Cardiovascular physiology Flashcards
What is the cardiovascular system ?
It is a highly flexible bulk flow system.
What is the cardiovascular system used to transport ?
CO2 O2 Nutrients Metabolites Hormones Heat
Is the cardiovascular system flexible ?
Yes
How is the CVS flexible ?
It allows the pump to vary its output
It allow the vessels to redirect
It allows the vessels to store blood
How many pumps does the heart have ?
2
What are the two pumps of the heart?
One pump to the lungs
One pump to the body
What is important to ensure that both heart pumps do?
Pump the same amount of blood
The two heart pumps are said to be in ….
series
Vascular bed are said to be in …
Parallel
What does it mean for vascular beds to be in parallel ?
They all get oxygenated blood from the same source and blood can be redirected to certain vascular beds
What is an example of a vascular bed which is in series ?
The gut and the liver because molecules from the gut need to be taken to the liver
Which areas of the body receive the largest portion of the cardiac output ?
the areas which use the most oxygen
What is an exception to the more oxygen more cardiac output rule?
Heart takes a greater % of oxygen than it receive and the kidney takes a lower % of oxygen than it receives (Blood passes through for cleaning)
is the flow though all vascular beds normally the same ?
no
Can the flow through vascular beds be varied ?
yes
What can be used to vary the flow through the vascular beds ?
exercise
etc.
Equation: Flow in a tube =
Change in Pressure / change in resistance
Equation: Change in pressure =
mean arterial pressure - central venous pressure
What is the main feature which controls the resistance of a vessel ?
the radius
What could arteries and veins be through off as?
taps which control the blood flow through them
What is regional distribution of blood ?
The control of blood in the arterioles
What is fractional distribution of blood ?
The control of blood in the veins
Describe the aorta
Wide lumen and elastic wall which expand and contract to dampen the different pressure variations
Describe the arteries
Wide lumen and muscular wall which allow easy flow of blood by helping to maintain its pressure
Describe the arterioles
Narrow lumen which creates resistance, thick muscular wall which controls the flow of blood allowing its regional redirection
Describe the capillaries
Narrow lumen and thin wall which allows for effective gas exchange
Describe the veins and venioles
Wide lumen with distensible wall, low resistance and blood reservoir, allows fractional distribution of blood.
What is the interventricular septum ?
The interventricular septum which splits the left and right side of the heart.
What is the myocardium ?
The myocardium is the muscle of the heart which is thicker on the left than the right.
What are the four chambers of the heart?
The chambers; the ventricles and atriums
What are the two major blood vessels of the heart?
Aorta and vena cave pulmonary trunk and pulmonary veins.
What are the valves of the heart ?
Aoritc, pulmonary, mitral and tricuspid valves which separate all the chambers
Which valve separates which compartment ?
Aortic - Aorta and the left ventricle
Pulmonary - Pulmonary trunk and the right ventricle
Tricuspid - right atrium and right ventricle
Mitral - Left atrium and left ventricles
What is the chordae tendinea ?
It stop the valves inverting
What is the papillary muscle ?
Papillary muscle which are attached to the chordae tendinea and contact to preventing it from inverting
Name the important features of the heart?
Interventricular and interatrial septum myocardium chambers major blood vessels valves chordae tendinea papillary muscles
Name to areas which take the most oxygen and cardiac output
Abdominal organs
Skeletal muscle
Name to areas which take the least oxygen and cardiac output
Skin
heart
Name the stages of the cardiac cycle
Late diastole Atrial systole Isovolumic ventricular contraction Ventricular ejection Isovolumic ventricular relaxation
What happens in late diastole ?
There is no contraction occurring and the ventriculus are filling passively
What happens in atrial systole ?
The atrial contraction forces a small amount of blood into the already fairly full ventriculus
What is isovolumic ventricular contraction ?
Ventriculus start to contract. The pressure increases so that it is greater than the pressure in the atria and so the AV valves close but the pressure it not great enough to open the semilunar valves
What is the ventricular ejection phase ?
