Circulatory Flashcards
Pericardium
Sac that surrounds the heart
Intraventricular Septum
Septum that divides the heat
Foramen ovale
Causes blood in right atrium to be shunted away from the lungs into the left atrium
Ductus arteriosis
Blood ejected by the right ventricle is returned to the systemic circuit via ductus arteriosus
What are the 2 atrioventricular valves
The tricuspid (right) and the bicuspid (left)
What do the chordae tendineae do?
prevent AV valves from being pushed into atria by connecting the valvue to the papillary muscles “pull on heart strings”
The bicuspid valve is also called the …
mitral valve
Blood flows from a region of …
high pressure to a region of low pressure
Contraction increases
pressure
Late distole
both sets of chambers are open and relaxed, ventricles fill passively
Atrial systole
Atrial contraction forces the small amount of reamining (20%) blood into the ventricles to fill them
Isovolumic ventricular contraction
Ventricular constraction pushes AV nodes closed (1st HB sound) but not enough to open semilunar valve, pressure keeps building (toothpaste with cap on)
Ventricular Ejection
as pressure rises the blood is ejected through the semi-lunar valve
Isovolumic ventricular relaxation
as ventricles relax pressure in the ventricles falls and blood flows backwards, semilunar valve snap closed (second HB sound)
systole is
contraction
diastole is
relaxation
End-diastolic (relaxation) volume (EDV)
maximum volume of blood in the ventricles (in atrial systole)
End-systolic (contraction) volume (ESV)
volume of blood in ventricles at the end of contraction (in ventricular ejection)
Stroke volume
volume of blood pumped by 1 ventricle in 1 heart beat
How to calculate SV?
EDV-ESV
Which side has a higher pressure ?
the left side because it need to pump to whole body and even go against gravity to get the brain
Cardiac output
Volume of blood pumped by the blood in 1 minute
How do you calculate Cardiac output?
SV = CO/HB Sooooo CO = SV*HB
Where does electrical activity originate
in the SA node
What is in the SA node
pacemaker cells
What do pacemaker cells do?
initiate CONDUCTION of the HB and are responsitble for the rhythm generated
What does the AV node and what is it’s function?
electrically connects the atria to the ventricles and slows the impulse
What do the branched bundles do?
conduct impulses though the interventricular septum
What do the purkinjee fibres do?
Depolarize the contractile cells of both ventricles, depolarization spreads upwards from the apex
What is the analogy for the pacemaker and contractile cells?
pacemaker cells initiate the AP like a officer giving orders to the soliders (contractile cells) telling them to move
How does the impulse spread accross the atria
through internodal pathways and gap junctions between contractile cells
What does the AV node allow for?
Causes a delay in ventricular contraction to ensure the atria have ejected all their blood
Contraction ends when the
ventricles repolarize and relax
What is the electrocardiogram record?
summed electrical activity of all the cells in the heart
P wave
atrial depolarization
PQ segment
Conduction through the AV nodes and AV bundle while atrial contracts
Q wave
ventricular contraction at the end of the Q wave
R wave
ventricle depolarizes
S wave
atrial redepolarizes but is masked by ventricle depolarization
ST segment
ventricles contract
T wave
ventricular repolarization and ventricular relaxation
Sinus bradycardia
slowed HB
First degree AV block
distance between P & QRS wave is longer, more delay
3rd degree AV block
P wave completely dissociated from QRS complex
Left ventricular hypertrophy
is incresd QRS size
Atrial fibrillation
Absense of P waves and irregular ventricular rhythm
Pressure created by ventricular contraction is the
driving force for blood flow
Why?
when the semilunar valvue opens the pressure from the contraction stretches the ateried and and they expand
What happend when isovenricular relaxation occurs
semilunar valvues shut and precent back flow, elastic recoil of arteries send blood forward
What does blood pressure depend on? (2)
volume of blood contained and compliance of the vessel wall
What is systolic pressure?
max pressure exerted in the arteries when blood is ejected in them during systol
What is distolic pressure?
min pressure in arteries when blood is draining into other vessels
What is pulse pressure
SP - DP (120-80)
Why do we calculate mean arterial pressure
because pressure pulsates so we use it to represent driving pressure
MAP is proportional to? (2)
cardiac output (V) * arteriolar resistance (compliance) ****both things that determine blood pressure
What are Korotkoff sounds?
sounds created by pulsatile blood flow through compressed artery
How to use a Sphygmomanometer for measuring BP
cuff inflated until above 120 in pressure
deflate pressure in cuff below 120, the first sound you heart is sytolic, the pressure once the korotkoff sounds stop is diastolic
flow does not depend on absolute pressure, it depends on a
pressure gradient
Flow is proportional to a pressure
gradient
Resistance opposes
blood flow
3 factors that affect resistance
- Length of blood vessel
- Vescosity of blood (how packed are the RBC)
- Radius of blood vessels (1/r^4) SO! a really small change can have a huge effect on resistance
BP is highest in the <3 and falls consistently throughout the rest of the body, T or F????
TRUE BITCH
Distribution of blood to the arteries depends on…(2)
- Number & size of arteries supplying the organ
2. Resistance to arterioles
Total blood flow through all the arterioles is
cardiac output
flow through individual arterioles depends on
their resistance
When blood flow is contricted somewhere, blood flow is the ____, its just going through other ________
same; vessels
What happens when precapillary sphincters are consticted?
blood moves through the metarterioles
Exchange at the capillaries can occur in what 3 ways?
- endothelial cells (paracellular) (at junctions or through pores)
- through the cells (transendothelial) (transcytosis or vesicle fusion)
- Bulk flow
Filtration
movement out of capillaries
Absorption
movement into capillaries
Hydrostatic pressure favours?
filtration
Colloid osmotic pressure favours?
absorption
Bulk flow
mass movement of fluid between the blood interstitial fluid
Baroreceptors
tonically active stetch sensitive mechanoreceptors in the walls of the carotid arteries and aorta
Increase BP does what to baroreceptors
increases them
How does the medullar respond ?
increases CP & PR
What would happen with a decrease in BP?
Sympathetic Neurons would kick in PSN = NO
- Heart rate increase (epinephrine increased released onto SA node)
- Force of contraction increases so more blood ejected
- vasocontriction
What control does the PSN have over BP changes
it decreases HR
WHat would happen if BP increased?
- A decrease in sympathetic output (less epinephrine release): vasodilation, decreased force of contraction, decreased HR,