Lecture 3: Vascular Reactivity

Question 1

The arterial system converts ___________ or ___________ outflow from the heart into a steady flow of blood through the ____________

Answer 1

Intermittent or Pulsatile

Capillaries

Question 2

Flow velocity is _________ proportional to the cross sectional area of all the blood vessels in a given part of the vascular tree

Answer 2

Inversely proportional

Question 3

As we move away from the heart what happens to the elasticity of the vessels?

Answer 3

They become less elastic

Question 4

Why do the aorta and large vessels have large diameters and high elasticity?

Answer 4

Allows them to handle large volumes of blood and propel them along the vessels

Question 5

Arterioles are high ___________ vessels with a relatively large amount of __________.

Answer 5

Resistance

Smooth Muscle

Question 6

What is the Windkessel effect?

Answer 6

Elastic vessels can expand when blood volume increases and then recoil to help propel blood along

Question 7

Blood flows ________ in the capillaries to facilitate gas exchange

Answer 7

slowly

Question 8

How do we calculate the rate of blood flow?

Answer 8

F=ΔP/R
F = flow rate
P = pressure
R = resistance

Question 9

What is axial streaming?

Answer 9

During fast blood flow, RBC congregate in the center of the vessel to reduce resistance or frictional force caused by collisions with the vessel walls

Question 10

In healthy blood vessels, blood flow is _________ and flow is faster in the _______.

Answer 10

Laminar

Center

Question 11

What is blood pressure?

Answer 11

The force exerted against a vessel wall, it depends on the volume of blood and the vessel compliance

Question 12

What is pulse pressure?

Answer 12

PP = SBP-DBP, it is directly affected by stroke volume and vessel compliance

Question 13

Why does SBP increase?

Answer 13

Blood is ejected into the aorta by the left ventricle

Question 14

Why does DBP decrease?

Answer 14

Due to peripheral run-off from the arteries to the microcirculation

Question 15

What are the formulas for Mean Arterial Pressure?

Answer 15

MAP = 2/3 DBP + 1/3 SBP = DBP + 1/3 PP

Question 16

Kortkoff sounds occur when there is _______________ through the vessels after it is no longer occluded

Answer 16

Turbulent blood flow

Question 17

Vessels compliance ____________ with age

Answer 17

decreases

Question 18

Why can we control the flow through the microcirculation?

Answer 18

Lots of smooth muscle in the arterioles

Question 19

What causes vasoconstriction?

Answer 19

↑ myogenic activity 
↑ P O2
↑ Sympathetic stimulation 
↓P CO2
Changes in the endothelium

Question 20

What causes vasodilation?

Answer 20

↑ P CO2
↑ NO
↓myogenic activity
↓ P O2
↓ Sympathetic stimulation

Question 21

What is flow-mediated dilation (FMD)?

Answer 21

Blood flow exerts a shear stress on the vessel wall this causes vasodilation via NO

Question 22

What causes NO release

Answer 22

Shear stress leads to the activation of endothelial Nitric Oxide Synthase (eNOS) via mechanotransduction.

Question 23

In the endothelium eNOS converts __________ to NO

Answer 23

L-Arginine

Question 24

In the smooth muscle, NO causes _____ to convert GTP to _______.

Answer 24

sGC

cGMP

Question 25

How does increasing age affect NO?

Answer 25

↓ NO production and ↑ NO breakdown

Question 26

What is active hyperaemia?

Answer 26

↑ blood flow caused by metabolic changes associated with ↑ muscle activity (Exercise –> ↓ P O2 –> vasodilation –> ↓ Resistance –> ↑ flow)

Question 27

What is reactive hyperaemia?

Answer 27

↑ Blood flow caused by metabolic changes associated with vessels occlusion. Blood flow ↑ after occlusion to remove metabolites that have accumulated (magnitude is proportional to the duration of occlusion)

Question 28

What is Autoregulation?

Answer 28

myogenic response to stretch, ↑ stretch –> vasoconstriction

Question 29

Autoregulation allows __________ regardless of a change in ____.

Answer 29

stable flow

MAP