Cardio Flashcards
name the layers outside the heart
fibrous pericardium, parietal pericardium
name the layers on the heart
visceral pericardium, myocardium, endocardium
where does pericardial fluid lie?
between the parietal and visceral pericardium
function of the pericardial fluid
prevents friction between the visceral and parietal pericardium when the heart contracts
which cells of the heart contract?
myocardial cells
what cells are in contact with the blood, inner lining of the heart
endocardium
what is the cardiac cycle?
the events that occur when blood is being moved in and out of the ventricles
what is systole
ventricles are contracting
what is diastole
ventricles are relaxing
how long is systole?
0.3s
how long is diastole
0.5s
cardiac cycle length
0.8s
typical resting heart rate, and range of healthy heart rates
72bpm, 60-100bpm
what does the cardiac cycle represent
one heartbeat
what events occur in systole?
ventricular isovolumic contraction and ejection
what is isovolumic contraction?
the ventricles contract but the volume of blood in the ventricles does not change
all valves are closed
during ejection, how much of the blood leaves the ventricles?
2/3rds
what events happen in diastole?
isovolumic relaxation, rapid inflow of blood, diastasis, atrial systole
what causes the rapid of inflow of blood into the ventricles
passive movement of blood from atria to ventricles down a pressure gradient
pressure in the atria exceeds ventricles
what is isovolumic relaxation
ventricles relax, all valves shut
ventricular pressure falls to below aortic pressure
what is rapid inflow?
pressure in the atria exceeds ventricles
AV valves open, blood flows from the atria to the ventricles down a pressure gradient
atria passively fill and blood trickles into ventricles
80% ventricle filling here
what is diastasis
Pressure in the ventricles approaches pressure in the atria
pressure gradient means passive filling rate falls
what is atrial systole
contraction of atria to fully empty into ventricles
what is the first heart sound and what causes it?
lubb, AV valve shuts
what is the second heart sound, and what causes it?
dubb, aortic valve shuts
what does a P wave represent?
atrial depolarisation
what does the QRS complex represent?
ventricular depolarisation and atrial repolarisation
what is the T wave?
ventricular repolarisation
what are the two types of blood vessel regulation?
intrinsic and extrinsic
what is intrinsic autoregulation?
higher volumes of blood mean vessels increase diameter to level out pressure
what is extrinsic autoregulation?
myogenic vasoconstriction/ dilation
what is hyperaemia?
an increase in blood flow to different tissues in the body
what is active hyperaemia
actively increasing perfusion to certain body parts
metabolic response e.g exercise, increase blood flow to calf muscles
what is reactive hyperaemia
occluded tissue
after occlusion removed, an increase of blood flow to that area
where are peripheral chemoreceptors found?
aortic arch
carotid sinus - dilation at the bifurcation of the common carotid artery, and the beginning of the internal carotid artery
what are the peripheral chemoreceptors sensitive to?
an increase in carbon dioxide
a decrease in oxygen
a decrease in pH
what are the responses of the peripheral chemoreceptors?
sympathetic response
an increase in blood pressure
impulses to pressor region of medulla
where are arterial baroreceptors located?
aortic arch
carotid sinus
what do arterial baroreceptors respond to?
increase in blood pressure
mode of action of arterial baroreceptors
higher blood pressure causes more distortion of baroreceptor
more distortion of baroreceptor means higher firing rate
more impulses to the depressor centre of the medulla
blood pressure decreases
parasympathetic response
where are cardiopulmonary baroreceptors located?
atria
ventricles
pulmonary artery
what do cardiopulmonary baroreceptors respond to?
an increase in blood volume
mode of action of cardiopulmonary baroreceptors
an increase in blood volume means an increase in blood pressure
higher blood pressure causes more distortion of baroreceptor
more impulses to depressor centre of medulla
blood pressure decreases
parasympathetic response
what part of the brain is the central control of blood pressure?
medulla
what are the two blood pressure centres of the medulla and what response to they elicit?
pressor - sympathetic
depressor - parasympathetic
equation for cardiac output
CO= SV x HR
equation for blood pressure
BP = CO x TPR
what is total peripheral resistance?
