Cardiopulm Unit 1 Flashcards
How does Blood Circulate through the body?
- The Superior/Inferior Vena Cava bring blood back to the heart, it has picked up CO2 from the metabolizing tissues of the body and has given up the oxygen to those tissues. It is entering the heart for gas exchange to remove the CO2 and pick up O2
- Blood is going to the Right Atrium slowly and it will fill it. Eventually the Tricuspid Valve (One of the 2 Atrial Ventricular Valves) will open up, at this point Diastole as a phase is set to begin
- Blood then falls to the Right Ventricle (When this happens Atrial Systole happens, this is when the Right and Left Atrium contract at the end of Diastole to “kick” extra blood into the ventricles)
- When the blood falls the Valve closes and its ready to contract and eject the blood it received through the Semilunar Valve (aka pulmonic valve)
- The blood then gets ejected through pulmonary circulation (through the pulmonary artery), the blood will then land in the capillaries (this is where gas exchange occurs, this is called alveolar capillary interface, where blood and air interact)
- Blood then returns to the heart via the pulmonary veins and lands in the left atrium
- The other AV valve called the Mitral Valve (aka bicuspid valve) will open and the blood will fall into the left ventricle, then atrial systole happens again. The Mitral valve will then close
- The left ventricle will then contract and blood will be ejected into the Aorta passing through the other semilunar valve called the aortic valve. Blood then travels and then it reaches the capillaries of the body where the opposite pattern of gas exchange happens (O2 is deliveres and CO2 is picked)
- The cycle then repeates
Which ventrical is typically more focused on and why?
The left ventricle, because its the biggest part of the heart, its the hearts “pump”. It pumps blood into the body, It has the most myocardium in the heart
With the semilunar valves of the heart (Aortic and Pulmonic) it has a ring around the valve, what is the name of the ring and what does it do?
Its called the Annulus, it surrounds itself around the valve and it anchors itself to the surrounding myocardium.
What are the Pathologies that relate to the 4 valves of the heart?
- Stenosis
- Valvular Insufficiency
Valve Pathologies
What is Stenosis?
A pathological narrowing or constriction that may cause reduced blood flow and potential clinical complications
What can stenosis result in?
If there is a narrowing in a valve, this will make the heart pump harder so it can squeeze blood through a smaller opening.
- Over time that increased stress/strain on the heart might produce changes in the heart structure
Valve Pathologies
What is Valvular Insufficiency?
Valves that do not close properly, often described as “regurgitant”, “insufficient”, or “leaky”
What can valvular insufficiency result in?
This can result in retrograde (backward) blood flow and chronically high-pressure levels, which may lead to arrhythmias
- Over time this may cause pathological changes to the heart
How can Valvular pathologies be assessed?
They can be assessed via ascultation to produce characteristic sounds (like murmurs, etc.)
What are the 3 layers of the heart?
- Pericardium (outermost layer)
- Myocardium
- Endocardium
Layers of the heart
What is the Pericardium?
Whats its function?
This is the outermost layer of the heart. Made of epithelial cells that form a membrane to cover the entire heart. This has sublayers called: Outer parietal pericardium and inner visceral pericardium. The space between both sublayers is known as the pericardial space/cavity and is usually filled with serous fluid to allow to expand and contract will less friction from surrounding structures
The parietal paricardiums function is to anchor the heart to the surrounding structures to prevent excessive movement
What are some examples of pathologies that correlate with the Pericardium?
- Pericarditis
- Pericardial Effusion/Cardiac Tamponade
Layers of the heart
What is the Myocardium?
The muscular layer of the heart. This is the part of the heart that contracts and pumps blood to the body. It has: automaticity, rhythmicity, and conductivity. It does not undergo miotic activity, meaning if there is a myocardial infarction the cells will not regenerate. There are 2 kinds: Mechanical (aka myocytes) and conductive (aka the syncytium)
What is an example of a pathology that correlates with the Myocardium?
Myocardial Infarction
Layers of the heart
What is the Endocardium?
Lines the inner surface of the heart, its valves, and chordae tendinae
What is an example of a pathology that correlates with the Endocardium?
Endocarditis
Where do the L and R Coronary Artery independently branch off of?
