Exam 1: AI Lecture 5 Flashcards
What is the primary function of the vagus nerve in heart innervation?
Keeps the brakes on the heart
Which vagus nerve typically innervates the SA node?
Right vagus nerve
Which vagus nerve typically innervates the AV node?
Left vagus nerve
True or False: Sympathetic innervation of the heart is more localized compared to vagus nerve innervation.
False
What happens to heart rate when vagus nerve input is removed?
Heart rate goes up significantly
What is the effect of removing sympathetic nervous system activity on heart rate?
Heart rate probably goes down to about 60
In a normal, healthy, resting heart, which nervous system is more active?
Vagus nerves
What is the inner-most layer surrounding the heart called?
Serous pericardium
What is the function of the visceral layer of the serous pericardium?
Covers the outside of the heart and reduces friction
What is the fibrous pericardium characterized by?
Thicker and more rigid layer
What connects the cusps of the AV valves to the ventricular muscle?
Chordae tendineae
What role do papillary muscles play during ventricular contraction?
Reinforce AV valves to prevent backflow
What is the anatomy term for the parts of the heart valves?
Cusps or leaflets
What is the normal ejection fraction for a healthy left ventricle?
58%
Fill in the blank: The valve between the left atrium and left ventricle is called the _______.
Bicuspid valve
How many cusps does the tricuspid valve have?
Three
What can happen if papillary muscles are damaged during a myocardial infarction?
Valve problems may arise
What is the purpose of the aortic and pulmonary valves?
Prevent backflow and allow blood ejection
What indicates a stenosis in heart valves?
Valves do not open fully
What is the structural feature of healthy heart valves?
Fit together tightly without leakage
What can lead to leaky heart valves?
Structural changes due to infection or cholesterol buildup
How many cusps do the pulmonary and aortic valves have?
Three
True or False: The coronary arteries receive blood flow from the aorta.
True
What happens to heart valves as a person ages or develops conditions like high cholesterol?
They may become calcified or have build-up
Fill in the blank: The left coronary artery opens from the _______ cusp of the aortic valve.
Left
What is the primary ion responsible for conducting action potentials in the heart?
Sodium
What anatomical feature aids in the efficient pumping of blood in the ventricles?
Crisscrossing pattern of muscle fibers
What is the function of the aortic valve during ejection?
The aortic valve allows blood to be pushed out of the ventricle into the aorta
What happens to the aortic valve after ejection?
The aortic valve closes due to high pressure in the aorta
How does the aorta assist in coronary perfusion during diastole?
The aorta’s high pressure can direct blood into the coronary arteries
What are the implications of valve dysfunction for coronary perfusion?
If valves are dysfunctional, blood may not be directed into coronary arteries
What is aortic stenosis and its impact on the heart?
Aortic stenosis increases resistance, making it hard for the heart to pump blood
What are the names of the cusps of the pulmonary artery?
Left cusp, right cusp, anterior cusp
What role does the cartilaginous ring play in the heart?
It acts as an insulator to separate electrical activity between the atria and ventricles
What happens if there is a continuous pathway between the atria and ventricles?
It can lead to problems and may require ablation
What is the function of the bundles of His?
They allow the AV node to transmit action potentials to the ventricles
How many cusps does the right ventricle have, and what are they?
Three cusps: anterior, posterior, and septal
What is the structure of the left AV valve or the ____ ?
It has anterior and posterior cusps, and a commissural cusp; bicuspid valve
What are the two main coronary arteries?
Right coronary artery (RCA) and left coronary artery (LCA)
What are the two main branches of the left coronary artery?
- Left anterior descending artery (LAD)
- Circumflex artery
What is the usual source of the posterior descending artery (PDA)?
It is commonly a branch of the right coronary artery (RCA)
What is the great cardiac vein?
A large vein situated on the posterior inferior part of the heart
Where does the coronary sinus drain?
Into the right atrium
What is the typical coronary blood flow requirement per minute?
Approximately 225 mL for the average heart
What is the coronary blood flow requirement per 100 grams of heart muscle?
70 mL per 100 grams
True or False: Coronary blood flow is independent of the heart’s metabolic demand.
