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