Lecture 11- Circulation of the Blood Flashcards
function of the cardiovascular system
maintain an adaptable supply for blood to tissues in order to supply nutrients and signalling molecules and remove waste
how is the cardiovascular system able to carry out its function
through generating pressure differentials across tissues to enable capillary exchange
hemodynamics
the physics of blood flow
what is the flow of blood determined by
the pressure difference between A and B
the resistance to flow (R)
Darcy’s Law
flow of a fluid through a porous medium
flow=change in pressure/resistance
the greater the difference in pressure….
the faster the rate of flow
the more resistance….
the smaller the rate of flow
rate of flow is directly proportional to?
pressure difference but indirectly proportional to the resistance
what are the 4 factors that affect the rate of flow
pressure
viscosity
vessel length
vessel radius
vascular resistance
what is flow directly proportional to (in terms of radius)
r^4
how does low viscosity affect resistance and flow
low viscosity means decreased resistance therefore increased flow
how may blood have a high viscosity
high red blood cell or protein content
how does a high viscosity affect resistance and flow
increases resistance therefore decreases flow
what factors affect resistance
vessel length, blood viscosity and vessel radius
in which vessel is the rate of flow the slowest
capillaries
which circuit does the right side of the heart do
pulmonary circuit
which circuit does the left side of the heart control
systemic circut
what generates the pressure gradient
contraction of the heart muscles
what is the pressure of the atrium during systole in the pulmonary circuit
2-6mmHg
what is the pressure of the ventricles during systole in the pulmonary circuit
15-30mmHg
what is the pressure of the ventricle during diastole in the pulmonary circuit
3-8mmHg
what is the pressure of the atrium in the systemic circuit during systole
6-12mmHg
what is the pressure of the ventricle in the systemic circuit during systole
100-140mmHg
what is the pressure of the ventricle in the systemic circuit during diastole
3-12mmHg
circulation of blood
heart->tissues->heart
where is blood pressure measured
brachial artery
what do the numbers of blood pressures represent
first number- max pressure in the artery during the cardiac cycle (systolic)
second number- min pressure in artery during the cardiac cycle (diastolic)
what is low blood pressure also known as
hypotension
what is high blood pressure known as
hypertensive
dicrotic notch
closure of the aortic valve during the elastic recoil in the arteries
mean arterial pressure
average blood pressure in the artery during one cardiac cycle
how to calculate man arterial pressure
DBP (diastolic blood pressure) +1/3 pulse pressure
how to calculate pulse pressure
systolic - diastolic pressure
how long is the hear in diastole and systole for
diastole-2/3
systole-1/3
the cardiac cycle
a series of electrical (cardiac conducting system) and mechanical events determining blood flow through the heart and into the circulation during one heartbeat
what occurs during systole
contraction -> ejection
what occurs during diastole
relaxation -> filling
-repolarisation of the cells
what are electrical events of the heart measured by
ECG
outline of the cardiac conducting system
sinoatrial node (pacemaker cells) -50msec
atrioventricular node (cell-cell conduction across atria/ 100 msec delay through AV node allows atrial contraction)-150msec
Bundle of His (Rapid conduction for coordinated ventricular contraction )
ventricular myocardium-225 msec
ECG
detects electrical activity (ionic movement) across the heart
it is an amalgamation of all the action potentials occurring in the heart
P wave
atrial depolarisation (contraction)
QRS complex
Ventricular depolarization (contraction)
atrial repolarisation also occurs at this stage but is masked by ventricular contraction (doesn’t appear on the trace)
T wave
ventricular repolarisation (relaxation)
why is diastole much longer than systole
maximises the time for the heart to fill with blood
what is the first heart sound (lub)
sound of the AV valves closing
What occurs during the isovolumic contraction phase of ventricular systole?
Ventricles contract with no volume change as all valves are closed, sharply increasing pressure
what is the second heart sound (dub)?
sound of aortic valve/ semilunar valves closing
What occurs during the isovolumic relaxation phase of ventricular diastole?
Ventricles relax without changing volume, as all valves are closed and pressure decreases
late diastole
atria and ventricles relaxed