total resistance of blood vessels to blood flow
equation for pulse pressure
systolic - diastolic pressure
equation for MAP (mean arterial pressure)
MAP = diastolic pressure + 1/3 pulse pressure
Pouisseile’s Law for blood flow
flow = (π x r^4)/ 8 x length x viscosity
equation for blood flow
flow = pressure / resistance
equation for blood flow
flow = pressure / resistance
what is Frank Starling’s Law
the stroke volume of the left ventricle will increase as the left ventricular volume increases
the more the heart chambers fill, the stronger the ventricular contraction, and therefore the greater the stroke volume
explain Frank Starling Law
higher EDV (end diastolic volume) = harder contraction
the more ventricles fill, the more myocytes stretched, therefore stroke volume increases and cardiac output increases
what are Starling forces on blood vessels?
physical forces that determine the movement of fluid between capillaries and tissue fluid
what is oncotic pressure?
force keeping blood in the vessel
(albumin)
what is hydrostatic pressure?
force squeezing fluid out
mechanisms of controlling blood pressure in the long term
RAAS
ADH (vasopressin)
fluid intake
what is the effect of heart failure on cardiac output?
decreases
how do we resolve heart failure?
usually by increasing stroke volume rather than increasing heart rate as tachycardia is unhealthy
increase ECF volume
how do we regulate circulation in the short term?
vasodilators and vasoconstrictors
give some local vasodilators
hypoxia
a decrease in pH
an increase in carbon dioxide/ increased acidity
bradykinin
NO
prostacyclin
an increase in K+
give a local vasoconstrictor
endothelin 1
when is endothelin 1 released?
injured endothelium
give some hormonal/ neurotransmitter vasodilators
Ach (acts on muscularinic 2 receptors)
ANP
give some hormonal/ neurotransmitter vasoconstrictors
angiotensin II
ADH
NAd
define stroke volume
volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction
define cardiac output
the volume of blood pumped out of the left ventricle in a minute
define TPR
total peripheral SYSTEMIC resistance (not pulmonary)
where is TPR the highest
arterioles
define preload
amount of myocyte stretch in ventricular filling (a volume)
define afterload
resistance myocytes contract against in ventricular systole (a resistance)
define contractility
force of contraction of the heart muscle
define compliance
how easily the heart fills in diastole
define Frank Starling Law
higher EDV = more ventricular filling = harder ventricular contraction
define diastolic distensibility
pressure to fill ventricles at diastole to EDV
describe parasympathetic action on the cardiovascular system
Ach acts on muscarinic type 2 receptors
negative chronotrophic response (decreased heart rate)
negative ionotrophic response (decreased force of contraction)
fewer Ca2+ enter myocytees
fewer action potentials are triggered
decreases contractility and cardiac output
describe parasympathetic action on the cardiovascular system
noradrenaline acts on beta 1 receptors in the heart
positive chonotrophic response (increased heart rate)
positive ionotrophic response (increased force of contraction)
fewer Ca2+ enter myocyte
fewer action potentials are triggered
decreased contractility and cardiac output
describe sympathetic action on the cardiovascular system
noradrenaline acts on beta 1 receptors in the heart
positive chonotrophic response (increased heart rate)
positive ionotrophic response (increased force of contraction)
more Ca2+ enter myocyte
more action potentials are triggered
increased contractility and cardiac output
example of an elastic artery
aorta
are elastic arteries generally closer or further away from the heart than muscular arteries?
closer
what is the difference between elastic and muscular arteries?
elastic arteries have more elastic tissue in the tunica media and a large lumen
muscular arteries have more muscle tissue in the TM and a smaller lumen
explain the specialisation of elastic arteries
need to withstand great pressures and maintain constant pressure by quick elastic recoil
explain the specialisation of muscular arteries
more muscle for vasodilation and vasoconstriction (regulation)
when does an artery become an arteriole?
3 or less muscle layers
site of TPR
arterioles
what percentage of blood is carried in veins?
