Circulatory system Flashcards
1
Q
What is the primary function of the circulatory system?
A
Distribution of gases/molecules for nutrition, growth and repair
2
Q
What are the secondary functions of the circulatory system? (3)
A
- Fast chemical signalling via hormones
- Dissipation of heat
- Mediates inflammatory/defence responses to invading pathogens
3
Q
What are the 3 functional parts of the circulatory system?
A
- Pump (heart)
- Fluid (blood)
- Containers (blood vessels)
4
Q
What are the two serial circuits in which the heart pumps blood?
A
- Left side (systemic circulation)
- Right side (pulmonary circulation)
5
Q
What is the systemic circulation?
A
Blood pumped from the left side of the heart
6
Q
Where in the body are there capillary beds in series?
A
Kidneys
7
Q
Where in the body are there capillary beds in series and parallel?
A
Spleen, intestines and liver
8
Q
What is blood pumped from the left side of the heart called?
A
Systemic circulation
9
Q
What is the pulmonary circulation?
A
Blood pumped from the right side of the heart
10
Q
What is blood pumped from the right side of the heart called?
A
Pulmonary circulation
11
Q
What is the pathway of pulmonary circulation?
A
Single pathway from right to left side of the heart via the lungs
12
Q
What is the radius of first order arterioles?
A
30 μm
13
Q
What is the radius of first order venules?
A
30 μm
14
Q
What is the radius of fourth order arterioles?
A
5 μm
15
Q
What is the radius of fourth order venules?
A
5 μm
16
Q
What is the order of arterioles in descending size?
A
- First order arterioles (biggest)
- Second order
- Third order
- Fourth order (smallest)
17
Q
What is the order of venules in descending size?
A
- First order venules (biggest)
- Second order
- Third order
- Fourth order (smallest)
18
Q
Which blood vessels are referred to as the resevoir?
A
Veins
19
Q
What is the microcirculation?
A
Diffusion and filtration systems (from the first order arteriole to first order venule)
20
Q
What is the radius of the capillaries?
A
3 μm
21
Q
Which blood vessels are oxygenated?
A
Arteries
22
Q
Which blood vessels are deoxygenated?
A
Veins
23
Q
What is the largest artery in the body?
A
Aorta
24
Q
What is the largest vein in the body?
A
Vena cava
25
What is the velocity of blood flow in the capillaries compared to the aorta?
Velocity massively decreases in the capillaries
26
Why is the velocity of blood flow slower in the capillaries?
To allow for efficient substance exchange
27
What is the combined cross sectional area of the capillaries compared to the aorta?
Much higher area than the aorta
28
What is oncotic pressure?
- Osmotic pressure within plasma
| - AKA colloid osmotic pressure
29
What is colloid osmotic pressure?
Same as oncotic pressure
30
What is albumin?
Plasma protein
31
What causes the oncotic pressure?
Plasma proteins i.e. albumin
32
What is the hydraulic conductance?
Permeability of the capillary wall
33
What is Starling's forces equation?
Jv = Kf [(Pc - Pi) - (πc - πi)]
34
What does Jv mean in Starling's forces equation?
Fluid movement (ml/min)
35
What does Kf mean in Starling's forces equation?
Hydraulic conductance (ml/min per mm Hg)
36
What does Pc mean in Starling's forces equation?
Capillary hydrostatic pressure (mm Hg)
37
What does Pi mean in Starling's forces equation?
Interstitial hydrostatic pressure (mm Hg)
38
What does πc mean in Starling's forces equation?
Capillary oncotic pressure (mm Hg)
39
What does πi mean in Starling's forces equation?
Interstitial oncotic pressure (mm Hg)
40
Where does net filtration occur in the capillary bed?
Arteriole end
41
Where does net absorption occur in the capillary bed?
Venous end
42
Which value in Starling's equation declines along the length of the capillary?
Pc (capillary hydrostatic pressure i.e. pressure of the plasma pushing out decreases due to filtration)
43
Is arteriole net filtration equal to venule net absorption?
