Cardiology Flashcards
How does the cardiovascular system relate to the electrical system?
Heart -> Generator -> producing a voltage which is the driving force of blood (produces blood pressure
Blood vessels -> are the electrical wires which conduct the electricity or blood from and to the heart
Blood -> The electrons which carry the electricity/ nutrients, waste, hormones and clotting proteins
What is the function of the cardiovascular system?
Transport substances
- *Oxygen and nutrients** to cells
- *Wastes** from the cells to the liver and kidneys
Hormones, immune cells, and clotting proteins to specific target cells.
Why is high blood pressure so dangerous and straining on the heart?
- The heart has to work harder to overcome the high pressure at the extremities to compensate so the heart hypertrophies (Enlarged heart) to supply enough blood to the extremities.
- Because the diameter of the left ventricle is bigger it is unable to produce enough pressure (larger diameter, less pressure). RESISTANCE!!!
- Pressure in the aorta needs to reach a high enough pressure to open the valve and if the pressure around the body is higher than what the heart can produce the valve will not open.
Heart cannot keep up with the pressure
Where is the location of the lowest pressure in the cardiovascular system/ body?
Veins
Think pressure gradient
They have the lowest pressure because in order to accept blood they need to have a lower pressure
A substance will move from an area of high pressure to low pressure most readily
What are venules?
Small converging vessels from the tissues will be full of CO2 as this is depleted blood leaving the tissues
They dump blood into the veins
What are veins?
These are relatively large low-pressure vessels that converge and carry blood to the heart
What are the two paths of blood flow through the heart and vasculature?
Series (through the cardiovascular system)
Parallel ( within the systemic or pulmonary circuit
What are the two circuits in series flow?
Pulmonary circuit
Systemic circuit
What is the pulmonary circuit?
Blood supplied by the right side of the heart to the lungs via the pulmonary arteries and from the lungs to the heart via the pulmonary veins
What is the systemic circuit?
The blood leaves the left side of the heart and the blood vessels from the heart go to systemic tissues
Depleted blood is taken from the tissues to the heart
What does series or parallel blood flow take into consideration?
Series blood flow is more of the general route that the blood has to take as it circulates the body. It assumes the blood is only going in one path.
Parallel blood flow takes into consideration the blood flow to the organs as the organs are in parallel so they can receive the same blood flow.
What are the two places in circulation that gas exchange take place?
In the lungs as the blood entering the lungs is oxygenated as gas diffuses from the alveolar sacs into the blood
In the systemic capillaries as the oxygenated blood passes in the capillary beds near to the tissues the gases diffuse to the tissues leaving depleted
How does the heart receive blood?
Coronary circulation
It is supplied by coronary arteries that derive from the base of the aorta and take blood that pools back into the aortic cusps to supply the heart with FRESH oxygenated blood.
Deoxygenated blood will then be returned back to the right atrium via the coronary sinus
Where is the heart located?
Thoracic cavity in the mediastinum
What separates the thoracic cavity from the abdominal cavity?
Diaphragm
What is the pericardium?
This is a serous membrane that surrounds the heart and provides protection from other organs
It is lubricated so the heart can beat without friction.
What is pericarditis?
Inflammation of the pericardium
It can cause fluid to build up around the heart and make the heart need to work harder to overcome the pressure
What are three layers of the heart wall?
Epicardium (outer external membrane)
Myocardium (middle cardiac muscle)
Endothelium (inner layer of simple squamous endothelial cells)
What drives blood flow?
Pressure difference drives all blood flow throughout the body as the blood needs the necessary push to get it where ti needs to go without damaging the organs at the end.
Does each chamber of the heart produce pressure equally?
No
The right ventricle produces less pressure than the left ventricle because its just pumping blood to the lungs whereas the left ventricle is sending blood systemically.
The atria are under less pressure because they are simple pumping blood to the ventricles
How do all valves open?
Passively based on a pressure gradient
If the pressure on the upper side of the valve is higher than that of the side below the blood will not be able to go up through the valve
What valves are present in the heart?
Tricuspid valve( between right atrium and right ventricle)
Bicuspid/Mitral valve (between left atrium and left ventricle)
Semilunar valves (base of pulmonary arterey and aorta)
How do papillary muscles and chordae tendinae prevent valves from everting(blowing back into the atrium)?
