Rob - The heart as a pump Flashcards
(36 cards)
What are the 3 things the heart does?
- Delivers oxygen, sugars to respiring tissues and hormones to sites of action.
- Removes CO2 and metabolic products
- Maintenance of environment -> Homeostasis
How much blood and gases can a heart deliver and remove in a minute?
Each side = 5l/min of blood
- Delivers 250ml O2/min
- Removes 200ml CO2/min
How much blood is pumped and beat numbers/day?
Beats: 100,000/day
Pumps: 7,000L/day
How big is the heart?
Slightly bigger than a fist
Adaptations and effects of size etc
Larger SA-Vol ration = more heat loss
More metabolism = higher heart rate
What are the adaptations of the LHS of the heart?
- Higher pressure
- Thicker ventricle walls
- Why? Pumps blood to whole body
Different functions of LHS and RHS of heart
LHS = pumps blood to all round the body
RHS = pumps blood only to the lungs
Diastole vs Systole
Systole:
- Ventricles contract
- ~300ms
Diastole:
- Relaxed heart
- Heart fills with blood
- ~500ms at 70 bpm
How to calculate mean arterial pressure?
MAP = 1/3 systole + 2/3 diastole
How many valves are there?
4:
- Tricuspid
- Mitral
- Pulmonary
- Aortic
What does the tricuspid valve do?
Shut in systole
Open in diastole
What does the mitral value do?
Shut in systole
Open in diastole
What does the pulmonary valve do?
Open in systole
Shut in diastole
What does the aortic valve do?
Open in systole
Shut in diastole
How to calculate cardiac output?
cardiac output = stroke volume x heart rate
What is starling’s law?
Energy of contraction is a function of the length of cardiac muscle fibres
How does starling’s law relate to the heart?
- Output of heart has to be equal on all sides
- Stroke volume depends on filling and muscle stretching
- More blood volume = more stretched myocardium = more force to pump blood out.
Phases of the cardiac cycle
Filling
Isovolumetric contraction
Outflow
Isovolumetric relaxation
What happens in filling?
Filling:
- Ventricles fill with blood until the pressure is equal to vein pressure (diastole)
- Atria contract (last 20% of filling) + increase ventricular pressure to be higher than the atria -> mitral valve closes.
What happens in isovolumetric contraction?
Isovolumetric ventricular contraction:
- Start of systole
- All valves closed => causes increased pressure in the ventricles.
What happens in the outflow phase?
- Ventricular pressure exceeds pressure in aorta.
- Causes aortic valves to open and blood pumped into arteries.
- Ventricles then relax and decrease ventricular pressure to less than in the aorta so aortic valve closes.
What happens in isovolumetric relaxation?
- All valves are closed
- Ventricles relax and reduce pressure causing the AVs to open and starts ventricular filling.
What type of muscle is the heart?
Myogenic muscle -> muscle contractions initiated by heartbeat.
How are electrical impulses passed through the heart?
- Sinoatrial node: pacemaker of heart
- Atrioventricular node: impulses travel through atrial muscle to AVN.
- Purkinje fibres + bundle of His: electrical impulses conducted through fibres to His and branches.
