Cardiovascular Flashcards
1
Q
What is isovolumetric contraction?
A
Ventricular contraction when all valves are closed. This increases ventricular pressure but as all the valves are closed the volume remains the same.
2
Q
What produces the first heart sound ‘lub’
A
closing of mitral valve
3
Q
what causes the mitral valve to close
A
when LVp exceeds LAp. Just before ventricular isovolumetric contraction
4
Q
describe systole
A
Wave of depolarisation arrives, Ca2+ channels open.
LVp>LAp and mitral valve closes.
LVp rises, isovolumetric contraction, LVp> aortic pressure
Aortic valve opens and ejection begins
5
Q
What produces the second heart sound ‘dub’
A
closing of aortic valve
6
Q
describe diastole
A
LVp decreases and there is a phase of reduced ejection.
LVp < aortic pressure so aortic valve closes
isovolumetric ventricular relaxation
LVp >LAp so mitral valve closes
7
Q
systole duration time?
A
0.3s
8
Q
diastole duration time?
A
0.5s
9
Q
what is the end systolic volume?
A
the volume of blood remaining in the LV following systole
10
Q
define preload
A
the volume of blood in the ventricles just before contraction (EDV)
11
Q
define afterload
A
the pressure which the heart must work against to eject blood in systole
12
Q
define contractility
A
the inherent strength and vigour of the hearts contraction during systole
13
Q
define elasticity
A
myocardial ability to recover its original shape after systolic stress
14
Q
define compliance
A
how easily a chamber of the heart expands when it is filled with blood (C=change in V/change in P)
15
Q
define diastolic distensibility
A
the pressure required to fill the ventricle to the same diastolic volume
16
Q
define resistance
A
a force that must be overcome to push blood through the circulatory system
17
Q
what is the basic principle of starlings law of the heart
A
Increased End Diastolic volume (EDV)= Increased stroke volume (SV)
18
Q
explain starlings law
A
the greater the EDV, the greater the sarcomeres stretch and the more forceful the contraction
19
Q
relate to starlings law, what is the effect of an increased venous return
A
EDV will increase so SV Increases so cardiac output increases
Cardiac output= stroke volume x heart rate
20
Q
stroke volume equation
A
SV=EDV-ESV
21
Q
cardiac output equation
A
CO=SVxHR
22
Q
Define cardiac output
A
volume of blood each ventricle pumps out per unit of time
23
Q
mean arterial pressure equation
A
MAP= DP +1/3 (SP-DP) DP= diastolic pressure SP= systolic pressure
24
Q
pulse pressure equation
A
PP=SP-DP
DP= diastolic pressure SP= systolic pressure
25
blood pressure equation
BP=COx Total peripheral resistance
26
ohms law?
V=IR
| So in this case force=change in pressure/ resistance
27
poiseuille's equation?
Q=r^4
Q= volumetric flow rate
r= pipe radius
28
the principle vessels for resistance
arterioles
29
what do arterioles respond to
Blood pressure changes. local,neural and hormonal factors
30
name 2 local factors that result in vasoconstriction
endothelin, internal blood pressure
31
name 6 local factors that result in vasodilation
hypoxia, nitrous oxide, K+ (accumulate from AP),CO2, H+, adenosine
32
what neural factors result in vasoconstriction
sympathetic nerves that release noradrenaline
33
what neural factors result in vasodilation
parasympathetic innervation
34
name 3 hormonal factors that result in vasoconstriction
angiotensin II, ADH, adrenaline (binds to alpha-adrenergic receptors in smooth muscle
35
name 2 hormonal factors that result in vasodilation
atrial natriuretic peptide, adrenaline (binds to beta2 receptors)
36
What is myogenic auto-regulation of the blood?
An intrinsic mechanism in smooth muscle blood vessels. If BP increases, the vessel constricts. This is important in regulating blood flow
37
Myogenic auto regulation of blood flow: what is the response to an increase in BP
Vasoconstriction and so blood flow decreases in blood vessels
38
Myogenic auto regulation of blood flow: what is the response to decrease in BP
Vasodilation so blood flow in blood vessels increases
39
What is hyperaemia
An increased blood flow to tissues
40
What is the cause of active hyperaemia
When blood flow increases due to an increase in metabolic activity.