When the muscles in the ventricle are relaxed during filling the papillary muscles are relaxed and the chordae tendinae are slack allowing there to be limited tension on the valves so they open allowing blood in
When the ventricle contracts this pulls the chordae tendinae causing it to hold down the valves so they do not flap open causing regurgitation.
What aids in the coordination of the contraction between the atria and then ventricles?
Intercalated disks connect the cardiac muscle cells ensuring that they stay in place and connected during contractions
Gap junctions between myocardial cells are what causes action potentials to travel from cell to cell to that all the muscles can contract together
What aids in the coordination of the contraction between the atria and then ventricles?
Intercalated disks connect the cardiac muscle cells ensuring that they stay in place and connected during contractions
Gap junctions between myocardial cells are what causes action potentials to travel from cell to cell to that all the muscles can contract together
What are the 5 components of the conducting system of the heart?
- Sinoatrial node
- Atrioventricular node
- Bundle of His
- Right and Left bundle branches
- Purkinje fibers
What is the internodal pathway?
These are fibers that come from the SA node to the AV node to supply the entire right atrium and they converge at the AV node
Why does the AV nodal delay to occur?
Nodal cells have a lot of gap junctions to transfer the action potentials, but the AV node has fewer gap junctions so it takes longer for the conduction to travel and it has smaller diameter muscle fibers so the signal travels slower.
What are the phases of contractile cardiac cell action potential?
As the Ca2+ ions from the nodal cells travel through gap junctions the membrane potential of the cell increases from -80mV to -70mV (threshold potential)
- Phase 0: @ -70mV the Na+ channels rush open allowing for the cell to because more permeable to Na+. This brings the membrane potential up to +10mV. (Big spike)
- Phase 1: @ +10mV the Na+ channels close and the cells decreases permeability to Na+.
- Phase 2: @ +10mV the K+ channels begin to open allowing some K+ ions to leave the cell which causes the membrane potential to drop to 0mV. As this happens the L-type Ca2+ channels open and Ca2+ ions flood in and K+ ions leave at about the same rate resulting in a plateau
- Phase 3: After the contraction at the plateau the Ca2+ ions close at + and the cell becomes more permeable to K+
- Phase 4: Cell is repolarized to resting potential as the K+ channels in the SA nodal cells open allowing K+ to flow out lowering the membrane potential. This means that less cations are flowing into the contractile cell causing the cell to repolarize
Excitation- Contraction coupling in cardiac muscle
- Current will spread through the gap junctions from an adjacent cell
- The AP will then travel across the sarcolemma and down the T tubules triggering Ca2+ channels in the membrane to open particularly around 0mV.
- The presence of Ca2+ accumulating in the sarcoplasm stimulates the ryanodine channels to open allowing Ca2+ to rush out of the SR. (Ca2+ induced Ca2+ release)
- The Ca2+ will then bind to the troponin causing a conformation change in it and tropomyosin. This leaves the myosin-binding sites open to myosin heads binding.
- Cross bridge
- When the cell needs to rest the Ca2+ is taken back up into the SR by Ca2+ ATPase and Na+ -Ca2+ counter-transporters and Ca2+ ATPase in the sarcolemma pumping out of the cell into the ECF.
- The troponin no longer bound to the Ca2+ will change conformation along with tropomyosin and block the myosin binding sites.
What do the different peaks in a EKG stand for?
P wave: atrial depolarization
•QRS complex: ventricular depolarization and atrial repolarization (masked by the ventricular event)
T wave: ventricular repolarization
PQ segment: AV nodal delay
T-Q segment: ventricular systole (from ventricular repolarization to depolarization and atrial depolarization)
QT interval: ventricular diastole
What is Tachycardia?
Fast heart rhythm of more than 100 beats/ mins AND less than 150 beats/mins
Extra : The space between the T and P waves is very short so the heart does not have enough time to rest.
What is Bradycardia?
Slow heart rhythm lower than 60 beats/ mins
What is heart block?
A group of diseases is characterized by an obstruction in the electrical conduction pathway.
The block may slow down or prevent the transmission of the signal throughout the myocardia
What is a first degree heart block?
Slowed/diminished conduction through AV node occurs in varying degrees
Increases PQ segment duration as there is an increased delay between atrial and ventricular contraction
