CVS ses 2 Cardiac Cycles And Valves Flashcards
Define the terms Systole and Diastole
Systole - when myocardium is contracting
Diastole - period between contractions when it is relaxed
7 phases of cardiac cycle
1) Atrial Contraction - AV valves are open and then close after contraction.
2) Isovolumetric Contraction - SL valves open.
3) Rapid Ejection
4) Reduced Ejection
5) Isovolumetric Relaxation - SL valves close.
6) Rapid Filling - AV valves open.
7) Reduced Filling - AV valves still open.
Explain the origin of the 1st and 2nd heart sounds
S1 - AV valves close
S2 - SL valves close
Define cardiac output and factors affecting it
Volume of blood pumped per min = SV x HR
SV depends on strength of contraction (EDV and contractility)
How hard it is to eject blood
Contractility and HR determined by sympathetic NS
Stroke volume definition
SV is the diff between end diastolic and systolic vol.
End systolic vol is vol of blood left after ejection.
Determines CO
SV - 2 main factors
Can be mechanic(intrinsic )or chemical(ex).
Intrinsic factors - Starling Law
Ensure that the output of the left and right ventricles match
Can be determined by:
Preload -Amount the ventricles are stretched in diastole –Determined by venous pressure as it gives higher diastolic end vol so more stretch so contracts harder.
Afterload -The load the heart must eject blood against. Determined by aortic pressure which is related to TPR which is mainly determined by arteriole blood pressure. If TPR is low, easier to eject blood so higher SV but lower rise in pressure of ventricles.
Factors affecting afterload and preload
Central venous pressure – The pressure in the large veins draining into the heart
Arterial pressure – pressure in the large arteries
Total peripheral resistance – resistance to blood flow offered by all the systemic vasculature. Highest resistance in arterioles.
Contractility definition and factors
Force of contraction for a given fibre length - inc force of contraction for a given EDP.
Factors:
Sympathetic stimulation and adrenaline
Extrinsic
Adrenaline and noradrenaline inc contractility so inc SV
Can also change HR
Abnormal valve functions - 2 types
Stenosis - does not open enough
Regurgitation - does not close enough - back leakage
Mitral valve regurgitation and stenosis - causes and effects
Mitral regurgitation causes:
Myxomatous degeneration can weaken chordae tendineae and papillary muscles leading to prolapse
Damage to papillary muscles after heart attack
Left sided heart failure leads to LV dilation which can stretch valve
Rheumatic fever can lead to leaflet fibrosis which disrupts seal formation
Effects:
Inc preload = LV hypertrophy
Mitral valve stenosis
Main cause = Rheumatic fever
Fusion of valve leaflets
Effects:
Inc LA pressure - passive inc in backwards pressure of pulmonary veins and pulmonary capillaries so blood flows into lung interstitium so 1. pulnomary oedema and 2. dyspnea. Inc pressure in vessels so 3. hypertension.
4. RV hypertrophy.
Inc LA pressure so dilation so 1. oesophagus compression so 2. dysphagia
OR
1. Atrial fibrillation so 2. thrombus formation
Aortic valve problems causes and effects
Atrial stenosis causes:
Degenerative- senile calcification/fibrosis
Congenital (bicuspid form of valve)
Chronic rheumatic fever –inflammation- fusion
Effects:
Left sided heart failure so syncope(fainting) and angina(reduced blood flow to heart)
Inc LV pressure so hypertrophy
Regurgitation - Blood flows back into LV during diastole:
Causes - Aortic root dilation (leaflets pulled apart)
Vlavular damage (endocarditis rheumatic fever)
Effects
Increases stroke volume
• Systolic pressure increases (of ventricle)
• Diastolic pressure decreases (of aorta as there is backflow of blood)
• Bounding pulse (head bobbing, Quincke’s sign -visualization of capillary pulsations upon light compression applied to the tip of the fingernail bed )
• LV hypertrophy
What is in the Wiggers diagram
Look at notion
What happens when you inc resistance in arterioles
Arterial pressure inc but venous pressure dec
