Anatomy - Cardiovascular system Flashcards
What does the circulatory system consist of
heart, blood vessels and blood
What is the primary function of the circulatory system
transport
What does the cardiovascular system consist of
heart and blood vessels.
What is cardiology
the study of the heart and its disorders
What is angiology
the study of vessels
What is haematology
the study of blood and its disorders
What are all of the functions of the circulatory system
Transport
Protection
Regulation
Transport
The circulatory system transports carbon dioxide and oxygen to and from the lungs, nutrients from digestive system, metabolic waste to kidneys, hormones from glands to target tissues and stem cells.
Protection
The circulatory system is involved in inflammation in response to infection, it includes white blood cells, which destroy pathogens, antibodies and other proteins that help destroy pathogens and is responsible fro blood clotting by using platelets.
Regulation
The circulatory system controls fluid distribution in the body, it helps to buffer pH of the extracellular fluid and it has a role in controlling body temperature by changing skin blood flow.
What are the two circulations
Pulmonary circulation - carries blood to and from the lungs for gas exchange
Systemic circulation - carries blood to and from all parts of the body.
How is circulation implemented
Both circulations are implemented by two pumps at the left and right sides of the heart which are synchronized to beat in unison.
What does each side of the heart do
The right side of the heart receives blood from the systemic circulation and deliver it to the pulmonary circulation and the left side receives blood from the pulmonary circulation and delivers it to the systemic circulation
What is the heart activity over 80 years
3 billions beats
200 million litres pumped
What is the position of the heart
The heart is found in the thoracic cavity, superior to the diaphragm, medial to the lungs and the bulk of the heart lies towards the left of the body.
What is the size of the heart
The heart is about 9cm at the base,
13 cm from base to apex,
and 6 cm anterior to posterior.
(about the size of your fist)
What is the heart contained in
within serous linings
What are the layers of the heart
pericardium (parietal and visceral)
Myocardium
Endocardium
Pericardium
It is the outermost layer of the heart. It has a lot of connective/fibrous tissue. It forms around the pericardial cavity that contains the pericardial fluid, which minimizes friction during beating.
It attaches to the diaphragm inferiorly and to the mediastinal tissue posteriorly.
There is visceral pericardium and parietal pericardium.
Myocardium
It is the cardiac muscle.
Endocardium
It is the inner lining of the heart.
What can we see from the anterior view of the heart
The main chamber observed is the right ventricle, we can see the superior vena cava going into the right auricle and atrium. The pulmonary trunk and left pulmonary artery are also in view. The ascending aorta and the aortic arch. There is aboundant fat coming out of the interventricular sulcus.
The left auricle and ventricle are showing a bit
What can we see from the posterior view of heart
The main chamber in view is now the left ventricle, but a bit of the right ventricle is showing too. And and the posterior interventricular sulcus. About veins, the coronary sinus in the coronary sulcus, the entry of the inferior vena cava, the left atrium and the pulmonary veins coming into the heart, the right and left pulmonary veins and the other side of the aorta.
Inside the heart: right atrium
It has a thin (about four milimiters) but rough wall because of muscular strands called pectinate muscles and then a smooth area called the fossa ovalis which is part of the atrial septum. On the outflow there is the pulmonary trunk and preventing the backflow there is the pulmonary or semilunar valve.
What is the atrial septum
The division between the right atrium and posterior left atrium. Sometimes, with surgery, it is used to cross devices from one side of the heart to the other.
Inside the heart: right atrioventricular valve
it connects the right atrium to the right ventricle, it is also known as tricuspid valve. It is tethered to the myocardium via tendinous chords to columnar papillary muscles. The role of these chords is to prevent the leaflets from going back into the atrium.
What are valves for
They prevent the backflow of blood.
Inside the heart: left atrium
It is much thicker (about 10 milimiters). It has a very smooth wall and it connects to the left ventricle via the atrioventricular, mitral or bicuspid valve.
Inside the heart: left ventricle
It is very thick compared to the left one because it pumps blood to the systemic circulation through the aorta.
Coronary circulation
It is a process in which the heart gets its very own blood supply and drainage.
How much is the coronary flow
250 ml per minute, about 5% of the total cardiac output. This is because the heart is highly metabolic.