No - arteriole filtration into the interstitial fluid exceeds venule absorption
44
What are the features of lymph capillaries? (1)
They have one-way valves to trap fluid inside once absorbed
45
What is oedema?
Blockage in the lymphatic system which causes a build up of fluid and therefore swelling
46
How is blood volume maintained after filtration?
Lymph fluid returned to the cardiovascular system via subclavian veins
47
Which blood vessels are used to return lymph fluid to the cardiovascular system?
Subclavian veins
48
What are the functions of the lymphatic system? (3)
- Drains excess interstitial fluid
- Transport of dietary lipids
- Lymph nodes involved in the immune system
49
What is a lacteal?
The lymphatic vessels of the small intestine which absorb digested fats
50
What are the 4 components of vascular walls?
- Endothelial cells
- Elastic fibres
- Collagen fibres
- Smooth-muscle cells
51
What are the 3 layers of blood vessel walls (veins and arteries)?
- Tunica Interna (intima)
- Tunica Media (media)
- Tunica Externa (adventitia)
52
What is the Tunica Interna composed of?
Endothelial cell layer resting on a basement membrane
53
What is the Tunica Media composed of? (2)
- Smooth muscle cells
| - Elastic fibres
54
What is the Tunica Externa composed of? (4)
- Collagen fibres
- Elastic fibres
- Vasa vasorum blood supply
- Nerve innervation
55
How does the structure of capillary walls differ from arteries and veins?
Capillaries only have the Tunica Interna (endothelium and basement membrane), not the other 2 layers
56
What is the pressure like in the aorta compared to the vena cava?
Much lower pressure in the vena cava due to bigger radius than the aorta
57
Why do arterioles and precapillary sphincters have thick walls of smooth muscle?
To allow them to vasoconstrict and cut off capillary beds if needed
58
What does high compliance mean?
Walls can stretch easily to accommodate pressure increases without tearing
59
What are the features of large arteries? (2)
- High compliance so can expand in high pressure
| - Recoil of elastic fibres force blood to move when the ventricles are relaxed
60
What are the large arteries called?
Elastic arteries
61
What are the features of medium arteries? (3)
- Smooth muscle cells arranged circumferentially
- Capable of more vasoconstriction/dilation to adjust blood flow
- Maintain a level of vascular tone
62
What are the medium arteries called?
Muscular arteries
63
What is vascular tone?
State of partial contraction in blood vessels to maintain pressure and efficient flow
64
What are the features of arterioles? (2)
- Smooth muscle enable regulation of blood flow into capillaries
- Precapillary sphincters regulate blood flow into capillaries
65
What are metarterioles?
Terminal regions of arterioles
66
What are terminal regions of arterioles called?
Metarterioles
67
What are the features of venules? (3)
- Porous so can act as exchange sites
- Have thin smooth muscle cell layer (less than arterioles)
- Walls allow expansion so can store blood (reservoirs)
68
What are the features of small veins? (2)
- Can adapt to variations in blood volume and pressure
| - Can act as reservoirs
69
What are the features of large veins? (2)
- Valves to prevent backflow
| - More muscular than small veins and venules
70
What happens when valves in veins become leaky?
- Allows backflow
| - Leads to varicose veins
71
What are the functions of capillaries? (5)
- Principal exchanges sites
- Skin temperature regulation
- Glomerular capillaries
- Hormone delivery
- Platelet delivery
72
How many types of capillaries are there?
3
73
What are the 3 types of capillaries?
- Continuous capillary
- Fenestrated capillary
- Sinusoidal (discontinuous)
74
What are continuous capillaries? (2)
- Least leaky capillary type
| - Have interendothelial junctions
75
What are fenestrated capillaries?
Have fenestrae which allow larger molecules to pass through
76
What are sinusoidal capillaries? (2)
- Leakiest type of capillary
| - Have large enough gaps to allow some blood cells through
77
Where are sinusoidal capillaries found in the body? (2)
- Liver
| - Bone marrow
78
Where are fenestrated capillaries found in the body? (3)
- Small intestines
- Kidneys
- Endocrine glands
79
What is the most dense component of blood?