Increased metabolic activity= decreased O2 and increased metabolites= arteriolar dilation = increased blood flow
41
What is the cause of reactive hyperaemia
When blood flow increases following occlusion of arterial flow
42
Describe excitation-contraction coupling
1. Na+ depolarises membrane
2. A small amount of Ca2+ is released from T tubules.
3. Ca2+ channels open in sarcoplasmic reticulum
4. Ca2+ flows into Cytosol. Cytosolic Ca2+ conc is raised
5. Ca2+ binds to troponin C which pulls troop myosin and exposes the myosin binding site on actin
6. Cross bridge cycling begins
7. After depolarisation, Ca2+ is returned to sarcoplasmic reticulum. K+ outflow= repolarisation
43
What effect does myocardial contraction have on A band of sarcomere
No effect, it stays same length
44
What effect does myocardial contraction have on I-band and H-Zone of sarcomere
They get shorter
45
Describe actin (thin filament)
A globular protein, single polypeptide. It polymerises other actin monomers to form double stranded helix. Together they form F actin
46
Describe myosin (thick filament)
2 heavy polypeptide chains and 4 light chains. The myosin heads have 2 binding sites; one for actin and one for ATP
47
Describe tropomyosin
An elongated molecule made of 2 helical peptide chains
48
Function of troponin I
Together with tropomyosin, inhibits actin and myosin binding
49
Function of troponin T
Binds to tropomyosin
50
Function of troponin C
Has a high affinity for Ca2+. Troponin C drives away troponin I and so allows cross bridge formation
51
Name 3 effectors in circulation control
1. Blood vessels- vasoconstrict/dilate and effect TPR
2. Heart- can affect rate or contractility
3. Kidneys- regulates blood volume and fluid balance
52
Where are baroreceptors located
Aortic arch and carotid sinus
53
What activates baroreceptors
They contain stretch receptors that respond to pressure
54
Are atrial baroreceptors involves in short-term or long term regulation of BP
Short term (Cardiopulmonary =long term)
55
Where are central chemoreceptors located
Medulla oblangata
56
What do central chemoreceptors respond to
Changes in pH (H+)
Increased PaCO2 increases H+ so decreases pH
Increased PaCO2 results in Vasodilation
57
What is the ligamentum teres a remnant of
The umbilical vein
58
What is the ligamentum venosus a remnant of
The ductus venosus
59
Briefly describe foetal circulation
Maternal circulation- umbilical vein (oxygenated blood) - ductus venosus - Inferior vena cava- RA- LA/RV- aorta- umbilical artery (deoxygenated blood)- maternal circulation
60
What layer of the trilaminar disc forms the cardiovascular system
The mesoderm
61
What does the first heart field produce
The left ventricle (LV)
62
What does the second heart field produce
The right ventricle, atria and outflow tracts
63
What are the 3 stages of heart formation
1. Formation of primitive heart tube
2. Cardiac looping
3. Cardiac septation
64
Describe the formation of primitive heart tube
2 endocardial tubes form (day19)
| The tubes fuse together and heart hearts (day22)
65
Describe what happens in cardiac looping
Nodes secrete nodal, this circulates to the left due to ciliary movement. Nodal causes a cascade of transcription factors that transduce looping
66
What happens in cardia septation
Endocardial cushions form. Fuse at midline to from atrioventricular septum.muscular ridge in the floor of primitive ventricle migrates to endocardial cushions forming interventricular septum
67
What does sinus venosus form
The coronary sinus and RA
68
What does primitive atrium form
Right and left atriums
69
What does primitive ventricle form
Most of left ventricle
70
What does bulbus Cordis form
Part of the ventricles
71
What does the truncus arteriosus form
Aorta and pulmonary trunk
72
What do the first and second aortic valves come from
Minor vessels in the head
73
What does the 3rd aortic arch form
Common carotid arteries
74
What does the left and right 4th aortic arch form
```
Left = aorta
Right = right subclavian artery
```
75
What does the 5th aortic arch form
There is no 5th arch lol
76
What does the the left and right 6th aortic arch form
```
Left = left pulmonary artery and ductus arteriosus
Right = right pulmonary artery
```
77
What does the 7th segmental aortic arch form
Left and right subclavian arteries
78
What does the dorsal aortae form
```
Left= descending aorta
Right= part of subclavian artery
```
79
What are chronotropic effects
These change the heart rate eg positive chronotropic= increased heart rate
80
What are inotropic effects
Alter the force of muscular contractions
81
What affect does parasympathetic stimulation have on heart rate
Decrease heart rate (negative chronotropic)
| Therefore cardiac output decreases
82
What affect does sympathetic stimulation have on force of contraction
Increases force ( positive inotropic)
83
What pump maintains the negative testing potential of a membrane
Sodium potassium pump
| Na+/K+ pump
84
Purpose of Nernst equation
Determines membrane potential
85
What is Nernst equation
E=60log(conc outside/conc inside)
86
What membrane channels are responsible for the plateau period in the cardiac Action Potential
Voltage gated Ca2+ ‘slow’ channels
87
Briefly describe the cardiac action potential in 5 steps
1. Na+ channels open; influx of Na+ into cell; depolarisation
2. When Na+ channels close a small number of K+ leave the cell resulting in partial repolarisation
3. Ca2+ channels open and there is a Ca2+ inflow. K+ channels are also open so there is a K+ outflow. This results in the plateau period.
