Cardiovascular Flashcards
1
Q
What is the the haemocrit for blood?
A
45% cellular component of blood.
2
Q
what is the fluid component of blood?
A
55%
3
Q
What lies between the red blood cell and fluid layers on a haemocrit?
A
it is the white blood cells and platelets.
4
Q
Where is haemopoesis in utero?
A
the yolk sac, liver and spleen, and bone marrow.
5
Q
Where is haemopoesis in children?
A
in all bones in the bone marrow
6
Q
Where in adults is haemopoesis?
A
in the axial skeleton. the spine and skull
7
Q
What is the name for production of RBCs?
A
Erythropoeisis?
8
Q
What is the name for production of white blood cells?
A
Myelopoiesis
9
Q
What is the name for the production of Platelets?
A
Thrombopoesis
10
Q
What cells does a common myeloid progenitoro lead to?
A
Megakaryocytes, erythrocytes, mast cells, myeloblasts
11
Q
What do myeloblasts lead to?
A
Basophils, neutrophils, eosinophils, and monocytes.
12
Q
What do common lympnoid proogenitors lead to?
A
lymphocytes
13
Q
What growth factor causes RBC production?
A
Erythropoietin
14
Q
What growth factor causes white blood cell production?
A
Granulocyte-macrophage-colony-stimulating factor
15
Q
Which growth factor stimulates growth of platelets?
A
Thrombopoietin
16
Q
Facts about RBCs?
A
simple cells no nucleus, no mitochondria, Biconcave disk around 7.5um contai haemoglobin and glycolysis enzymes.
17
Q
Describe the haemoglobin molecule
A
quaternary structure. 2 alpha chains 2 beta chains. contain Fe2+ in haem group
18
Q
What are the types of haemoblobin in an adult and proportions?
A
HbA 2 alpha 2 beta, 96-98%, HbF 2 alpha 2 gamma 0.5-0.8%, HbA2 2 alpha 2 delta 1.5-3.2%
19
Q
What are the signs and symptoms of anaemia?
A
signs pallor tachycardia, signs related to underlying cause. symptoms tiredness/lethargy shortness of breath on exertion angina claudications symptoms related to underlying cause.
20
Q
What changes in acute blood loss?
A
Volume of blood no change to haemocrit as all components lost equally.
21
Q
How long do RBCs last for?
A
120 days aproximately 9 billion in an hour.
22
Q
Which organs are involved in the removal of RBCs?
A
Spleen, Liver Bone marrow
23
Q
Define Hypoplastic
A
not enough/ under development
24
Q
Dyshaemopoietic
A
ineffective production
25
Haemolytic
breaking of red blood cells
26
What is hypoplastic anaemia?
Not enough RBC produced causes renal failure endocctine problems can be inherited or idiopathic.
27
What are causes of iron deficiency anaemia
chronic bleeding poor diet malabsorption or hookworm
28
Length of life of a neutrophil?
6-10 hours
29
Length of life of a monocytes?
20-40 hours
30
Length of life of a lymphocyte?
weeks to years
31
Length of life of a basophil?
days
32
Length of life of a eosinophils?
days
33
Which white blood cells are the most numebrous?
The neutrophils
34
What is the function of neutrophils?
To phagocytose bacterial and foreign material they also release chemotaxins and cytokines which are important in the inflammatory response
35
What are macrophages?
They are cells that phagocytose bacteria and foreign material can differentiat to specific ones in tissues
36
What are macrophages derived from?
Monocytes
37
What are dendritic cells?
they present antigens to the immune system
38
What are basophils?
they migrate to tissues and they are important in immunity and allergic response primarily against bacteria and fungi
39
Eosinophils what do they do?
They have a role in inflammation and allergic response especially in protection against parasites.
40
What are the two types of lymphocytes?
B lymphocytes and T lymphocytes.
41
What do B lymphocyts do?
mature in bone marrow and generate antibodies becoming plasma cells.
42
What do T lymphocytes do?
Mature in the thymus and aid B cells and generate cell mediated immunity.
43
What is Haemostatis?
The balance keeping blood fluid in the vessels and clotting outside the vessels
44
What acts to cause clotting?
Platelets and proteins of coagulation cascade
45
What acts to prevent clotting?
Endothelial cells, the anticoagulant pathway and fibrinolytic pathway.
46
How are platelets produced?
There are megakaryocytes that release platelet precursors from their surface as blebs. they are anucleate and circulate in an inactive state.
47
What are the stages of action of platelets?
They bind to collagen via glycoprotein 1a (GP1a) on the platelet membrane. they can also stick to collagen via factors like von Willebrand factor through GP1b GP2a/b.once the platelets are activated they change shape to help them stick together to make a platelet plug. They release granules. finally GPVI causes stable adhesion and aggregation
48
What are in electron dense granules of patelets?
Calcium ADP and ATP and serotonin
49
What are in the alpha granules of platelets?
Platelet derived growth factor fibrinogen, heparin antagonist PF4 and vonWillebrand factor
50
What is thrombocytopenia?
too few platelets
51
What is thrombocytosis?
having too many platelets which can lead to thrombosis.
52
What are some of the components of Plasma?
Proteins- albumin, carrier proteins coagulation proteins and immunoglobulins.
53
What does albumin do where is it produced?
produced in the liver helps maintain oncotic pressure of the blood to keep fluid in the blood.
54
What are immunoglobulins?
they are proteins produced by B lymphocytes that are in the blood for immune response.
55
How many clotting factors are there?
13 but no 3,4,6
56
What is haemophillia A?
genetic condition males defficiency of clotting factore VII bleeding into muscles and joints
57
What is haemophillia B
Defficiency in factor IX bleeding into muscles and joints
58
What is an example of acquired bleeding disorder?
liver disease because of vitamin K deficiecy(found in vegetables.
