[Exam 1] Lecture 1: Review, CV Function [1/16/26] Flashcards
What units do you use for Clearance?
mL/min
What does renal clearance measure?
Volume of plasma cleared of a compound per unit of time
Renal clearance is a function of how the kidney handles that compound, whether it’s easily filtered or secreted.
What is the definition of free water clearance?
Volume of water removed from the body per unit time
Free water clearance does not take into account any electrolytes or solutes dissolved in the water.
How does ADH affect free water clearance?
High ADH levels result in low free water clearance
Conversely, absence of ADH leads to high free water clearance.
What are normal blood pressure values for systolic and diastolic pressure?
Systolic: 120 mmHg, Diastolic: 80 mmHg
Normal blood pressure is often simplified to around 100 mmHg.
What is the formula for calculating Mean Arterial Pressure (MAP)?
MAP = DBP + 1/3 (SBP – DBP)
DBP = Diastolic Blood Pressure, SBP = Systolic Blood Pressure.
What is the expected blood pressure at the right atrium in a healthy individual?
Zero mmHg
In critically ill patients, right atrial pressure may be significantly higher.
What is the normal pressure profile in the pulmonary circuit?
Normal pulmonary arterial pressure is about 16 mmHg
This is sometimes referred to as mean pulmonary arterial pressure (mPAP).
What is pulse pressure?
Difference between systolic and diastolic pressures
Normal pulse pressure in the aorta is around 40 mmHg.
How does arterial stiffness affect pulse pressure?
How/Why?
Increased stiffness leads to higher pulse pressure
Stiff arteries do not accommodate blood volume well, resulting in higher pressure spikes.
What happens to blood pressure as it moves through high resistance areas?
Blood pressure decreases downstream of high resistance areas
Arterioles are considered the highest resistance blood vessels.
What is compliance in the context of the cardiovascular system?
Change in volume over change in pressure (delta V / delta P)
Compliance applies to both blood vessels and airways.
What is the relationship between stroke volume and pulse pressure?
Increased stroke volume leads to increased pulse pressure
Conversely, decreased stroke volume results in reduced pulse pressure.
What is the expected pressure at the venular end of capillaries?
Approximately 10 mmHg
The arterial end of capillaries has a pressure of around 30 mmHg.
What is the delta P of the systemic circulation?
100 mmHg
This is calculated as the difference between pressure at the aorta and the right atrium.
What is the expected pressure at the left atrium in a healthy person?
2 mmHg
This is the pressure at the end of the pulmonary circuit.
True or False: Veins have high compliance.
True
This allows them to accommodate large volumes of blood without significantly increasing pressure.
What happens to pulse pressure in the pulmonary circulation compared to systemic circulation?
Pulse pressure is lower in the pulmonary circulation
This is due to the lower vascular resistance in the pulmonary circuit.
What does low compliance in a rigid container indicate?
It requires lots of pressure to put a little bit of volume into the container.
Low compliance indicates that a small change in volume requires a large change in pressure.
What is the relationship between pressure and volume in determining compliance?
Higher pressure with low volume results in low compliance.
Compliance can be calculated using the formula Delta V / Delta P.
What indicates high compliance in a container?
A large volume can be accommodated easily with low pressure.
High compliance is represented by a high ratio of Delta V over a low Delta P.
What are the units typically used for measuring pressure in the cardiovascular system?
Millimeters of mercury (mmHg)
lung pressure units are centimeters of water (cmH2O).
What is the pressure in the left atrium typically measured at?
About 2 mmHg.
This value is important for understanding the pressure dynamics in the heart.
What occurs to left ventricular pressure during diastole?
It should be fairly low to permit filling.
Diastole is the phase of the heartbeat when the heart muscle relaxes.
What happens to left ventricular pressure during contraction?
It increases significantly to pump blood into the aorta.
The pressure must be higher than aortic pressure for ejection to occur.
What is the pressure range in the left ventricle during filling and ejection?
Low during filling and high during ejection.
This variability is crucial for understanding cardiac function.
What is the pressure behavior of the right atrium?
It is the end of the systemic circuit feeding into the right ventricle.
The right atrium receives deoxygenated blood from the body.
What is the pressure in the right ventricle during filling?
It is low during filling.
This allows for the accommodation of blood before contraction.
What is the peak systolic pressure in the right ventricle during ejection?
Approximately 25 mmHg.
This is the pressure at which blood is pumped into the pulmonary artery.
Fill in the blank: Delta V / Delta P will be ______ important all semester.
super
Understanding this relationship is fundamental in cardiovascular physiology.
What pressure is the right ventricle approximately equal to during ejection?
Pulmonary arterial pressure.
