Cardiovascular Flashcards
What are the 2 phases of the blood and what percentages are they?
cellular (45%) and fluid component (55%)
How many litres of blood are the approximately in the body?
5
What does haematocrit mean what what is the normal value?
the volume of red blood cells
0.45
What is haemopoiesis?
the process of the production of blood cells and platelets which continues throughout life
Where does haemopoiesis occur in adults?
bone marrow
What is the lifetime of a red blood cell?
120 days
What is the lifetime of platelets?
7-10 days
What is the lifetime of white blood cells?
6 hours
Where are the precursor cells of red blood cells in an adult, child and in utero?
axial skeleton
all bones
yolk sac, then liver and spleen
What are precursor cells in the blood a sign of?
leukaemia
What are the hormonal growth factors that stimulate precursor stem cells to proliferate and differentiate into blood cells?
RBC = erythropoietin WBC = Granulocyte colony stimulating factor Platelets = Tpo
What way will an oxygen dissociation curve shift if pH is decreased?
right
What way will an oxygen dissociation curve shift if temperature is decreased?
left
What are young red blood cells known as?
reticulocyte
What does haemoglobin do?
carries oxygen from the lungs to tissues where it transfers oxygen to myoglobin in muscles
Why is blood type AB a universal recipient?
has neither anti-A or anti-B antibodies in their plasma and has A and B antigens on surface of RBCs
Why is blood type O a universal donor?
has both anti-A and anti-B antibodies and no A or B antigens
What antigens does Rhesus refer to?
C,D,E antigens but D is the most important
What is normal haemoglobin level?
12.5-15.5
What condition is caused by low haemoglobin in the blood?
anaemia
What condition is caused by high haemoglobin in the blood?
polycythaemia
How is red cell size measured and what is a normal range?
Mean cell volume
82-96
What is macrocytic anaemia?
large red blood cells
MCV > 100
How is B12 absorbed?
intrinsic factor produced by the gastric parietal cells in the stomach where B12 binds to and is absorbed in the terminal ileum
What is Pernicious anaemia?
antibodies made against gastric parietal cells so less intrinsic factor is produced
What is haemolysis?
normal or increased cell production but decreased life span
What is the role of neutrophils?
- phagocytose and kill bacteria
- release chemotaxins and cytokines
What is the general role of lymphocytes?
- vital to immunity
- generate antibodies against specific foreign antigens
- immunological memory
Where are B lymphocytes made, stored and what is their role?
made in the bone marrow
stored in secondary lymphoid organs
differentiate into plasma cells and produce immunoglobulins when stimulated by exposure to foreign antigen
Where are T lymphocytes made, matured and what is their role?
made in bone marrow
mature in thymus
helper cells (CD4, help B cells in antibody generation) and cytotoxic cells (CD8)
What is acute myeloblastic leukaemia (AML)?
malignant proliferation of the precursor myeloblasts in the bone marrow
What is acute lymphocytic leukaemia (ALL)?
malignant proliferation of the lymphoblast precursor cells in the bone marrow
What is high grade lymphoma?
lymphocytes in the lymph nodes becoming malignant, usually spreads to the liver, spleen, bone marrow and blood
What does reduced numbers of platelets lead to?
Thrombocytopenia (risk of cerebral bleeding)
What does increased numbers of platelets lead to?
Thrombocytosis (can lead to arterial and venous thrombosis leading to increased risk of heart attack and stroke)
What are 5 proteins found in the blood?
- coagulation proteins
- plasma proteins
- albumin
- carrier proteins
- immunoglobulins
Where are coagulation proteins produced and what is the key enzyme?
produced in the liver, key enzyme is thrombin
Where is albumin produced, what is its role and what does it carry?
produced in the liver
maintains oncotic pressure
carries fatty acids, steroids and thyroid hormones
What is the coagulation cascade?
series of proteolytic enzymes activated by exposure to tissue factor generate thrombin to form fibrin polymer (a clot)
How do platelets adhere to collagen fibres?
via intermediary called Von Willebrand Factor that is already attached to collagen by glycoprotein 1b receptor
What happens when platelets bind to collagen fibre wall?
release contents of secretory vesicles via exocytosis
What is platelet activation?
platelet changes from a smooth discoid shape to a more spiky shape with psuedopodia increasing its surface area
What is platelet aggregation?
increase in glycoprotein receptors on platelets that bind to fibrinogen enabling new platelets to adhere
Why does cardiac muscle have a striated appearance?
repeating sarcomeres
How are the cardiac muscle cells joined together?
at intercalated discs
What are present in intercalated discs?
desmosomes that hold the cells together and attach to the myofibrils, and gap junctions
What is the structure of myosin?
2 large polypeptide heavy chains and 4 smaller light chains
2 globular heads and long tail formed by 2 intertwined heavy chains
What does the globular head of myosin contain?