59
What is the shape of IgM antibodies?
pentagonal shape
60
what is the shape of IgA antibodies?
two normal stuck to each end.
61
What causes a transfusion reaction?
The production of antibodies whcih react with the antigens on the surface of a foreign RBC
62
What type of antibodies are usually involved with blood reactions?
IgM ones
63
Which types of antibodies can cross the placenta?
IgG
64
What is the difference between ABO and RhD antbodies?
RHd is an immune antibody they are warm agglutins while ABO are naturally present and they are cold agglutanins that means they like to react at colder temperatures.
65
Why is RhD a problem in pregnancy?
When the mother is Rhesus negative so doesn't have D antigen. If the baby has go D antigens. All pregnant women are tested all who are negative are given antiD antibodies to stop sensitisation Haemolytic disease of the newborn.
66
What is cross matching in transfusions?
mix donor blood and patient to check for agglutination. could have antibodies from previous transfusions.
67
What are the early transfusion risks?
ABO incompatability, allergic reactons pyrogenic reactions bacterial contamination. couagulopathy. circulatory overload, transfusion related lung injury. post transfusion purpura
68
Late transfusion risks
RhD sensitisation, Delayed transfusion reaction, transfusion related iron overload, viral infection, prion infection
69
What is packed red cells?
Blood which has less plasma and higher haematocrit
| can be given with diuretic usually over 2-3 hours
70
What product is used for poor clotting?
platelets given over 30mins when have very low platelet count
71
What is FFP?
Fresh frozen plasma. Frozen in less than 6 hours contains proteins and inhibitors useed fro massive transfusion and dilutional coagulopathy liver disease and
72
What is cryoprecipitate?
rich in fibrinogen factor 1 used in massive transfusion.
73
What is HAS?
Human albumin solution plasma expander increases osmotic pressure and reduce oedema.
74
What layer of the embryo contributes to the arteries and cardiac outflow?
The mesoderm
75
Which layer of the embryo forms the blood and heart?
mesoderm
76
What is the shape of the heart fields?
They are sausage shaped sitting on top of each other the first on top of the second the lowest part will form the atria
77
What does the first heart field give rise to?
the left ventricle
78
What does the second heart field give rise to?
The future right ventricle the atria and outflows
79
What does the truncus arteriosis or bulbus cordis do and where is it?
It is at the top of the fused heart tubes and forms the aortic arch and most of the right ventricle
80
What does the primitive ventricle form?
The left ventricle
81
Where is the primitive atrium?
it is below the bulbus cordis and primitibve ventricle like carina. it forms the left and right atria
82
what are the sinus venosis?
they are at the bottom they produce the inferior vena cava and the right atrium
83
What happens to the heart after the formation of regions?
Dextro rotation to the right. the cordis and primitive ventricle moves down and to the front
the primitive atrium moves up the back
84
What is cardiac septation?
formation of septum from the primus
85
what are the endocardial cushions?
they grow up and down to form the separation of the AV canal.
86
Describe the formation of the interatrial septum.
First There is the growth of the septum primum to join with the endocardial cussion making a hole the foramum primum at the bottome, then the foramen primum dissapears then forms foramen secundum at top.then the septum secundum which is thicker and more muscular than the septum secundum contains the foramen ovale. the septum primum acts a valve flap for the atria.
87
Where is most of the blood in the body?
In veins
88
Where are the elastic arteries?
main ones like aorta brachiocephalic carotids subclavian and pulmonary.
89
What are the three types of capillaries?
Continuous which are most common, fenestrated in kidney small intestine and endocrine glands and discontinuous in the liver sinusoids
90
What advantage does valves give veins?
Muscular return of blood can take places.
91
When does vasculargenesis commence?
day 18
92
Which part of the primitive heart makes the aortic arch?
the truncus arteriosis/bulbus cordis
93
how many arches of the aorta are there?
6 main ones but there is no 5th
94
What does the 1st arch become?
part of the maxillary artery
95
What does the 2nd arch become?
the stapedial artery
96
what does the 3rd arch become?
the left or right internal and external carotid
97
What does the 4th arch become?
on left part of the aortic arch on the right the right subclavian.
98
What does the 6th arch develop into?
left the pulmonary artery and ductus arteriosis, on the right the right pulmonary artery
99
What does the 7th segmental artery become?
the left subclavian artery and part of the right subclavian artery
100
what does the dorsal aorta do?
It becomes the decending thoracic aorta on the left and regresees to be part of the right subcavian on the right.
101
What does the aortic sac become?
ascending aorta and part of brachiocephalic trunk.
102
What is the importance of platelets in pathology?
will cause Thrombosis
103
Describe the stages of Thrombosis
A fatty streak builds up on the lining, becomes a fibrous plaque, (atherosclerotic plaque)
then this can rupture or fissure and cause the clot to block that artery or pass to a critical area like the heart or brain.
104
What happens when a platelet it activated?
It changes shape from smooth to spiculates and pseudopodia (legs). increasing SA so increased interactions. more receptors and increased affinity to fibrinogen
105
Which receptors are used to cause adhesion?
attachement via GPIIb/IIIa integrin alphaIIb beta3
106
What can activate platelets?
Thrombin- also cleavs fibrinogen into fibrin. by PAR1 and PAR4
Thromboxane A2- comes from platelets when its bound to collagen, asprin stops this.
Collagen GPVI receptor
ADP- P2Y1
107
What biochemical changes occur at activation of platelets?
