Cardiovascular Physiology Flashcards
What carries the blood from the right ventricle to the lungs?
The pulmonary artery
What is the role of the pulmonary artery?
To carry deoxygenated blood from the right ventricle to the lungs
What carries the blood from the lungs to the left atrium?
The pulmonary veins
What is the role of the pulmonary veins?
To carry oxygenated blood from the lungs to the left atrium
What carries the blood from the left ventricle to the tissue?
Systemic arteries
What is the role of systemic arteries?
To carry oxygenated blood from the left ventricle to tissue in the body
What carries the blood from the body to the right atrium?
Systemic veins
What is the role of systemic veins?
To carry deoxygenated blood from the body to the right atrium
What is functional syncytium?
Refers to a group of cells that function as a coordinated unit such as in the heart
What is the TP interval?
When the heart muscle is completely at rest
What is in one cardiac cycle?
One systole and one diastole cycle
What makes the ‘lub’ sound in the heartbeat?
When blood hits the closed AV valves
What makes the ‘dub’ sound in the heartbeat?
When blood hits the closed aortic and pulmonic valve
What is stroke volume?
The amount of blood pumped out of each ventricle
How is stroke volume calculated?
End diastolic volume - end systolic volume
What is ejection fraction?
A measurement expressed as a percentage of how much blood the left ventricle pumps out with each contraction
How is ejection fraction calculated?
Stroke volume/end diastolic volume x 100
How is cardiac output measured?
Stroke volume x heart rate
What is cardiac output?
The total volume of blood pumped by 1 ventricle in 1 minute
What usually changes the heart rate?
Altered autonomic nervous system activity
What part of the brain controlles the cardiovascular system?
The medulla oblongata
What are the two types of control of the stroke volume?
Intrinsic and extrinsic
What is intrinsic control related to stroke volume?
To the extent of venous return
What is extrinsic control related to stroke volume?
To the amount of sympathetic stimulations
What are the three factors effecting stroke volume?
- Preload
- Contractility
- Afterload
How is stroke volume calculated?
Preload + Contractility − Afterload
What is preload?
Is the stretch of the heart muscle at the end of diastole determined by the volume of blood returning to the heart
How does increased preload affect stroke volume?
Leads to greater stretch of the ventricular walls resulting in a stronger contraction and increase stroke volume
What is the Frank Starlin Law?
The physiological principle that explains the relationship between preload and stroke volume
What is contractility?
It is the strength of the heart’s contraction independent of preload influenced by sympathetic stimulation and cellular calcium levels
How does increased contractility affect stroke volume?
Results in a stronger heart contraction which increases stroke volume
What is afterload?
Is the pressure or resistance the heart must overcome to eject blood during systole
How does increased afterload affect stroke volume?
It makes it harder for the heart to pump blood out which decreases stroke volume
What generates pressure in the circulatory system?
The contraction of the myocardium
What percentage of blood is in the pulmonary circulation and heart?
About 25%
What percentage of blood is in the systemic circulation?
About 75%
Which vessels act as blood reservoirs and what are they called?
Veins and are called capacitance vessles
What is the typical circulatory filling pressue?
7 mmHg
In which direction does blood flow in terms of pressure?
From high to low pressure
What causes resistance in blood vessels?
Friction between bloods and vessel walls
What happens to blood flow if resistance increases?
Blood flow decreases
What is the equation that relates pressure, flow and resistance?
ΔP = Flow × Resistance
How does vessel radius affect resistance?
Resistance is inversely proportional to the fourth power of vessel radius
What is the most important factor controlling resistance?
Arteriole radius
How can blood flow to a tissue be increased?
By increasing pressure or decreasing resistance
What effect does gravity have on blood pressure?
Gravity affects the pressure gradient influencing blood flow based on posture
What determines blood flow to an organ?
The resistance of arterioles supplying the organ
Why do arterioles cause a large pressure drop?
Because they have a small radii and contribute around 60% of total vascular resistance
How do arterioles affect capillary pressure?
They smooth out pressure fluctuations making capillary pressure more constant
Which nervous system controls arterioles?
The sympathetic nervous system
What are the two types of control of arteriolar resistance?
- Intrinsic control
- Extrinsic control
What does intrinsic control regulate?
Blood flow to meet the metabolic needs of specific tissues
What does extrinsic control regulate?
