The Heart As A Pump Flashcards
Why could the circulatory system not be a static system?
All the blood would go to easiest places and head woudln’t get any blood. It allows blood to vary depending on the need of the tissues.
It is, instead, dynamic (made of resistance and capacitance vessels)
What are resistance vessels in the circulatory system?
Arterioles. They restrict blood flow to drive supply to hard to perfuse areas of the body.
What are capacitance vessels?
They are present in the venous system. They enable the system to vary the amount of blood pumped around the body.
How does the proportion of blood getting to each place change when at rest or undergoing moderate exercise?
Describe the pathway of blood group the heart.
Deoxygenated return from body through the vena cava and into the right atrium. (Atriums are storage vessels to supply ventricles which are the main pump)
When pressure is greater in RA than RV, the tricuspid valve opens and atria contract, moving the blood to the RV.
When the ventricles contract and the pressure in RV is greater than PA, blood then goes from RV through pulmonary valve and to pulmonary arteries .
Oxygenated blood from lungs enters LA from the pulmonary veins.
When pressure in LA > LV , blood flows into ventricles though mitral valve.
Then, when the pressue in the LV is higher than in the aorta (during ventricular sytole), the blood moves from the LV into the aorta.
What is the difference between Left and Right sides of heart?
Left side works at much higher pressure than the right side of the heart. But they both pump the same volume of blood.
What is systole?
The contraction and ejection of blood from the ventricles.
What is diastole?
The relaxation and filling of ventricles.
How many L of blood pumped per minute?
4.9 L/ min
What are the features of heart muscle? And heart muscle action potential?
They are descrete cells but are interconnected electrically. - form a functional syncytium as connected via gap junction.
The cells contract in response to action potentials in membrane.
Action potentials cause a rise in intracellular calcium.
Cardiac action potential is relatively long - It lasts for the duration of a single contraction of a heart (280ms)
Action potentials are triggered by spread of excitation from cell to cell.
How is heart muscle arranged?
Hearty Muscles form a figure of eight which reflects how the ventricles contract.
What prevents inversion of the vales during systole?
Cusps of mitral and tricuspid valves attach to papillary muscles via chordate tendineae. This prevents inversion of the valves during systole.
What is the hearts conduction system?
Pacemaker cells in sinoatrial node (specialised cardiac myocytes) generate an action potential.
The activity spreads over atria during atrial systole.
It reaches the atrioventricular node and is delayed for 120ms.
From the AV node, excitation spreads down the septum between the ventricles.
Next, it spreads though the ventricular myocardium from inner (endocardium) to outer (epicardial) surface. Ventricles contract from the apex up forcing blood through outflow of valves.
What are the seven phases of the cardiac cycle?
- Atrial Contraction
- Isovolumetric contraction
- Rapid ejection
- Reduced ejection
- Isovolumetric relaxation
- Rapid filling
- Reduced filling.
What changes when heart beat is faster?
When heart rate increases, diastole gets shorter but, systole stays the same.
What happens during atrial contraction?
What happens in isovolumetric contraction?
PIC
What occurs during rapid ejection?
What happens in reduced ejection?
..
What happens in isovolumetric relaxation?
What happens in rapid filling?
What happens in reduced filling?
What happens in mitral valve stenosis?
