Physiology > Circulation > Flashcards

Circulation Flashcards

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1
Q

Name the 3 parts of the circulation

A
  • Resistance part (Arteries)
  • Exchange area (Capillaires)
  • Reservoir (Veins)
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2
Q

Location of resistance part of the circulation

A

Left ventricle → Capillary bed

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3
Q

Location of the exchange area of the circulation

A

Locations of bidirectional transport of material

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4
Q

Location of the reservoir system of the circulation

A

Venules → Right atrium

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5
Q

Under normal conditions, the largest part of blood volume is located in…

A

The reservoir system

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6
Q

Describe the structure of an artery

A
  • Muscular
  • Elastic
  • Thick walled
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7
Q

Describe the structure of an arteriole

A
  • Muscular
  • Little connective tissue
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8
Q

Describe the structure of a capillary

A
  • Endothelial layer
  • No muscle
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9
Q

Describe the structure of a venule

A
  • Thin walls
  • Some smooth muscle
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10
Q

Describe the structure of a vein

A
  • Thin-walled
  • Smooth muscle
  • Flacid
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11
Q

The resistance part is composed of…

A
  • Elastic arteries
  • Muscular arteries
  • Arterioles
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12
Q

Elastic arteries

A
  • Aorta & large arteries
  • Loaction of passive contraction (due to elastic elements)
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13
Q

Muscular arteries are the sites of…

A
  • Regulated resistance
  • Smooth muscle → active contraction
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14
Q

Arterioles

A
  • Most important part of regulated resistance
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15
Q

During diastole, the aorta…

A

Passively contracts

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16
Q

‘Windkessel’ function of the aorta

A
  • A simple pump with a closed air buffer
  • Storage of pressure in the Windkessel
  • Results in a near-constant pressure
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17
Q

What is the location of capillary exchange?

A

Area of microcirculation

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18
Q

List the types of capillary

A
  • Continuous
  • Fenestrated
  • Porous
  • Sinusoid
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19
Q

Location of continuous capillaries

A
  • Muscle
  • Skin
  • CNS
  • Lung
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20
Q

Location of the fenestrated capillaries

A
  • Intestinal mucosa
  • Endocrine glands
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21
Q

Location of the porous capillaries

A

Glomeruli of the kidney

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22
Q

Describe the structure of continuous capillaries

A
  • Endothelium (Inside layer)
  • Lamin basalis
  • Pericytes (Outside layer)
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23
Q

