Lecture 1 - Jan 16 Flashcards
What is clearance by the kidney?
The volume of plasma that’s cleared of a substance per unit of time.
What does kidney filtration (GFR) reflect?
The filtration capacity of the kidney.
What is free water clearance?
The volume of water that’s being removed from the body per unit time.
What happens to free water clearance when ADH levels are high?
Free water clearance is probably low because we’re conserving volume.
What is the normal blood pressure value for systolic pressure?
120 mmHg.
What is the normal blood pressure value for diastolic pressure?
80 mmHg.
What is the formula for Mean Arterial Pressure (MAP)?
MAP = DBP + 1/3 (SBP – DBP).
What should the MAP be for a blood pressure of 120/80?
93 mmHg.
What happens to blood pressure as it moves further from the heart?
Blood pressure drops.
Where is the highest resistance in the circulatory system found?
In the arterioles.
What is the capillary blood pressure on the arterial end?
30 mmHg.
What is the capillary blood pressure at the venular end?
10 mmHg.
What is the normal blood pressure at the right atrium?
0 mmHg.
What is the normal pulmonary arterial pressure (mPAP)?
16 mmHg.
What is pulse pressure?
The difference between systolic and diastolic pressures.
What is the pulse pressure in the aorta?
Around 40 mmHg.
What causes widening of pulse pressure in large arteries?
Stiffer walls that do not accommodate volume easily.
What happens to pulse pressure with increased stroke volume?
Pulse pressure increases.
What is compliance in the context of the cardiovascular system?
Change in volume over change in pressure (ΔV/ΔP).
What characteristics make arterioles high resistance vessels?
- Narrow opening * Thick walls.
What are the properties of veins?
- More stretchy * Wider internal diameter * More compliant.
What pressure range is expected in the left ventricle during filling?
Low pressure.
What is the pressure in the right ventricle during peak systole?
Approximately 25 mmHg.
In the pulmonary circuit, what is the reason for lower pressures?
Low vascular resistance.
Fill in the blank: The formula for compliance is ΔV / ΔP, where ΔV is change in _______.
[volume].
What are the properties of veins?
Veins have a few smooth muscle layers that are thinner than those in arterioles, allowing them to adjust wall tension to maintain reasonable pressures.
How do arterioles differ from veins in terms of blood flow control?
Arterioles can completely cut off blood flow, while veins can only tighten slightly without fully impeding flow.
What type of cells make up capillaries?
Capillaries are made up of endothelial cells.
What is the primary role of capillaries?
Capillaries are specialized for nutrient and gas exchange.
What is the diameter of a healthy aorta?
The aorta has a wide opening of approximately 2.5 cm.
What happens to the aorta as we age?
The aorta becomes more rigid, leading to a higher pulse pressure.
What is the normal cardiac output for a healthy individual?
5 L per minute.
What is the normal heart rate?
72 bpm.
What is the normal stroke volume?
70 cc.
How does blood velocity differ between the aorta and vena cava?
Blood velocity is high in the aorta and lower in the vena cava.
What factors determine the velocity of blood flow?
Velocity is determined by blood flow to the tissue and the cross-sectional area available.
True or False: Systemic circulation is a parallel system.
True.
What occurs at the capillary level regarding filtration and reabsorption?
Filtration favors fluid at the arterial end, while reabsorption favors it at the venous end.
What is the capillary pressure at the arteriolar end?
30 mmHg.
What is the capillary pressure at the venous end?
10 mmHg.
How does gravity affect blood pressure in the cardiovascular system?
Gravity increases pressure the further below a pressure source you go.
What is the isogravimetric point?
The isogravimetric point is the point where there is no effect of gravity on blood pressure, typically located at the middle of the tricuspid valve.
What is the expected venous pressure around the umbilicus in an upright position?
About 22 mmHg, primarily due to gravity.
What is the expected venous pressure above the knee in an upright position?
About 40 mmHg.
What is the expected venous pressure in the foot when standing?
About 90 mmHg.
Why is the pressure in the neck veins approximately zero?
The neck veins are wide and thin-walled, preventing negative pressure from building up.