Overall blood pressure across the body
What is autoregulation of blood flow?
The ability of tissue to adjust blood flow by changing arteriole diameter
What three factors contribute to intrinsic control?
- Nitric oxide
- Histamine
- Temperature
Which 3 organs rely heavily on intrinsic control?
- Brain
- Heart
- Skeletal muscles
What system is most important in extrinsic control?
The sympathetic nervous system
What happens when sympathetic activity increases?
- General vasoconstriction
- Increasing arteriolar resistance
What happens when sympathetic activity decreases?
- General vasodilation
- Decreasing arteriolar resistance
What does TPR stand for?
Total peripheral resistance
What equation relates blood pressure, cardiac output and TPR?
Blood pressure = cardiac output x TPE
What percentage of blood is in capillaries at any one time?
Around 5%
How far is any cell from the nearest capillary?
No more than 100 micrometers
What happens to blood velocity in capillaries and why?
Blood slows down as it has a huge total cross-sectional area
What are the two main ways substances move across capillaries?
- Diffusion
- Bulk flow
What law governs the rate of diffusion
Fick’s Law
Why does diffusion increase with higher cellular activity?
High activity increases the concentration gradient speeding up diffusion
What is bulk flow?
The movement of fluid and solutes together due to pressure differences
What does the capillary wall act like during bulk flow?
Acts like a sieve allowing water and solutes through but keeping proteins and cells in
What forces drive bulk flow?
- Hydrostatic pressure
- Osmotic pressure
What does hydrostatic pressure do?
Pushes water out of capillaries into the interstitial fluid
What does osmotic pressure do?
Pulls water into capillaries from the interstitial fluid
What happens to excess fluid not reabsorbed by capillaries?
It is picked up by the lymphatic system
What is the function of the lymphatic system in fluid balance?
It returns excess fluid from tissues to the venous system
What are the smallest vessels of the lymphatic system called?
Initial lympatics
Where are initial lymphatics found?
They permeate almost all tissue
How does fluid enter the lymphatic system?
Fluid enters through one-way valve like opening in the vessel wall
What helps move lymph through the vessels?
Skeletal muscle contractions and intrinsic contraction of vessel walls
Where does lymph eventually empty?
Into large veins near the heart
What are the three functions of the lymphatic system?
- Returning excess fluid
- Immune surveillance
- Fat absorption
After capillaries where does blood flow next?
Into the venous system
What are the two main goals of blood flow?
- Transport gases
- Maintain arterial blood pressure
Why is maintaining blood pressure important?
It ensures blood can overcome gravity and support ultrafiltration
Which is more immediately dangerous high blood pressure or low blood pressure?
Low blood pressure
What do peripheral chemoreceptors detect?
Low oxygen and high carbon dioxide levels
What does central chemoreception detect?
High CO2 levels
What effect does lactic acid have on blood pH?
Lowers blood pH
How does the body restore pH during intense exercise?
By increasing respiration which removes CO2 and raises pH
What two signals can trigger increased respiration during exercise besides pH?
- Neurons in cerebral cortex
- Sensory cells in limbs
What happens to skeletal muscle arterioles during exercise?
They dilate to increase blood flow
How does arteriole dilation affect blood pressure during exercise?
It lowers the arterial blood pressure
How does the body respond to the drop in BP during exercise?
Increase:
- Sympathetic tone
- Heart rate
- Contractility
What are the three factors involved in BP maintenance?
- Short term neural control
- Long tem hormonal control
- Baroreceptor reflex
What does short term BP control adjuct?
Cardiac output and total peripheral resistance via the autonomic nervous system
What does long term BP control involve?
The regulation of total blood volume through hormonal and kidney mechanisms
What is the baroreceptor reflex?
Short term reflex that responds to changes in mean arterial pressure
What do baroreceptors sense?
Stretch in vessel wallks
What happens to baroreceptor firing when BP increases?
Frequency increases
Where are the main baroreceptors located?
In the carotid sinus and aortic arch
Where are baroreceptor reflex integrated?
In the cardiovascular control centre of the medulla
What are the effectors in the baroreceptor reflex?
The heart and bloos vessel
What happens if blood pressure stays high for too long?
The baroreceptor set point resets which can lead to chronic hypertension
