Blood pressure Flashcards
Outline the differences between series and parallel blood flow
series: 2 paths in a row, flow is the same in both, the pressure is higher in the first path than the second.
parallel: branching paths, flow is split, the pressure is the same at the start and both have identical resistance.
Define stroke volume
The volume of blood pumped out of the ventricle during one beat of the heart
Define heart rate
measured in beats per min
Define cardiac output and what is the equation
The volume of blood pumped out of a ventricle per min
CO= HR*SV
What is the end-diastolic volume
the volume of blood in a ventricle at the end of diastole, associated with preload.
What is the end-systolic volume
the volume of blood remaining in a ventricle at the end of systole. SV: EDV-ESV
What is the ejection fraction
The percentage of filled ventricular volume pumped out during a heartbeat: SV/EDV
What is the effect of a smaller radius in blood vessels
it increases resistance and leads to a lower flow rate
What is the effect of exercise on blood pressure
peripheral vasodilatation: muscle/skin
vasoconstriction: splanchnic circulation (gut)
BP: systolic (increase), diastolic (decrease), HR increases
Describe how endothelial cells achieve vasodilatation
Releases nitric oxide which causes the smooth muscle to relax and leads to vasodilatation.
Outline autonomic control of BP
Baroreceptors located in the transverse aortic arch detect BP which relay the information to the medulla that acts to increase or decrease HR, PR, pressure, CO.
Outline the Frank-Starling mechanism
The stroke volume of the heart increases in response to an increase in the stretching of blood filling the heart (EDP)
define venous return
the rate of blood flowing back to the heart through the veins
define preload
The initial stretching of the cardiomyocytes during diastole, dependant on venous return
What is volume overload
Results when preload becomes too large
State some factors affecting preload
Atrial contractility, HR, aortic pressure, ventricular compliance, central venous pressure.
What is afterload
The resistance that the chambers of the heart must overcome to eject blood out of the heart. Pressure in LV compared to the aortic valve.
What is the thoracic pump
Pulls the blood (from below) towards the right atrium, during inspiration.
What is the muscle pump
Rhythmic contractions of limb muscles due to normal locomotor activity squeezes blood out of nearby veins towards the heart.
hypertension
due to high BP, often asymptomatic and can lead to CAD and MI
What can chronic hypertension lead to
Kidney failure, HF, cardiac hypertrophy, MI and aneurysm or stroke.
Orthostatic hypertension
low bp on standing, dizziness or syncope, causes include drugs, hypovolaemia and age.