Sinusoid capillaries lack…

A

Pericytes

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24
Q
A

Disse-space

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25
Location of sinusoid capillaries
* Liver * Haemopoietic organs
26
What limits the enlargement of veins?
Collagen
27
List the types of Venule
* Postcapillary venule * Collecting venule * Muscular venule
28
The function of venules is determined by...
The structure of the wall and valves
29
Potential energy
The pressure exerted onto the wall of the container (vessels)
30
Kinetic energy =
1/2 m x v2
31
Cause of energy loss in circulation
Flow friction
32
Resistance is determined by...
Flow rate
33
Kinetic energy =
Total energy - Potential energy * Pitot-system
34
Narrowing of blood vessels causes....
* A increase of kinetic energy * A decrease of potential energy
35
Viscosity is higher in...
Larger vessels | (Fahraeus-Lindquist effect)
36
The viscosity of blood is a function of...
The hematocrit value
37
Factors maintaining the BP in Arteries
* Work of heart * Total peripheral resistance (TPR) * Distribution of blood * Types of blood flow
38
Runoff (Qr)
Volume of blood which moves from: Arterial part → Venous part
39
The artificial increase in work of the heart is by...
Pacemakers
40
The natural increase in work of the heart is by...
Sympathetic activation
41
Increase in TPR causes...
Increase of blood pressure
42
What allows arteries to distend?
* Elastic elements * Myogenic elements
43
Critical closing pressure
Pressure where vessels are collapsing
44
Arterial distensibility
* Volume change related to pressure change related to the original volume * D = dV / dP x Va
45
What is compliance?
Volume change per unit pressure change
46
When is distensibility used for blood pressure?
If different circulations are compared
47
When is compliance used for blood pressure?
When absolute change is of interest
48
Compliance decreases with...
Age
49
Law of Laplace related to blood vessels
* In order to maintain BP * There should be an increase in wall tension
50
An increase in arterial volume causes...
An increase of blood pressure
51
Parallel attachment of organs is beneficial because...
Changes in perfusion of one organ don't suddenly change the work of the heart
52
Examples of serially coupled elements of the circulation
* Arteries * Capillaries * Veins
53
Perfusion
* Flow of volume * Determined by Ohm's law
54
Reynolds number =
55
Laminar blood flow
Re\<2320
56
Turbulent flow
Re\>2320
57
The physiological relevance of laminar flow
* Low resistance, less work of the heart * Blood cells arranged in the axis of the flow
58
Capillary blood pressure is maintained by...
Microcirculation
59
Factors maintaining venous blood pressure
* Gravitation * 'Vis a tergo' (work of the heart) * Valves * Skeletal muscle pump * Central venous pressure (CVP)
60
Skeletal muscle pump
* Muscle tension pumps blood * Valves cause centripetal flow * Weak muscle tension → Blood accumulation → Increased pressure → Oedema
61
Pressure changes in chest and abdomen
* Inspiration → Intrathoracic pressure decreases (RA fills) * Abdominal pressure → Transmural pressure of veins in abdomen
62
Peripheral blood pressure is maintained by...
Cardiovascular regulatory mechanism
63
Static pressure
* Blood pressure measured *post mortem* * Approx 7mmHg​
64
Blood pressure above and below the heart
* Higher below the heart * Lower above the heart
65
Pulse pressure
Systolic pressure - Diastolic pressure * *e.g 120 - 80 = 40 mmHg*
66
Mean arterial pressure
* _Weighted_ average of the systolic and diastolic pressure * Diastole 2 times longer than systole, therefore: * (Psyst + (2xP diast)) /3
67
Relationship of blood pressure and body size
68
Types of blood pressure measurement
* Direct method * Indirect method * Palpation * Auscultation
69
Direct blood pressure measurement
* Glass catheter inserted into carotis * Height of fluid volume measured
70
Palpation blood pressure measurement
* Closing a BP cuff * Opening and recording Systolic BP when a pulse is felt ## Footnote *Cannot measure diastolic pressure*
71
Auscultation blood pressure measurement
* Closing cuff around an arm * Opening cuff and listening for first pulse (Systolic pressure) * Continue opening, listening for the sound to stop (Diastolic pressure)
72
What is the diagram? What is indicated?
**Pressure pulse** * Anacrotic limb
73
Steepness
74
Pulse pressure
75
Dicrotic notch
76
Catacrotic limb
77
Speed of a palpable pulse
7m/sec
78
Dicrotic notch of pressure pulse
* Effect of the reflected pressure wave * Increases with distance from the aorta
79
Flow rate in the aorta
40cm/sec
80
Flow rate in capillaries
0.33mm/s
81
Pulse diagnosis is carried out with...
A sphygmograph
82
The sphygmograph shows which components?
* Frequency * Rhythm * Amplitude * Steepness * Tension
83
Which two kinds of substance exchange occur during microcirculation?
* Diffusion * Filtration/resorption
84
What % of capillaries are open during rest?
5-10%
85
Filtration is blocked by...
The precapillary sphincter
86
Components of microcirculation
* Arterioles * Metarterioles * Precapillary sphincters * Capillaries * Venules
87
The two types of capillary exchange
* Flow limited * Diffusion-limited
88
What is exchanged by capillaries?
* Gas * Ions * Small substances
