Cardiovascular Flashcards
What are the two phases that make up the blood? Give their proportions also.
Cellular phase 45%
Fluid phase 55%
What makes up the majority of the cellular component of the blood?
RBCs (44%)
Define heamatorcrit and give its usual value
The proportion of the cellular component of the blood, 0.45.
Define serum
Fluid component of blood with all the clotting factors removed
What happens to the haematocrit during acute anaemic (bleeding) and why?
Stays the same, 0.45. Cellular and fluid components of blood lost in the same proportion
What happens to the haematocrit during chronic anaemia?
Decreases (0.2)
Define haematopoesis
Production of blood cells
Where are a haemopoetic stem cells in an adult?
Bone marrow at axial skeleton
Where are haemopoetic stem cells found in a child?
Bone marrow at all bone
Where are haemopoetic stem cells found in utero?
Yolk sac, liver and spleen
What growth factor causes haemopoetic stem cells to proliferate into RBCs? And where is the factor secreted?
Erythropoetin (EPo)
Kidneys
Where are mature blood cells found?
In circulation
What growth factor causes haemopoetic stem cells to proliferate into WBCs?
Granulocyte-colony stimulating factor (GCSF)
What growth factor caused haemopoetic stem cells to proliferated into platelets?
Thrombopoetin (TPo)
Give the average life span of RBCs
120 days
Give the average life span of WBCs
6 hours
Give the average life span of platelets
7-10 days
Which of the blood cells are anucleate/ have no membrane bound organelles?
RBCs and platelets
Erythrocyte is the proper name for which type of blood cell?
RBC
Describe the shape of RBCs and state why they are this shape?
Biconcave
Increases SA:V for rapid diffusion of O2/CO2
What is a reticulocyte?
A young erythrocyte still containing its ribosomes (1% of circulating erythrocytes)
What are the main sites of RBC breakdown?
Liver and spleen
What is the major breakdown product of haemoglobin (and therefore RBCs)?
Bilirubin
What is the function of RBCs?
Contain haemoglobin to allow the transport of gases O2/CO2
Describe the structure of Hb
4 polypeptide chains (2 alpha and 2 beta)
4 haem groups each with an Fe 2+ (ferrous group)
How does the presence of CO2 affect the binding of O2 to Hb? What is the name of the shift that results on an oxygen dissociation curve and in which direction does it occur?
Increase in CO2 Decrease in pH Conformational change of Hb Decreased affinity for O2 Increased unloading of O2
Bohr shift
To the right
What is the proper name for WBCs?
Leukocytes
What are the two main types of leukocytes
Granulocytes
Agranulocytes
Give the normal range of Hb
12.5-15.5g/dL
Give the 3 types of granulocyte, give in order of most to least abundant
Neutrophil
Eosinophil
Basophil
State the 2 types of agranuolocyte, giving the most abundant type first
Lymphocyte
Monocyte
Describe the features and role of a neutrophil
Multi-lobar (4) lobes
Phagocytic
Release cytokines in inflammatory response
Describe the features and role of eosinophils
2-3 lobes
Pink staining granules
Protect against parasite infection
Describe the structure and function of basophils
Blue staining granules
Secrete histamine and anticlotting factors that increase blood flow and therefore attracts infection fighting cells to accumulate at site of infection
Describe the features and role of lymphocytes
Small, darkly stained nucleus, & very little cytoplasm
Role in specific/adaptive immunity
T - thymus - cyctotoxic
B - bone marrow - antibodies/immunoglobulins
Describe the features and role of monocytes
Kidney shaped nucleus
Phagocytes in blood
Migrate and mature at tissue - macrophages
Define haemostasis
The prevention of blood loss
Give the 3 mechanisms of haemostasis when an injury to a blood vessel occurs
Vasoconstriction
Platelet plug formation
Coagulation/clotting cascade
Define what is meant by a haematoma
Accumulation of blood within tissues (increase interstitial pressure prevents continues blood loss)
Where are the majority of clotting factors synthesised? Which of the clotting factors are synthesised here?
Liver I II V VII VII IX X XI
What is clotting factor I?
Fibrinogen
What is clotting factor II?