What are the characteristics of vessels in the cranium?
They have thick walls and are rigid, leading to sub-atmospheric pressure when upright.
What happens if a cranial sinus with sub-atmospheric pressure is exposed to the environment?
Air will be sucked in, potentially causing an air embolus.
How does the anatomy of veins affect blood pressure measurements in the upper arm?
The curving anatomy creates a column of blood that affects pressure readings, leading to an overestimate of blood pressure.
What role do one-way valves play in the venous system?
They prevent backflow and help combat the effects of gravity on venous pressures.
What happens to venous pressure when one-way valves are patent?
They help limit the effects of gravity on venous pressure.
What condition can result from prolonged standing and gravity effects on veins?
Varicose veins.
What is the primary function of valves in the venous system?
To permit blood moving back towards the heart and limit retrograde blood flow.
Describe the condition of varicose veins.
Varicose veins occur when veins are stretched out, leading to ineffective one-way valves and increased pressure in the lower extremities.
What happens to venous pressure when standing compared to a supine position?
Venous pressure increases significantly when standing due to the effect of gravity.
What is the expected venous pressure at the bottom of the foot when standing?
About 90 mmHg.
Fill in the blank: The formula for vascular compliance is _______.
Delta V over Delta P.
What does high compliance in a container indicate?
A large volume generates small amounts of pressure.
What is the term synonymous with expandability?
Distensibility.
True or False: Conductance is the inverse of resistance.
True.
What primarily controls blood flow in blood vessels?
Changes in resistance in the vessels.
How does a small change in diameter affect resistance and flow?
It results in a huge change in conductance and resistance.
Fill in the blank: The driving force in the cardiovascular system is _______.
Blood pressure.
What does the formula V = IR represent in the cardiovascular system?
Pressure = Blood flow x Vascular resistance.
What happens to blood flow if there is less difference in pressure between two ends of a vessel?
Blood flow is reduced.
What is vascular resistance calculated from?
Delta P divided by Blood Flow.
In terms of pressure, what is the expected delta P for systemic circulation?
100 mmHg (pressure at the beginning is 100 mmHg and at the end is 0 mmHg).
What is the formula for calculating systemic vascular resistance (SVR)?
SVR = Delta P / Blood Flow
Delta P represents the pressure difference across the vascular system.
What is the acceptable range for systemic vascular resistance (SVR) values?
800-1600 resistance units
These values are commonly used to assess vascular resistance in the circulatory system.
How is blood flow expressed in the context of systemic vascular resistance?
Blood flow can be expressed as 5L/min or 83 mL/sec.
What is the volume of blood in the systemic arterial circulation?
Approximately 700 mL
This volume represents a small portion of the total blood volume.
What is the volume of blood in the systemic venous system?
Approximately 2500 mL.
Describe the pressure and volume characteristics of the arterial system.
High Pressure / Low Volume
Describe the pressure and volume characteristics of the venous system.
High Volume / Low Pressure
What does a steep slope in a volume vs. pressure graph indicate?
Low compliance system
This means that a small change in volume results in a large change in pressure.
What does a low slope in a volume vs. pressure graph indicate?
High compliance system
This means that a large change in volume results in a small change in pressure.
How does sympathetic stimulation affect arterial blood pressure?
Increases blood pressure.
What happens to arterial blood pressure when sympathetic tone is removed?
Blood pressure crashes.
What is the relationship between central venous pressure (CVP) and right atrial pressure?
Increase in CVP leads to an increase in right atrial pressure.
What happens to cardiac output when right atrial pressure is increased?
Cardiac output typically increases.
What must venous return equal in a healthy circulatory system?
Cardiac output.
True or False: Cardiac output is solely determined by the heart’s pumping ability.
False
Cardiac output is also influenced by venous return.
What is a major factor that can cause problems with blood pressure unrelated to the heart?
Poor venous return.
What type of system behavior is observed when sympathetic stimulation is applied to the veins?
Increased venous pressure.
What is indicated by a central venous pressure of 20?
It could be good or bad, depending on the context.
What is the significance of compliance in the cardiovascular system?
It determines how easily blood vessels can accommodate changes in volume.