89
Transport of small molecules during diffusion is dependent on...
Blood flow _Flow limited_ needed
90
Transport of large molecules during diffusion required
Diffusion limited exchange
91
What are the determining factors of diffusion?
* Conc. gradient * Permeability * Surface area
92
The extent of gas diffusion is dependent on...
Partial pressure
93
The higher the O2 consumption, the faster the drop of...
pO2 | (Partial pressure of oxygen)
94
The drop of pO2 leads to... How is it mitigated?
* Hypoxia * More capillaries open → Local autoregulation
95
Partial pressure of a gas
Measure of how much gas is present
96
Major/Starling forces of substance exchange
* Hydrostatic pressure difference (Ph) * Permeability * Oncotic pressure (Ponc) * Pressure of tissue (Pinterst)
97
The direction of substance movement is determined by...
Effective filtration pressure
98
Peff =
Phydrostatic - Poncotic - Ptissue
99
Net filtration
Phydrostatic \> Poncotic
100
Net reabsorption
Phydrostatic \< Poncotic
101
Phydrostatic at the arteriolar end of the capillary
35mmHg
102
Phydrostatic at the venule end of the capillary
15mmHg
103
Pressure profile of the capillary is...
Linear
104
Phydrostatic of ISF
5 mmHg
105
Colloid Oncotic pressure
* Sucking force * Absorbing H2O from the ISF to the plasma * Proportional with [protein]
106
Oncotic pressure of plasma
28mmHg
107
Oncotic pressure of ISF
3mmHg
108
Net oncotic pressure value
25mmHg
109
The balance of effective partial pressure can be altered by
* Changes in capillary pressure near arterioles or venules * Alterations in oncotic pressure
110
Vasodilation
Increased BP at the capullaries
111
Characteristics of the venous system
* Capacitance system * Redistribution * Large distensibility
112
What % of blood is found in the veins?
55-75%
113
What sets the limit of distensibility of veins?
Collagen networks of vessels
114
Pressure goes...from veins to venules
Down
115
_Local/intrinsic_ regulation of circulation
Dependent on oxygen and nutrient demand of organs
116
_Central/Extrinsic_ regulation of circulation
Maintaining the optimal working condition of organs
117
List all forms of the regulatory systems
* Intrinsic short term * Intrinsic long term * Extrinsic short term * Extrinsic long term
118
Intrinsic short term regulation
* Fast adjustment of perfusion rate * Autoregulation & myogenic regulation * _Constant_ _perfusion rate_ * Endothel derived regulation * Metabolites related regulation
119
Autoregulation by myogenic tone
* Microcirculation not influenced by BP (Myogenic adaptation) * Bayliss effect
120
Bayliss effect
* Pressure changes → Metarteriole sphincter contraction/relaxation * Stable pressure maintained
121
Autoregulation of perfusion exists within which pressure range
40-140mmHg
122
Endothel-related humoral factors
* Endothelium-derived relaxing factor (EDRF) * Endothelium-derived contracting factor (EDCF)
123
Describe detection during endothel-related regulation
1. BP expressed on endothelium 2. Deformation + plasma factors 3. Humoral signals generated 4. Contraction of smooth muscle
124
Causes of EDRF regulation
* Nitrogen monoxide * Prostacyclin (PGI2 hormone) * Endothelial-factor
125
Mechanism of nitrogen monoxide in endothelial related regulation
* NO → Smooth muscle * cGMP increases * Smooth muscle relaxes
126
Mechanism of Prostacyclin (PGI2 hormone) in endothelial related regulation
Increases production of NO
127
Mechanism of endothelial-factor in endothelial related regulation
* Hyperpolarisation by activating ATP dependent K-channels * K is an indirect vasodilator
128
Causes of EDCF regulation
* Endothelins * Cyclooxygenase dependent factors * Angiotensins
129
Mechanism of Cyclooxygenase dependent factors in the Endothelial related regulation
* TXA2 * Stimulates NO degradation Also a direct effect resulting in contraction
130
Mechanism of Endothelins in Endothelial related regulation
* Strong constrictors * ET-1-3 (in tissues) * ET-4 (In lung)
131
Mechanism of Angiotensin-II in Endothelial related regulation
Direct vasoconstrictor * Stimulates endothelin production * Increases sympathetic vasoconstriction
132
ET-1
* Binds to ET receptor * Vasoconstriction of airways and lung * Formation of new blood vessels * Survival of specific cell types
133
Role of acetylcholine in endothelial related regulation
* Through nerve endings * Direct stimulation * Vasoconstriction * From lumen of the blood vessel * Increase NO production * Vasodilation
134
During endothelial related regulation through metabolites, increased metabolic activity results in...
* Increased O2 consumption * Increased [adenosine] * Increased [H+] * Increased [CO2] * Increased [K+] All stimulate EDRF stimulation
135
What is the response to EDRF stimulation through increased metabolic activity?
* NO production increases * PGI2 released * Hyperpolarising factors released
136
Lack of oxygen at a tissue level (hypoxia) causes...
* Automatic increase of perfusion * Better O2 supply
137
Intrinsic long-term regulation
* Morphologic changes * Stimulation of revascularisation
138
Hyperemia
Increased local perfusion
139
Give the types of hyperemia
* Active (functional) hyperemia * Reactive hyperemia
140
Active hyperemia
Caused by increased metabolic activity of the tissue
141
Reactive hyperemia