Causes more GPIIb/IIIa receptors,
108
Describe the action of COX1 and 2
Cyclooxygenases. both convert arachidonic acid into prostaglandin H2
COX-1 turns into thromboxane A2 in platelets
and COX-1 and COX-2 in endothelial cells convert prostaglandin H2 into prostacyclin
109
What is the effect of thromboxane A2?
causes platelet aggregation, and vasoconstriction.
110
What is the effect of prostacyclin?
Inhibits platelet aggregation and vasoconstriction. it mediates inflamation
111
What do NSAIDs do?
Block COX-1 and 2 to stop prostacyclin being formed meaning a clot is more likely.
112
What does low dose asprin do?
it inhibits COX-1 in platelets which stops thromboxane A2 production which leads to less clotting
113
What does high dose asprin do?
Block COX-1 and 2 to stop prostacyclin being formed meaning a clot is more likely.
114
What does high dose asprin do?
Block COX-1 and 2 to stop prostacyclin being formed meaning a clot is more likely.
115
What are P2y1 and P2y12?
both ADP receptors:
P2Y1 is a Gq receptor which releases PLC and this induces Ca mobilisation and activation of platelets
P2Y12 is a Gi GPCR. This inhibits adenylate cyclase producing cAMP. Normally cAMP would inhibit platelet activation and therefore the inhibition increases platelet activation
116
What are amplification pathways on the platelet?
P2y12 activated by ADP releases dense granules to re stimulate itself.
GPIIb/IIIa causes granule release.
Collagen binding to GPVI causes release of thromboxane A2.
Thrombin activates dense granule release.
thrombin produced on membrane
117
Describe the changes to lipid bilayer in platelets that faciltate production of thrombin
usually has amiophospholibids that are kept on inner layer of plasma membrane by translocase. when activated Ca released which scramblase is activated and translocase inhibited which means amino phospholibids allows prothrombinase can bind to the membrane and convert prothrombin to thrombin factor 2 and 2a
118
Describe the fibrinolytic system
the endothelium releases tPA tissue plasminogen activator. converts plasminogin into plasmin which converts fibrin into degreded productsthere are inhibitors are PAI-1 and antiplasmin
119
What is the significance of platelete alpha granules?
release coagulation factors and inflammatory mediators which help the wound healing with WBCsallow monocytes to bind.
120
What lies on the right heart border?
Superior vena cava, right atrium
121
Where does the right heart border lie?
It is to the right of the sternum
122
Where is the inferior border of the heart.
Sits on the diaphragm and below the xiphoid sternum.
123
Where is the let heart border?
left mid clavicular line
124
Where is the apex beat?
left midclavicular line 5th intercostal space.
125
What is the pleural refelction?
it is an area below the xiphoid sternum it is an area on inferior surface of the heart and is a gap in pleural membrane used to drain fluid from the heart without openning the pleural.
126
What lies on the left heart border
aorta left atrial appendage and most is left ventricle.
127
what makes the anterior border of the heart?
right ventricle and left ventricle
128
What is the posterior border of the heart?
the left atrium.
129
What is the importance of the sternal angle?
2nd costal cartilage, defines the superior and inferior mediastinum. T4/5 level
130
What is in the anterior mediastinum?
the thymus
131
What is in the middle mediastinum?
pericardium and heart
132
What is in the posterior mediastinum?
oesophagus the aorta intercostal arteris bronchial arteries the throacic duct azygous veins and hemiazygous vein sympathetic trunks
133
What is the pericardium like?
Fibrous layer parietal and visceral on the surface of the heart.
134
which great vessels are at the front of the heart
aorta and pulmonary artery.
135
What are the two areas of the right atrium?
the smooth parts and the trabeculated part(with ridges) they are separated by the crista terminalis
136
Where is the coronary sinus?
it drains into the right atrium directly runs in the atrioventricular goove
137
What is the aortomitral continuity?
the aortic and mitral valves are connected by a fibrous area.
138
What are the branches of the right coronary artery?
it runs through the atriventricular sinus then at edge gives right marginal artery, continues to the back potentally giving posterior interventricular artery.
139
What are the first branches of the aorta?
the coronary arteries
140
describe the branches of the left coronary artery.
The circumflect comes off to go in atrioventricular groove to back to give posterior interventricular also gives obtuse marginal artery. the LAD runs between the ventricles. it gives the septal arteries that go into the septum and diagonal across the front.
141
Explain dominance in terms of coronary arteries
what artery suplies the posterior descending. 70% right dominant 20% co dominant and 10% left dominant
142
How many electrodes are there on an ECG?
10. left arm right arm left leg right leg. then V1-6 V1 on Rhs of sternum 4th intercostal space. V2 right ternal border 4th intercostal space. V3 between V2V4 V4 5th iCS mid clavicular line V5 anterior axillary V6 mid auxillary
143
What does each small square represent on an ECG?
40ms
144
What does each big square represent?
0.2s
145
Why are there 12 leads but 10 electrodes?
different views between them
146
how many bipolar leads are there?
3
147
how many unipolar leads are there?
3 arm 6 chest
148
Which leads give lateral view?
Lead 1 avL V5 V6
149
which give inferior view?
lead 2 lead3 avF
150
which give septal view?
V1 and V2
151
Which ECG lead gives anterior view?
V3 V4
152
Which lead(s) are P waves negative?
aVR
153
What does a P wave represent?
atrial depolarisation(not systole)
154
How to interpret an ECG?
```
Rate
Rhythm
Axis
P wave
PR interval
QRS
ST segment
T waves
QT interval
```
155
How can you calculate ventricular rate on an ECG
300 divided by big squares between 2 QRS complexes
156
How can you tell if it is sinus rhythm?
