The Heart As A Pump Flashcards
What type of vessels are found in the arterial blood supply? Why?
Resistant vessels
Restrict blood flow to drive supply to hard to perfused areas of body
What type of vessels are found in the venous blood supply? Why?
Capacitance vessels
Enable system to vary amount of blood pumped around body
What are the valves of the heart?
Tricuspid (RA to RV)
3
Semilunar/pulmonary (RV to P)
2
Mitral (biscuspid) (LA to LV)
3
Semilunar/aortic (LV to A)
3 (1-2%- congenital defect=2 cusps)
What is systole?
Contraction and ejection of blood from ventricles
What is diastole?
Relaxation and filling of ventricles
What is the stroke volume?
Volume of blood pumped out by heart with every beat (~70ml)
What is the approx volume of blood in the body?
5 litres (70 ml x 70bpm=4.9 litres per minute)
List some features of heart muscle (6)
- striated
- discrete cells but interconnected electrically (intercalated discs)-functional syncytium
- formed of cardiomyocytes/myocardiocytes
- single nucleus
- branched structure
- have diads (1 T tubule+terminal cisterna of SR)
How long is the average cardiac action potential?
~280 ms
What structures prevent the valves inverting during systole?
Chordae tendineae attach to the valves and are held in place by the papillary muscles
How long does the AV node delay the action potential in the heart?
~120ms
After the action potential in the heart has spread down the septum between the ventricles, how does it spread through the ventricular myocardium?
From endocardial to epicardial
In to out
List the 7 phases of the cardiac cycle
What stages are systole and which are diastole?
1 atrial contraction 2 isovolumetric contraction 3 rapid ejection 4 reduced ejection 5 isovolumetric relaxation 6 rapid filling 7 reduced filling
(2-4)systole
(5-1) diastole
During exercise what part of the heart cycle reduces to allow the heart to pump faster?
Diastole
Which side of the heart is more susceptible to abnormal valve function
The left valves (mitral and aortic)
What are the two main types of valve abnormalities? Explain them
Stenosis-valve doesn’t open enough- obstruction to blood flow when valve normally open
Regurgitation (incompetence/insufficiency)-valve doesn’t close all the way-back leakage when valve should be closed
Describe Aortic valve regurgitation: causes, impact and sounds
Causes:
- Aortic root dilation (leaflets pulled apart)
- valvular damage (endocarditis rheumatic fever)
Impact:
- blood flow back into LV during diastole
- increase stoke volume
- systolic pressure increases
- diastolic pressure decreases (because we lose blood in the aorta)
- bounding pulse (quincke’s sign)
- LV hypertrophy
Sound:
Early decrescendo diastolic murmur (lub, dub, whoosh)
Describe mitral valve regurgitation: causes, impact and sounds
Causes:
- myxomatous degeneration weakens the tissue leading to prolapse
- damage to papillary muscle after heart attack
- Lsided heart Failure=LV dilation which can stretch valve
- rheumatic fever can lead to leaflet fibrosis which disrupts seal formation
Impact:
Blood leaks back into LA, increases preload as more blood enters LV in subsequent cycles…can cause LV hypertrophy
Sound: Holosystolic murmur (lub, whoosh-no change in intensity, dub)
Describe Aortic valve stenosis: causes, impact and sounds
Cause:
- degenerative (senile calcification/fibrosis)
- congenital (bicuspid form of valve)
- chronic rheumatic fever-inflammation-commissary fusion
Impact:
- less blood through valve
- increase LV pressure- hypertrophy
- Lsided heart failure (reduced blood supply)-syncope (in NS)/angina (in heart)
- microangiopathic haemolytic anaemia (shear stress as blood is forced through and RBCs are damaged)
Sound:
Crescendo-decrescendo murmur (lub-whoosh-dub)
Describe mitral valve stenosis: causes, impact and sounds
Causes:
- rheumatic fever (99.9% of cases)- consequence of severe strep throat
- commissary fusion of valve leaflets
Impact:
- Increased LA pressure
- pulmonary oedema, dyspnea, pulmonary hypertension= RV hypertrophy
- LA dilation= atrial fibrillation and thrombus formation/ oesophagus compression and dysphagia (difficulty swallowing)
