CVS Week 4 Flashcards
What are reconditioned organs
Reconditioned organs receive more blood than needed to perform homeostatic adjustments
Examples of reconditioned organs
Digestive tract: collects nutrients
Kidneys: Adjust water & electrolytes and remove wastes
Define flow rate
Volume of blood passing through per unit time
Factors of flow rate
Directly proportional to pressure gradient
Inversely proportional to resistance
Define blood pressure
Force exerted by blood against vessel
Define pressure gradient
Difference in pressure between beginning and end of vessel
Define resistance
Friction between blood and vascular wall
What allows for pulse pressure
Elastic properties of arteries help convert pulsatile flow of heart into more continuous flow in capillaries
How to calculate pulse pressure
Systolic pressure - diastolic pressure
Where can pulse waves be felt
Major arteries
What causes pulse waves
Difference between systolic and diastolic pressure
What determines the pulse wave strength
Stronger difference between systolic and diastolic pressure = stronger pulse wave
What is the function of arteries
Rapid transit passageways to organs and acts as a pressure reservoir
What factors determine the blood pressure
Depends on
1) distensibility of vessel walls
2) volume of blood within vessel
Define systolic pressure
max pressure when blood ejected into arteries
define diastolic pressure
minimum pressure when blood draining into rest of vessel during diastole
Define mean arterial pressure
Main driving force of blood flow
Average pressure driving blood forward
Constantly monitored and regulated by body’s blood pressure reflexes
How is Mean Arterial Pressure calculated
Diastolic pressure + 1/3 pulse pressure
OR
2/3 diastolic pressure + 1/3 systolic pressure
Why does pressure drop from arteries to veins
Due to increasing non-pulsatile property (smoother flow)
In arteries, there is little resistance and hence little pressure lost which means…
pressure constant throughout arterial tree
Notch formed in a blood pressure graph is due to…
Aortic valve closing
What is the blood flow like in capillaries compared to arteries
Slower than arteries
How are RBCs aligned in capillaries
Single file
Why are capillaries designed as sites of exchange
Thin walled, extensive branching and close proximity to cells for exchange
What changes occur when blood goes from arteries to capillaries to veins
Flow velocity drops at capillaries but goes back up to normal
Cross section area increases at capillaries but goes back down to normal
Why is the total flow rate of capillaries the same throughout circulatory tree
Due to increased surface area
What is the flow rate like in capillaries
5L/min
What has the same flow rate of capillaries
Cardiac output
Can plasma proteins cross the capillary wall
No
Can exchangeable proteins pass through capillaries
Yes via vesicular transport
Can water soluble substances pass through capillaries
Yes through water filled pores
Name examples of water soluble substances in capillaries
Na+, K+
Can lipid soluble substances pass through capillaries
Yes via endothelial cells
Name examples of lipid soluble substances in capillaries
O2, Co2
The more metabolic active tissues have more capillaries
True
Why do we have pre-capillary sphincters
Many capillaries are not open under resting conditions and capillaries have no smooth muscle
What do pre-capillary sphincters do
Control blood flow at capillaries
What happens to pre-capillary sphincters when metabolic activity occurs
Increased metabolic activity = sphincters relax = more capillaries open = increased blood flow to active tissues
What is endothelin
Potent vasoconstrictor
How are arterioles regulated
Vasoconstriction and vasodilation
How is vasodilation induced
Increased CO2, Nitric Oxide
Decreased O2, sympathetic stimulus
How is vasoconstriction induced
Increased O2, endothelin, sympathetic stimulus (cold, vasopressin, angiotensin II)
Decreased CO2
Local control of arteriolar radius is important for what
Determining cardiac output distribution
What are local vasoregulators of arterioles
Vasoconstriction, vasodilation, vascular tone
What is vascular tone
State of partial constriction of arteriolar smooth muscle
Establishes baseline of arteriolar resistance
What determines the blood flow to organs
Difference in vascularization
Difference in resistance by arterioles supplying organs
What is nitric oxide
potent vasodilator
Which area does sympathetic fibers not supply arteriolar smooth muscle
The brain because it needs constant cardiac output regardless of situation
Increased sympathetic stimulation causes
generalized Vasoconstriction
decreased sympathetic stimulation causes
generalized vasodilation
Why is extrinsic control of arteriolar radius important
Important in regulating blood pressure
Does arterioles have parasympathetic innervation
No except penis and clitoris
When does local controls override sympathetic vasoconstriction
Exercise