False
What occurs to coronary blood flow when the heart’s workload increases?
It requires more than the normal amount of coronary blood flow
When does the majority of coronary blood flow occur?
When pressures in the wall of the heart are low
What is the relationship between heart rate and coronary blood flow?
An increase in heart rate typically reduces the time available for coronary perfusion.
This is particularly concerning in individuals with coronary artery disease.
When does the majority of coronary blood flow occur?
The majority of coronary blood flow occurs during diastole when pressures in the heart wall are low.
What happens to coronary perfusion during systole?
Coronary perfusion decreases during systole due to high resistance and pressures in the heart walls.
What is the difference between epicardial and endocardial blood vessels?
Epicardial vessels are superficial, while endocardial vessels are embedded in the walls of the heart.
True or False: The left coronary artery typically supplies blood to the lower pressure areas of the heart.
False
What causes negative coronary blood flow in the left coronary artery?
Negative coronary blood flow can occur due to retrograde perfusion during early systole.
Fill in the blank: Delta P drives _______.
coronary blood flow.
What are the two components of driving pressure for coronary blood flow?
Aortic pressure and wall pressure.
How does increased heart rate affect coronary perfusion time?
Increased heart rate reduces the time available for coronary perfusion.
What is the significance of the area under the curve in coronary perfusion?
It represents the product of delta P and time available for perfusion.
What occurs during the middle third of diastole regarding ventricular filling?
Not much filling occurs during the middle third of diastole.
How does aortic stenosis affect left ventricular pressure and coronary perfusion?
Aortic stenosis requires higher left ventricular pressures or increase demand. If there is cholesterol and gunk around the coronary inlets, then coronary perfusion would go down on top of SV likely being lower as well. Demand up, supply or perfusin down
What is the typical pattern of blood flow from the left and right coronary arteries?
Left coronary blood flow is typically high during diastole; right coronary blood flow is continuous throughout the cardiac cycle.
What happens to coronary perfusion when wall pressure exceeds aortic pressure?
Reverse coronary blood flow can occur.
What is the effect of high interventricular pressures on coronary perfusion?
It increases the metabolic demand and makes perfusion more difficult.
True or False: The right side of the heart has high pressures throughout the cardiac cycle.
False
What is the consequence of a high heart rate in patients with coronary artery disease?
It can significantly reduce the time available for coronary perfusion.
What determines the vascular resistance of embedded blood vessels in the heart?
The surrounding tissue and its tension.
During which phase of the cardiac cycle is coronary blood flow the highest?
Diastole.
What happens to blood flow in the coronary arteries during early systole?
Blood can be pushed backward due to the high pressures generated.
Describe the filling pattern of the ventricle during diastole.
Rapid filling occurs at the beginning, minimal filling in the middle, and some additional filling at the end.
What is the effect of higher wall pressures on coronary perfusion?
It makes coronary perfusion more difficult even if the coronaries are healthy
Higher wall pressures increase the metabolic demand of heart tissue, complicating blood perfusion.
What is aortic stenosis characterized by?
Narrowed pulse pressure, peak systolic pressure around 110, and trough pressure around 90
Normal pulse pressure is about 40, but it is reduced in aortic stenosis.
What is the consequence of mitral stenosis on atrial pressures?
Atrial pressures are elevated due to difficulty filling the ventricle
This condition can lead to reduced cardiac output and blood pressure.
How does aortic regurgitation affect diastolic blood pressure?
Diastolic blood pressure is low due to blood leaking back into the ventricle
This results in widened pulse pressure.
What happens during mitral insufficiency?
Blood is ejected into both the aorta and the atria due to a leaky valve
Atrial pressures rise significantly as blood fills from both the ventricle and pulmonary veins.
What is the relationship between ventricular pressure and aortic pressure during valve ejection?
Ventricular pressure must be higher than aortic pressure to open the valve
This also leads to retrograde coronary perfusion.
What happens to cardiac output during deep spinal anesthesia?
Cardiac output is low due to reduced filling pressure, not a heart pumping problem
The sympathetic nervous system’s activity is diminished.
Define the A wave in the CVP waveform.