About the coronary arteries
The left and right, blood flows during the relaxation phase of the ventricles and provide to the heart, if they become blocked it leads to angina and myocardial infarction.
About the coronary veins
they drain via the coronary sinus into the right atrium
Blood flow through the heart
1 Deoxygenated blood comes in through the inferior and superior vena cana.
2 Then it goes through the tricuspid valve into the right atrium
3 Out through the right semi lunar valve into the pulmonary trunk
4 Pulmonary circulation
5 Then it comes back into the left atrium through the pulmonary veins
6 Then into the left ventricle through the mitral valve
7 and out through the left semilunar valve to the aorta to supply the systemic circulation.
Cardiac muscle
Cardiac muscle is its own type of muscle, separated from the skeletal and smooth muscle. Cardiac cells are called myocytes.
What are myocytes
They are mono-nuclear, relatively thick cells: 10 to 20 micrometers thick and relatively short, 50 to 100 micrometres long. These cells have branches that connect to other myocytes, allowing them to form the myocardium by connecting via intercalated discs.
What are the interdigitating discs
They are interdigitating folds that connect through junctions
What two types of junctions can you find in myocardium
Mechanical junctions - desmosomes
Electrical junctions - gap junctions
Desmosomes
They prevent myocytes from separating and they are formed by the fascia adherens anchoring the actin of the thin filaments to the plasma membrane, and connects adjacents cells via transmembrane proteins.
Gap junctions
They provide electrical connections that allow the whole atrial and ventricular myocardium to act together.
Why is the heart a functional syncytium
Because the whole myocardium works as a single contractile element.
What are two very important properties of myocytes
Pacemaker cells - The ability to depolarise and depolarize at regular cycles.
Fast conduction - they are able to conduct the electrical signal, the action potential very quickly.
Conduction system: where does electrical activity start?
In the right atrium, at the sinoatrial node, which undergoes cyclic action potentials.
Conduction system: How is the electrical activity happening at the same time in both every cell of each myocardium
All atrial myocytes are connected together via gap junctions, so the whole atrial myocardium depolarizes when the node does. Ventricular myocardium does not depolarise immediately because it is insulated from the atrial myocardium by a layer of connective tissue.
Conduction system: How does electrical activity pass from atrial myocardium to ventricular
Through the atrioventricular node, which delays the signal by 200 milliseconds. It passes through the atrial septum all the way to the high part of the ventricular septum to reach the atrioventricular bundle, or the bundle of his. The bundle branches out into the bundle branches and then to the purkinje fibres.
What is the electrical activity trace of the pacemaker cells
1 gradual depolarization
2 Reaching of threshold
3 Action potential
What causes the action potential of pacemakers
The influx of calcium and sodium, and outflow of potassium
How is the rate or frequency of the beatings regulated
By the permeability of the sodium channels, which cause gradual depolarization.
Pacemakers: What is the normal heart rhythm called and what is it
Sinus rhythm, 70-80 bpm
Pacemakers: what cells qualify to be pacemakers
All cells can be pacemakers by the sinoatrial node has the highest intrinsic frequency so it becomes a dominant pacemaker.
What is an ectopic focus
Any other region of spontaneous firing, ectopic beats.
Pacemakers: What cells take over if the SA gets damaged
the region in the myocardium with the next highest frequency, so the atrioventricular node, which beats at 40-50 bpm.
Pacemakers: What happens if both nodes are damaged
If both nodes are damaged other regions can only fire 20-40 bpm, which is not enough blood supply for the brain and an artificial pacemaker is needed.
What are abnormal rhythms called
arrhythmias, which are lead in patients with cardiovascular disease.
How does the action potential of a myocyte (not a pacemaker) differ from normal cells
The action potential on a myocyte is longer than other cells, e.g. neurons, because it includes a plateau period, makin it 250 miliseconds longer. This is to allow time for blood to physically transfer between the chambers of the heart.
Action potential of myocytes: depolarization
The uptake is caused by the rapid opening of sodium channels, causing the potential to rise.
Action potential of myocytes: start of repolarization
The repolarization is caused by the opening of voltage gated potassium channels, which leave the cell causing the voltage to decrease.
Action potential of myocytes: plateau phase
However, after sodium channels are closed, calcium channels open at the same time as there is some leakage of potassium, this causes a delaying effect in the repolarization.