Ventricular pressure is great enough to open semi-lunar valves and blood is ejected
What is the isovolumic ventricular relaxation phase?
The ventriculus relax and blood flows back to the semi-lunar valves closing the valves
What is a phonocardiogram ?
A way of hearing the heart sounds
How many normal heart sounds are there ?
4
What is heart sound 1 ?
AV valves closing
What is the second heart sound ?
Semi-lunar valves closing
What is the third heart sound ?
No found in all patients
Sound of the rapid filling phase
What is the fourth heart sound?
No found in all patients
Sound of the active filling phase
What are the two broad phases of the cardiac cycle ?
Systole - the ejection phase
Diastole - The filling phase
What happens at the beginning of systole ?
Mitral and tricuspid valve closes
What happens at the start of diastole ?
Mitral and tricuspid valves open
Describe the changes in pressure of the atrium during the cardiac cycle
Slight increase in pressure for atrial contraction,
Close of AV valves
Increase in pressure for Isometric ventricular contraction phase.
Drop in pressure for ejection phase.
Pressure slowly builds through ejection phase until mitral valves are opened and then it falls again
Describe the changes in pressure of the ventricles during the cardiac cycle
Slight increase in pressure for atrial contraction
Large increase in pressure for isometric contraction phase and half of the ejection phase
Decrease in pressure for the rest of the ejection phase and the isometric relaxation phase
pressure low during diastole
Draw the graph showing pressures and EDV etc .
-
What is the name for an abnormal heart sound ?
A murmur
What are the different types of murmur ?
Systolic
Diastolic
Continuous
What can a systolic murmur be causes by ?
Aortic stenosis
Mitral regurgitation
What can a diastolic murmur be causes by ?
Mitral stenosis
Aortic regurgitation
What can a continuous murmur be caused by ?
A septal defect
Describe the structure of cardiac cells
Cardiac muscle is made up of cells.
These cells are joined by electrical connections called gap junctions and physical connections called desmosomes.
The connected cells form intercalated discs which allow the cardiac muscle to act cohesively and transfer a signal between each other.
What is the name cardiac cells work together called ?
A functional syncytium
Excitation-contraction coupling
Where does Ca2+ come from in the cardiac muscle ?
Some from the sarcoplasmic reticulum
Some from outside the cell
How do pacemaker cells work ?
They have an unstable resting membrane potential and therefore can initiate an action potential. This is called autoahythmicity and means that the heart would continue to beat even if it was removed from the body.
Special sodium channels in pacemaker cells called ‘funny channels’ open which allows an influx of sodium ions, this depolarised the cell to a certain point where calcium channels open. The calcium channels depolarise the cell so that it passes the action potential threshold and fires. At some point during the flow of calcium the ‘funny’ sodium channels close. The calcium then close and the potassium channels open. The movement of potassium repolarises the cell. There is no real resting phase in pacemaker cells but there are other pumps which are continually restoring ions to the correct side of the membrane so that depolarisations can continue to occur.
How does the contraction of cardiac muscle cells work ?
Depolarisation in a pace maker cell then causes an wave of action potential through the rest of the non-pacemaker cardiac muscle.
In these cardiac cells fast sodium channels open and allow a fast influx of sodium ions into the cell. This causes slow (L-type) calcium channels also open and add to the depolarisation of the cell. These calcium ions then trigger a much greater release of calcium from the sarcoplasmic reticulum and therefore the contraction of muscle. On the cell membrane the sodium channels close and potassium channels open. The combination of open potassium and calcium results in a small repolarisation and then a plateau phase. Muscle contraction occurs during the plateau phase. The calcium channels then close and repolarisation occurs. Pumps move the ions back to there starting position.
The plateau phase means that cardiac muscle has a longer action potential and a longer refractory period (the period of time where the muscle is not able to contract again) than skeletal muscle. It also means that tetanus is not possible.
How is an electrical signal passed through the heart ?