Pwave morphology suggest its from SA node eg positive in all but aVR and that its followed by a QRS complex
157
name sone other rhythms?
sinus, supraventricular, ventricular heart block
158
What is a normal cardiac axis?
-30 to 90 degrees
159
How long should the P wave be?
3 small squares.
160
What kind of abnormalities can be present in P waves?
Tall peaks, right atrial enlargment.
bifid p wave left atrial enlargement.
inverted non sinus origin
161
PR interval should be how long?
3 to 5 squares long can show poor conduction.
162
How long should the QRS complex be?
3 small squares or 120msec
163
What does the QRS complex represent?
Verntricular depolarisation (not systole)
164
What are some common QRS comples abnormalities?
Broad complex- Ventricular origin, BBB, hyperkalemia, ventricular pacing.
High voltage QRS-ventricular hypertrophy
165
What does the ST segment show?
Interval between depolarisation and repolarisation.
166
What does T wave show?
Ventricular repolarisation
167
What is a common ST abnormalities?
ST segment depression often due to ischemia or digitoxin toxicity hypokalemia ventricular hypertrophy
168
T wave inversion is caused by what?
ischemis pulmonary embolism, ventricuar hypertrophy, often normal like this in children.
169
What is the QT interval? how long is too long?
Time of depolarisation and repolarisation. 440 for men 460 for women
170
Which organs of the body use the most blood(in order)>
Liver Kidneys, muscle, brain
171
Where does blood flow the fastest in the circulatory system?
in the aorta and vena cava
172
What are the adaptations of the arteries?
Elastic to cushion systole and maintain blood flow to organs during diastole.
173
Which blood vessel is the principal site of resistance tovascular flow?
the arterioles
174
What is TPR?
Total peripheral resistance = total arteriola resistance it can be varied and plays a major role in detrmining arterial pressure and distribution of flow to organs
175
what happens when vascular smooth muscle constricts?
radius decreases and resistance increases and flow decreases.
176
Is vascular smooth muscle ever completely relaxed?
No this is called the myogenic tone
177
What happens to blood in capillaries?
it slows down to allow for blood do drop off nutrients.
178
What is the average pressure of a vein?
10mmHg
179
What mediates vasoconstriction?
the sympathetic nervous system
180
What is the purpose of lymphatics?
To drain excess filtered fluid from capillaries and the tissues
181
Where is the return of the interstitial fluid?
The throacic duct at the left subclavian vein.
182
What aids the flow of lymph?
respiratory pump skeletal muscle pup smooth muscle in lymphatic vessels?
183
What is cardia output?
heart rate x stroke volume
184
Equation for blood pressure?
cardiac output x total peripheral resistance
185
What is pulse pressue?
systolic- diastolic pressure
186
what is the mean arterial pressure?
diastolic +1/3 of the pulse pressure
187
What changes the flow?
the pressue and resistance flow= pressure gradient/resistance Ohm's law
188
Which is poiseullie's equation?
Flow = radius to the power of 4
189
What is the frank starling mechanism?
more stretch in ventricle or of muscle the sronger it contracts causing a higher pressure and larger cardiac output
190
What happens whe venous return is higher?
end disastolic volume is higher stroke volume is therefore higher and then the cardiac output is higher
191
What is an important factor in long term blood pressure?
Blood volume
192
Which systems change blood volume?
Renin-angiotensin-Aldosteroe System and ADH
193
why does the circulation need controlling?
maintain the flow of blood, maintain pressure
194
What is systolic and diastolic blood pressure?
systolic is the highest blood pressure when the ventricles contract. the diastolic is the lowest when the ventricles relax
195
Why do you measure blood pressure using the brachial artery?
convenient to compress and it is at the level of the heart.
196
which Korotkoff sounds are important for measuring BP?
1 and 5
197
What is myogenic autoregulation?
the innate response of a vessel to contract against an expansion.
198
Which organs have good autoregulation which have bad?
renal cerebral coronary are very good.
skeletal and splanchnic are moderate
Cutaneous is poor
199
What is intrinsic control?
registration of blood flow through the body due to the control from the Autonomic Nervous system and the smooth/cardiac muscle
200
What are the local humoral factors for vasoconstriction?
Endothelin-1 and internal blood pressure
201
What are the local humoral factors of vasodilation?
Hypoxia Adenosine Bradykinin NO potassium CO2 Hydrogen ions tissue breakdown and prostacyclin
202
What is the role of the endothelium in control of the circulation?
Produces NO, prostacyclin and endothelin.
203
What are circulating(hormonal) vasoconstrictors?
Adrenaline, Angiiotensin 2, vasopressin(ADH).
204
what are circulating (hormonal) vasodilators?
Epinephrine, Atrial natriuretic peptide
205
Where are the primary baroreceptors of the body?
Carotid sinus and aortic arch
206
Where are the secondary baroreceptors?
in the veins myocardium and pulmonary vessels
207
What are the afferent nerves for baroreceptors?
Glossopharengeal 9th
208
What are the efferent nerves for baroreceptors?
Sympathetic and Vagus 10th
209
How do arterial baroreceptors affect central control?
If pessure increases then they fire more which decreases sympathedic coutflow to the heart and arterioles but increases parasympathetic outflow to the heart
210
Where are the cardiopulmonary baroreceptors found?
in the atria and verticals and pulmonary artery.
| if they are stimulated they act to reduce BP.
211
What are the main neural influences on the medulla?
Baroreceptors, chemoreceptors, hypothalamus, cerebral cortex, skin, canges in O2 and CO2
212
What does stimulation of the hypothalamus do?
reduce blood pressure. it can regulate skin blood flow
213
Where are the central chemo receptors?
in the medulla.