70%
what blood vessels are responsible for EDV?
veins
by which mechanisms is blood returned to the heart in veins?
skeletal muscle contraction - exercise
respiratory pump
peristalsis (smooth muscle contraction)
function of capillaries
oxygen and nutrient delivery to tissue
carbon dioxide and waste removal from tissue
how is blood flow from arterioles to capillaries regulated?
precapillary sphincters
describe continuous capillaries
fully intact endothelium
describe fenestrated capillaries
endothelial gaps
basement membrane intact
describe discontinuous capillaries
large gaps in endothelium
incomplete BM
pressure of the pulmonary circulation
25/8
why is the pressure of the pulmonary circulation much lower?
prevent oedema
how do pulmonary vessels react to hypoxia?
vasoconstriction
pressure of the systemic circulation
120/80
how does the systemic circulation react to hypoxia?
vasodilation
lifespan of erythrocytes
120 days
lifespan of WBC
6-10 hours
lifespan of platelets
7-10 days
hormone that stimulates erythrocyte production
erythropoietin
where is erythropoietin synthesised?
kidney
hormone that stimulates WBC production
GM-CSF (granulocyte macrophage colony stimulating factor)
hormone that stimulates platelet production
thrombopoetin
name of a young RBC
reticulocyte
what is the term for blood plasma without clotting factors?
serum
constituents of blood
plasma and cellular components
what is haematocrit?
red blood cells as a proportion of total blood volume
normal value for haematocrit?
0.45
precursor to all blood cells
haematocytoblast
name for the formation of blood cells
haematopoiesis
percentage of blood that is plasma and cellular
55% plasma
45% cellular
what percentage of the cellular component of blood are erythrocytes?
99%
stages of formation of platelets from haematocytoblasts
common myeloid progenitor - megakaryoblast - megakaryocyte, platelet
stages of formation of macrophages from haemocytoblasts
common myeloid progenitor - myeloblast - monocyte - macrophage
precursor for a RBC
proerythroblast
precursor for a monocyte
monoblast
precursor for B and T lymphocytes
lymphoblasts
stages of formation of basophils, eosinophils and neutrophils from a haematocytoblast
haematocytoblast - myeloblast - progranulocyte - basophil/ eosinophil/ neutrophil
what type of cell is a haematocytoblast
pluripotent stem cell
which white blood cells are granulocytes
neutrophils, eosinophils, basophils
which white blood cells are agranulocytes
monocytes, lymphocytes
neutrophil function
acute inflammatory response
appearance of neutrophil on a histological slide
multi lobed nucleus
faint granules
monocyte function
immature cells that become macrophages and APCs
appearance of monocyte on a histological slide
reniform nucleus (kidney bean shape)
first white blood cells visible in a parasitic infection e.g worms
eosinophil
eosinophil functions
antagonist to an allergic response by producing antihistamines
parasitic infections
appearance of an eosinophil on a histological slide
pink cytoplasmic granules (think ‘eosinophilic’)
name of basophils inside tissue
mast cells
basophil function
produce histamines - allergic response
basophil appearance on a histological slide
dark blue granules (think b for blue)
what receptors do basophils bear?
IgE receptors
lymphocyte function
cell mediated and innate adaptive immune response
appearance of lymphocytes on a histological slide
very little cytoplasm
large nucleus
describe platelet formation
megakaryocytic undergoes endomitosis (DNA doubles but cell doesn’t divide)
CSM blebs (ejects platelet functions)
appearance of inactive platelets
smooth and discoid - circular without any ridges
appearance of active platelets
increase in surface area, pseudopoid
which types of granules do platelets release when they’re activated
electron granules
alpha dense granules
function of electron dense granules
provide energy to produce a platelet plug
what do electron dense granules store?
ADP
ATP
Ca2+
serotonin
what is the function of alpha dense granules?
formation of the platelet plug scaffolding
what do alpha dense granules contain?
PDGF (platelet derived growth factor)
VWF (Von Willebrand factor)
fibrinogen
heparin antagonist PF4
name for too many platelets
thrombocytosis
risks of thrombocytosis
increased clot risk
name for too few platelets
thrombocytopenia
risks of thrombocytopenia
increased risk of bleeding
what triggers platelet formation?
endothelial damage
what is the first event after the endothelium is damaged?
vascular constriction/ spasm
which chemical mediators released form healthy endothelium keep vessels open?
NO (nitrous oxide) and prostacyclin
when the vessel is damaged, which chemical mediator is released?
endothelin-1
effect of endothelin-1
causes vasoconstriction
what is the second event after a blood vessel is damaged?
primary platelet plug formation
what is vWF and what does it do?