Red blood cells
80
What are erythrocytes?
Red blood cells
81
What is the hematocrit?
Measurement of the proportion of red blood cells in your blood
82
How do you calculate the hematocrit?
- Centrifuge blood sample
| - Divide height of red blood cells by the total height of the sample
83
What are leukocytes?
White blood cells
84
What are the components of blood? (4)
- Plasma
- Erythrocytes
- Leukocytes
- Platelets
85
What are the main plasma proteins? (4)
- Albumin
- Fibrinogen
- Globulins
- Other coagulation factors
86
What is the most abundant element in blood?
Erythrocytes
87
What is the structure of erythrocytes? (2)
- No nucleus
| - Biconcave discs
88
Why are erythrocytes shaped how they are?
Maximises SA:Vol
89
How is the shape of erythrocytes maintained?
Cytoskeleton anchored to the plasma membrane
90
Which proteins are in the cytoskeleton of erythrocytes? (3)
- Spectrin
- Glycophorins
- Actin
91
What are the 3 major functions of erythrocytes?
- Carry oxygen from lungs to systemic circulation
- Carry carbon dioxide from tissues to lungs
- Buffering of acids/bases
92
What are the 3 broad categories of leukocytes?
- Granulocytes
- Monocytes (non-granular)
- Lymphocytes (non-granular)
93
What are the 3 kinds of granulocytes?
- Neutrophils
- Eosinophils
- Basophils
94
What do neutrophils do?
Phagocytose bacteria
95
What do eosinophils do?
Combat parasites and viruses
96
What do basophils do? (4)
Release:
- IL-4
- Histamine
- Heparin
- Peroxidase
97
What is heparin?
Anti-coagulant
98
What are the 2 kinds of lymphocytes?
- B-cells
| - T-cells
99
What do T-cells do?
Cellular immunity
100
What do B-cells do?
Humoral immunity (produce antibodies)
101
What are the 2 kinds of monocytes?
- Macrophages
| - Dendritic cells
102
Where do platelets come from?
Bud off from megakaryocytes in bone marrow
103
Which molecules is platelet production dependant on? (2)
- TPO
| - IL-3
104
What is the feedback mechanism involved in platelet production?
- Platelets have TPO receptors so abundant receptors can bind TPO
- Less TPO available so megakaryocytes aren't generated
- Less megakaryocytes so no platelets are made so no TPO receptors available
- More TPO stimulates megakaryocyte production which produce platelets
105
Which molecule is needed for megakaryocyte production?
TPO
106
What do platelets contain? (6)
- No nucleus
- Mitochondria
- Lysosomes
- Peroxisomes
- Alpha granules
- Dense-core granules
107
What do alpha granules in platelets contain? (3)
- Von Willebrand's factor
- Fibrinogen
- Clotting factor 5
108
What do dense-core granules in platelets contain? (4)
- ATP
- ADP
- Serotonin
- Ca2+
109
What is the structure of platelets? (3)
- No nucleus
- Platelet receptors on external coat
- Inner skeleton of tubulin microtubules
110
How does increasing haematocrit affect blood flow?
Blood flow decreases
111
What is blood viscosity dependant on? (5)
- Haematocrit
- Fibrinogen plasma concentration
- Vessel radius
- Linear velocity
- Temperature
112
Where in the blood vessel does blood flow the fastest?
In the centre
113
What is the parabolic profile of laminar blood flow?
- Blood flowing in layers of increasing velocities from wall to centre
- Vmax at the centre
- V = 0 at the wall
114
How is the parabolic shape of blood flow affected by blood viscosity?
- Low viscosity = extended parabolic shape
| - High viscosity = stunted
115
What is plasma skimming?
Reduction of haematocrit in branched microvessels due to red blood cells accumulating in the centre of blood vessels
116
How is plasma skimming prevented?
Arterial cushions
117
What is 'tank treading'?