214
What is excitation- contraction coupling?
When the membrane is stimulated it releases calcium which leads to the contraction of the muscle.
215
What type of process does calcium use to move into the muscle cytosol?
passie diffusion
216
How is relaxation of the heart initiated?
When calcium is pumped out of the cells.
217
What does the heart use for energy?
Free fatty acids as this is the most efficient. it can use glucose anaerobically if required.
218
What is the A band?
a reigone of the sarcomere that has thick filaments and is dark
219
What is the I band?
It is light and is only occupied by thin filaments that extend toward the centre of the sarcomere from the z lines it also contains tropomyosin and troponin
220
Where is the Zline?
In the middle of each I band
221
How does the power stroke contraction happen in ECC?
Sliding of actin over mysosin by ATP hydrolysis by ATP ase in the myosin heads
222
Describe the structure of myosin
2 heavy chains that are responsible for the dual heads and 4 light chains the heads are perpendicular at rest and bend towerds the middle.
223
Describe the structure of actin
It is a globular protein with a double stranded macromolecular helix and form F actin
224
Describe the structure of tropomyosin.
it is an elongated molecule made of two helical peptide chains. it is in the grooves of the actin strands and regulates the interaction with the other strands
225
What are the components of troponin?
I T C
226
What do the components of troponin do?
I with tropomyosin inhibit actin and myosin interaction
T binds troponin complex to the tropomyosin
C has a high affinity for calcium. this allows the Tn I to move away from actin allowing interaction.
227
At what angle are all the heads of myosin?
40 degree angle
228
What is the ventricular contraction of the heart cycle?
LV contraction there is isovolumic contraction where the volume doesn't change and pressure increases. then maximal ejection where it actually ejects. at the start of relaxation there is reduced ejection. then isovolumic relaxation and it fills passively
229
What is the atrial booster?
when the atria contract to fill the ventricle .
230
What is the first heart sound made from?
After the atrial booster which closes the mitral valve
231
What is the second heart sound?
After the aortic valve closes after relaxation of the ventricle
232
What is the 3th heart sound
when the ventricle jitters which coincides with early filling passively of ventricle
233
What is the 4th heart sound
Just before mitral valve closes it is pathogenic stenosis.
234
What is diastasis?
when the ventricle rises to same pressure as the atrium just before the ventricle contracts again.
235
Where should you feel a pulse for the timing of heart sounds?
the carotid pulse pressing against transverse process of C6
236
What is isovolumetric contraction.
Ventricular contraction when all valves are closed. This increases ventricular pressure but as the valves are closed the volume remains unchanged.
237
What produces the first heart sound?
Closing of the mitral valve.
238
What causes the mitral valve to close?
When LVp exceeds LAp. Just before ventricular isovolumetric contraction.
239
Describe systole.
Wave of depolarisation arrives, Ca2+ channels open. LVp>LAp and the mitral valve closes.LVp rises, isovolumetric contraction, LVp>aortic p. Aortic valve opens and ejection begins.
240
What produces the second heart sound?
Closing of the aortic valve.
241
Describe diastole.
LVp decreases and there is a phase of reduced ejection. LVp is less than aortic pressure and the aortic valve closes: isovolumetric ventricular relaxation. LVp is less than LAp and mitral valve opens - ventricles fill with blood. Atria contract - atrial booster. LVp > LAp and mitral valve closes.
242
What is the duration of systole?
0.3s.
243
What is the duration of diastole?
0.5s.
244
What is end systolic volume?
The volume of blood remaining in the LV following systole.
245
Define preload.
The volume of blood in the ventricles just before contraction (EDV).
246
Define afterload.
The pressure against which the heart must work to eject blood in systole.
247
Define contractility.
The inherent strength and vigour of the heart's contraction during systole.
248
Define elasticity.
Myocardial ability to recover it's original shape after systolic stress.
249
Define compliance.
How easily a chamber of the heart expands when it is filled with blood (C=ΔV/ΔP).
250
Define diastolic distensibility.
The pressure required to fill the ventricle to the same diastolic volume.
251
Define resistance.
A force that must be overcome to push blood through the circulatory system.
252
What is the basic principle of Starling's law of the heart?
Increased EDV = increased SV.
253
Explain Starling's law.
The greater the EDV, the greater the sarcomeres are stretched and the more forceful the contraction.
254
With relation to Starling's law, what is the effect of an increased venous return?
EDV will increase and so SV increases and so Cardiac output also increases as CO=SVxHR.
255
Give the equation for stroke volume.
SV=EDV-ESV.
256
Give the equation for cardiac output.
CO=SVxHR.
257
Define cardiac output.
The volume of blood each ventricle pumps per unit time.
258
Give the equation for mean arterial pressure.
MAP = DP + 1/3(SP-DP).(SP - systolic pressure, DP - diastolic pressure).
259
Give the equation for pulse pressure.
PP=SP-DP.
260
Give the equation for blood pressure.
BP=COxTPR.
261
What is Poiseuille's equation?
Q=r^4.
262
What is Ohm's law?
F=ΔP/R.
263
What are the principle vessels of resistance?
Arterioles.
264
What do arterioles respond to?
Blood pressure changes. Local, neural and hormonal factors.
265
Name 2 local factors that result in vasoconstriction.
Endothelin, internal BP.
266
Name 5 local factors that result in vasodilation.
Hypoxia, NO, K+ (accumulate from AP), CO2, H+, adenosine.
267
What neural factors result in vasoconstriction?
Sympathetic nerves that release noradrenaline.
268
What neural factors result in vasodilation?
Parasympathetic innervation.
269
Name 3 hormonal factors that result in vasoconstriction.