Prothrombin
Describe the platelet plug formation
Exposure of collagen
von Willerbrand factor bind to collagen
Platelets bind to vWF by GP1b receptor
Binding causes the release of alpha and dense granules
ADP (from dense granules) binds to P2 (purinergic receptors) which activates the cell
Activation
- change in shape to psuedopodia
- change in metabolism
- change in surface membrane
* activation of GPIIb/IIIa receptor, increased affinity for fibrin
* thromboxane A2 release, derived from arachidonic acid
Thromboxane A2 and ADP stimulate platelet aggregation
Fibrinogen forms bridges between aggregating platelets
PLATELET PLUG
Surrounding non-damaged cells release prostaglandin and NO that inhibit aggregation and stop the platelet plug spreading any further
Define thrombosis
The formation of a clot inside a vessel
What is the proper name for platelets
Thrombocytes
Describe the features and role of platelets
Cytoplasmic fragment of megakaryocytes Anucleate Circulate in the inactive form Alpha and dense granules (also lysosomes and peroxisomes) Role in heamostatis
What have if the no. of platelets are decreased to less than 20% of their normal amount
Spontaneous bleeding
What is the importance of cascade reactions?
Bio amplification
Tight regulation/graduated response
What is the penultimate step in the coagulation cascade? And what is this step catalysed by?
Prothrombin to thrombin
Prothrombinase (Xa) (Also requires Ca2+)
What is the final step in the coagulation cascade? And what is it catalysed by?
Fibrinogen to fibrin
Thrombin (Also requires Ca2+)
What is found in the alpha granules of platelets?
Fibrinogen
vWF
V
What is found in the dense granules of platelets?
ADP
Ca2+
Serotonin
Where does thromboxane 2 come from?
Derived from arachidonic acid which itself comes from the plasma membrane of platelet
Give the functions of thrombin
Converts fibrinogen to fibrin
Positive feedback on itself - activates other clotting factors
Activates platelets
What is the main component of a blood clot
Fibrin (forms insoluble meshwork)
Describe the intrinsic pathway of the clotting cascade
Slow
Everything it requires w/i blood
When is the intrinsic pathway of the clotting cascade activated?
When blood comes in to contact with a negatively charged surface e.g. exposed collagen
At which clotting factor does the intrinsic pathway of the coagulation cascade start?
XII
Describe the extrinsic pathway of the coagulation cascade
Fast
Requires cellular component - tissue factor
When is the extrinsic pathway of the clotting cascade activated
When tissue factor is released from damaged cells
What is the role of tissue factor in the extrinsic pathway of the coagulation cascade?
Tissue factor binds to and therefore activates factor VII
Factor VII is involved in the activation of which other clotting factors (this is the point at which the intrinsic and extrinsic pathways merge)
IX
X
What is vitamin K required for (in terms of haemostasis)?
Synthesis of clotting factorsWh
What happens to the prothrombin (bleeding) time in someone who develops liver disease? And why?
Increased prothrombin time
Due to decrease coagulation as most clotting factors synthesised at the liver
Give the 3 types of plasma proteins
Albumin
Globulins (immunoglobulins)
Fibrinogens
State the roles of albumin
Maintain oncotic/osmotic pressure
Transport and binding of substances
Free radical scavenging
Anticoagulant effects
Where are immunoglobulins produced?
B lymphocytes
What causes the plateau of the membrane potential in a cardiac myocyte during contraction
Slow influx of Ca2+
How long does the absolute refractory period last for in a cardiac myocyte? And why does it exist?
0.2 s
Allows the heart to fill with blood
What does the P wave on an ECG show?
Atrial depolarisation
What does the QRS complex show on an ECG?
Ventricular depolarisation
What does T wave on the ECG show?
Ventricular repolarisation
What does the PR segment (not the same as PR interval) of an ECG show?
Delay at AV node
What does the PR interval of an ECG represent? Give the normal time range of a PR interval
The time it takes for an electrical impulse to spread from the SAN to the AVN. 0.12-0.2s
What does a longer PR interval indicate?
Heart block
At what speed do electrical impulses travel in atrial/ventricular muscle fibres?
0.3-0.5 m/s
At what speed to electrical impulses travel in purkinje fibres?
4m/s
What does the ST segment represent? How long does it last for?
State of ventricular contraction
When might ST segment become elevated?
Myocardial infarction
Why might ST segment become depressed?
Angina
How long does QRS complex normally last?
0.6 - 1.0 s
Give a reason for QRS complex widening
Bundle branch block
What does the QT interval represent? How long does it last for?
Ventricular depolarisation followed by ventricular repolarisation. 0.4 s
Why is the T wave a positive reflexion?
Repolarisation in the opposited direction of lead II (double negative)
In which direction does septal depolarisation occur? And what is it shown by on an ECG
Left to right
Q of QRS
What does the R of the QRS complex represent?
Depolarisation of the mass of the ventricles
What does the S of the QRS complex represent?
