Big Picture
What is the main function of the heart that we've discussed?
To pump blood throughout the body in a "figure 8" way so that blood gets oxygenated and deoxygenated appropriately.
What are auricles and what is their purpose?
Auricles are on top of the atria (hence external structures) and increase blood flow by opening their flaps to let the atrium increase it's volume.
What is the purpose of the blood valves? Why is it important that this purpose is achieved?
To make sure that there is only one direction of blood flow! We do not want to have oxygenated and deoxygenated blood mix as this can lead to many issues.
What are the two cardiac cells we have covered?
Contractile cells (big % of cardiac cells) - these are not autorhythmic but are instead responding to the signals made by pacemaker cells.
Pacemaker cells (small % of cardiac cells) - these are able to generate their own action potential.
What does the P-R interval of an ECG indicate? Describe what this looks like on an ECG.
P-R interval indicates the duration of atrial depolarization & AV node delay.
Multiple answers can be accepted. Basically, from the first hump of the ECG right before the spike to the top of this spike.
**Much easier to see than to describe**
What's the difference between arteries and veins?
Bonus points if you can describe what the coronary sinus is!
Arteries - drive blood away from the heart and to the different capillaries/systems.
Veins - brings blood back to the heart from the different capillaries/systems.
Coronary sinus - vein that collects deoxygenated blood from other coronary veins and brings it back to the right atrium of the heart.
Which chamber is going to have thicker myocardium and why?
The left ventricle will have the thickest myocardium and heart wall because ventricles always pump blood out to arteries. However, the left ventricle pumps blood to the systemic circuit (basically everywhere) while the right ventricle only pumps blood to the pulmonary circuit, hence the left ventricle will have to contract harder.
If deoxygenated blood leaves from the right ventricle, what is the next chamber of the heart it will enter?
The left atrium! The blood will now be oxygenated because it went through the pulmonary capillaries.
What is the refractory period? Why is it important?
During the initial repolarization and the plateau phase, it is crucial that a flat mV exists for a extended period of time. This is because the chambers of the heart need to fill with blood before contracting again (during depolarization).
Which is more critical: atrial fibrillation or ventricular fibrillation?
Why is defibrillation used for the answer above?
Which circuit (pulmonary/systemic) is going to have higher pressure and why?
The systemic circuit will have higher pressure because the heart must pump blood out to the whole body. The pulmonary circuit is lower in pressure because the lungs are very close to the heart in comparison.
How is the heart wall organized?
From within the heart to out we have:
Lumen of heart
Endocardium - made of squamous epithelial tissue
Myocardium - made of cardiac muscle and connective tissue (also makes up most of heart mass)
Epicardium - visceral pericardium and adipose tissue
Pericardial layers protecting heart (connective tissue with low distensibility)
What is the difference between atrioventricular valves and semilunar valves?
Atrioventricular valves - control flow of blood from atria to ventricles. Includes bicuspid valve and tricuspid valves (LaB RaT).
Semilunar valves - control flow of blood from ventricles to arteries. Includes aortic (L) valve and pulmonary (R) valve.
During the full depolarization phase, which channel opens and which channel closes?
Bonus points if you can identify which type of cell has this phase to begin with!
Calcium channels open to allow Ca2+ ions in.
HCN channels close.
The full depolarization phase happens only for pacemaker cells.
Describe the process of cardiac conduction.
1) The SA node sends impulses to the AV node and atria.
2) After the AV node delay, the action potential is conducted to the AV bundle and then to the right and left bundle branches.
*The AV bundle is what connects atria to ventricles*
3) Bundle branches conduct impulses through septum and along Purkinje fibers.
4) Purkinje fibers depolarize the contractile cells of the ventricles.
What are the four chambers of the heart? Which side will carry deoxygenated blood and which side will carry oxygenated blood?
Left Atrium, Left Ventricle, Right Atrium, Right Ventricle
Left side always carries oxygenated blood, right side always carries deoxygenated blood
What are the four great vessels?
For each describe:
Are they arteries or veins? Do they carry oxygenated or deoxygenated blood?
Vena cavae (both superior and inferior): Veins carrying DO blood to right atrium.
Pulmonary trunk: Artery taking DO blood to pulmonary capillaries.
Pulmonary veins: Veins carrying O blood to left atrium.
Aorta: Artery taking O blood to systemic capillaries.
If blood goes through the systemic capillaries to get deoxygenated, what is the next valve the blood will pass through? Where is this valve located?
The blood will go to the right atrium first. Then it will pass through the tricuspid valve, which is between the right atrium and the right ventricle.
Why do pacemaker cells have a slow initial depolarization phase?
HCN channels are open during this period and are letting cations in AND out of the cell at the same time, causing depolarization to start off slowly.
If the SA (sinoatrial) node were to fail as the normal pacemaker of the heart, which node/bundle/system would replace it?
Bonus points if you can say what would happen if the above answer also failed!
If the SA node failed, the AV (atrioventricular) node would become the pacemaker of the heart.
If the AV node failed, the Purkinje fiber system would be the new pacemaker of the heart. This, however, would not be strong enough to sustain life.
What is the term described for the hollowness of the heart (or any other hollow organ)?
Does the blood ever pass directly between the right and the left side of the heart?
Lumen
No. The blood must go through a whole circuit before going to the other side of the heart. There should NOT be blood going between the right and left side of the heart directly.
What are the three conditions of the pericardium we discussed and how do they relate?
Pericarditis - inflammation of the pericardium leading to:
Pericardial Effusion - fluid built up from inflammation leading to:
Cardiac tamponade - fluid built up that squeezes the heart and compresses it.
What is CAD? What are possible effects of CAD?
Coronary Artery Disease - plaques are created causing blood flow to be blocked within the coronary arteries. This can lead to ischemia.
Possible effects include:
-Angina pectoris - chest pain, especially when exerting oneself
-Myocardial infarction - "heart attack", cell death in the heart causing scar tissue to be created which isn't excitable
Compare & contrast pacemaker cells and contractile cells.
(For scoring the points, at least three distinctions must be made for each category)
Pacemaker Cell:
- uses HCN bidirectional channels
- lower depolarization mV threshold
- has no resting membrane potential
- has autorhymicity
- has no plateau phase since the K+ and Ca2+ channels open at different times
Contractile Cells:
- uses Na+ channels
- has resting membrane potential
- has plateau phase since both K+ and Ca2+ channels open at the same time
- starts from electrical signal
- depolarizes faster
Both:
- have K+ and Ca2+ channels
- have repolarization phases
- have Ca2+ enter the cell and K+ exit the cell
Define each term:
Dysrhythmia
Bradycardia
Tachycardia
Asystole
Dysrhythmia - bad rhythm
Bradycardia - abnormally slow heart rate
Tachycardia - abnormally fast heart rate
Asystole - "flat-lining"; no heart rhythm present on ECG.