Angiotenisn 2, ADH, Adrenaline (binds to alpha-adrenergic receptors in smooth muscle).
270
Name 2 hormonal factors that result in vasodilation.
Atrial natriuretic peptide, Adrenaline (binds to beta2 receptors).
271
What is myogenic auto-regulation of blood flow?
An intrinsic mechanism in smooth muscle blood vessels. If BP increases the vessel constricts. This is important in regulating blood flow.
272
Myogenic auto-regulation of blood flow: What is the response to an increase in BP?
Increased BP will result in vasoconstriction and so blood flow decreases.
273
Myogenic auto-regulation of blood flow: What is the response to a decrease in BP?
Decreased BP will result in vasodilation and so blood flow increases.
274
What is hyperaemia?
An increased blood flow to tissues.
275
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.
276
What is the cause of reactive hyperaemia?
When blood flow increases following occlusion to arterial flow.
277
Describe excitation-contraction coupling.
1. Na+ depolarises membrane. 2. A small amount of Ca2+ is released from T tubules. 3. Ca2+ channels in sarcoplasmic reticulum open. 4. Ca2+ flows into cytosol. Cytosolic Ca2+ conc raised. 5. Ca2+ binds to troponin C, this pulls tropomyosin and exposes the myosin binding site on actin. 6. Cross bridge cycling begins.7. After depolarisation, Ca2+ is returned to SR. K+ outflow = repolarisation.
278
What effect does myocardial contraction have on the A-band of a sarcomere?
No effect, it stays the same length.
279
What effect does myocardial contraction have on the I-band and H-zone of a sarcomere?
They get shorter.
280
Describe actin (thin filament).
A globular protein, single polypeptide. It polymerises with other actin monomers to form a double stranded helix. Together they form F actin.
281
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.
282
Describe tropomyosin.
An elongated molecule made of 2 helical peptide chains.
283
What is the function of troponin I?
Troponin I, together with tropomyosin, inhibits actin and myosin binding.
284
What is the function of troponin T?
Troponin T binds to tropomyosin.
285
What is the function of troponin C?
Troponin C has a high affinity for Ca2+. TnC drives away TnI and so allows cross bridge formation.
286
Name 3 effectors in circulation control.
1. Blood vessels - vasoconstrict/dilate and effect TPR.2. The heart - can affect rate or contractility. 3. Kidneys - regulates blood volume and fluid balance.
287
Where are baroreceptors located?
Aortic arch and carotid sinus.
288
What activates baroreceptors?
Baroreceptors contain stretch receptors that respond to pressure.
289
Are atrial baroreceptors involved in short-term or long-term regulation of BP?
Short-term. (Cardiopulmonary = long-term).
290
Where central chemoreceptors located?
In the medulla oblangata.
291
What do central chemoreceptors respond to?
Changes in pH/(H+). Increased PaCO2 increases H+ and so decreases pH. Increased PaCO2 results in vasodilation.
292
What is the ligamentum teres a remnant of?
The umbilical vein.
293
What is the ligamentum venosus a remnant of?
The ductus venosus.
294
Briefly describe foetal circulation.
Maternal circulation - umbilical vein (oxygenated blood) - ductus venosus - IVC - RA - LA/RV - aorta - umbilical artery (deoxygenated blood) - maternal circulation.
295
What layer of the tri-laminar disc forms the cardiovascular system?
The mesoderm.
296
What does the first heart field produce?
The left ventricle.
297
What does the second heart field produce?
The right ventricle, atria and outflow tracts.
298
What are the 3 stages of heart formation?
1. Formation of primitive heart tube.2. Cardiac looping.3. Cardiac septation.
299
Describe what happens in the formation of the primitive heart tube.
Two endocardial tubes form (day 19). The tubes fuse together and the heart beats (day 22).
300
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.
301
Describe what happens in cardiac septation.
Endocardial cushions form. Fuse at mid-line to form atrio-ventricular septum. Muscular ridge in the floor of the primitive ventricle migrates to endocardial cushions forming interventricular septum.
302
What does the sinus venosus form?
The coronary sinus and RA.
303
What does the primitive atrium form?
RA and LA.
304
What does the primitive ventricle form?
Forms most of LV.
305
What does the bulbus cordis form?
Part of the ventricles.
306
What does the truncus arteriosus form?
The aorta and pulmonary trunk.
307
What do the 1st and 2nd aortic arches form?
Minor vessels in the head.
308
What does the 3rd aortic arch form?
The common carotid arteries.
309
What does the left and right 4th aortic arch form?
Left - aorta. Right - Right subclavian artery.
310
What does the 5th aortic arch form?
There is no 5th arch!
311
What does the left and right 6th aortic arch form?
Left - left pulmonary artery and ductus arteriosus. Right - right pulmonary artery.
312
What does the 7th segmental aortic arch form?
Left and right subclavian arteries.
313
What does the dorsal aortae form?
Left dorsal aortae - descending aorta. Right dorsal aortae - part of right subclavian artery.
314
What are chronotropic effects?
Those that change the heart rate. Positive chronotropic = increased heart rate.
315
What are inotropic effects?
Those that alter the force of muscular contractions.
316
What affect does parasympathetic stimulation have on heart rate?
Decreases heart rate (-ve chronotropic). Cardiac output therefore decreases with parasympathetic stimulation. (CO=HRxSV).
317
What affect does sympathetic stimulation have on force of contraction?
Increases force (+ve inotropic).
318
What pump maintains the negative resting potential of a membrane?
Na+/K+ pump.
319
What is the purpose of the Nernst equation?
It is used to determine a membranes potential.
320
Give the Nernst equation.
E = 60log(conc outside/conc inside)
321
What membrane channels are responsible for the plateau period in the cardiac AP?