Von Willebrand factor binds to exposed collagen at the site of injury
what receptor does vWF bind too?
GP1b (glycoprotein 1b)
what is platelet adhesion?
platelets bind to vWF on collagen via GPIIa OR IIIb receptors (glycoprotein 2a or 3b)
what is platelet activation?
change in shape from discoid to pseudopoid
exocytosis of alpha dense and electron dense granules
is platelet activation positive or negative feedback and why?
positive
activates more platelet activation and aggregation
what is the third step after a vessel is damaged?
the coagulation cascade
what is the coagulation cascade?
forming a mesh of fibrin over the primary platelet plug to form a stable secondary platelet plug
what are the two initial pathways of the coagulation cascade
intrrinsic and extrinsic pathway
what triggers the intrinsic pathway of the coagulation cascade?
trauma inside the blood vessel
internal damage
what triggers the extrinsic pathway of the coagulation cascade?
extravascular trauma
which pathway is more common?
extrinsic
what is the order of factor activation in the intrinsic pathway?
12, 11, 9, 8 to factor 10 (factor 10 is the start of the common pathway)
remember this as descending order from 12 - 8 missing out 10
what is factor 3 and when is it released?
tissue factor
released from damaged tissue
what is the order of factor activation in the extrinsic pathway?
3, 7, 10 (remember this as 3+7=10)
what is the order of factor activation in the common pathway?
10, 2, 1
factor 5 aids the activation of factor 2 by factor 10
(remember this as 5 x 2 x 1 = 10)
what is inactive factor 2 called?
prothrombin
what is active factor 2 called?
thombrin
what is inactive factor 1 called?
fibrinogen
what is active factor 1 called?
fibrin
how is the secondary platelet plug broken down (fibrinolysis)?
tPa converts plasminogen to plasmin
plasmin converts fibrin to fibrinogen
where are most clotting factors produced?
liver
which clotting factor is not produced in the liver, and where is it produced?
factor 8 - vWF
which are the vitamin K dependent factors?
10, 9, 7, 2 (remember as 1972)
what produces different blood groups?
antigens on the surface of red blood cells
features of ABO antigens
carbohydrate antigens
cannot cross the placenta
produced by the spleen
what are the blood groups?
A+, A-, B+, B-, O+, O-, AB+, AB-
can Rhesus positive individuals donate to Rhesus negative individuals?
can Rhesus negative individuals donate to Rhesus positive individuals?
no
yes
which blood group is the universal acceptor?
AB+
which blood group is the universal donor?
O-
what type of antigens are Rhesus antigens?
peptide
can Rhesus antigens cross the placenta?
yes
describe haemolytic disease of the fetus and newborn
mother is Rhesus D negative (dd) and becomes pregnant with Rhesus D positive baby (Dd)
mother makes anti D antibodies but the first child is unaffected
if the mother becomes pregnant with another RhD positive baby, her body produces antibodies more rapidly
causes anaemia in the child
what does myogenic mean?
heart contracts without external nervous control
the heart muscle initiates it own contraction
what is the heart’s pacemaker?
sinoatrial node (SAN)
where is the heart’s pacemaker?
wall of the right atrium
how do impulses travel from the SAN to the left atrium?
Bachmann bundles
where is the atrioventricular node?
Posteroinferior interatrial septum wall, within triangle of atrioventricular node (Koch’s triangle)
what is the function of the delay at the AVN?
allow ventricles to fill before they contract
how long is the delay path the AVN?
120ms
how is the delay physiologically caused?
AVN has fewer gap junctions
- gap junctions allow transmission of ions between cells
- slower rate of impulse
AVN has smaller fibres diameter
what is the Bundle of His? (atrioventricular bundle)
continuation of the specialised tissue of the AV node
transmits the electrical impulse from the AV node to the Purkinje fibres of the ventricles.
describe the path of the bundle of His
descends down the membranous part of the interventricular septum before dividing into the left and right bundle branches
Right bundle branch – conducts the impulse to the Purkinje fibres of the right ventricle
Left bundle branch – conducts the impulse to the Purkinje fibres of the left ventricle.
where is the fastest conduction?
