Lecture 12: Control of blood flow

Question 1

Acute control of blood flow

Answer 1

Rapid changes in local vasodilation/vasoconstriction
Occurs in seconds/minutes
Theories include vasodilator theory and oxygent lack theory

Question 2

Long term control of blood flow

Answer 2

Increase in sizes/numbers of vessels

Occurs over days, weeks or months

Question 3

Vasodilator theory

Answer 3

Increased metabolism causes decreased oxygen availability, which causes formation of vasodilators

Question 4

Vasodilators include

Answer 4

Adenosine
Carbon dioxide
Adenosine phosphate compounds
Histamine
Potassium/hydrogen ions

Question 5

Oxygen lack theory

Answer 5

Decreased oxygen causes blood vessel relaxation causes vasodilation

Question 6

Vasomotion is

Answer 6

Cyclical opening and closing of precapillary sphincters

Number of precapillary sphincters open at any given time is roughly proportional to nutritional requirements of tissues

Question 7

Autoregulation

Answer 7

In any tissue, rapid increase in arterial pressure leads to increased blood flow
Within minutes, blood flow returns to normal even with elevated pressure

Question 8

Theories to explain autoregulation

Answer 8

Metabolic theory

Myogenic theory

Question 9

Metabolic theory

Answer 9

Increase in blood flow–>too much oxygen/nutrients–> washes out vasodilators

Question 10

Myogenic theory

Answer 10

Stretching of vessels–> reactive vasculature constriction

Question 11

Blood flow control mechanism in kidneys

Answer 11

Tubuloglomerular feedback- involves the macula densa/juxtaglomerular apparatus

Question 12

Have you looked at endothelial derived mechanism for blood flow control

Answer 12

OK maybe do that

Question 13

Humoral circulation control- Vasoconstriction

Answer 13

Norepinephrine
Epinephrine
Angiotensin II (Normally acts to increase total
Vasopressin (aka: ADH- very powerful vasoconstrictor)

Question 14

Humoral circulation control- Vasodilation

Answer 14

Bradykinins (also increases capillary permeability)

Histamine

Question 15

Adrenal medulla secretes

Answer 15

Epinephrine and norepinephrine

Question 16

Sympathetic system innervates

Answer 16

All vessels except capillaries

Primarily results in vasoconstriction

Question 17

Vasoconstrictor area in brain

Answer 17

Anterolateral portions of upper medulla
Transmits continuous signals to blood vessels
Continuous firing results in sympathetic vasoconstrictor tone
Partial state of contraction of blood vessels= vasomotor tone

Question 18

Vasodilator area in brain

Answer 18

Bilateral in the anterolateral portions of lower medulla

Inhibits activity in vasoconstrictor area

Question 19

Sensory area in brain

Answer 19

Bilateral in tractus solitarius in posterolateral portion of medulla
Recieves signals via Vagus nerves (CN X) and glossopharyngeal nerves (CN IX)

Question 20

Controlled by higher nervous centers

Answer 20

Reticular substance (RAS)
Hypothalamus
Cerebral cortex

Question 21

Baroreceptors function/location

Answer 21

Inhibit vasoconstrictor center
Stimulate vasodilator center
Located in carotid and aortic sinus

Question 22

Carotid sinuses baroreceptors are stimulated by pressure

Answer 22

Greater than 60mm Hg

Question 23

Aortic sinus baroreceptors are stimulated by pressure

Answer 23

Greater than 80mm Hg

Question 24

Signals from baroreceptors do what

Answer 24

Inhibit vasoconstrictor center
Excite vasodilator center
Signals cause either increase or decrease in arterial pressure
Primary function is to reduce the minute by minute variation in arterial pressure

Question 25

Chemoreceptors location

Answer 25

Carotid bodies in bifurcation of the common carotids and in aortic bodies

Question 26

Chemoreceptors are

Answer 26

Chemosensitive cells sensitive to lack of oxygen, carbon dioxide excess and hydrogen ion excess Signals pass through herrings nerves and vagus nerves

Question 27

Chemoreceptors play important role in

Answer 27

Respiratory control

Question 28

Increase atrial stretch results in

Answer 28

``` Reflex dilation of kidney afferent arterioles Increase in heart rate Signals to hypothalamus to decrease ADH Atrial natriuretic peptide to kidneys Decreased sodium reabsorption ```

Question 29

Reflex dilation of kidney afferent arterioles causes

Answer 29

Increases kidney fluid loss | Decreases blood volume

Question 30

Atrial natriuretic peptide (ANP) function

Answer 30

Signals kidneys to increase GFR and decrease Sodium reabsorption