A small increase in atrial and CVP pressures resulting from atrial contraction
This increase is due to blood being pushed forward and backward.
What is the C wave in the CVP waveform?
A pressure wave generated by the backward bulging of AV valves during ventricular contraction
It occurs at the beginning of systole.
Describe the V wave in the CVP waveform.
Result of atrial filling while AV valves are closed, leading to increased atrial pressure
This pressure builds until the AV valve opens.
What is the X descent in the CVP waveform?
A decrease in atrial pressure following the C wave as the atria empty
It reflects the phase after the AV valves stop bulging backward.
Explain the Y descent in the CVP waveform.
A decrease in atrial pressure after the V wave when the AV valves open
This allows rapid filling of the ventricle.
What are normal values for systemic vascular resistance (SVR)?
Approximately 800 to 1600
SVR is significantly higher than pulmonary vascular resistance (PVR), which ranges from 40 to 180.
What is the formula for calculating systemic vascular resistance (SVR)?
SVR = (MAP - CVP) / Cardiac Output
MAP is mean arterial pressure, and CVP is central venous pressure.
True or False: The pulmonary vascular resistance (PVR) is higher than systemic vascular resistance (SVR).
False
SVR is several times higher than PVR due to the pressure differences in the circulation.
What is the normal mean pulmonary arterial pressure?
16
A healthy individual in the ICU might have a higher mean pulmonary arterial pressure.
What does pulmonary arterial wedge pressure estimate?
Pressure in the left atrium
It is an estimate and typically higher than the actual left atrial pressure.
What is the normal pulmonary arterial wedge pressure value?
8
This is a rough estimate for a healthy individual.
What is the formula for calculating systemic vascular resistance (SVR)?
Subtract 8 from 16 divided by cardiac output multiplied by 80
This formula aims to yield values within the range of 40 to 180 CGS units.
What do CGS units stand for?
Centimeters, grams, seconds
These units can also be expressed in different formats, such as dynes*seconds divided by centimeters to the fifth power.
What is the normal range for systemic vascular resistance (SVR)?
800 to 1600
This range can vary based on individual health conditions.
What does PRU stand for?
Peripheral resistance unit
It correlates with delta P divided by flow.
What is the expected value for normal peripheral vascular resistance (SVR) in PRU?
1
This corresponds to mmHg/ml/sec.
How do you convert PRU into CGS units?
Multiply by 1333
This conversion helps to align with the normal range of 800-1600.
What is the typical mean pulmonary atrial pressure?
16
When calculating pulmonary circulation resistance, left atrial pressure should be approximately 2.
What happens to cardiac output and blood pressure during a normal breathing cycle?
Cardiac output can move left and right depending on pleural pressure
Low thoracic pressure generally helps with cardiac output.
What effect does increased pleural pressure have on venous return to the heart?
Reduces venous return
Higher chest pressure makes it harder for blood to return to the heart.
What happens to central venous pressure (CVP) during inspiration?
CVP drops dramatically
This drop is due to reduced pressure in the chest and affects venous return.
What is a consequence of reduced CVP during inspiration?
Increased blood flow into the thorax
This increase leads to a delay in filling the heart.
What happens to preload during a deep breath?
Preload initially drops
This occurs because blood is drawn into the thorax.
During inspiration, what happens to the afterload for the right heart?
Afterload decreases
This is due to a drop in pulmonary arterial pressure.
What is the effect of inspiration on the left side of the heart?
Preload drops significantly
Afterload remains normal during inspiration.
How does thoracic pressure affect pulmonary circulation during inspiration?
Pulmonary arterial and venous pressures decrease
This influences preload for the left heart.
What is the relationship between right heart output and thoracic pressure during inspiration?
Output may drop slightly
This is because both preload and afterload are affected.
What is the potential outcome for cardiac output during early inspiration?
It may drop briefly
Eventually, increased blood flow into the thorax will improve cardiac output.
What happens to preload for the left side of the heart during early inspiration?
Preload drops for the left side of the heart
This reduction in preload leads to a decrease in cardiac output from the left ventricle.
How does early inspiration affect afterload for the right heart?