- RBC membrane rolls around the cytoplasm in small blood vessels
- Causes the plasma between RBCs to spin
118
What happens when RBCs enter vessels which are smaller than them?
- Deformed
| - Causes blood viscosity to fall
119
What happens in the blood vessels at a high flow rate?
- Blood flow is turbulent rather than laminar
| - Parabolic profile is blunted
120
What causes turbulence in blood vessels? (3)
- Large radius
- High velocity
- Local stenosis
121
What is stenosis?
Narrowing/restriction of the blood vessels
122
What does turbulent flow cause?
- Murmurs
| - Laminar flow is silent
123
What is haemostasis?
Prevention of haemorrhage
124
What is haemorrhage?
Blood loss
125
What are the 4 mechanisms of haemostasis?
- Vasoconstriction
- Increased tissue pressure
- Platelet plug
- Coagulation/clot formation
126
What are some examples of vasoconstrictors? (4)
- Thromboxane A
- Serotonin
- Thrombin
- Endothelin-1
127
What is the most potent vasoconstrictor?
Endothelin-1
128
What is transmural pressure?
Difference between the intravascular pressure and the tissue pressure
129
What are the 3 steps of platelet plug formation?
- Adhesion
- Activation
- Aggregation
130
What does injured endothelium expose? (3)
- Collagen
- Fibronectin
- Laminin
131
What triggers Von Willebrand factor release from endothelial cells? (3)
- High shear forces
- Cytokines
- Hypoxia
132
What is hypoxia?
Low oxygen
133
How does platelet adhesion occur?
- Von Willebrand factor from injured endothelium binds to receptor on a platelet
- Von Willebrand factor has a collagen binding site to bind to exposed collagen in injured endothelium
134
How does platelet activation occur?
- Ligand binding causes conformational changes in the receptors leading to an intracellular signalling cascade
- Exocytosis of contents of dense storage granules and alpha granules
- Cytoskeletal changes
135
How does platelet aggregation occur?
Activation allows binding of fibrinogen which forms bridges between platelets
136
What is in a blood clot? (4)
Semisolid mass of:
- Erythrocytes
- Leukocytes
- Serum
- Mesh of fibrin and platelets
137
What is a thrombus?
Intravascular blood clot
138
What are the 2 pathways of clotting?
- Intrinsic
| - Extrinsic
139
What is the intrinsic pathway of clotting?
- Factor XII (12) cleaved and activated into factor XII, anchored by HMWK
- Allows prekallikrein to be cleaved and activated into kallikrein, anchored by HMWK
- Kallikrein speeds up first reaction
- Factor XI (11) cleaved and activated into factor XIa
- Allows factor IX (9) to be cleaved and activated into factor IXa
- Factor VIII (8) cleaved and activated into factor VIIIa, mediated by thrombin
- Factor IXa and VIIIa combine with Ca2+ to form trimolecule tenase
- Tenase is able to activate factor X (10)
140
What is HMWK?
High Molecular Weight Kininogen
141
When does the extrinsic clotting pathway happen?
When blood contacts material from a damaged cell
142
When does the intrinsic clotting pathway happen?
Platelet receptors activated by factors in the blood
143
What is the extrinsic pathway of clotting?
- Factor VII (7) binds to tissue factor in cell membrane and becomes activated factor VIIa
- Factor VIIa, tissue factor and Ca2+ form a trimolecule which can activate factor X (10)
144
What is the common pathway of clotting?
- Both pathways end with factor Xa
- Factor V (5) activated by thrombin
- Complex forms of Xa, Va and Ca2+, which can convert prothrombin to thrombin (self-regulating)
- Thrombin accelerates the whole cascade
- Thrombin cleaves fibrinogen into fibrin
- Factor XIII (13) activated by thrombin
- XIIIa allows fibrin monomers to form stable fibrin
145
How do endothelial cells maintain normal blood fluidity?
- Paracrine factors
| - Anticoagulant factors
146
What are 2 anticoagulant factors?
- TFPI
| - Antithrombin III
147
How does TFPI work?
