Session 2-The Heart As A Pump Flashcards
What do capacitance vessels allow?
Allow the system to vary the amount of blood pumped around the body
What do resistance vessels do?
Restrict blood flow to drive supply to hard to perfume areas of the body
Give an example of resistance vessels
Arterioles
True or false:
The heart is two pumps acting in series
TRUE
True or false:
The systemic circulation has low pressure
FALSE - systemic circulation has high pressure, pulmonary circulation has low pressure
Does the output of the left and right sides of the heart over time have to be equal?
YES
What do atria act as for the ventricles?
“Priming pumps”
What happens in systole?
Contraction and ejection of blood from the ventricles
What happens in diastole?
Relaxation and filling of ventricles
At rest, how much blood does the ventricle pump per beat and what is this called?
~70ml
Stroke volume
What type of cell is a cardiac muscle cell?
Functional syncytium
How are functional syncytiums connected?
By gap junctions so that action potential can pass readily and quickly
In heart muscle cells, what does an action potential cause a rise in?
Intracellular calcium
Complete the sentence:
Cardiac action potential is relatively _____ and lasts for the duration of a single contraction of the heart (~____ms)
Long
280
Which four valves determine the pathway of blood flow through the heart?
1) tricuspid valve
2) pulmonary valve
3) mitral valve
4) aortic valve
Which of the four valves have two leaflets as opposed to three?
Mitral valve (also called the bicuspid valve)
Which are the valves on the right side of the heart?
Tricuspid valve (in) Pulmonary valve (out)
Which are the valves on the left side of the heart?
Mitral (in)
Aortic (out)
What does the opening and closing of a valve depend on?
Blood pressure on each side
Why do valve cusps close?
To prevent backflow
What are the cusps of mitral and tricuspid valves attached to and what does this prevent?
PAPILLARY muscles via CHORDAE TENDINEAE
Prevents inversion of valves on systole.
What type of cells are in the sinoatrial node?
Pacemaker cells (specialised cardiac myocytes)
What do the cells in the SAN (sinoatrial node) do?
Generate an action potential and the activity spreads over the atria, stimulating atrial systole
Why is the activity delayed at the atrioventricular node for ~120ms?
To allow the atria to finish contracting before the ventricles contract
Complete the sentences:
From the AV node, the excitation spreads down the ________ between the ventricles. Next, it spreads through the ventricular myocardium from the inner (___________) to the outer (____________) surface.
Septum
Endocardial
Epicardial
What are the seven phases of the cardiac cycle?
1) atrial contraction
2) isovolumetric contraction
3) rapid ejection
4) reduced ejection
5) isovolumetric relaxation
6) rapid filling
7) reduced filling
On the Wiggers diagram, at which point does the cycle start?
Atrial contraction
What is the difference between a Wiggers diagram for the left and right sides of the heart?
Very similar but right side would be at lower pressures
What is the A wave?
When atrial pressure rises due to atrial systole
Which valves are open during atrial contraction?
Mitral
Tricuspid
What is the term for the volume at the end of phase 1 when ventricular volumes are maximal?
End-diastolic volume (EDV)
True or false:
Atrial contraction accounts for the final ~10-20% of ventricular filling and this value varies with age and exercise
TRUE
What does the P wave on an ECG signify?
Onset of atrial depolarisation
Why is phase 2 called “isovolumetric”?
All valves are closed so there is no change in ventricular volume
When does the mitral valve close?
When intraventricular pressure exceeds atrial pressure
What causes the C wave in the atrial pressure curve?
The closing of the mitral valve
What does QRS complex in ECG signify?
Onset of ventricular depolarisation
What gives rise to the first heart sound (S1)?
Closure of the mitral and tricuspid valves
Which valves are open in phase 3 of the cardiac cycle?
Aortic
Pulmonary
When does ejection begin in phase 3 of the cardiac cycle?
When the intraventricular pressure exceeds the pressure within the aorta, causing the aortic valve to open
What is the X descent in phase 3?
Atrial pressure initially decreases as the atrial vase is pulled downward as the ventricle contracts
Which valves are open in phase 4 of the cardiac cycle?
Aortic
Pulmonary
What is the V wave in phase 4?
Atrial pressure gradually rises due to continued venous return from the lungs
What depicts ventricular repolarisation in ECG?
T wave
Which valves are open in phase 5?
NONE
Why is there brief backflow of blood in phase 5?
Intraventricular pressure falls below aortic pressure and aortic valve shuts
What causes the dicrotic notch in the aortic pressure curve?
Valve closure
What is the equation for stroke volume?
EDV - ESV (end systolic volume)
Which valves are open in phase 6?
Mitral
Tricuspid
What is the Y descent in phase 6?
Fall in atrial pressure that occurs after opening of the mitral valve
What results in the second heart sound (S2)?
Closure of the aortic and pulmonary valves in phase 5
What could a third heart sound be a sign of?
Heart failure
True or false:
A third heart sound is normal in children
TRUE
Which valves are open in phase 7?
Mitral
Tricuspid
Where are abnormal valve functions most common?
Mitral valve
Aortic valve
What is stenosis?
When the valve doesn’t open enough and there is obstruction to the blood flow
What is regurgitation?
When the valve doesn’t close all the way and there is backflow of blood
What is regurgitation also called? (2)
Incompetence
Insufficiency
What are the three causes of aortic valve stenosis?
1) Degenerative (senile calcification/fibrosis)
2) Congenital (bicuspid rather than tricuspid form of valve)
3) Chronic rheumatic fever - inflammation-commissural fusion
In aortic valve stenosis, what does an increased LV pressure result in?
LV hypertrophy
In aortic valve stenosis, what does left sided heart failure lead to? (2)
1) syncope
2) angina
In aortic valve stenosis, RBCs can get damaged. What can this lead to?
Microangiopathic haemolytic anaemia
What are the two causes of aortic valve regurgitation?
1) Aortic root dilation (leaflets pulled apart)
2) Valvular damage (endocarditis rheumatic fever)
True or false: Aortic valve regurgitation decreases systolic pressure and increases diastolic pressure
FALSE - increases systolic and decreases diastolic
What is Quincke’s sign?
When the nail beds blanch and flush in response to aortic valve regurgitation
What normally prevents prolapse in systole?
Chordae tendineae and papillary muscles
What can weaken tissue and lead to prolapse?
Myxomatous degeneration
What causes mitral valve regurgitation? (3)
1) damage to papillary muscle after MI
2) left sided heart failure leading to LV dilation which can stretch valve
3) rheumatic fever can lead to leaflet fibrosis which disrupts seal formation
What is the main cause of mitral valve stenosis?
Rheumatic fever (99.9% cases)
In mitral valve stenosis, increased LA pressure leads to which three conditions? And what do all of these result in?
1) pulmonary oedema
2) dyspnea
3) pulmonary hypertension
RV hypertrophy
In mitral valve stenosis, increased LA pressure leads to LA dilation. Which two conditions can this result in and what can these conditions lead to?
1) atrial fibrillation leads to thrombus formation
2) oesophagus compression leads to dysphagia
