Lecture 2: The Heart Flashcards
Why is it important to have myocardium attached to the skeleton of the heart?
Prevents it from overexpanding and helps return to its normal shape after contraction
List some functions of the skeleton of the heart.
- It electrically separates the atria from the ventricle.
-helps return heart back to normal size and shape after contraction
-physical support for cardiac muscle
-prevents overexpansion of heart
-fibrous structure
When all four chambers of the heart contracts at once, it doesn’t work well. Why?
If the ventricles contract while the atria contracts, there’s no place to put the blood. When the atria sits on top of the skeleton of the heart, and ventricles are below it, the electrical signal being shared in the atria can’t get pass through into the ventricles.
What are valves?
They are the entrance and exit to ventricles
What are atrias?
They are receiving channels with thin myocardium
How do ventricles contribute in the heart?
The power of pump. Pressure is so much higher than atrium.
Trace the pathway of blood flow through the heart starting from the Inferior Vena Cava and end in the Aorta.
IVC > RA > TV > RV > Pulmonary Valve > PT > PA / Lungs > Pulmonary Veins > LA > MV / BV > LV > AV > Aorta
What is coronary circulation?
The blood vessels that are giving blood to the myocardium.
What are the first two branches off of the aorta?
The left coronary artery and right coronary artery
When the aortic valve is open ( blood flows from LV to Aorta) , what happens?
The flaps of the aortic valve covers the openings to the R and L coronary arteries.
Why do you cover the coronary arteries?
It closes the blood vessel not letting blood get in. Blood goes pass the openings to the R & L coronary arteries
Explain the physiological process of how the blood goes passed the openings to the R & L coronary arteries.
When ventricles contract and blood is getting pumped out into the aorta, we cover the openings. When ventricles start to relax, the pressure starts to drop and won’t be high. The valve closes so it won’t go back into the ventricle. The blood hits the valve flaps and gets directed straight into the R & L coronary arteries.
The Left coronary artery branches into what?
Anterior ventricular artery ( runs into the Anterior interventricular sulcus) and Circumflex Artery ( runs around to backside of heart)
The Right coronary artery branches into what?
Marginal artery and Posterior interventricular artery ( runs into the posterior interventricular sulcus)
What do the Left and Right Coronary arteries do?
Provide blood to the myocardium of both ventricles.
Why is it important that the L & R coronary arteries provide blood to the myocardium of BOTH ventricles?
When one gets blocked, you still have at least still some blood flow from the coronary artery.
Atria only get blood supply from the coronary artery on THEIR side. What does this mean?
R coronary artery provide blood to the myocardium of the R Atrium.
L coronary artery provide blood to the myocardium of the L atrium.
Anterior interventricular arteries have two names. What is it?
Left anterior descending artery
& Widowmaker ( slang)
What’s the most common place for blockage for a fatal heart attack?
Anterior interventricular arteries ( Left Anterior Descending Artery) because it supplies MOST of the blood to the left ventricular myocardium. This is the most effective by a decrease in O2 bc more muscle needs more O2.
What ventricle gets the most blood?
Left Ventricle because it does the most work. It needs the most O2 and glucose.
As an energy source, what does your heart work with?
Fatty acids and glucose
What is Anastamosis?
Blood vessels connect to each other WITHOUT any capillaries in between.
Where the Anterior ventricular artery runs into branches of the marginal artery.
How does Anastamosis affect myocardium?
It can be a way to bypass smaller blockage
What can induce development of Anastamosis?
Low O2 levels in region of myocardium. BUT is way too long to do much good.
The majority of the cardiac veins empty into what?
Coronary Sinus
Where does the Coronary Sinus put the blood into?
Right Atrium
Where does the Great Cardiac Vein travel in?
Travels in the Interventricular sulcus w/ Anterior interventricular artery.
Goes up into the coronary sulcus and go around to posterior side of the heart.
What forms the Coronary sinus?
The broadening of the Great cardiac vein
In the posterior interventricular sulcus with the posterior interventricular vein, it forms the …
The Middle cardiac vein where it empties directly into the coronary sinus.
What cardiac veins empty into the coronary sinus before entering the RA?
Great cardiac vein, posterior cardiac vein, middle cardiac vein, and small cardiac vein.
The only veins that directly empty into the RA without sending blood to coronary sinus are…
Anterior cardiac veins
What is the wiring system of the heart?
The Conduction System of the Heart
All of the cells in the conduction system are…
modified cardiac muscle cells.
Modification is that they don’t have modified contractle proteins
The cells of the conducting system are ….
Autorhythmic
What does Autorhythmic mean?