Binds to tissue factor, VIIa, Ca2+ complex in the extrinsic pathway to prevent it from activating factor X and causing the downstream cascade
148
How does antithrombin III work?
Prevents activation of factors in the cascade
149
What does thrombomodulin do?
Binds to thrombin and prevents it acting in the clotting cascade
150
What is atherothrombosis?
Formation of a thrombus in an artery
151
What are the risk factors for Deep Vein Thrombosis (DVT)? (3)
- Venous stasis
- Vascular injury
- Hypercoagulability
152
What is venous stasis?
Reduced blood flow in the veins
153
What is the pericardium?
Fluid filled sac around the heart
154
What kind of blood is in the right atrium?
Receives deoxygenated systemic venous blood via the vena cava
155
What kind of blood is in the right ventricle?
Pushes deoxygenated blood to the pulmonary circulation via the pulmonary artery
156
What kind of blood is in the left atrium?
Receives oxygenated blood from the pulmonary circulation via the pulmonary vein
157
What kind of blood is in the left ventricle?
Pushes oxygenated blood to the systemic circulation under high pressure via the aorta
158
Where are the atrioventricular valves?
Between the atrium and ventricle
159
What are the types of atrioventricular valves? (2)
- Tricuspid
| - Mitral
160
What connects the atrioventricular valves to the cardiac wall? (2)
- Chordae tendineae (heart strings)
| - Papillary muscles
161
Where are the semilunar valves?
Between the ventricle and its associated artery
162
What are the types of semilunar valves? (2)
- Aortic
| - Pulmonary
163
What are the 3 layers of the heart?
- Epicardium
- Myocardium
- Endocardium
164
What is the epicardium?
Outer layer of the heart
165
What is the epicardium made of? (3)
- Loose connective tissue
- Elastic fibres
- Adipose tissue
166
What is the function of the epicardium? (2)
- Involved in production of pericardial fluid
| - Protection
167
What is the myocardium made of? (2)
- Involuntary striated muscle
| - Cardiac muscle cells encased in collagen fibres
168
What is the endocardium made of? (2)
- Smooth muscle
| - Elastic fibres
169
Where are the conducting cells of the heart? (5)
- Sinoatrial node (SAN)
- Atrial internodal tracts
- Atrioventricular node (AVN)
- Bundle of His
- Purkinje fibres
170
What are intercalated discs? (2)
- Structures which link adjacent cardiac muscle cells
| - Contain gap junctions and desmosomes
171
What are myocytes?
Muscle cells
172
What is the sarcolemma?
Excitable cell membrane of the muscle cells
173
What is the function of gap junctions in the intercalated discs?
Allows the spreading of action potentials from cell to cell (cardiac muscle cells are electrically coupled) which allows for coordinated contraction
174
What is the function of desmosomes in the intercalated discs?
Anchor cells together
175
What are T-tubules?
Deep invaginations of the sarcolemma
176
What is the function of T-tubules?
- Enable the current to be spread to the core of the cells
| - This allows Ca2+ to be released simultaneously from the sarcoplasmic reticulum
177
What are sarcomeres?
- Contractile unit of muscle
| - Repeating units between Z-lines (intercalated discs)
178
Is cardiac muscle striated or non-striated?
Striated
179
Is smooth muscle striated or non-striated?
Non-striated
180
What are the thick filaments in sarcomeres?
Myosin
181
What are the thin filaments in sarcomeres?
- Actin
- Tropomyosin
- Troponin
182
What is the sliding filament theory?
- Depolarisation breaks the cross-bridges between actin and myosin
- Thick and thin filaments move over each other causing the Z lines to come closer together
183
What are the steps of the cardiac cycle?
- Cells of the SAN spontaneously depolarise
- Electrical coupling of cardiac cells allow the action potential to spread across the atria causing atrial systole
- AP reaches AVN which conducts the AP down the septum of the heart via the bundle of His to the Purkinje fibres around the sides of the ventricles causing ventricular systole from the bottom upwards
184
What is the primary pacemaker of the heart?