Exercise = increased sympathetic stimulus = generalized vasoconstriction = metabolic activity of skeletal muscles (ex: leg) induces vasoconstriction override = more blood goes to leg = less blood to rest of organs (ex: arm)
What does cardiovascular control center do
Controls sympathetic stimulus
What are examples of adrenal hormones
Norepinephrine and epinephrine
What does norepinephrine do
Induce generalized vasoconstriction
What does epinephrine do
Reinforces local vasodilatory mechanisms mostly in skeletal muscles and heart
To a weaker extent, generalized vasoconstriction
What are angiotensin II and vasopressin
Potent vasoconstrictors
What does vasopressin do
Maintain H2O balance
What does angiotensin II do
Regulates salt balance
What do vasopressin and angiotensin II do
Both help with water retention and maintaining blood volume and pressure
What are the effects of exercise
Increased HR, CO, SV, venous return, blood flow to active skeletal and heart muscle, skin, MAP
Decreased TPR, blood flow to digestive tract, kidneys and other organs
No effect on brain
Why does TPR drop when exercise occurs
Skeletal muscles, heart and skin decrease to a greater extent than resistance in other organs
Why does blood flow increase to active skeletal muscles and heart
Epinephrine vasodilatory effect overpowers weaker sympathetic vasoconstrictor effect
Why is blood pressure closely regulated
Must be sufficient to maintain blood flow and tissue perfusion (fluid exchange)
What is blood pressure affected by
CO and TPR
What is TPR affected by
Blood viscosity and arteriolar radius
What happens when BP is too high
Heart is overworked = vascular damage = small vessel rupture
What is venous return
Blood returning to heart
What are the properties of veins
Low resistance, low elastic tissue, low smooth muscle
What do veins function as
Blood reservoir
What can veins do to increase BP
Decrease storage size to increase venous return
What is venous capacity
Amount of blood veins can hold
What does venous capacity depend on
Distensibility of blood vessels and other pressures such as skeletal muscle pressing on it
How is venous return regulated
Sympathetic innervation, gravity, respiratory activity, cardiac suction, skeletal muscle activity
What does sympathetic innervation do to veins
Vein vasoconstriction
- increased flow from decreasing capacity (squeeze more blood already present)
Arteriole vasoconstriction
- decreased flow from increasing resistance
How does skeletal muscle activity regulate venous return
Muscles contract = veins compressed = decreased venous capacity = increased venous pressure
What is venous return like when lying down
Equal
What does gravity do when standing up in terms of venous return
Vessels below heart subjected to gravity
Distensible veins yield under hydrostatic P
In leg, post capillary blood pools in extended veins
- decreased venous return = decreased cardiac output
Lying down and stand up effect on venous return
Triggers sympathetic venous vasoconstrictions which drives blood forward but is interrupted by skeletal muscle pump
What is the term used when someone stands up after lying down
postural hypotension
Why do people faint after standing still for hours
Decreased blood flow to brain = decreasing circulating volume despite reflexes to maintain MAP = fainting in horizontal position
What is the effect of gravity on valves
Valve stop blood from going backwards and minimize backflow
What causes varicose veins
Incompetent venous valves aggravated by frequent long duration of standing and cannot support column of blood above it and collapses
What is the sound heard when doing BP analysis
Korotkoff sound
What are the types of hypertension
primary and secondary
What are the complications of hypertension
progressive vision loss, kidney failure, heart attack, stroke, left ventricular hypertrophy
What are the potential causes of hypertension
Excessive dietary salt and disturbance of renin-angiotensin system leading to increased blood volume
What happens to baroreceptor for those with hypertension
Adapts to operate at a higher level
How is BP regulated in short term
By baroreceptors
BP drops = baroreceptor detects it = transmits intel to cardiovascular control center = increased sympathetic and decrease parasympathetic stimulus = increased HR, SV, arteriole vasoconstriction (increased TPR), venous vasoconstriction (increased CO) = increased BP
How is BP regulated in long term
Renin angiotensin system of kidney (less urine made)
Reabsorption of fluid by kidney to maintain salt and water
Respiratory activity influence on venous return
External pressure gradient between lower veins (atm P) and chest veins (less than atm P)
Cardiac suction effect on venous return
Ventricular contraction
- AV valves close but drawn downward = atrial cavity enlarges = atrial pressure temporarily drops below 0mmHg and sucks more blood into atria
Ventricular relaxation
- AV valves open = rapid expansion of ventricles = suction effect created = more blood sucked in