A secondary increase of perfusion Compression of artery → hyperemia
142
Causes of extrinsic short-term regulation of circulation
* Sympathetic effects * Parasympathetic effects * Humoral effects * Vessel-related reflexes
143
Extrinsic regulation of circulation
* Compensation of organ perfusion differences * *via* redistribution * Balance of: * Sympathetic-vasoconstrictor tone * Sympathetic-vasodilator tone * _Results in permanent vasoconstriction_
144
Location of the cardio-vasomotor centres
Medulla oblongata | (formatio reticularis)
145
List the cardio-vasomotor centres
* Pressor area * Depressor area * Cardioaccelerator area
146
Pressor area responsibilities
* Spontaneous activity of the heart * General sympathetic vasoconstriction * Increasing blood pressure
147
Depressor area responsibilities
* Blood pressure decrease * Vasodilation * Decrease chronotropic and dromotropic effects * Direct inhibition of pressor centre
148
Effect of the depressor centre on heart rate
Inhibits cardiac activity *via* vagal stimulation * n. vagus determines the work of the heart
149
Sympathetic effect on the circulation
* The depressed activity of the pressor area * The decrease of sympathetic vasoconstrictor tone * Vasodilation
150
Parasympathetic effects on the circulation
Decrease of sympathetic vasoconstrictor tone (No parasympathetic effect is actually expressed)
151
Indirect parasympathetic vasodilation
Bradykinin release → Vasodilation
152
During exercise, redistribution of blood is mainly to the...
Skeletal muscles
153
Redistribution in regulation of circulation
* Resistance vessels * (under influence of sympathetic postganglionic fibres)
154
Vasomotor effect of regulation of circulation
* Decreased sympathetic predominance → vasodilation * Epinephrine release → Dilates vessels of skeletal muscle * Increased perfusion to the skeletal muscle * + Increased Cardiac output
155
Humoral regulation of circulation effects
* Epinephrine * Nor-epinephrine * Other hormones
156
Small epinephrine dose causes...
* Skeletal muscle vasodilation * Through ß-adrenergic receptors * Skin/splanchnic muscle vasoconstriction * Through α-adrenergic Receptors
157
High dose of epinephrine causes...
General α-adrenergic constriction
158
Effect of norepinephrine dose
Has only α-adrenergic vasoconstrictive effect
159
Humoral regulation of circulation effect
* Transport *via* blood (endocrine) * Epinephrine + norepinephrine
160
List the blood vessel related reflex mechanisms
* Baroreceptors * Volume receptors * Bainbridge-reflex * Effect of pO2 and pCO2
161
Location of baroreceptors
* *Arcus aortae* * Baroreceptors & Chemoreceptors​*​​* * *Sinus* *caroticus* * Baroreceptors & Chemoreceptors
162
Function of baroreceptors
Fast resetting of blood pressure
163
Describe Heimans' crossed-dog experiment
1. Dog B blood → Dog A (*via* *carotis*) 2. Dog A BP changes reciprocally to dog B
164
What is the effective range of baroreceptors?
50-170mmHg
165
Volume receptors functions
* Atrial stretching → ADH release * ANF (atrial natriuretic factor) release during hypervolaemia
166
Volume receptors
Regulate cardiovascular and renal volume
167
What does this figure show
The Starling mechanism/Bainbridge effect on heart rate
168
Intravenous infusion
169
Atrial pressure increases
170
CNS pressor response
171
HR increase
172
Transient increase in cardiac output
173
* Baroreceptor reflex * (Overrides the Bainbridge reflex) * CNS depressor response
174
HR decrease
175
Location of peripheral receptors of pO2 and pCO2
* *Glomus* *caroticum* * *Glomus* *aorticum*
176
What stimulates peripheral differentiation?
Decrease of pO2
177
What stimulates central afferentation?
Increase of pCO2
178
What stimulates efferentation?
Sympathetic activation
179
Extrinsic long-term regulation
* CV system adapts to the needs of the organism * Adaptation in climatic changes * Long-term changes in oxygen supply
180
Organs with specialised circulations
* Heart * Brain * Skin * Liver * Fetus
181
Coronary circulation during systole
* Fast ejection: * High pressure ensures coronary flow * Slow ejection: * Aortic pressure drops → slow coronary perfusion
182
Coronary circulation during diastole
Maximal coronary flow (More than when in systole)
183
What occurs in the coronary circulation during the beginning of systole?
* Blood pressed out from coronary vessels * Reversed flow of blood
184
What occurs in the coronary circulation during the end of systole?
* Fast ejection * Slow ejection
185
Describe the blood flow entering and leaving the brain
Both are of equal value
186
Blood pressure in the brain
Between 60-160 mmHg * Blood flow doesn't change when in this range
187
Splanchnic circulation
* Double, serially-attached capillary system * Main regulator → Alpha-receptor (Sympathetic tone)
188
Blood entering the fetal circulation
* *Via* umbilical vein * 85% spO2 * 35 mmHg pO2 * Travels to the liver and heart
189
Describe circulation at birth
1. After delivery → Increase of pulmonary circulation 2. The onset of breathing → Surfactant factors appear 3. Pulmonary resistance decreases dramatically 4. More blood passes through the lung
190
Which process closes the ductus arteriosus?
Prostaglandin liberation
191
Placenta
192
Liver
Physiology
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