Voltage gated Ca2+ 'slow' channels.
322
Briefly describe the cardiac action potential in 5 steps.
1. Na+ channels open; influx of Na+ into cell; depolarisation. 2. When the Na+ channels close, a small number of K+ leave the cell resulting in partial repolarisation. 3. Ca2+ channels open and there is Ca2+ inflow. K+ channels are also open and there is K+ outflow. This results in the plateau period. 4. Ca2+ channels close and K+ channels remain open. K+ leaves the cell resulting in repolarisation.5. Maintaining the resting potential (approx -90mV). Na+ inflow, K+ outflow.
323
Where is the SAN located?
In the RA under the crista terminalis.
324
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. There is a brief delay to ensure the 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.
325
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 gap junctions.
326
What is the function of the refractory period?
1. It prevents excessively frequent contractions. 2. It allows time for the atria to fill.
327
What does the P wave on an ECG represent?
Atrial depolarisation. Duration is less than 0.12s.
328
What does the QRS complex on an ECG represent?
Ventricular depolarisation. Duration is 0.08-0.1s.
329
What does the T wave on an ECG represent?
Ventricular repolarisation.
330
What might an elevated ST segment be associated with?
Myocardial infarction.
331
ECG: where would you place lead 1?
Right arm (-ve) to left arm (+ve).
332
ECG: where would you place lead 2?
Right arm (-ve) to left leg (+ve).
333
ECG: where would you place lead 3?
Left arm (-ve) to left leg (+ve).
334
What is Einthoven's triangle?
An imaginary formation of the 3 limb leads in a triangle shape.
335
ECG: where would you place lead aVR?
Left arm and left leg (-ve) to right arm (+ve).
336
ECG: where would you place lead aVF?
Right arm and left arm (-ve) to left leg (+ve).
337
ECG: where would you place lead aVL?
Right arm and left leg (-ve) to left arm (+ve).
338
ECG chest leads: In which intercostal space would you place V1 and V2?
The 4th intercostal space. V1 is right of the sternum and V2 in left.
339
ECG chest leads: In which intercostal space would you place V3-V6.
The 5th intercostal space. V3 is left of the sternum, V4 is in the mid-clavicular line, V5 is left of V4 and V6 is under the left arm.
340
What are the average systolic and diastolic pressures for the pulmonary circulation?
25 and 10 mmHg.
341
What are the average systolic and diastolic pressures for the systemic circulation?
120 and 80 mmHg.
342
Why might someone with liver injury experience prolonged bleeding time?
Because the liver produces clotting factors.
343
What is exposed if you damage the endothelium of a vessel?
Underlying connective tissue and collagen.
344
What is the role of vWF?
vWF binds to collagen and platelets bind to vWF.
345
What happens in platelet activation?
The change shape: smooth to spiculated. This increases their surface area. New platelets adhere to old ones = platelet aggregation. This forms a platelet plug.
346
What do activated platelets synthesise?
Thromboxane A2.
347
What is the function of Thromboxane A2 (TXA2)?
Platelets binding to collagen through GPVI causes the release of TxA2.
This leads to further platelet aggregation by binding to the receptor TPalpha on the platelet
348
What are the platelet receptors for fibrinogen?
glycoprotein IIb/IIIa. Fibrinogen forms 'bridges' between platelets.
349
What does an undamaged endothelium release in order to prevent platelet activation in undamaged areas?
Prostacyclin (inhibits platelet aggregation) and NO (inhibits platelet adhesion).
350
What are platelets made from? and where are they made?
In the bone marrow from megakaryocytes.
351
In haemostasis what is prothrombin converted into?
Thrombin.
352
Give 3 functions of Thrombin.
1. Converts fibrinogen into fibrin.2. Activates factor XIII into XIIIa.3. Has a positive feedback effect resulting in further thrombin production.
353
What is the essential component of a blood clot?
Fibrin.
354
Briefly describe the Fibrinolytic system.
Plasminogen is converted into plasmin. Plasmin cuts the fibrin at various places leading to the formation of fragments.
355
What is the purpose of the fibrinolytic system?
It acts to prevent blood clots from growing and becoming problematic.
356
What is the structure of Hb?
2 alpha and 2 beta chains. 4 haem groups.
357
Describe the composition of blood.
Plasma - 55%.Cellular - 45% - RBC: 44%, WBC: 1%.
358
Does blood flow to the heart occur during diastole or systole?
Diastole.
359
What does the left coronary artery divide into?
The left anterior descending, and the circumflex.
360
Why is the O2 saturation in coronary venous blood very low?
O2 extraction by the heart muscle is very high.
361
What surface of the heart does the right coronary artery supply?
The inferior surface (underside) of the heart.
362
What is released upon cell activation and contains a high concentration of a molecule that acts as an agonist at the platelet P2Y12 receptor?
Platelet dense granules.
363
What valve prevents high pressures developing in the jugular veins during ventricular systole?
Tricuspid valve.
364
What is the normal duration for the PR interval?
0.12-0.2 seconds.
365
What ECG lead yields complexes that are normally inverted compared to the anterior and inferior leads?
Lead aVR.
366
Is there a point in the cardiac cycle when both atrial and ventricular diastole occur together?
Yes: when the ventricles are relaxing and the atria are filling (before atrial contraction).
367
Why does an increase in LVEDV 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 and so LVEDV increases.
368
Which pressure is most likely to increase in left sided heart failure?
LV EDP.
369
Which pressure is most likely to decrease in left sided heart failure?
Mean aortic pressure. (Less blood is being pumped into the aorta).
370
What is stenosis?
Narrowing.
371
Which pressure is most likely to increase in mitral valve stenosis?
