CV VII

Question 1

What are two examples of local control of arteriolar resistance

Answer 1

1. Myogenic autoregulation
2. Paracrines

Question 2

Myogenic autoregulation

Answer 2

Ability of vascular smooth muscle in arterioles to constrict in response to stretch (stretch activated channels)
- maintain regular blood flow
- prevent damage from pressure

Question 3

What stretches smooth muscle of arterioles and causes constriction (Myogenic autoregulation)

Answer 3

• increased tension due to increased blood flow

Question 4

What stretch activated channels do arterioles have

Answer 4

TRP channels
Lead to mechanodepolarization

Question 5

What do paracrines do to alter vascular smooth muscle

Answer 5

Local control of blood flow is important in individual tissues regulating their own blood supplies

Question 6

Metabolism related paracrine signalling molecules

Answer 6

Decrease O2, increase CO2, NO, H+, lactate, adenosine

Question 7

Non-metabolism related paracrine signalling molecules?

Answer 7

Kinins and histamine (inflammation), serotonin

Question 8

What is the main determinant (>60%) of resistance in majority of arterioles

Answer 8

Sympathetic NS

Question 9

How do sympathetic neurons innervate arterioles

Answer 9

Tonically control arteriolar diameter through activation or deactivation of alpha 1 adrenergic receptors

Question 10

What does increased release of norepinephrine onto a receptors do to arteriolar diameter

Answer 10

As AP signal rate increases, blood vessel constricts

Question 11

What does decreased norepinephrine release onto a receptors do to arteriole diameter

Answer 11

As AP signal rate decrease, blood vessel dilates

Question 12

What is the secondary muscle involving sympathetic control of vascular smooth muscle

Answer 12

Release of epinephrine from adrenal medulla

Question 13

What does epinephrine had a low affinity and a high affinity for
What does it depend on

Answer 13

Low affinity for alpha receptors which lead to vasoconstriction
High affinity for B2 adrenergic receptors which lead to vasodilation
- depends on relative amount of each receptor

Question 14

What is an example of the body selectively alters blood flow to organs

Answer 14

Skeletal muscle receives ~20% of cardiac output at rest, but can increase as high as 85% during strenuous exercise

Question 15

What does regional amount of blood flow depend on at rest

Answer 15

Number and size of arteries feeding the organ

Question 16

How do arterioles all receive blood at the same time

Answer 16

Final ones that feed into capillaries are arranged in parallel

Question 17

What does the total blood flow through all the arterioles equals

Answer 17

The cardiac output

Question 18

What does flow for each arteriole depend on

Answer 18

The resistance
If arteriole constricts resistance increases and blood flow decreases

Question 19

How does arterioles take path of least resistance

Answer 19

Diverts away from high resistance arterioles towards low resistance ones

Question 20

What is blood flow in 4 equal vessels where all are same size with same resistance

Answer 20

Equal blood flow
Total flow in equals total flow out

Question 21

What does the CNS coordinate in cardiovascular function

Answer 21

Coordinates reflex control of blood pressure and distribution of blood to tissues

Question 22

What’s the main integrating centre of cardiovascular function in CNS

Answer 22

Medullary cardiovascular control center (CVCC)

Question 23

What is CVCC

Answer 23

Main output region where parasympathetic and sympathetic outputs go to CV tissues and can change HR, SV, level of resistance

Question 24

What is primary function of CVCC

Answer 24

Ensures adequate blood flow to brain and heart by maintaining sufficient mean arterial pressure at all times

Question 25

How does CVCC work

Answer 25

Receives input from sensory receptors and other brain regions and has ability to alter function in a few organs or tissues
E.g., thremoregulatory centres in hypothalamus altering skin blood flow

Question 26

Baroreceptor reflex from CVCC

Answer 26

Primary reflex pathway for homeostatic control of mean arterial blood pressure
Ensures adequate pressure to pump blood to brain

Question 27

What are baroreceptors

Answer 27

Tonically active stretch sensitive mechanoreceptors that are situated on aorta and carotid artery

Question 28

When do baroreceptors increase firing rate

Answer 28

When increase in BP and they sense stretch in artery walls

Question 29

When do baroreceptors cause decrease in firing rate

Answer 29

Decreased BP

Question 30

How quickly does baroreceptor reflex happen

Answer 30

Very rapidly, within a few heart beats

Question 31

Local control of constricted arteriole causes

Answer 31

Increased resistance -> increased TPR
Increase TPR x same CO = increase MAP
Increase MAP -> baroreceptors fire -> baroreceptor reflex
Reflex -> decrease CO x increase TPR = MAP restored to normal

Question 32

Why does CO fall from 5L/min to 3L/min when stand up out of bed

Answer 32

Blood rapidly flows to lower extremities

Question 33

How long does it take baroreceptors to be activated after standing in morning

Answer 33

Two heart beats activation increases CO and peripheral resistance to increase MAP

Question 34

Why does baroreceptor reflex not work after extended bed rest

Answer 34

Unable to return MAP due to loss of blood volume