Action potential of myocytes: end of repolarization
When plateau phase is over, potassium channels fully open and potential drops; the calcium also causes myocardial contraction.
Action potential of myocytes: return to resting potential state
Then calcium exits the cell, potassium comes back in, and the cell goes back to a resting state.
Why do electrocardiograms work
Atrial myocytes are connected by gap junctions, adn ventricular myocytes too, therefore, each region acts together at the same time. This means that the electrical activity sums and can be measured from the surface of the body using electrodes and an amplifier to display the electrical information.
What is a complex
A collection of defections together in an electrocardiogram
What is the P wave caused by
the electrical activation of the atrium
What is the QRS complex caused by
The electrical activation of the ventricles
Why does the QRS complex have a greater amplitude than the P wave
Because the ventricular myocardium’s mass is greater than the atrial’s
What is the T wave
the repolarization of the ventricle.
Why can’t we see the wave of atrial repolarization
because it gets obscured by the QRS complex
Cardiac cycle: left atrium
The pressure at the left ventricle is lower than the left atrium, so the mitral valve will be opened and blood will be flowing into the ventricle. Therefore we also see on the graph for the ventricular blood volume that it rises during this time. The T wave happens and the atrium contracts and there is a sudden increase in the blood inflow to the ventricle
Cardiac cycle: left ventricle
Now the ventricle is full at 160 milliliters and ventricles depolarize. The ventricular pressure starts rising as the ventricle contracts and as soon as the ventricular pressure exceeds the atrial pressure the mitral valve closes. Aortic pressure is higher than the left ventricular pressure, so only when ventricular pressure has raised to reach it will the aortic valve open and blood flows out into the aorta. When this happens we see that the ventricle volume graph decreases.
Cardiac cycle: aorta
The ventricle start to repolarize and myocardium relaxes. Ventricular pressure drops below aortic pressure closing the aortic valve to close. When ventricular pressure is below atrial pressure the atrioventricular valve opens and the ventricle begins to fill again.
Cardiac sounds
The heart sounds are caused by the closing of the valves, the first heart sound is caused by the mitral and tricuspid valves and the seconds sound is the closing of aortic and pulmonary valves.
What is the end-systolic volume (ESV)
the minimum ventricular volume occurs after ventricular ejection.
What volume is ESV
60 mL
What is passive inflow
The inflow during atrial diastole
What is the passive inflow
30 mL
When does most of the inflow happen
during atrial systole
What is the rapid inflow volume
40 mL
What is the stroke volume
70mL
What is the end-systolic volume
volume when the chambers are relaxes and full
What volume is EDV
130mL
What is the cardiac output
volume of blood ejected by per minute
When does tachycardia happen
+100 bpm
When does brachycardia happen
-60 bpm
What is a positive chronotropic agent
anything that causes heartbeat to rise
What is a negative chronotropic agent
anything that causes heartbeat to lower
What can affect heart rate
The autonomic nervous system
Receptors that feedback the CNS and activate the autonomic nervous system
chemicals
What can the autonomic nervous system do to affect heart rate
it affects the slow sodium leakage of the pacemaker cells at the SA node. The sympathetic is excitatory the parasympathetic is inhibitory.
What receptors can affect heart rate
proprioceptors - sense joint activity
baroreceptors - sense pressure
chemoreceptors - sense CO2
They all indicate activity which require an increase in heart rate
What can chemicals do to affect heart rate
hormones from the adrenal medulla like adrenaline and noradrenaline increase the heart rate.
Potassium, hypokalaemia and hyperkalaemia cause a decrease in heart rate.
Calcium, hypercalcaemia causes a decrease in heart rate and viceversa.
What three variables does stroke volume depend on
Preload
Contractility
Afterload
What is preload
The amount of passive tension in ventricular myocardium, it depends on end-diastolic volume and venous return.
More preload means more active tension and therefore more stroke volume
What is Frank-Starling
SV is proportional to EDV
What is contractility
How hard myocardium contracts for a given preload. Factors that increase contractility are positive inotropic agents and those that decrease it are negative inotropic agents.
What is afterload
the blood pressure in the aorta and pulmonary artery; high afterload cecreasesastrikek volume because the heart had to work harder to oppose this column in order to open the semilunar valves.
