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30 Cards in this Set

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resistance is series
blood vessel arrangement one after the other (aorta-->artery-->arteriole-->capillary-->venule-->vein)
Total resistance is additive
resistance in parallel
multiple ducts flowing in same direction (i.e. multiple capillaries for every artierole)
This decreases total resistance (reciprocals of each resistance mechanism are added)
What's the difference between flow and velocity?
flow=volume/unit time
velocity=distance/unit time
velocity=flow/cross sectional area
What is the flow velocity in the blood vessels?
fastest in arteries, drops down in arterioles, slowest in capillaries, speeds up in venous system (relates to cross sectional area)
What is the benefit of slow blood flow in the capillaries?
allows for greater exchange and diffusion into and out of the tissues
Where is the majority of the blood volume contained in the blood vessels, and why?
Venous system
veins can be distended more than arteries, allowing them to carry a larger volume of blood.
Veins can constrict, which will put more blood into the systemic circulation when needed (exercise)
What's the difference between laminar and turbulent flow?
laminar flow-smooth flow, low resistance
turbulent flow-narrowing of blood vessel, increased velocity, mixing of layers, creation of vibrations/sounds
turbulence doesn't always indicate pathology (exercise), but does if it occurs during rest
In which blood vessel is the greatest resistance, and therefore, the greatest drop in pressure? Why? What are the effects?
Arterioles
Arterioles can constrict, regulating amount of blood flow into different organs. Everything downstream of arterial constriction will be reduced pressure (functions like a dam)
What does arterial pressure appear to increase downstream in systole?
Added pressure of cardiac output from ventricle contraction and reflex pressure of arteries downstream
What is the effect of arteriole constriction/dilation on downstream capillaries?
Arteriole constriction-decreases capillary pressure, allows for greater exchange/diffusion into tissues
Arteriole dilation-increases capillary pressure, decreases capillary exchange/diffusion
What is total peripheral resistance?
AKA Systemic Vascular Resistance (SVR)
This is a major determinant of mean arterial blood pressure.
The largest percentage of TPR is in the systemic arterioles.
What is compliance? How does it affect blood vessels?
compliance=change in volume/change in pressure
compliance=elasticity
Arterial vessels have very small compliance
Venous vessels have large compliance; this allows them to hold large volumes of blood (serve as blood reservoirs)
What is mean arterial pressure (MAP)? How can you calculate it?
MAP=CO * TPR (CO *SVR)
MAP=Diastolic pressure + 1/3 pulse pressure (pulse pressure=systolic - diastolic pressure)
works best at resting heart rate
What is a factor that would change compliance? How does it change compliance?
Age-atherosclerosis will decrease compliance
What are the major components of pulse pressure?
Stroke volume-directly related
Compliance-inversely related
With age, stroke volume will decrease, but compliance will also decrease, usually resulting in overall increased pulse pressure
What's the difference in mechanisms of electrochemical coupling vs pharmacomechanical coupling in vascular smooth muscle contraction?
Electromechanical coupling-occurs because the smooth muscle surface membrane contains voltage-operated channels for calcium. Membrane depolarization increases the open-state probability of these channels and thus leads to smooth muscle cell contraction and vessel constriction.
Pharmacomechanical coupling-chemical agents (eg, released neurotransmitters) can induce smooth muscle contraction without the need for a change in membrane potential.
How does local metabolic vasodilation work?
Vasodilator factors (CO2, K, ATP, H, adenosine) enter the interstitial space from the tissue cells at a rate proportional to tissue metabolism. These vasodilator factors are removed from the tissue at a rate proportional to blood flow. Whenever tissue metabolism is proceeding at a rate for which the blood flow is inadequate, the interstitial vasodilator factor concentrations automatically build up and cause the arterioles to dilate. This, of course, causes blood flow to increase. The process continues until blood flow has risen sufficiently to appropriately match the tissue metabolic rate and prevent further accumulation of vasodilator factors.
What effects do endothelial cells have on vasoconstriction/vasodilation?
release substances:
vasodilators-nitric oxide, prostacyclin, "endothelial-derived hyperpolarizing factor"
vasoconstrictors-endothelin
What are the major neural influences in regulation of arterial blood pressure?
Sympathetic noradrenergic vasoconstrictor nerves
What are hormonal influences in regulation of blood pressure?
Vasocontriction-circulating epinephine and norepinephrine, aginine vasopressin, and angiotensin II
What controls venous tone?
Sympathetic noradrenergic nerves
What is the mechanism of arterial baroreceptors?
baroreceptors send afferents to synapse in the medulla, which upon processing will have three different responses:
1. enhance parasympathetics (decrease cardiac output)
2. enhance sympathetics (increase CO, vasoconstriction)
3. inhibit sympathetics (decrease CO, vasodilation)
What are barareceptor effects?
short term (within seconds/minutes) response
baroreceptor discharge is directly related to mean arterial pressure (MAP)
Decrease in MAP-->decrease in baroreceptor discharge-->increased sympathetic activity; decreased parasympathetic activity-->increased MAP
(initial increased MAP will have opposite effect)
What is the role of cardiopulmonary reflexes on arterial pressure?
Sense the pressure (or volume) in the atria and central venous pool. Increased central venous pressure and volume cause receptor activation by stretch, which elicits a reflex decrease in sympathetic activity. Decreased central venous pressure produces the opposite response
What are the role of chemoreceptors on arterial pressure?
Low PO2 and/or high PCO2 levels in the arterial blood cause reflex increases in respiratory rate and mean arterial pressure due to arterial chemoreceptors, located in the carotid arteries and the arch of the aorta, and central chemoreceptors, located somewhere within the CNS
What is the cerebral ischemic response?
An extremely strong reaction triggered by inadequate brain blood flow (ischemia) and can produce a more intense sympathetic vasoconstriction and cardiac stimulation than is elicited by any other influence on the cardiovascular control centers (last ditch effort to increase arterial pressure in order to perfuse the brain)
What is the long term regulation of blood pressure? How does it work?
fluid balance-works through mechanisms of the kidney and urinary output rate
What is the mechanism of fluid balance?
Decreased arterial pressure-->decreased glomerular capillary pressure-->decreased glomerular filtration rate-->decreased urine output
decreased glomerular filtration rate-->increased release of renin, then angiotensin II, then aldosterone-->increased renal sodium resorption-->increased renal fluid resorption-->decreased urinary output
(increased arterial pressure will have opposite effects)
explain regulation of arterial pressure via urine output
highly regulated-small changes in arterial pressure have big affects on urine output (very steep curve on graph)
How does hypertension affect the regulation of arterial pressure via urine output?
In hypertension, this mechanism is not as highly regulated. Changes in arterial pressure will have the same affects on urine output, but the affects are minimized (curve is not as steep)
Diuretics will help to get the regulation closer to normal (increase the slope of the graph)