- Sinoatrial node (SAN)
| - Can be affected by sympathetic/parasympathetic innervation
185
How long does it take for the action potential from the SAN to reach the AVN?
0.1 seconds
186
What is the secondary pacemaker of the heart?
AVN
187
What is the function of the fibrous atrioventricular ring?
Non-conductive tissue which prevents the AP from the SAN spreading over the ventricles
188
What happens during atrial systole?
- Contraction causes increased pressure in the atria
| - Relaxed ventricles fill with blood as mitral/tricuspid valves are open
189
What happens during isovolumetric ventricular contraction?
- Ventricles contract due to electrical activation from the Purkinje fibres so pressure increases
- When ventricular pressure exceeds atrial pressure, atrioventricular valves shut which produces the first heart sound
- Volume in the ventricles remains the same
190
What happens during rapid ventricular ejection?
- Ventricular pressure rises until it exceeds aortic pressure which opens the semilunar valves
- Blood ejected, ventricular volume decreases
- Arterial pressure rises
- Atrial filling begins causing small increase in pressure
191
What happens during reduced ventricular ejection?
- Ventricles begin to repolarise
- Pressure falls
- Blood still ejected through open semilunar valves at a reduced rate
- Arterial volume falls
192
What happens during isovolumetric ventricular relaxation?
- Ventricles are fully repolarised
- When pressure decreases below arterial pressure the semilunar valves close which produces the second heart sound
- Ventricular volume is constant, all valves are closed
193
What happens during rapid ventricular filling?
- Ventricular pressure falls below atrial pressure causing mitral/tricuspid valves to open
- Ventricles begin to fill so volume increases but pressure is still low
194
What happens during reduced ventricular filling?
Most of ventricular filling occurs during diastole
195
What does the P wave in an ECG indicate?
Depolarisation of the atria from the SAN causing systole
196
What does the duration of the P wave in an ECG mean?
Atrial conduction time
197
Why isn't repolarisation of the atria visible on an ECG?
Masked by the QRS wave
198
What does the PR interval on an ECG mean?
AVN conduction
199
What does the QRS wave on an ECG indicate?
Depolarisation of the ventricles
200
What does the T wave on an ECG indicate?
Repolarisation of the ventricles
201
What does an ECG record?
Summed electrical activity of the heart
202
What kind of muscle is in the heart?
Cardiac muscle
203
Which blood vessels have the highest resistance to blood flow?
Arterioles
204
What kind of neurons innervate the arterioles?
Sympathetic adrenergic neurons
205
Which receptors are present on arterioles?
- Alpha 1 adrenergic receptors (main)
| - Beta 2 adrenergic receptors (skeletal muscle, less common)
206
Which G protein are alpha 1 adrenergic receptors coupled to?
Gq
207
What happens when alpha 1 receptors on arterioles are activated?
Vasoconstriction
208
What happens when beta 2 receptors on skeletal muscle arterioles are activated?
Vasodilation
209
Which branch of the nervous system innervates the smooth muscle in blood vessels?
Sympathetic
210
Which blood vessels have the slowest blood flow?
Capillaries (small area, large combined area)
211
What is the equation for calculating velocity of blood flow?
V = Q/A
212
What is the total peripheral resistance (TPR)?
Resistance of entire systemic vasculature
213
What is the equation for calculating blood flow?
Q = ΔP/R
214
What does blood viscosity depend on?
Haematocrit
215
What is the equation for calculating blood flow?
R = 8ηl/πr^4
216
What is resistance to flow directly proportional to? (2)
- Vessel length
| - Viscosity
217
What is resistance to flow inversely proportional to?
Radius^4
218
What happens to pressure in blood vessels arranged in series?
Pressure decreases through each sequential component
219
What happens to pressure in blood vessels arranged in parallel?
Pressure is maintained
220
What does diastolic blood pressure indicate?
When ventricles are relaxed
221
What does systolic blood pressure indicate?
Blood being ejected from the ventricles during systole
222
Which blood pressure reading is the highest?
Systolic
223
Which blood pressure reading is the lowest?