4. Ca2+ channels close and K+ channels remain open. K+ leaves cell resulting in repolarisation
5. Maintaining the resting potential (approx -90mV) Na+ inflow, K+ outflow
88
Where is SAN located?
Right atrium under cristae terminalis
89
Briefly describe the electrical conduction pathway in the heart
1. The SAN generates an electrical impulse
2. This generates a wave of contraction in the atria
3. Impulse reaches AVN
4. Their is a brief delay to make sure atria have fully emptied
5. The impulse then rapidly spreads down the Bundle of His and Purkinje Fibres
6. The purkinje fibres then trigger coordinated ventricular contraction
90
Why is there rapid conduction in the bundle of his and purkinje fibres?
1. The fibres have a large diameter
| 2. There is high permeability at the gap junctions
91
What is the function of the refractory period
1. Prevents excessive frequent contractions
| 2. It allows time for the atria to fill
92
What does the P wave on an ECG represent and what’s the duration
Atrial depolarisation. Duration less than 0.12s
93
What does the QRS complex on an ECG represent? And it’s duration
Ventricular depolarisation. Duration 0.08-0.1s
94
What does the T wave on an ECG represent
Ventricular repolarisation
95
What might an elevated ST segment be associated with on an ECG
Myocardial infarction. (STEMI- ST elevated myocardial infarction)
96
ECG: where would you place lead 1
Right arm (-ve) to left arm (+ve)
97
ECG: where would you place lead 2
Right arm (-ve) to left leg (+ve)
98
ECG: where would you place lead 3
Left arm (-ve) to left leg (+ve)
99
What is einthovens triangle
An imaginary formation of the 3 limb leads in a triangle shape
100
ECG: where would you place lead aVR
Left arm and left leg (-ve) to right arm (+ve)
101
ECG: where would you place lead aVF
Right arm and left arm (-ve) to left leg (+ve)
102
ECG : where would you place lead aVL
Right arm and left leg (-ve) to left arm (+ve)
103
ECG chest leads : in which intercostal space would you place V1 and V2
The 4th intercostal space. V1 is on right of the sternum and V2 in left.
104
ECG chest leads: in which intercostal dove would you place V3-V6
The 5th intercostal space. V3 is left of the sternum, V4 is in the midclavicular line, V5 is left of V4 and V6 is under the left arm
105
What are the average systolic and diastolic pressures of the pulmonary circulation
25 and 10mmHg
106
What are the average systolic and diastolic pressures of the systemic circulation
120 and 80mmHg
107
Why might someone with liver injury experience prolonged bleeding time
Because the liver produces clotting factors
108
What is exposed if you damage the endothelium vessel
Underlying connective tissue and collagen
109
What is the role of von willebrands factor
Binds to collagen. Platelets also bind to the von willebrands factors
110
What happens in platelet activation?
Platelet changes shape: smooth to spiculated
This increases its surface area.
New platelets adhere to old ones = platelet aggregation
This forms a platelet plug
111
What do activated platelets synthesise
Thromboxane A2
112
What is the function of thromboxane A2 (TXA2)?
Leads to further platelet aggregation
113
What are the platelet receptors for fibrinogen
Glycoprotein IIb/IIIa. Fibrinogen forms ‘bridges’ between platelets.