Depolarisation of the ventricles at the base of the heart
Describe the features of cardiac muscle
Striated Sarcoplasm T-tubules Single nucleus Branched Intercalated discs w/ gap junctions and desmosomes
What is the purpose of gap junctions between cardiac muscle cells and T-tubules within cardiac muscle cells
To allow the rapid propagation of action potentials throughout the entire heart allowing simultaneous contraction of cells
Where is calcium stored within a cardiac myocyte?
Terminal cisternae of the sarcoplasmic reticulum
What impact does an increase in cytosolic Ca2+ have on the strength of contraction in skeletal muscle?
None, a single action potential releases sufficient Ca2+ to fully saturate troponin sites
What impact does an increase in cytosolic Ca2+ have on the strength of contraction in cardiac muscle?
Increases
Give the 3 subunits of troponin and their roles
Troponin C - binds with Ca2+
Troponin I - with tropomyosin inhibits actin/myosin interaction
Troponin T - binds troponin complex to tropomyosin
Describe the excitation part of excitation-contraction coupling
Pacemaker potential arrives at cardiac myocyte
Action potential at cardiac myocyte w/ slow influx of Ca2+ through L-type channel
Ca2+ binds to ryanoide receptors at sarcoplasmic reticulum, releases Ca2+ into cytoplasm
Describe the contraction phase of excitation-contraction coupling
Ca2+ released into cytoplasm binds to troponin C which induces a conformational change in troponin I
Tropomyosin moves and exposes action-myosin binding sites
(At rest) ATP bound to myosin head is hydrolysed to ADP + Pi. Myosin head is energised
(Ca2+ present) Energised myosin heads form cross bridges with actin
Binding causes the release of ADP + Pi + ENERGY from myosin head, ratchet/angular movement occurs
ATP binds to myosin head and breaks cross bridge
ATP bound to myosin is hydrolysed to ADP + Pi. Myosin head re-energised.
Cycle repeats for as long as Ca2+ remains bound to troponin (C)
Describe the composition of myosin
2 heavy chains
4 light chains
Define a sarcomere
A functional unit of the contractile apparatus
What is used for myocardial metabolism during:
a) aerobic respiration
b) anaerobic respiration
a) FAs
b) Glucose
In a sarcomere what does the A-band show?
Myosin and actin (thickest/dArkest)
In a sarcomere what does the I-band show?
Actin only (thinest/LIghtest)
In a sarcomere what does the H zone represent
Myosin only
Describe the composition of actin
Double helix of F(ilament) actin
F actin made up of polymerised globular actin molecules
State the equation for Mean Atrial Pressure
MAP = Total Peripheral Resistance X CO
Which vessels are main determinant of TPR and therefore MAP?
Arterioles
What law describes resistance in a vessel? State it’s equation
Poiseuille's law R= 8nl/πr^4 R= resistance n=viscosity l=length r=radius
Where are the traberculae carnae located? What are they?
RV & LV
Ridges of muscle
Where are the musculi pectinati found? What are they?
RA
Ridges of muscle
What is the cristae terminalis and where is it found?
Crest of muscle in the RA dividing the smooth and ridged parts of the atria wall
What is the surface marking of the tricuspid valve?
Right 4th IC
What is the surface marking of the aortic valve?
Left 3rd IC
What is the surface marking of the pulmonary artery?
Left 3rd CC
What is the surface marking of the mitral valve
Left 4th CC
Where would you listen for the mitral valve?
Apex
Left 5th IC mid-clavicular line
Where would you listen for the tricuspid valve?
Right 5th IC
Where would you listen for the aortic valve?
Right 2nd IC
Where would you listen for the valve of the pulmonary artery
Left 2nd IC
In the fetus, where is the ductus arteriosus found? What does it become?
Between the PA ->aorta
Ligamentum arteriousus
In the fetus where is the ductus venosus found? What does it become?
Between placenta - IVC
Ligamentum venosus
Where is the foramen ovale found? What does it become?
Between right atrium -> left atrium
Fossa ovalis
Where do the coronary arteries arise from?
Aortic sinus
What branches does the RCA usually give
- nodal
- posterior interventricular
- marginal
What branches does the LCA usually give?
- left anterior descending (interventricular)
- circumflex
In what percentage of the population does the posterior interventricular artery arise from the RCA (only) (RIGHT DOMINANCE)
70%
In what percentage of the population does the posterior interventricular artery arise from the RCA and LCA (circumflex branch) (CODOMINANCE)
20%
In what percentage of the population does the posterior interventricular artery arise from the LCA (circumflex branch) (only)
10%
In what percentage of the population is the SAN supplied by the RCA
60%