purkinje fibres
what is the difference between nodal cells and myogenic cells
nodal cells carry out conduction of the electrical impulse
myogenic cells are contractile
describe what a syncytium is
heart contracts as one unit
what are the phases of the ventricular action potential in order?
phase 4, phase 0, phase 1, phase 2, phase 3
what is the change in potential during phase 4, and which ion is responsible?
resting potential
K+
what is the change in potential during phase 0, and which ion is responsible?
rapid depolarisation
Na+ inflow
what is the change in potential during phase 1, and which ions are responsible?
partial repolarisation
K+ outflow
inflow of Na stops
what is the change in potential during phase 2, and which ions are responsible?
plateau
Ca2+ slow inflow
what is the change in potential during phase 3, and which ions are responsible?
repolarisation
K+ outflow
inflow of Ca2+ stops
what is the change in potential during phase 4, and which ions are responsible?
K+ outflow
describe the action potential in ventricular cells/ myocardial cells
action potential exits SAN and spreads to other cells by gap junctions called connexions
cardiac myocytes are depolarised by Na+ ions
activation of myocardium results in
- resting potential -90mV
- depolarisation of cell to reach threshold of -70mV which leads to sodium gated fast channels opening
- rapid influx of Na+, membrane is depolarised to +20mV
- K+ channels open and K+ leaves the cell, membrane potential falls to -15mV
- voltage gated Ca2+ channels open and Ca2+ move in and counter the K channels, resulting in a plateau for 200ms
- entry of Ca2+ results in contraction of myocyte
- Ca2+ channels close and repolarisation occurs
why is there no hyper polarisation with excitation contraction coupling in contractile cells?
contractions are auto rhythmic and continuous - needs to be consistent
which phases are the absolute refractory period?
phase 1 and 2
which phases are the relative refractory period?
phase 3
resting membrane potential of nodal cells
-60mV
describe nodal cell depolarisation
- action potential is generated
- at -60mV it leads to the opening of HCN channels (hyperpolarisation gated cyclic nucleoside channels). HCN allows for Na+ ions to move into the cell
- depolarisation from -60mV to -40mV
- voltage gated Ca2+ channels open
- Ca2+ influx results in depolarisation of cell membrane to +20mV
- results in the opening of K+ channels
- K+ moves out of the cell and repolarisation occurs
- hyperpolarisation threshold gets reached and this then reopens HCN and Na+ moves into the cell again
- this is a cycle and does not need to be activated by a different cell
what does a p wave represent?
atrial systole (depolarisation)
why is the p wave smaller?
atria have less muscle
what part of the ECG represents the delay at the AVN?
PQ interval
what does the QRS complex represent?
ventricular systole (depolarisation) and atrial repolarisation
what does the T wave represent?
ventricular repolarisation
what does each big square on an ECG represent?
0.2s/ 200ms
what does each mini square on an ECG represent?
0.04s/ 40ms
what does the ST segment represent?
interval between depolarisation and repolarisation
what is ST elevation?
ST segment isn’t isoelectric
ventricles repolarise (relax) less
decrease in EDV and CO
duration of the P wave?
80-100ms
duration of the PR interval? (start of p to start of QRS)
120-200ms
duration of the QRS complex?
0.06s-0.1s
what heart rate indicates bradycardia?
less that 60bpm
what heart rate indicates tachycardia?
over 100bmp
what does the term ‘lead’ mean in a 12 lead ECG? how many physical electrodes are there actually?
view of the heart
10
which leads are unipolar?
aVR, aVL, aVF
which leads are bipolar?
II, II, III
describe the location of the bipolar leads
form a triangle between both wrists and left leg
describe the location of the unipolar leads
bisect the angles of the triangles
combine two electrodes as reference
how many unipolar V chest leads are there?
6
where is lead V1?
right of sternum 4th, intercostal space
where is lead V2?
left of sternum, 4th intercostal space
where is lead V4?
left midclavicular line, 5th intercostal space
where is lead V3?
between second and 4th
where is lead V5?
5th intercostal space, left anterior axillary line
where is lead V6?
5th intercostal space, left mid axillary line
which leads give the septal heart view?
V1 and V2
which leads give the anterior heart view?
V3, V4
which leads give the lateral heart view?
V5, V6, I, aVL
which leads give the inferior heart view?