This ensures effective blood flow to the lungs for oxygenation.
True or False: The left ventricle has a consistent pressure throughout the cardiac cycle.
False
The pressure varies significantly depending on whether the ventricle is filling or contracting.
What are the two main properties of arteries that contribute to their high resistance?
1) Narrow opening
2) Very thick wall
What gives arteries their thick walls?
Smooth muscle cells
What are the three properties of veins compared to arteries?
1) More stretchy
2) Wider internal diameter
3) More compliant
How does the amount of smooth muscle in veins compare to arteries?
Veins have much thinner smooth muscle layers than arteries
What is the primary function of capillaries?
Nutrient and gas exchange
What type of cells make up capillaries?
Endothelial cells
What is the normal diameter of the aorta?
2.5 cm
What happens to the aorta as a person ages?
It becomes less stretchy and more rigid
What is the normal cardiac output for a healthy adult?
5 liters per minute
What is the average heart rate used for calculations in this context?
72 beats per minute
What is the normal stroke volume in cc’s?
70 cc’s
How does velocity of blood flow relate to cross-sectional area?
Velocity is inversely proportional to cross-sectional area
What is the blood pressure in a large vein in the foot when standing still?
90 mmHg
What is the capillary pressure at the arteriolar end?
30 mmHg
What is the capillary pressure at the venous end?
10 mmHg
What is the conversion factor for pressure related to distance below a pressure source?
13.6 millimeters gives a rise in pressure of 1 mmHg
What is the isogravimetric point?
The point in the heart where there is no effect of gravity on blood pressure
What happens to pressure in the veins of the neck above the isogravimetric point?
Pressure is about zero due to the wide and thin-walled veins
What is the typical blood pressure in the superior sagittal sinus when upright?
Negative 10 mmHg
True or False: Blood flow velocity is highest in the capillaries.
False
Fill in the blank: The _______ layer is continuous throughout the entire circulation.
Endothelial
What is the primary reason for the high pressure in veins of the lower extremities when standing still?
The tall column of blood due to gravity
What can happen if a sinus with sub-atmospheric pressure is exposed to the atmosphere?
It can suck air in, leading to an air embolus.
What happens when a rigid venous structure is opened to the atmosphere?
An air embolus may be sucked in
This is especially concerning when working above the heart.
What is the effect of gravity on cuff pressure measurements in the upper arm?
The height of the blood column affects pressure readings
The anatomy of veins creates a curve that impacts measurements.
What should be the reference point for measuring blood pressure with a cuff on the upper arm?
The middle of the heart
This is where one would expect accurate blood pressure readings.
How does the anatomy of veins affect blood pressure measurements?
Veins curve from the arm to the shoulder, affecting pressure
This creates a column of blood that can alter measurements.
What is the approximate venous pressure in the upper arm due to the blood column?
6 to 8 mmHg
This pressure is caused by the weight of the blood in the small column.
How does the body position (upright vs. supine) affect blood pressure measurements?
Upright position leads to overestimated pressures, supine gives better estimates
The vertical column of blood influences readings in an upright position.
Is the blood pressure reading from pharmacy equipment in the upright position accurate?
It’s a little higher than the actual pressure at the heart
While the reading is generally reliable, it can be an overestimate.
True or False: The weight of arterial blood is different from venous blood.
False
Both types of blood weigh the same, affecting pressure measurements.
Fill in the blank: If measuring blood pressure with a cuff in the upright position, the measurement is likely a _______ of the actual pressure at the heart.
overestimate
This is due to the gravitational effects on the blood column.
What is the primary function of venous one-way valves?
Prevent backflow of blood towards the heart
These valves ensure blood flows in one direction, counteracting the effects of gravity.
How do one-way valves in veins support blood flow?
Act as shelves to limit the effects of gravity
They help prevent high pressures in the lower extremities as long as they are patent.
What happens to venous one-way valves as we age?
They may not fit together properly, leading to backflow
This contributes to increased pressure and the formation of varicose veins.
What are varicose veins?
Enlarged veins caused by prolonged standing and valve dysfunction
They are associated with increased pressure in the lower extremities and can pose a risk for blood clots.
What is the expected pressure in the veins of a supine patient?
Approximately 0 mmHg at the end of the venous system
Blood pressure is significantly lower due to reduced gravitational effects.
How does gravity affect arterial pressure in an upright position?
Increases pressure due to the height of the blood column
The pressure at the foot combines the heart’s output and the gravitational effect.
What is the formula for vascular compliance?
Delta V over Delta P
This represents the change in volume divided by the change in pressure.
What does high vascular compliance indicate?
Large volume generates small changes in pressure
High compliance means the container can accommodate volume with minimal pressure increase.