114
What does an undamaged endothelium release In order to prevent platelet activation in undamaged areas
Prostacyclin (inhibits platelet aggregation)
| And Nitric Oxide (NO)(inhibits platelet adhesion)
115
What are platelets made from and where are they made
Made from megakaryocytes in the bone marrow
116
In haemostatsis what is prothrombin converted to
Thrombin
117
Give 3 functions of thrombin
1. Converts fibrinogen to fibrin
2. Activates factor XIII to XIIIa
3. Has a positive feedback effect resulting in further thrombin production
118
What is the essential component of a blood clot
Fibrin
119
Briefly describe the fibrinolytic system
Plasminogen is converted to plasmin.
| Plasmin cuts the fibrin at various places leading to the formation of fragments
120
What is the purpose of the fibrinolytic system
It acts to prevent blood clots from growing and becoming problematic
121
What is the structure of haemoglobin
2 alpha and 2 beta chains. 4 haem groups
122
Describe the composition of blood
Plasma - 55%
| Cellular - 45% —> RBC: 44% and WBC: 1%
123
Does blood flow to the heart occur during diastole or systole
Diastole
124
What is diastole and systole
Diastole - relaxing and refilling of heart with blood
| Systole - contraction and pumping of blood
125
What does left coronary artery divide into
Left anterior descending and the circumflex
126
Why is O2 saturation in coronary and venous blood very low
O2 extraction by the heart muscle is very high
127
What surface of the heart does the right coronary artery supply
The inferior surface of the heart (underside)
128
What is release upon cell activation and contains a high conc of a molecule that’s acts as an agonist of the platelet P2Y12 receptor
Platelet dense granules
129
What valve prevents high pressures developing in the jugular veins during ventricular systole
The tricuspid valve
130
What is the normal duration of PR interval
0.12-0.2 secs
131
What ECG lead yield complexes that are normally inverted compared to the anterior and inferior leads?
Lead aVR
132
Is there a point in the cardiac cycle when both atrial and ventricular diastole occur together
Yes: when the ventricles and replacing and the atria are filling ( before atrial contraction)
133
Why does an increase in LVEDV (left ventricle end diastolic volume)signify heart failure
Heart failure is the inability to pump blood out of the heart. There is blood remaining at the end of systole. The blood therefore accumulates so LVEDV increases
134
Which pressure is most likely to increase in left sided heart failure
LV EDP
| Left ventricular end diastolic pressure
135
Which pressure is most likely to decrease in left sided heart failure
Mean aortic pressure ( less blood being pumped to aorta)
136
What is stenosis
Narrowing
137
Which pressure is most likely to increase in mitral valve stenosis
Left atrial end systolic pressure
138
What does it means if a heart valve is incompetent
It is regurgitant
139
Which pressure is most likely to increase when the aortic valve is incompetent
Left ventricular end diastolic pressure
140
Pulmonary oedema is a sign of what
Left heart failure
141
What can severe pulmonary hypertension cause
Right heart failure
| The heart has to pump harder to get blood into the pulmonary circulation due to an increased after load
142
Shortness of breath and severe peripheral oedema and ascites after heart attack can indicate what
Biventricular failure
143
What is ascites
Accumulation of fluid in the peritoneal cavity and can cause abdominal swelling
144
What does the PR interval represent and how long is it
The slow conduction between the AVN and the His-Purkinje system.
It’s 0.12-0.2 secs long
145
Diastole: what is diastasis
When left ventricle pressure = right atrial pressure. Net movement of blood is 0. This is the time between ventricular suction and atrial contraction
146
What branch does the right coronary artery give off as it reached the inferior border of the heart
Right marginal branch
147
What artery does the RCA anastomose with on the diaphragmatic surface of the heart
The circumflex artery
148
What does the left anterior descending anastomose with on the diaphragmatic surface of the heart
The posterior inter-ventricular branch of the right coronary artery
149
Where is the coronary sinus found
Between the left atrium and left ventricle
| The left atrioventricular sulcus
150
What does the coronary sinus drain into
The right atrium
151
What artery arises from the RCA in 90% of hearts, the circumflex in 30% and in 20% arises from both the RCA and circumflex
The posterior inter-ventricular branch
152
What equation explains why small changes in the diameter of a flood vessel have a great effect on the resistance to flow fluid through that vessel
Poiseuilles equation
| Q=r^4
153
What is the role of fibrinogen in platelet aggregation.
It forms cross links between aggregating platelets
154
Give 2 reasons why liver is important for clotting
1. The liver produces many clotting factors
2. The liver produces bile salts that are needed for vitamin K absorption. vitamin K is needed for clotting factor production.