II, III, aVF
what does the right coronary artery supply?
SAN, AVN, posterior IV septum
what does the right marginal artery supply?
right ventricle and apex
what does the posterior descending artery (posterior interventricular artery) supply?
right ventricle, left ventricle, posterior third of IV septum
what does the left coronary artery supply?
left atrium, left ventricle, IV septum, AV bundles of His
what does the left anterior descending supply?
anterior third of IV septum, right ventricle, left ventricle
what does the left marginal artery supply?
left ventricle
what does the circumflex supply?
left atrium and left ventricle
what is systolic failure?
heart doesn’t pump hard enough
what is diastolic failiure?
heart doesn’t fill to full volume
normal EDV
110ml
consequences of left sided heart failure
blood backs up in lungs
pulmonary oedema
consequences of right sided heart failure
blood backs up in rest of body
peripheral oedema - commonly in legs
at what stage of embryonic development does the heart form?
3rd week, gastrulation
what does the heart form from?
primitive heart tube
describe the embryological development of the heart from days 20-35
pre-19 - cardiogenic region (horseshoe)
two endocardial tubes are created
day 21 - fusion into a primitive heart tube
where does the cardiogenic area begin?
in the middle of head pole
draw and label the primitive heart tube
superiorly to inferiorly:
truncus arteriosus
bulbs cordis
primitive ventricle
primitive atrium
sinus venosus
describe the process of cardiac looping
bulbs cordis moves inferiorly, anteriorly and right
primitive ventricle shifts left
primitive atrium and sinus venosus moves superiorly and posteriorly
why is there asymmetry in the heart ?
cilia waft molecules from the right to left side
what does the bulbus cordis form?
right ventricle and outflow tracts
what does the truncus arteriosus form?
aortic arches and arteries
what does the primitive ventricle form?
left ventricle
what does the primitive atrium form?
parts of right and left atrium
what does the sinus venosus form?
superior vena cava and right atrium
describe septation
superior and inferior endocardial tissues grow and meet at the central AV canal
superior grows from top down to divide atria (interatrial septum)
inferior grows from bottom up to divide ventricles (interventricular septum)
what is the foramen ovale?
allows blood to flow from the right atrium to left atrium
what happens to the foramen ovale after birth?
closed off to form the fossa ovale
which part of the IV septum is membranous and muscular?
upper part is membranous
lower part is muscular
origin of the aortic arches
branch off truncus arteriosus
what is the ductus arteriosus?
connection between the pulmonary artery and aorta
what is the ligamentum arteriosus?
small ligament attaching the aorta to the pulmonary artery
what do the 1st and 2nd aortic arches become?
minor head vessels
1st - small part of maxillary
2nd - artery to stapedius
what happens to the 3rd aortic arches?
portion between the 3rd and 4th arch disappears
become common carotid arteries and proximal internal carotid arteries
distal internal carotids come from extension of dorsal aortae
what happens to the right dorsal aorta and right 4th aortic arch?
right dorsal aorta loses connections with midline aorta and 6th arch, remaining connected to right 4th arch
acquires branch 7th cervical intersegmental artery, which grows into right upper limb
right subclavian artery is derived from right 4th arch, right dorsal aorta, and right 7th intersegmental artery
what happens to the left dorsal aorta and left 4th aortic arch?
left dorsal aorta continues into trunk
left cervical intersegmental artery, which grows into left subclavian artery
right subclavian artery is derived from right 4th arch, right dorsal aorta and right 7th intersegmental artery
what happens to the 5th aortic arch?
there are no 5th arches
happens to the 6th aortic arches?
right arch may form part of pulmonary trunk
left arch forms ductus arteriosus - communication between pulmonary artery and aorta
where do you auscultate the aortic valve?
2nd intercostal space, right sternal edge (counterintuitive because the aorta leaves the left ventricle!)
where do you auscultate the pulmonary valve?
2nd intercostal space, left sternal edge (counterintuitive because the pulmonary artery leaves the right ventricle)
where do you auscultate the tricuspid valve?
right 5th intercostal space
where do you auscultate the bicuspid valve?
left 5th intercostal space
contents of the anterior mediastinum
thymus
lymph nodes
internal thoracic vessels
thyroid tissue