What is the difference between compliance and distensibility?
Distensibility includes the original volume of the container
It measures how much a container can expand based on its starting size.
What happens when blood pools in the legs?
It can lead to low cardiac output and potential fainting
Lack of muscle activity prevents blood from returning to the heart.
What is the effect of skeletal muscle contraction on venous blood flow?
It helps push blood back towards the heart
Muscle contraction compresses veins, reducing pressure and preventing stasis.
True or False: Arteries have one-way valves to prevent backflow.
False
Arteries are open tubes without valves, relying on high pressure for blood flow.
What pressure is expected at the bottom of a 1.5-meter tall beaker filled with blood?
Approximately 90 mmHg
If you do the math, this doesn’t work. In Lecture 2 Scmidt tells us this
This pressure results from the gravitational effect on the column of blood.
Fill in the blank: The pressure in the foot when standing without muscle activity can reach _____ mmHg.
95 mmHg
This is due to the combined effect of heart output and gravity.
What happens to venous pressure when one-way valves fail?
Venous pressure increases significantly due to gravity
Without functional valves, the pressure can rise to levels seen in the foot.
What is the relationship between distensibility and the original volume of a container?
High distensibility occurs with small original volumes
A container that expands easily from a small size is considered highly distensible.
What is resistance in the context of blood flow?
A measure of how difficult it is to move blood from one point to another
High resistance indicates more difficulty in blood flow.
What does distensibility refer to?
The ability of a container to expand based on its original size
Distensibility factors in the original size of the container being dealt with.
What does resistance measure in a flow system?
The difficulty of flow
High resistance indicates difficulty in moving something from one point to another.
What is the relationship between conductance and resistance?
Conductance is the inverse of resistance
High conductance corresponds to low resistance.
What primarily controls blood flow (F) in the cardiovascular system?
Changes in resistance in blood vessels
Relaxation or constriction of blood vessels affects blood flow significantly.
How does a small change in diameter of blood vessels affect flow?
It results in a huge change in resistance and conductance
A minor dilation can lead to a massive increase in blood flow.
What is Ohm’s law in the context of the cardiovascular system?
V = IR, where V = pressure, I = blood flow, R = vascular resistance
P = F x R | Pressure = Blood Flow x Vascular Resistance
This equation relates pressure to blood flow and resistance in the cardiovascular context.
What does Delta P represent?
The difference in pressure at one end of the system versus the other end
A higher Delta P allows for more blood flow.
How do you calculate vascular resistance (R)?
R = Delta P / Blood Flow
This formula allows determination of vascular resistance using pressure and flow measurements.
What is the typical range for systemic vascular resistance (SVR)?
800 to 1600 resistance units
SVR values can be calculated using Delta P divided by blood flow.
What characterizes the arterial system in terms of pressure and volume?
High pressure and low volume
Adding small volumes to arteries results in significant pressure increases.
What characterizes the venous system in terms of pressure and volume?
High volume and low pressure
The veins can accommodate large volumes with minimal pressure change.
What does a steep slope in a volume vs. pressure graph indicate about compliance?
Low compliance
Arteries have a steep slope, indicating they do not stretch easily with added volume.
What does a shallow slope in a volume vs. pressure graph indicate about compliance?
High compliance
Veins have a shallow slope, indicating they accommodate volume easily.
How does sympathetic stimulation affect arterial blood pressure?
Increases pressure significantly
Removal of sympathetic tone causes a drop in arterial blood pressure.
What happens to venous pressure when sympathetic stimulation is removed?
Venous pressure drops significantly
Strong contraction of the venous walls can increase pressure.
What determines the pressure in the central veins?
Volume status and the need for blood pressure and cardiac output
The body regulates central venous pressure based on these factors.
What is the normal cardiac output level?
About five liters per minute
In a healthy heart where normal right atrial pressure is zero.
What is the normal right atrial pressure?
Zero
How does an increase in CVP affect right atrial pressure?
It causes an increase in right atrial pressure
What happens to cardiac output with an increase in right atrial pressure?
Cardiac output can significantly increase
What is the relationship between venous return and cardiac output?
Venous return must equal cardiac output
What two factors determine cardiac output and blood pressure?
The properties of the circulatory system and the pumping capacity of the heart
True or False: The heart’s pumping capacity is the only determinant of cardiac output.
False
Fill in the blank: Typically, cardiac output is more determined by _______ than the pumping output of the heart.
venous return
What can cause problems with blood pressure unrelated to the heart?
Blood pooling in the legs or blockages in perfusion
What is the relationship between cardiac output and venous return in terms of volume?
Both must equal the same volume
What should be considered when evaluating the heart’s performance?
The amount of blood being returned to it
