Lesson 24: Topic 20 - Regulation of Blood Flow

Question 1

the stimuli that causes vasodilation or vasoconstriction originates where?

Answer 1

in the specific tissue or organ which will then be a local regulatory mechanism
OR
can originate ‘centrally’ which will then be a systemic regulatory mechanism

Question 2

what is the purpose of having a local regulation of blood flow?

Answer 2

it is designed to ensure that a specific organ receives the blood flow it wants (not to regulate MAP)

Question 3

when a stimuli to cause vasodilation or constriction originates centrally, what is the main purpose?

Answer 3

to regulate MAP

Question 4

what does “intrinsic” regulatory mean in regards to local control of blood flow?

Answer 4

• signals within an organ are responsible for controlling blood flow to that organ
• not dependent on nerves or circulating hormones

Question 5

what are the “intrinsic” regulatory mechanisms of local control of blood flow?

Answer 5

1. active hyperemia / reactive hyperemia
2. flow auto-regulation

Question 6

what is active hyperemia / reactive hyperemia driven by?

Answer 6

a metabolite-dependent mechanism

Question 7

what does hyperemia refer to?

Answer 7

an increase in blood flow

Question 8

what is flow auto-regulation

Answer 8

somehow we are maintaining blood flow to a given organ

Question 9

true or false: as tissue metabolic activity increase, so does blood flow.

Answer 9

true

Question 10

active hyperemia occurs where?

Answer 10

in tissues with high but variable metabolic need like the skeletal muscle and the WITHIN brain (the blood within the brain already is being diverted to areas within the brain with high metabolic activity)

Question 11

what type of feedback loop is active hyperemia?

Answer 11

negative feedback loop

Question 12

what is the negative feedback loop of active hyperemia?

Answer 12

increased metabolic activity –> decreased O2 concentration and increases metabolites concentration like K+ and ATP –> nitric oxide production and smooth muscle relaxation –> vasodilation of arterioles –> increased blood flow –> reduces hyperemic response because the increased blood flow increases O2 concentration to then decrease metabolites and start back at step 2 (but nothing else happens)

Question 13

why is active hyperemia a negative feedback loop?

Answer 13

because once blood flow increases, it then goes to increase O2 concentration to stop the feedback loop and reduce the active hyperemia response and cause vasoconstriction

Question 14

what type of feedback loop is reactive hyperemia?

Answer 14

negative feedback loop

Question 15

what is an example of when we will need to use reactive hyperemia?

Answer 15

ischemia

Question 16

what starts / activates reactive hyperemia?

Answer 16

lack of blood flow
- often caused by a temporary compression of blood vessels

Question 17

whats the difference between active and reactive hyperemia?

Answer 17

active hyperemia is activated by metabolic activity and reactive hyperemia is activated by lack of blood flow
- the rest of the process is the same otherwise, even the negative feedback loop

Question 18

where does reactive hyperemia happen?

Answer 18

in skeletal muscle. if we have a very big contraction during exercise, that will stop blood blow and reduce blood flow and increase metabolites so we will relax our skeletal muscles, blood blow perfusion increases in skeletal muscle

Question 19

what does occlude blood flow mean?

Answer 19

stop blood flow

Question 20

when does reactive hyperemia happen?

Answer 20

during heart or skeletal muscle contraction
- also because of a blood pressure cuff

Question 21

ventricular contraction is the accumulation of?

Answer 21

metabolites

Question 22

during diastole, there is a period of flow recovery during ventricular relaxation, which type of local intrinsic control of blood flow is this because of?

Answer 22

reactive hyperemia

Question 23

where does flow auto-regulation occur?

Answer 23

in the kidney, brain

Question 24

what is the definition of flow auto-regulation?

Answer 24

blood flow to an organ is kept steady despite changes in BP or pressure gradients (delta P)

Question 25

when can flow auto-regulation not occur in blood flow?

Answer 25

not at very low pressure or very high pressures - because you cannot vasoconstrict strongly enough or vasodilate more than physiologically possible

Question 26

vasoconstriction is maintained by?

Answer 26

smooth muscle

Question 27

why is flow auto-regulation important in the kidneys?

Answer 27

because you want to make sure that the kidneys are filtering the blood and if you have too high of pressures, you do not want to exceed the ability of the kidneys to filter the blood and too high of blood flow to damage the kidneys

Question 28

what is flow auto-regulation due to?

Answer 28

the myogenic response

Question 29

what is a myogenic response?

Answer 29

refers to a reflux response of the arterioles to change blood pressure

Question 30

what does myo mean?

Answer 30

muscle

Question 31

true or false: flow auto-regulation is a muscle dependent response.

Answer 31

true

Question 32

in flow auto-regulation, increased arterial blood pressure leads to?