2 binding sites, one for attaching to the thin filament and one for ATP
What is the structure of actin?
thin filament also containing troponin and tropomyosin
single polypeptide with other actin monomers to make 2 intertwined helical chains
each actin molecule has a binding site for myosin
What is the structure of tropomyosin?
elongated molecule that occupies the grooves between 2 actin strands, overlies myosin binding sites on actin
What is the purpose of troponin?
changes shape when Ca2+ binds to it, pushing the tropomyosin exposing myosin binding sites
What is the A band region of the sarcomere?
all of myosin with some overlapping actin
What is the I band region of the sarcomere?
only occupied by actin
What are Z lines on the sarcomere?
defines the end of a sarcomere
What is the H zone on a sarcomere?
only contains myosin
What is the M line on a sarcomere?
centre of the H zone
What is titin?
elastic protein filaments from Z line to the M line that maintain alignment of the thick filaments in the middle of each sarcomere
What is the sarcoplasmic reticulum and what is its role?
membrane network that surrounds the contractile proteins
releases Ca2+ when Ca2+ binds to it ryanodine receptor
When an action potential is generated, there is an influx of Ca2+ via the T tubules, what does this then cause to happen?
small increase in cytosolic Ca2+ concentration, the ions bind to ryanodine receptors on sarcoplasmic reticulum, causing release of many Ca2+ into cytoplasm, initiating cardiac muscle contraction
What is the power stroke?
myosin head drops ADP to pull actin filament over the myosin, decreasing the z lines
Does contraction last longer in skeletal or cardiac muscle and why?
longer in cardiac muscle due to slower calcium channels
What is the refractory period?
time after an action potential where a second impulse cannot cause a second contraction of muscle
What supplies blood to myocardial cells?
coronary arteries
Where do the coronary arteries exit from?
behind the aortic valve cusps in first part of aorta
Where do the coronary arteries drain into?
single vein called the coronary sinus which empties into the right atrium
What 3 ion channels contribute to pacemaker potential?
K+ channels, F-type channels and Ca2+ channels
What cells does the atrioventricular node consist of?
modified cardiac cells that have lost contractile capability but conduct action potentials with low resistance
Why is the AV node being elongated an important feature?
enables the atria to empty blood into the ventricles before ventricular excitation
What cells do the purkinje fibres make contact with to spread the action potential through the ventricles?
ventricular myocardial cells
How are parasympathetic fibres transmitted to the heart?
vagus nerve
What 3 things are decreased for parasympathetic stimulation of the heart?
heart rate
force of contraction
cardiac output
How are sympathetic fibres transmitted to the heart?
Postganglionic fibres innervate the entire heart
What is the P wave on an ECG?
atrial depolaristion
What is the PR interval on an ECG?
time taken for atrai to depolarise and electrical activation to get through AV node
What is the QRS complex on an ECG?
ventricular depolarisation
What is the ST segment on an ECG?
interval between depolarisation and repolarisation
What is the T wave on an ECG?
ventricular repolarisation
What is dextrocardia?
heart on the right side of the chest instead of left
What would an ECG show for acute anterolateral myocardial infarction?
ST segments raised in anterior (V3, V4) and lateral (V5, V6) leads
What would an ECG show for acute inferior myocardial infarction?
ST segments raised in inferior (II, III, aVF) leads
Where would you palpate for the left ventricle?
5th left intercostal space and midclavicular line
What is stroke volume?
volume of blood ejected from each ventricle during systole
What is cardiac output?
volume of blood each ventricle pumps as a function of time
What is total peripheral resistance?
the total resistance to flow in systemic blood vessels from beginning of aorta to vena cava
What is preload?
volume of blood in left ventricle which stretches the cardiac myocytes before left ventricular contraction
What is afterload?
the pressure the left ventricle must overcome to eject blood during contraction
What is compliance?
how easily the heart chamber expands when filled with blood volume
What is hyperemia?
increase in blood flow
What happens on day 19 of embryology of the heart?
2 endocardial tubes form that fuse together 2 days later to form a single heart tube
What does the proximal 1/3 of the bulbus cordis give rise to?
muscular right ventricle
What does the conus cordis (lower part of bulbus cordis) give rise to?
smooth outflow portion of the right and left ventricles
What does the truncus cordis (upper part of bulbus cordis) give rise to?
proximal aorta and pulmonary trunk
What does the primitive ventricle give rise to?
the left ventricle
What does the primitive atrium give rise to?
anterior part of right atrium, entire left atrium and the right and left auricles
What does the sinus venosus give rise to?
part of the right atrium, vena cava and coronary sinus
What does the aortic sac give rise to?
aorta and pulmonary artery
What fuses to become the interatrial septum around 3 months after birth?
the septum secundum and valve of the foramen ovale