Diastolic
224
What is the dicrotic notch?
Small blip in blood pressure when the aortic valve closes
225
How do you calculate the pulse pressure?
Systolic - diastolic pressure
226
What does pulse pressure indicate?
Blood volume ejected from the left ventricle (stroke volume)
227
What is the stroke volume?
Blood volume ejected from the left ventricle
228
How do you calculate the mean arterial pressure?
Diastolic pressure + 1/3 pulse pressure
229
What is the mean arterial pressure?
Average pressure in a complete cardiac cycle
230
When is blood pressure the highest?
During the day
231
When is blood pressure the lowest?
During the night
232
Where are baroreceptors located? (2)
- Carotid sinuses
| - Aortic arch
233
What do baroreceptors detect?
Level of stretch on vascular walls i.e. pressure changes
234
Which nerve are the carotid sinus baroreceptors linked to?
Cranial nerve IX (9)
235
Which nerve are the aortic arch baroreceptors linked to?
Cranial nerve X (10)
236
Which area of the brain do baroreceptors send information to?
Solitary nucleus in the medulla
237
What is the reticular formation?
Complex network of nuclei in the brain stem which regulate cardiovascular functions (medulla and pons)
238
How is blood pressure regulated in the short term?
- Baroreceptors in the carotid sinuses and aortic arch send information to the solitary nucleus in the medulla
- Solitary nucleus directs changes in parasympathetic and sympathetic output via the cardiovascular centres in the reticular formation in the brainstem (medulla and pons)
239
How does the parasympathetic nervous system influence blood pressure?
- Parasympathetic innervation via the vagus nerve targets the SAN
- Increased firing causes a decrease in heart rate and therefore blood pressure
240
How does the sympathetic nervous system influence blood pressure? (4)
- Can target the SAN to increase heart rate
- Can target cardiac muscle to increase contractility and stroke volume
- Can cause arteriole vasoconstriction to increase TPR
- Can cause vein vasoconstriction
(Causing increased blood pressure)
241
How is blood pressure regulated in the long term?
Renin-angiotensin II-aldosterone system
242
How does the renin-angiotensin II-aldosterone system influence blood pressure?
- Decreased arterial pressure causes decreased renal perfusion which causes prorenin to be converted to renin
- Angiotensinogen converted to angiotensin I by renin
- Angiotensin I converted to angiotensin II by ACE
- Angiotensin II works to increase blood pressure
243
What is ACE?
Angiotensin Converting Enzyme
244
How does angiotensin II influence blood pressure?
- Causes adrenal cortex to secrete aldosterone which causes more Na+ reabsorption
- Acts on hypothalamus to increase thirst and vasopressin secretion
- Causes vasoconstriction of arterioles to increase TPR
(All causing increase in blood pressure)
245
How do oxygen chemoreceptors influence blood pressure?
Cause arteriole vasoconstriction via the sympathetic nervous system when activated
246
Where are oxygen chemoreceptors located?
- Carotid sinuses
| - Aortic arch
247
How do carbon dioxide chemoreceptors influence blood pressure?
Cause arteriole vasoconstriction via the sympathetic nervous system when activated
248
Where are carbon dioxide chemoreceptors located?
The brain
249
How does vasopressin influence blood pressure?
- Stimulates V1 receptors in vascular smooth muscle causing vasoconstriction
- Stimulates V2 receptors on renal collecting ducts causing water reabsorption
(Causing increase in blood pressure)
250
How does atrial natriuretic peptide (ANP) influence blood pressure?
Secreted by the heart and promotes salt excretion by the kidneys to decrease blood pressure
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What happens in chronic hypertension?
- Baroreceptors are desensitised so hypertension isn't corrected
- Don't experience dip in BP at night time
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What drugs can be used to treat chronic hypertension? (8)
- ACE inhibitors
- Angiotensin II receptor blockers (ARBs)
- Diuretics
- Beta blockers
- Ca2+ channel blockers
- Alpha-blockers
- Alpha-agonists
- Renin inhibitors
