4 - Heart As A Pump Flashcards
What are resistance and capacitance vessles?
What is systole and diastole?
What is the difference in pressure between the left and right side of the heart?
Output of both sides of the heart are equal
How does the cardiac muscle contract?
Pacemaker cells send out action potential. Cells are a functional syncitium with action potential lasting 280 ms
Briefly describe how the electrical impulse gets from the SAN to the apex of the heart?
- Pacemaker cells in SAN send electrical impulse over atria causing atrial systole
- Delay for 120ms
- Excitation spreads through septum to apex
Why can you survive atrial fibrillation but ventricle fibrillation can be fatal?
Atria do not need to contract to empty the blood into the ventricle. This is when SAN fires electrical impulses all over the atria
What are the phases of the cardiac cycle?
- Atrial contraction
- Isovolumetric contraction
- Rapid ejection
- Reduced ejection
- Isovolumetric relaxation
- Rapid Filling
- Reduced filling
How long does a cardiac cycle take?
When the heart beats faster what part of the cardiac cycle shortens?
Diastole gets shorter but systole stays the same
Draw a Wiggers diagram and label the stages of the cardiac cycle onto it
What happens on the Wiggers diagram in atrial contraction?
- Atrial pressure slightly rises so A wave
- Small increase in ventricle volume
- P-wave on ECG is atrial depolarisation
- EDV at end of this phase
What happens on the Wiggers diagram in isovolumetric contraction?
- Both valves are closed
- Rapid rise in ventricle pressure due to ventricle systole
- C-wave on atrial pressure due to closing on mitral valve
- QRS on ECG is ventricle depolarisation
- Closing of mitral and tricuspid valve causes S1 lub
What happens on the Wiggers diagram during rapid ejection?
- Aortic valve opens and rapid decline in ventricular volume
- X-descent on atria pressure due to atrial base being pulled down
What happens on the Wiggers diagram during reduced ejection?
- Ventricular repolarisation causes T wave on ECG
- Arterial pressure has V-wave due to venous return
What happens on the Wiggers diagram during isovolumetric relaxtion?
- Dichrotic notch in aorta pressure due to closing of valve
- ESV. Use EDV - ESV to work of SV
- S2 from closure off valves, dub
Draw a wave for atrial pressure and label it
Draw an ECG and label it
What are two conditions that can happen to valves and which side of the heart are they more likely to occur in?
What are the causes of aortic valve stenosis?
- Chronic rheumatic fever
(inflammation and commisural fusion due to streptococcal bacteria and autoimmune response)
- Congenital (bicuspid)
- Degenerative (fibrosis/calcification age)
What are the symptoms of aortic stenosis?
- Crescendo-decrescendo murmur
- Microangiopathic haemolytic anaemia
- LV hypertrophy
- Syncope
- Angina
What are the causes and symptoms of aortic regurgitation?
Causes:
- Aortic root dilation
- Vlavular damage (endocarditis rheumatic fever)
Symptoms:
- LV hypertrophy
- Bounding pulse (headbobbing and Quinke’s sign)
- Blood flows back into LV so stroke volume increases, systolic pressure increases and diastolic pressure decreases
What is mitral valve regurgitation caused by and what are the symptoms?
Causes:
- Myxomatous degeneration (jelly valves)
- Damage to papillary muscles are heart attacl
- Rheumatic fever leading to fibrosis
- Left sided heart failure leading to LV hypertrophy
Symptoms:
- Holosystic mumur
- Increased preload so LV hypertrophy
What causes mitral valve stenosis and whar are the symptoms?
RHEUMATIC FEVER 99.9% CASES
Why do babies have holes in the heart?
The septum in the atria is open in utero as the lungs are not as well perfused, when the baby takes its first breath the pressure changes in the thorax causes the valves to close and the hole to close, sometimes this doesnt close properly