The Aorta
The L Coronary Artery spits up into what two arteries? What do they supply?
- The Circumflex A.: supplies the L atrium and lateral/posterior walls of the Left ventricle
- Left Anterior Descending A. (LAD): this supplies the anterior wall and septum (area between the left and right ventricle) of the Left ventricle
What does the R Coronary Artery Supply?
The R Atrium and Ventricle, inferior an posterior wall fo the L ventricle. Supplies SA and AV nodes in most people
What does the Posterior Descending A. (a branch off of the Right Coronary A.) supply?
Supplies inferior Left ventricle and posterior septum. In some people, it also supplies some of the R ventricle
Why are anastamoses important?
These provide collateral circulation. This may be important in the contex of coronary artery disease or other conditions that impair blood flow to the heart muscle
What does the SA Node do?
The Sinoatrial Node (SA) is where the cardio cycle begins in normal circumstances. It depolarizes and will send electrical signals through different fibers where it would reach the AV node and the SA node will dictate the firing of the AV node
Signals start at the SA node and it will sends waves to the AV node. The AV node will then itself depolarize and then send signals down the Bundle of His which will then split into the L and R Bundle Branch then they branch again in to Purkinje fibers. These Purkinje fibers innervate the myocardium of the L and R Ventricle
What is the firing rate of the SA node?
60-100 bpm
The PNS has a constant influence in the SA node, Vagal Tone
What is the firing rate of the AV node?
40-60 bpm
However it doesnt really pace itself. The SA node paces the AV node because it fires faster
What would happen if the SA node failed?
Since the AV node has its own firing rate, it can sustain cardiac functioning. Its just slower (40-60 bpm)
What supplies the SA node?
Its supplied by R Coronary A. in ~ 70% of people and the Circumflex A. in other ~30%
What supplies the AV node?
Its supplied by the R Coronary A. in 90% of the people and by the Circumflex A. in the other 10%
What does the Autonomic Nervous System influence in the Heart?
It influences the Rate of Impulse Generation and Contraction/Relaxation of the Myocardium to meet metabolic demands.
What 2 structures are the Central components that regulate the autonomic control of the heart?
The cortex and the Medulla
What 2 structures are the Peripheral Components of the autonomic nervous system?
Cardiac Plexus and Splanchnic Nerves
Where does the Sympathetic input arise? What does it innervate?
Arises from cervical and upper 4-5 thoracic ganglia and course through the sympathetic trunk and cardiopulmonary splanchnic nerves.
- Innervates the SA/AV nodes and the atrial and ventricular myocardium to INCREASE HR and Contractility
“Fight or Flight”
- Releases neurotransmitters called catacolamines, mainly epinephrine and norepinephrine
Where does the Parasympathetic input arise? What does it innervate?
Arises from the Medulla and courses through the Right and Left Vagus nerves.
- Innervates SA/AV nodes but other components are sparse. Mainly works to SLOW DOWN HR. It does NOT AFFECT CONTRACTILITY
- Releases neurotransmitters, acetocholyne
With the heart, what does the term “Preload” refer to?
Preload refers to the amount of blood the heart receives during diastole (End systolic volume + venous return).
What does Preload do when the heart receives blood during diastole?
The amount of blood stretches the myocardium, preparing for contraction. The more blood the heart receives, the more it stretches, and the greater the preload.
Analogy: Like filling a ballon with water - the more water you put in, the more the ballon will stretch
With the heart, what does the term “Afterload” refer to?
Afterload refers to the resistance the heart has to overcome to pump blood out
What are 2 factors/conditions that may increase Preload?
- Hypervolemia
- Regurgitation of cardiac valves
Hypervolemia is fluid overload, which means that there is too much fluid or blood in your body, which causes swelling.
What are 2 factors/conditions that may increase Afterload?
- Hypertension
- Vasoconstriction
What is Ejection Fraction (EF)?
This is Stroke Volume / End-Diastolic Volume
What is normal EF?
(Ejection Fraction)
60-70%
What is Cardiac Output?
The amount of blood (in liters) ejected by the heart per minute, depends on HR (beats/min) and SV (mililiters of blood ejected during ventricular systole).
SV = Stroke Volume
An increase in either SV or HR results in an increase Cardiac Output