155
When are the platelet receptors for fibrinogen exposed
During platelet activation
156
Which of the ABO blood groups is recessive
A and B are co-dominant
157
Why is the O blood group a universal donor
It has no A or B antigens
158
What are the 2 ways of determining someone’s ABO blood group
1. Test using antibodies
| 2. Test for the presence of antibodies using A or B antigens
159
Describe how testing for the presence of antibodies against A and B antigens will determine their blood group
The presence of antibodies in the blood will indicate that this person does not have these antigens on their RBCs. For example, if a persons blood contains antibodies against B antigens then they can’t be AB or B blood groups
160
Describe how testing using antibodies determines someone’s blood group
If the antibodies bind it indicates the presence of a specific antigen. For example, if antibodies against the B antigens bind to the patients RBC then the person must either be AB or B blood group
161
What antigens are part of the Rhesus blood group system
C,D and E
| D is the most important
162
What problems arise if a pregnant lady is found to be Rhesus D negative
If exposed to D RBCs the lady will have antibodies against the D antigen. The antibodies can cross the placenta and cause haemolysis of the babies RBCs. This can result in in-utero death.
163
What can be given to Rhesus D negative mothers to prevent sensitisation
Anti-D
164
Describe the arterial baroreceptor reflex in response to increase blood pressure
- Increase parasympathetic outflow to the heart means contractility and heart rate are reduced so cardiac output is reduced: CO=HRxSV
- Decreased sympathetic outflow to the arterioles results in vasodilation and so the total peripheral resistance (TPR) is reduced
- BP=COxTPR and so blood pressure is lowered
165
Describe the arterial baroreceptor reflex in response to decrease in blood pressure
- Increased sympathetic outflow to the heart means contractility and heart rate are increased so cardiac output is increased : CO=HRxSV
- Increased sympathetic outflow to the arterioles results in vasoconstriction and so the total peripheral resistance (TPR) is increased
- BP=COxTPR and so blood pressure is increased
166
What phase of the cardiac action potential coincides with diastole
Phase 4
167
What part of the ECG does the plateau phase of the cardiac action potential coincide with
QT interval
168
Give 4 factors that affect the gating of ion channels
Voltage, drugs, hormones, temperature
169
What is Virchows triad
Describes 3 categories thought to contribute to thrombosis.
1. Stasis of blood flow
2. Endothelial injury
3. Increased coagulation ability
170
Define ischaemia
A decrease in blood flow to the tissue
171
Define infarction
No blood flow to the tissue - tissue death
172
Explain the formation of fluid exudate in inflammation
Chemical mediators cause vasodilation of vessels and an increase in permeability
173
What are the roles of lymphatics in acute inflammation
Drain exudate and carry antigens
174
What happens in phase 4 of the cardiac action potential
Pace maker potential- na+ inflow and slowing of K+ outflow. Slow depolarisation begins= innate contractility
175
Where is Ca2+ released from in excitation contraction coupling
The T tubules and sarcoplasmic reticulum
176
What is the resting potential of SA node
-55 to -60mV
177
How to central chemoreceptors respond to an increase in PaCO2
Vasoconstriction
178
Why do central chemoreceptors stimulate vasoconstriction in resin to an increase in PaCO2
They act to counter the affect of CO2 as a vasodilator and so maintain blood flow to tissues
179
What reaction does adenyl Cyclase catalyse
The conversion of ATP to cAMP
180
How do muscarinic M2 receptors cause a decrease in cAMP
They inhibits adenyl cyclase
181
What 2 channels are closed during the refractory period in the cardiac action potential
Fast Na+ and Ca2+ channels
182
What is the normal duration of the PR interval in ms
120-200ms
183
What would an absent P wave on an ECG be a sign of
Atrial fibrillation
184
What is the heart supplied by
Left and right coronary arteries
185
Blow flow to the myocardium occurs when
Mainly during diastole
186
ECG: what represents atrial systole
PR interval
187
ECG:What assesses the electrical activity whir in the lateral myocardial territory
Leads I,aVL, V5 and V6
188
ECG:Yields completed that are normally inverted compared to anterior and inferior leads
Lead aVR
189
ECG:Assesses electrical activity within the inferior myocardial territory
Leads II,III and aVF
190
Haematocrit:what is it, how do you calculate it?, what is the percentages of the 2 components it’s made up of?
Volume percentage of red blood cells in blood
Haematocrit= ratio of RBC volume - total blood volume
45% is erythrocytes
55% is plasma
<1% is WBC
191
RBC: how long do they live?, organelles?, where are they made?, stimulated by?, production process name?
120 days, Anucleate & no mitochondria ( glycolysis enzymes convert glucose to pyruvate, liver pyruvate to lactate), made in bone marrow, stimulated by erythropoietin (made in liver and kidney)! RBC production process called erythropoesis
192
Describe RBC shape and structure
7.5um in diameter so can just about fit through capillaries
Biconcave disc for large SA
Thin plasma membrane
4 globin chains - 2 alpha & 2 gamma