Pacemaker cells are found in the SA node. Depolarisation here causes depolarisation of the atria. The signal then hits the annulus fibrosis which do not conduct the signal. The signal then sits in the delay box where it conducts very slowly before entering the bundle of his and then the purkinje fibres and depolarising the ventricles very quickly. If however the SA node is not working there are other pacemaker cells found within the AV node and in the bundle of his which would cause the heart to contract (all be it slower).
What is an ECG ?
When the heart contracts the summation of the electrical potentials creates a large extracellular electrical wave. This can be picked up by a peripheral (on the skin) electrocardiogram. Therefore it gives an indication of the electrical activity of the heart.
What cant an ECG tell you ?
The ECG doesn’t indicate how effective the heart is at pumping blood
What is a ECG lead ?
Two point between which is electrical activity is measured
When will a wave be positive on an ECG ?
Depolarisation coming towards the receiver
Repolarisation going away from the receiver
When will a wave be negative on an ECG ?
Repolarisation coming towards the receiver
Depolarisation going away from the receiver
What are the basic features of a ECG reading ?
P wave which is the wave of atrial depolarisation. The QRS complex is the ventricular depolarisation (and hidden in it the atrial repolarisation) and the T wave is the ventricular repolarisation
What is the PR interval ?
the time from atrial depolarisation to ventricular depolarisation
What should the length of a PR interval be ?
0.12s to 0.2s
or
3 small boxes to 5 small boxes
What length should the QRS complex be ?
0.08secs (2 small boxes) but really it should be less than 3 small boxes
What is the QT interval ?
The time spent while the ventricles are depolarising
How longs should the QT interval be ?
about 0.42 secs
or 11 small boxes
The QRS complex is complex because …
Different parts of the ventricles depolarise at different times
What part of the ventriculus depolarise when in the QRS complex ?
Frist the interventricular septum depolarises L to R
The bulk of the ventricle depolarises from the endocardial to the epicardial
The upper part of the interventricular septum depolarises
Why is the T wave a +ve blip if it is a repolarisation ?
If depolarisation creates a positive blip why does repolarisation also create a positive blip and its because it moves in the opposite direction. A negative moving away creates a positive blip (-ve and –ve make + ve).
Which plane are the 3 standard limb leads in ?
coronal
What events are measured by the standard limb leads ?
Fast events - Depolarisations and repolarisations
Slow events -The plateau
Why does SLL II have the biggest recordings ?
Because it is in the same direction as the majority of the depolarisation of the heart
What other leads are in the coronal plane ?
3 augmented leads
What leads are in the transverse plane ?
Precordial chest leads. V1 will be -ve and V6 +ve and they gradually change from -ve to + ve as you move around. This is known as progression
What is a rhythm strip ?
continuous SLL II recording
What is the rhythm strip set at ?
25mm/sec
How is the rhythm strip calibrated ?
Calibrating Pulse should be 0.2s and should lie over 1 box
How can you work out the HR from an ECG ?
The RR can be caused using SLL II by counting the number of boxes between the two R waves and then dividing 300 by that number. You can also count the number of R waves in 30 boxes and multiply it by 10. Bradycardia < 60bpm and tachycardia is > 100 bpm.
Arrythmias can be …. or ….
Problems with conduction or
Problems with rhythm
Name some problems with conduction
- 1st degree block
- 2nd degree block
- 3rd degree block
What is 1st degree block ?
An increase distance between the P and QRS complex
What is 2nd degree block ?
An increasing delay between the P and QRS complex
What is 3rd degree block ?
P waves are not followed by a QRS complex
Name some problems with rhythm
Atrial flutter
Atrial fibrillation
Ventricular fibrillation
What is atrial flutter ?
Depolarisations occurring too quickly. Looks like a saw blade.
What is atrial fibrillation ?
QRS complexes but not much else
What is ventricular fibrillation ?
Uncoordinated depolarisation and contraction. Looks like a total mess.
What are the stages of diastole ?
Rapid filling phase
Passive filling phase
Active filing phase
