Lecture 2 - Jan 21 Flashcards
What is the Reynolds number?
A hypothetical number that is unitless.
What indicates turbulent flow in relation to Reynolds number?
A Reynolds number greater than 2000.
What are the implications of turbulent flow?
Wasted energy and risk for clotting.
What factors increase the risk of turbulent flow?
- Elevated velocity
- Wide diameter
- Higher density
- Viscosity
Which blood vessels are most prone to turbulent flow?
Large arteries close to the heart, such as the aorta.
How does blood viscosity differ from density?
Viscosity refers to thickness, while density is mass per volume.
What is the compliance difference between the arterial and venous systems?
Arterial system has low compliance; venous system holds larger volume with little pressure change.
What happens to pressure when sympathetic stimulation is removed?
Pressure in arteries decreases faster than in veins.
What measurement tools can be used to assess blood flow?
- Flow meters
- Electromagnetic probes
- Ultrasonic flow meters
- Lasers
What does the pressure-volume loop represent?
Different pressures and volumes in the heart chambers during the cardiac cycle.
What occurs during Phase 1 of the cardiac cycle?
Filling phase where the ventricle fills primarily passively.
What is preload and what influences it?
Preload is the initial stretching of the cardiac muscle, influenced by venous return, heart rate, arterial elastance, and myocardial contractility.
What is the role of atrial contraction in ventricular filling?
Atrial contraction provides a small additional volume to the ventricle.
What defines the end of diastole?
When the ventricle starts to contract.
What happens during Phase 2 of the cardiac cycle?
Isovolumetric contraction where pressure increases without a change in volume.
What is stroke volume and how is it calculated?
The difference between end-diastolic volume and end-systolic volume.
What causes the aortic valve to close?
When ventricular pressure is lower than aortic pressure.
What occurs during Phase 4 of the cardiac cycle?
Isovolumetric relaxation where ventricular pressure decreases until the mitral valve opens.
What is the significance of the pressure volume curve?
It reflects the contractile state of the heart and the pressures generated.
What does a high contractile state indicate about the pressure volume loop?
It may be positioned differently on the graph, indicating higher internal and external pressures.
What electrical events precede changes in pressures during the cardiac cycle?
The QRS complex precedes the increase in ventricular pressure.
What defines diastole in the context of the cardiac cycle?
Diastole starts when the aortic valve closes.
What is the starting point of diastole?
Diastole starts when the aortic valve closes.
When does systole officially start?
Systole starts officially at the end of phase one.