Left atrial end-systolic pressure.
372
What does it mean if a heart valve is incompetent?
It is regurgitant.
373
Which pressure is most likely to increase when the aortic valve is incompetent?
Left ventricular end-diastolic pressure.
374
Pulmonary oedema is a sign of what?
Left heart failure.
375
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 afterload.
376
Shortness of breath, severe peripheral oedema and ascites after a heart attack can indicate what?
Biventricular failure.
377
What is ascites?
Accumulation of fluid in the peritoneal cavity, this can cause abdominal swelling.
378
How long is the PR interval on an ECG?
0.12-0.2 seconds.
379
What does the PR interval represent?
The slow conduction between the AVN and the His-Purkinje system.
380
Diastole: what is diastasis?
When LVp = LAp. Net movement of blood is zero. This is the time between ventricular suction and atrial contraction.
381
What branch does the right coronary artery give off as it reaches the inferior border of the heart?
The right marginal branch.
382
What artery does the RCA anastomose with on the diaphragmatic surface of the heart?
The circumflex artery.
383
What does the LAD anastomose with on the diaphragmatic surface of the heart?
The posterior inter-ventricular branch of the RCA.
384
Where is the coronary sinus found?
Between the LA and LV - left atrio-ventricular sulcus.
385
What does the coronary sinus drain into?
The RA.
386
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.
387
What equation explains why small changes in the diameter of a blood vessel have a great effect on the resistance to flow of a fluid through that vessel?
Poiseuille's equation. Q=r^4.
388
What is the role of fibrinogen in platelet aggregation?
It forms cross-links between aggregating platelets.
389
Give 2 reasons why the liver is important in 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.
390
When are the platelet receptors for fibrinogen exposed?
During platelet activation.
391
Which of the ABO blood groups is recessive?
O, A and B are co-dominant.
392
Why is the O blood group a universal donor?
It has no A or B antigens.
393
What are the two ways of determining someones ABO blood group?
1. Test using antibodies. 2. Test for the presence of antibodies against A or B antigens.
394
Describe how testing for the presence of antibodies against A or B antigens will determine someones blood group?
The presence of antibodies in the blood will indicate that this person does not have these antigens on their RBC's. For example, if a persons blood is found to contain antibodies against the B antigen then they can't be of the AB or B blood groups.
395
Describe how testing using antibodies will determine someones blood group?
If the antibodies bind it indicates the presence of a specified antigen. For example, if antibodies against the B antigen bind to the patients RBC then the person must be of either the AB or B blood groups.
396
What are antigens are part of the Rhesus blood group system?
C, D and E.(D is the most important).
397
What problems can arise if a pregnant lady is found to be rhesus D negative?
If exposed to D RBC's the lady will have antibodies against the D antigen. The antibodies can cross the placenta and cause haemolysis of the babies red blood cells. This can result in in-utero death.
398
What can be given to rhesus D negative mothers to prevent sensitisation?
Anti-D.
399
Describe the arterial baroreceptor reflex in response to an increase in blood pressure.
- Increased parasympathetic outflow to the heart means contractility and heart rate are reduced and so cardiac output is reduced: CO=HRxSV.
- Decreased sympathetic outflow to the arterioles results in vasodilation and so TPR is reduced.
- BP=COxTPR and so blood pressure is lowered.
400
Describe the arterial baroreceptor reflex in response to a decrease in blood pressure.
```
#- Increased sympathetic outflow to the heart means contractility and heart rate are increased and so cardiac output is increased: CO=HRxSV.
- Increased sympathetic outflow to the arterioles results in vasoconstriction and so TPR is increased.
```
- BP=COxTPR and so blood pressure is increased.
401
What phase of the cardiac action potential coincides with diastole?
Phase 4.
402
What part of the ECG does the plateau phase of the cardiac action potential coincide with?
ST segment
403
Give 4 factors that affect the gating of ion channels.
Voltage, drugs, hormones, temperature.
404
What is Virchow's triad?
It describes 3 categories thought to contribute to thrombosis.
405
What are the 3 categories of Virchow's triad?
1. Stasis of blood flow. 2. Endothelial injury.3. Increased coagulation ability.
406
Define ischaemia.
A decrease in blood flow to a tissue.
407
Define infarction.
No blood flow to a tissue - tissue death.
408
Explain the formation of fluid exudate in inflammation.
Chemical mediators cause vasodilation of vessels and an increase in permeability.
409
What are the roles of lymphatics in acute inflammation?
Lymphatics drain exudate and carry antigens.
410
What happens in phase 4 of the cardiac action potential?
Pacemaker potential - Na+ inflow and slowing of K+ outflow. Slow depolarisation begins = innate contractility.
411
Where is Ca2+ released from in excitation contraction coupling?
The T tubules and the sarcoplasmic reticulum.
412
What is the resting potential of the SA node?
-55 to -60 mV.
413
How do central chemoreceptors respond to an increase in PaCO2?
Vasoconstriction.
414
Why do central chemoreceptors stimulate vasoconstriction in response to an increase in PaCO2?
They act to counter the affect of CO2 as a vasodilator and so maintain blood flow to tissues.
415
What reaction does adenyl cyclase catalyse?
The conversion of ATP into cAMP.
416
How do muscarinic M2 receptors cause a decrease in cAMP?
They inhibit adenyl cyclase.
417
What 2 channels are closed during the refractory period in a cardiac action potential?
Fast Na+ and Ca2+ channels.
418
What surface of the heart does the RCA supply?
Inferior.
419
What is the normal duration of the PR interval?
120-200ms.
420
What would an absent P wave on an ECG be a sign of?
Atrial fibrillation.
