ROT 2: Hemodynamics

Question 1

Type of vessel with most elastic connective tissue

Answer 1

arteries

Question 2

type of vessel with most smooth muscle

Answer 2

arterioles

Question 3

which vessel aids in the control of arterial blood pressure the most?

Answer 3

arterioles, because they have more contractile smooth muscle.

Question 4

T/F: capillaries have smooth muscle

Answer 4

false. they are very thin with no smooth muscle to permit exchange of substances with tissues.

Question 5

Name the vessels involved in microcirculation

Answer 5

arterioles, metaarterioles, terminal arterioles, capillaries, and venules

all vessels with a diameter less than 100 micrometers.

Question 6

How can a portion of the blood bypass circulation?

Answer 6

1) through AV capillaries

2) through AV shunts.

Question 7

Poiseuille’s law applies to ___,___ flow of ___ fluids

Answer 7

steady, laminar flow of Newtonian fluids.

Question 8

What is steady flow?

Answer 8

signifies the absense of variations of flow in time. Aka, nonpulsatile flow

Question 9

What is a Newtonian fluid?

Answer 9

a homogenous fluid such as water

Question 10

____ is one of the main determinants of flow (Q)

Answer 10

PRESSURE

Question 11

Flow (Q) is directly related to

Answer 11

change in pressure

Question 12

Flow is inversely proportional to the ____

Answer 12

length of the tube

Question 13

How does flow relate to radius of a pipe?

Answer 13

flow varies DIRECTLY as the FOURTH POWER of the radius.

Question 14

How is Resistance related to radius of pipe?

Answer 14

Resistance is indirectly related to the fourth power of the radius.

Question 15

Resistance of ___ is a limiting factor of flow

Answer 15

arterioles

Question 16

How would manipulation of artery diameter affect flow?

Answer 16

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.

Question 17

If you shorten the arteriole by half, the flow volume will ____,

Answer 17

increase by 2. Flow is indirectly proportional to length. F = 1/L

Question 18

if you open additional arterioles in parallel, what would happen to the flow?

Answer 18

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.

Question 19

decreasing radius of arterioles should ___ flow. Why/

Answer 19

Decreasing radius of arterioles should DECREASE FLOW because there is MORE RESISTANCE .

Recall: resistance of arterioles is the limiting factor.

Question 20

Why is flow rate greater during periods of exercise?

Answer 20

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)

Question 21

Why are the effects of ARTERIAL radius greater during exercise than in non excersise

Answer 21

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

Question 22

What happens to flow when you mimic gravity in a rigid tube? distensible tube?

Answer 22

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.

Question 23

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?

Answer 23

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