ROT 2: Hemodynamics Flashcards
Type of vessel with most elastic connective tissue
arteries
type of vessel with most smooth muscle
arterioles
which vessel aids in the control of arterial blood pressure the most?
arterioles, because they have more contractile smooth muscle.
T/F: capillaries have smooth muscle
false. they are very thin with no smooth muscle to permit exchange of substances with tissues.
Name the vessels involved in microcirculation
arterioles, metaarterioles, terminal arterioles, capillaries, and venules
all vessels with a diameter less than 100 micrometers.
How can a portion of the blood bypass circulation?
1) through AV capillaries
2) through AV shunts.
Poiseuille’s law applies to ___,___ flow of ___ fluids
steady, laminar flow of Newtonian fluids.
What is steady flow?
signifies the absense of variations of flow in time. Aka, nonpulsatile flow
What is a Newtonian fluid?
a homogenous fluid such as water
____ is one of the main determinants of flow (Q)
PRESSURE
Flow (Q) is directly related to
change in pressure
Flow is inversely proportional to the ____
length of the tube
How does flow relate to radius of a pipe?
flow varies DIRECTLY as the FOURTH POWER of the radius.
How is Resistance related to radius of pipe?
Resistance is indirectly related to the fourth power of the radius.
Resistance of ___ is a limiting factor of flow
arterioles
How would manipulation of artery diameter affect flow?
increasing resistance to artery will NOT BE NOTICES as much as arterioles would be noticed, unless the artery’s radius is constricted to the point of being smaller than the arteriole.
If you shorten the arteriole by half, the flow volume will ____,
increase by 2. Flow is indirectly proportional to length. F = 1/L
if you open additional arterioles in parallel, what would happen to the flow?
there will be more volume of blood running through the arterioles.
flow will be the SUM of the flow in each arteriole as if they were separate.
decreasing radius of arterioles should ___ flow. Why/
Decreasing radius of arterioles should DECREASE FLOW because there is MORE RESISTANCE .
Recall: resistance of arterioles is the limiting factor.
Why is flow rate greater during periods of exercise?
the arterioles are dilated/expanded. this results in DECREASED RESISTANCE of arterioles, allowing for blood to flow easier through them.
The arterioles are no longer being the limiting factor of flow, there is now more resistance coming from the artery, which is having to deal with increased cardiac output volumes (may be getting more narrow/less space)
Why are the effects of ARTERIAL radius greater during exercise than in non excersise
when not exersising, arteries do not play a role in limiting flow, typically its the arteriolar resistance that limits flow at rest.
when exercising, the arterioles dilate and have less resistance. Arterioles no longer
What happens to flow when you mimic gravity in a rigid tube? distensible tube?
Rigid tube: nothing happens
Distensible tube: needs to be fully filled with water to establish EQUAL hydrostatic pressure on both sides of the vein in order for flow to continue. Mimics standing up.
what happens to flow in the lwoer limbs and to venous return when we stand up from reclining? What is the physiological response to correct this situation?
there is a sharp decrease in venous return when standing up due to gravitational effects. There is unequal hydrostatic pressure on both sides of the distensible vein, causing a huge decrease in BP
The baroreceptors recognize this drop in BP and send afferent signals to the medulla. Sympathetic activity is increased and venous vasoconstriction is initiated through alpha adrenergic receptor activation, causing an increase in pressure and increased flow rate