Afterload for the right heart probably decreases
However, afterload on the left heart remains unchanged.
What is the approximate afterload pressure for the left heart during inspiration?
About 80 mmHg
This value indicates that afterload for the left heart does not change significantly during early inspiration.
What effect does decreased preload for the left heart have on cardiac output?
Cardiac output from the left side of the heart is probably reduced
This reduction occurs while the afterload is normal.
True or False: Cardiac output changes significantly during early inspiration.
False
The exact change in cardiac output during early inspiration is uncertain.
What happens to central venous pressure (CVP) during early inspiration?
CVP goes way down
This decrease reduces preload for the right side of the heart.
What happens to pulmonary arterial pressures during inspiration?
Pulmonary arterial pressures drop
This drop is due to the negative thoracic pressure surrounding them.
What is the relationship between pulmonary arterial pressure and pulmonary venous pressure during inspiration?
Both drop during inspiration
The drop in both pressures contributes to the reduction of preload for the left side of the heart.
What characterizes the blood vessels involved in pulmonary pressures?
They are compliant and thin-walled
This characteristic contributes to their responsiveness to pressure changes.
What happens to cardiac output later during inspiration?
Cardiac output eventually increases
However, this increase does not occur immediately and is not instantaneous.
Fill in the blank: The changes in cardiac output during the respiratory cycle illustrate that there is a little bit more to what’s going on with respect to _______.
cardiac output
This suggests that the respiratory cycle has complex effects on cardiac output.
What is noted about the overview of cardiac output changes during inspiration?
It is an oversimplified view
A closer look reveals finer details that are also important.
Right vagus nerve controls the
SA node
Left vagus nerve controls the
AV node
What would the heart rate be if you take away the basal activity of the SNS?
60
What pericardial layer can you see through?
Serous pericardium, visceral layer
Which layer is glued to which layer of the pericardium?
The serous pericardium, parietal layer is glued to the Fibrous pericardium (external layer)
Which pericardium layer helps the heart slide around?
The serous pericardium of the parietal layer
Not the visceral serous pericardium layer
Which pericardium layers are visible in this pic?
None, they have all been peeled off
What connects the ____ or the ____ to the inside of the ventricles?
cusps; leaflets
Chordae Tendineae
Which muscle is considered to be continous with the ventricular muscle fibers?
The Posterior papillary muscle
The papillary muscle serve as ____ and help to ____ the ____ from being blown back into the ______
Support; renforce; AV valves; atria
Normal ejection fraction for our class is
70/120 mLs = 58.3%
How would aortic valve regurgitaion be related with angina?
If the aortic valve is leaky, during diastole, some of the blood that would fill the cups of the aortic valve leaks back into the ventricle resulting in less blood flowing into the coronary artery inlets = less perfusion of the myocardium which increases risk for demand ischemia or ischemia in general
I you put the heart in a ____ , it would reveal the _______.
bucket of acid; cartilaginous ring
In coronary perfusion, in most ppl, the ____ is a branch off of the ____ , but in some ppl it can branch off of the ____ .
Posterior descending artery (PDA); Right Coronary artery (RCA); the Circumflex artery which is a branch of the Left coronary artery (LCA)
How much does the heart weigh? How do we find it?
321.4 grams without counting the blood weight
The heart needs 70 mL of blood per 100 grams of heart muscle, and it needs 225 mL/min of blood so 225/70 * (100) = 321.4
if 350 mL of blood in heart (7% of 5L), that weighs 371 grams, 321.4 + 371 = 692.4 grams including blood weight
Where in, or directly around the heart does blood flow away from the heart in an artery?
In the pulmonary artery - blood flows from the heart into the lungs
In the left coronary artery during the early portion of systole - blood flows away from the heart muscle tissue and back toward the aorta
In regards to coronary perfusion, what is the highest flow or delta P? Where is it?
Highest is 100 - 0 so 100 mmHg and it happens at the end of phase IV and the beginning of phase I
In regards to coronary perfusion, what is the lowest flow or delta P? Where is it?
Lowest is during the final third of diastole or the end of phase I. Delta P is 80 - ~5 so 75 mmHg