and increased pressure in abdominal cavity. Results in compression of abdominal veins pushing greater volume of blood through thoracic cavity towards the heart
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Describe what is occurring in the Respiratory Pump during Exhalation?
Diaphragm moves upward causing an increase in thoracic cavity pressure and decreased pressure in abdominal cavity. Results in valves closing preventing backflow from thoracic veins into abdomen
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Where is the Cardiovascular (CV) Center located?
Medulla Oblongata
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What role does the Cardiovascular Center play in control of Blood Pressure and Flow?
- Helps regulate heart rate and stroke volume
| - Controls neural, hormonal, and local negative feedback systems (help regulate BP)
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What does the CV center regulate?
- Heart Rate
- Contractility
- Blood Vessel Diameter
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These are not clearly separated anatomically but they communicate with each other and function together to make up the CV center in it entirety?
- Cardiostimulatory Center
- Cardioinhibitory Center
- Vasomotor Center
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The Cardiostimulatory Center has?
Neurons that stimulate the heart
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The Cardioinhibitory Center has?
Neurons that inhibit the heart
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The Vasomotor Center is made up of and each has?
- Vasoconstrictor Center- Neurons that cause constriction of vessels
- Vasodilator Center- Neurons that cause dilation of vessels
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What provides input to the CV Center?
- Cerebral Cortex, Limbic System, Hypothalamus
| - Sensory Receptors (Proprioceptors, Baroreceptors, Chemoreceptors)
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What function do Proprioceptors serve?
Monitor movement of joints and muscles, accounts for rapid rise in heart rate at beginning of exercise
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What function do Baroreceptors serve?
Monitor Changes in pressure and stretch in vessel walls
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What function do Chemoreceptors serve?
Monitor the concentration of various chemical in blood
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Output from CV Center travels along?
Sympathetic and Parasympathetic Neurons of the Autonomic Nervous System (ANS)
Vasomotor Nerves
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How do Sympathetic Impulses reach the heart?
Cardiac Accelerator Nerves (Thoracic Vertebrae)
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Cardiac Accelerator Nerves will have what effect on the heart?
Increased Heart Rate and Contractility
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Parasympathetic Impulses travel along what nerve?
Vagus Nerve
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Vagus Nerve has what effect on the heart?
Decrease in Heart Rate
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Output from CV Center through Vasomotor nerves sends impulses to what?
Smooth muscle in blood vessel walls
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What is the Moderate State of Tonic Contraction
Vasomotor/Vascular Tone
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This sets the resting level of vascular resistance?
Vasomotor/Vascular Tone
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These two types of reflexes allow the nervous system to regulate blood pressure (Negative Feedback Loop)?
- Baroreceptor Reflexes
| - Chemoreceptor Reflexes
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What is the function of Baroreceptors and Chemoreceptors?
Sense blood pressure and chemical composition of blood for feedback to the circulatory and endocrine system
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What are Baroreceptors?
Pressure-sensitive sensory receptors
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What are the locations and function of Baroreceptors?
Aorta, Internal Carotid Arteries, other large arteries in neck and chest. Function: Send impulses to CV center to help regulate BP
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What are the two most important Baroreceptor Reflexes?
Carotid Sinus Reflex
| Aortic Reflex
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Carotid Sinus Reflex Function?
Helps regulate BP in the Brain
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What is the location of the Carotid Sinus?
Small Widening of right and left internal carotid arteries just superior to where they branch from common carotid arteries
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What occurs when BP stretches the wall of Carotid Sinus?
Baroreceptor is stimulated, nerve impulses propagate from sinus baroreceptors over sensory axons of carotid sinus branch of glossopharyngeal nerves (CN IX) then into the CV Center
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The Aortic Reflex is initiated by?
Baroreceptors in the Ascending Aorta and Arch of Aorta
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The Aortic Reflex regulates what?
Systemic BP
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Nerve impulses from baroreceptors in the Aortic Reflex reach the CV Center Via?
Sensory axons of Vagus Nerve (CN X)
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What occurs when baroreceptors are stretched less (Drop in BP)?