Answer 32

passive distension of arteriole wall - AKA leading to a passive stretch of the arteriole wall

Question 33

a passive stretch of the arteriole wall does what to the arteriole? (hint: diameter)

Answer 33

increases the arteriole diameter (makes sense because the wall is being stretched)

Question 34

when we have increased arteriole diameter, what happens?

Answer 34

vasodilation which leads to increased blood flow

Question 35

what happens to the smooth muscle cells when the arteriole wall is being stretched?

Answer 35

smooth muscle cells also stretch (they are literally apart of the arteriole silly)

Question 36

an increase in the stretch of the smooth muscle cells triggers what?

Answer 36

an increase in the cytosolic calcium inside the smooth muscle

Question 37

an increase in cytosolic calcium concentration will increase?

Answer 37

force generation of that muscle (increases contraction which will cause vasoconstriction in order to reduce blood flow)

Question 38

what type of feedback loop is flow auto-regulation?

Answer 38

negative feedback loop

Question 39

why is flow auto-regulation a negative feedback loop?

Answer 39

because we decrease blood flow which will then cause the blood vessel walls to relax and allowing blood flow to increase

Question 40

local regulatory mechanisms of blood flow is always which feedback loop?

Answer 40

negative

Question 41

if our smooth muscle is contracting more, does this cause the arteriole to constrict or dilate?

Answer 41

constrict

Question 42

low O2 and high CO2 causes vaso?

Answer 42

vasodilation (we want more blood flow for more oxygen)

Question 43

high NO generation causes vaso?

Answer 43

vasodilation

Question 44

increased endothelin causes?

Answer 44

vasoconstriction as well to reduce muscle blood flow at the level of the arteriole

Question 45

true or false: vasodilation is caused by decreased stretch reflex activity.

Answer 45

true

Question 46

what is systemic control of blood flow controlled by?

Answer 46

1. neural 2. hormonal

Question 47

the neural systemic control of blood flow is regulated by?

Answer 47

the sympathetic nervous system

Question 48

what is the main purpose of the systemic control of blood flow?

Answer 48

the regulate MAP

Question 49

true or false: there is no influence of the parasympathetic nervous system on the blood vessels or blood flow regulation.

Answer 49

true

Question 50

what is the baseline state (regular state) for the sympathetic nerves?

Answer 50

- sympathetic nerve is activated by CNS (response to stress or exercise) - cause sympathetic neuron to fire - produce repeated action potentials - going to stimulate the sympathetic neuron - increase sympathetic neuron activity - going to produce norepinephrine - norepinephrine attaches to alpha-adrenergic receptors that are located throughout the whole entire body but mostly on the smooth muscle - causes vasoconstriction

Question 51

what happens to SNS activity during exercise?

Answer 51

increased SNS activity

Question 52

how does exercise cause more vasoconstriction?

Answer 52

increased SNS activity, more norepinephrine to attach to a-adrenergic receptor on smooth muscle to cause vasoconstriction

Question 53

after exercise, SNS activity decreases. how does this cause vasodilation?

Answer 53

firing of APs and sympathetic neuron are low so that decreases the production or norepinephrine which leads to vasodilation

Question 54

increased vasoCONSTRICTION means what from MAP?

Answer 54

increases MAP

Question 55

constriction on the venous side of the vascular system is called?

Answer 55

vENoconstriction

Question 56

smooth muscle cells of arterioles and venules have alpha adrenergic receptors which cause?

Answer 56

vaso/veno-constriction

Question 57

arterioles in skeletal muscle have beta adrenergic receptors which induce?

Answer 57

vasodilation

Question 58

what does beta adrenergic receptors do?

Answer 58

counter the effects of alpha adrenergic receptors

Question 59

there is a greater binding affinity for norepinephrin or epinephrine on alpha adrenergic receptors?

Answer 59

norepinephrine

Question 60

there is a great binding affinity for norepinephrine or epinephrine on beta adrenergic receptors?

Answer 60

epinephrine

Question 61

epinephrine is produced by?

Answer 61

the adrenal medulla gland

Question 62

epinephrine produced by the adrenal medulla gland is released into?

Answer 62

plasma

Question 63

when epinephrine binds to the beta adrenergic receptors, it causes?

Answer 63

vasodilation

Question 64

in the arterioles, are there more alpha or beta adrenergic receptors?

Answer 64

more alpha adrenergic receptors in the arterioles

Question 65

true or false: by activating beta adrenergic receptors, there is less vasoconstriction than if only alpha adrenergic receptors were active

Answer 65

true - b-adrenergic counters the affects of alpha adrenergic receptors

Question 66

epinephrine causes vasodilation via?

Answer 66

beta adrenergic receptors

Question 67

true or false: usually both norepinephrine and epinephrine are present

Answer 67

true

Question 68

true or false: both norepinephrine and epinephrine can bind to the alpha adrenergic receptor

Answer 68

true