Heart makes its own pulse through electrochemical stimuli from the SA node
Why is the conduction system built?
So we can get electrical signal spread rapidly in an organized way. (something always comes b4 contraction = > depolarization)
What is the interatrial bundle?
Where the SA node travels to the Left atrium
What does the interatrial bundles do?
Needs to get a signal from the RA to LA to contract at approximately the same time.
The SA node is connected to the AV node by what?
3 or 4 groups of fibers called “internodal bundles”.
Runs from one node to the next node
Bundle of His branches into
R & L bundle branches that go into the septum
What are Purkinje fibers?
carry the signal to the free wall of the ventricles
In a normal healthy heart, the SA node should be…
the pacemaker
Why is the SA node the pacemaker?
What controls the heart rate is which cell has the fastest rate without any innervation. Going from resting membrane potential to threshold. The cell that does THAT the fastest in the WHOLE heart, will be the pacemaker.
If the fastest depolarizing cell dies, the next fastest cell will take over. The next cell would be in ….
The SA node
What sets your heart rate?
The fastest depolarizing cell in the SA node
The normal rate of depolarization is what?
70 - 75 depolarizations / minute = 70-75 BPM
if no hormones or nervous system is working on it, SA node contracts
When signal leaves the SA node, it can go to two places. What are they?
Invisible interatrial bundle ( takes signal to LA) and Internodal bundles ( takes to AV node)
What is the slowest conducting part of the whole system?
AV node
Why do we want the signal to go slowly in the AV node?
So that the atria can finish contracting before the ventricles start.
The AV node receives the signal and does what?
Slows the signal and send it out to the AV bundle
What is an ectopic pacemaker?
outside the usual place
SA nodes regular rate is
70 - 75 regular BPM
AV nodal pacemaker heart rate is
40 - 60 BPM
The further we get away from the SA node, what happens to the contractions?
The weirder the contraction gets from the electrical signal is traveling
Bradycardia
HR < 60 BPM
Tachycardia
HR > 100 BPM
EKG ( ECG)
Electrocardiogram
Measure electrical signals from the surface of the body
What does an EKG show you?
electrical activity that lets you evaluate the conduction system and the direction in which those electrical signals are moving. (DOES NOT show contractions)
In a healthy person, the shape of the P wave should be…
should be rounded.
T wave is what?
when ventricles repolarize
When the signal is moving toward an electrode, what does it show?
an Upward wave
When the signal is moving away from the electrode, what does it show?
an Downward wave
What is the bump at the end of a T wave called?
U wave
A Normal U wave is caused by what?
Late repolarization of papillary muscle
Abnormal U wave is caused by what?
Degoxin ( Heart Medicine) and Hypokalemia ( lower than normal blood levels of Potassium)
When a patient has a U wave, how can you determine if it is Normal or Abnormal?
Ask if they’re taking Degoxin. If yes, then test for it. If not, they will be tested for their Potassium level.
In the atria, the first cell that depolarizes is
the first cell that repolarizes
The QRS is
Ventricular Depolarization and Atrial Repolarization
P-R Interval starts and ends where?
Beginning of P wave to the beginning of the QRS
S-T Interval starts and ends where?
Begins at the end of the S wave to the end of the T wave
Q-T wave starts and ends where?
beginning of the Q wave to the end of the T wave
Dysrhythmia
Abnormal
Arhythmia
No rhythm
Why is there a plateau?
Slow calcium channels that take a while to open and stay open for a while so we can get enough calcium in.
Has a longer refractory period.
Why is the absolute refractory period so long?
There’s no way to add the signals together.
What are the two things that are impossible in cardiac muscle?
Fatigue ( skeletal muscle doesn’t die when it fatigues, can’t get tired) and tetanic contractions ( isn’t ongoing, needs to relax)
What is Systole?
A chamber of the heart contracts
What is Diastole?
A chamber of the heart is relaxing or relaxed.
Why do we need cardiac veins?
When we send blood to the myocardium to deliver oxygen and nutrients, we need to bring it back from the myocardium and get it back into the RA to send out to the lungs and get reoxygenated.
Where is the AV node placed?
The roof of the RV and the floor of the RA
What do you see in an EKG that isn’t normal?
ST segment is NOT at baseline and If T wave is downward projection
Cardiac muscle has a longer or shorter action potential?
LONGER
Why does skeletal muscle have a highly developed sarcoplasmic reticulum?
Stores all the calcium you need for a contraction in the sarcoplasmic reticulum.
Due to the sarcoplasmic reticulum being underdeveloped in the cardiac muscle, what needs to happen?
Needs to activate certain types of calcium channels to get the rest of calcium we need into the cell.