- Nerve Impulses sent at slower rate to CV Center
- CV Center decreases parasympathetic stimulation through Vagus Nerve and increases sympathetic stimulation through Cardiac Accelerator nerves
- Hormones stimulated to be secreted in the body
- Heart Beats faster and more forcefully (Cardiac output and systemic vascular resistance increase)
- This increases BP to normal levels
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What hormones are stimulated to be secreted in the body in response to increased sympathetic stimulation
Epinephrine and Norepinephrine
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What occurs when baroreceptors are stretched more (Increase in BP)?
-Nerve impulses sent at a faster rate to CV Center
-CV Center increases parasympathetic stimulation through Vagus Nerve and decreases sympathetic stimulation through cardiac accelerator nerves
-Heart Beats flower and less forcefully (Cardiac output and systemic vascular resistance decrease)
-Slows rate of impulses to vasomotor neurons that
cause vasoconstriction, results in vasodilation
-This decreases BP to normal levels
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What are Chemoreceptor Reflexes?
Sensory receptors that monitor chemical composition of blood. Detect changes in blood concentration of O2, CO2, Hydrogen ions
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Chemoreceptors are located very close to what?
Baroreceptors
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Name the two location of Chemoreceptors?
Carotid Bodies- Chemoreceptors in carotid arteries
| Aortic Bodies- Chemoreceptors in Aortic Arch
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What will stimulate Chemoreceptors?
Hypoxia- reduced plasma O2
Acidosis- increase in H+ concentration
Hypercapnia- Increase in CO2 in plasma
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What occurs when Chemoreceptors are stimulated?
- Impulse is sent to CV Center
- CV Center increases sympathetic stimulation to arterioles and veins causing vasoconstriction
- Vasoconstriction increases BP
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What is Autoregulation (Regarding BP)?
- Ability of tissue to automatically adjust blood flow to match the metabolic demands
- Local changes occurring in capillary beds regulating vasomotion
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What occurs with an increased O2 demand?
- Vasodilators dilate arterioles and relax precapillary sphincters allowing for more blood
- Opposite occurs as well with vasoconstrictors
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Autoregulation also plays what role in blood flow in the brain?
Regional blood flow in the brain will change distribution to various regions for different mental and physical activities (Speaking or listening, blood is increased to the regions that control speech and auditory areas)
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What two different stimuli cause autoregulatory changes in blood flow?
Physical Changes
| Vasodilation and Vasoconstriction Chemicals
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Physical Changes: Warming and Cooling promote what regarding Vasodilation and Vasoconstriction?
Warming- Vasodilation
| Cooling- Vasoconstriction
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What types of cells release chemicals that indirectly alter blood-vessel diameter?
WBC's, platelets, smooth muscle fibers, macrophages, endothelial cells
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Name some Vasodilating Chemicals?
K+, H+, Lactic Acid, Adenosine, Nitric Oxide (NO), Kinins, Histamine
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Name some Vasoconstricting Chemicals?
Thromboxane A2, Superoxide Radical, Serotonin, Endothelins
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Regarding Autoregulation of BP what occurs in response to low O2 in Systemic Circulation?
Systemic vessels dilate to allow for more oxygenated blood flow
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Regarding Autoregulation of BP what occurs in response to low O2 in Pulmonary Circulation?
Pulmonary vessels constrict to push blood to areas that are highly ventilated by "fresh air" to increase O2 Rapidly
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What is Pulse Pressure?
Difference between systolic and diastolic pressure (normally 40mmHg)
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What can cause a Narrow Pulse Pressure (<25% of systolic)
Blood loss; anything that reduces left ventricular function
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What can cause a Wide Pule Pressure (can be 100mmHg+)?
- Exercise, not a problem as long as a return to normal occurs within 10 min of rest
- Pathologic- stiffness of major arteries; Aortic regurg; hyperthyroidism
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What makes up Systemic Circulation?
- All arteries/arterioles that carry oxygenated blood from left ventricle to systemic capillaries
- All venules and veins that carry deoxygenated blood returning to right atrium after flowing through body organs
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Name the subdivisions of systemic circulation?
- Coronary
- Cerebral
- Hepatic Portal
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What are considered Other Circulatory Routes?
- Pulmonary Circulation
| - Fetal Circulation
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What is Pulmonary Circulation?
Deoxygenated blood pumped from right ventricle through pulmonary arteries into lungs through pulmonary veins to left atria.
