Lecture 12: Control of Blood Flow I

Question 1

What is acute control of local blood flow?

Answer 1

rapid changes in local vasodilation/vasoconstriction
occurs in seconds to minutes
basic theories: vasodilator and oxygen lack theories

Question 2

What is long term control of local blood flow?

Answer 2

increases in size/ numbers of vessels

occurs over a period of days, weeks, or months

Question 3

What is vasodilator theory?

Answer 3

as metabolism increases, oxygen availability decreases resulting in formation of vasodilators

Question 4

What is the oxygen lack theory?

Answer 4

decrease in oxygen, the blood vessels relax resulting in vasodilation

Question 5

What is vasomotion?

Answer 5

cyclical opening and closing of precapillary sphincters

Question 6

Number of precapillary sphincter open at any give time is ______ to nutritional requirements of tissues

Answer 6

proportional

Question 7

What is reactive hyperemia?

Answer 7

tissue blood flow is blocked and once becoming unblocked blood flow increase 4-7x normal

Question 8

What is active hyperemia?

Answer 8

when any tissue becomes active, rate of blood flow increases

Question 9

What is blood flow auto regulation?

Answer 9

rapid increase in arterial pressure leads to increased blood flow
within minutes, blood flow returns to normal even with elevated pressure

Question 10

What theories explain auto regulation?

Answer 10

metabolic theory

myogenic theory

Question 11

What is the metabolic theory?

Answer 11

increase in blood flow —too much oxygen or nutrients —washes out vasodilators to reduce blood flow

Question 12

What is the myogenic theory?

Answer 12

stretching of vessels– reactive vasculature constriction to reduce blood flow

Question 13

How does the kidney control acute blood flow?

Answer 13

by tuboglomerular feedback

Question 14

How does the brain control acute blood flow?

Answer 14

increase in CO2 or H+ —–cerebral vessel dilation —washing out excess CO2 or H+

Question 15

How does the skin control acute blood flow?

Answer 15

blood flow linked to body temperature

sympathetic nerves via CNS

Question 16

What contributes to vasoconstriction in humoral circulation control?

Answer 16

norepinephrine
epinephrine
angiotensin II
vasopressin

Question 17

What contributes to vasodilation in humoral circulation control?

Answer 17

bradykinin

histamine

Question 18

the sympathetic system innervates all vessels except ______

Answer 18

capillaries

Question 19

Where is the vasoconstriction area in the brain?

Answer 19

anterolateral portions of upper medulla

Question 20

What does the vasoconstriction area in the brain do?

Answer 20

transits continuous singles to blood vessels

continual firing results in sympathetic vasoconstrictor tone

Question 21

where is the vasodilation area of the brain located?

Answer 21

bilateral in the anterolateral protons of lower medulla

Question 22

What does the vasodilator area of the brain do?

Answer 22

inhibits activity in vasoconstrictor area

Question 23

Where is the sensory area of the brain?

Answer 23

bilateral in tractus solitarius in posterolateral portion of medulla

Question 24

What does the sensory area of the brain do?

Answer 24

receive signals via

• vagus nerve
• glossopharyngeal nerves

Question 25

What areas of the brain are controlled by higher nervous centers?

Answer 25

reticular substance (RAS)
hypothalamus
cerebral cortex

Question 26

What causes neural rapid control of arterial pressure?

Answer 26

simultaneous changes
rapid response
increased blood pressure during exercise
alarm reaction

Question 27

What are the simultaneous changes that cause neural rapid control of arterial pressure?

Answer 27

constriction of most systemic arteries
constriction of veins
increased heart rate

Question 28

Where are baroreceptors located?

Answer 28

carotid sinuses and aortic sinus

Question 29

When are carotid sinuses stimulated?

Answer 29

by pressure >60 mm Hg

Question 30

When are aortic sinuses stimulated?

Answer 30

> 80 mm Hg

Question 31

What are the signals from baroreceptors?

Answer 31

inhibit vasoconstrictor center
excite vasodilator center
signals cause either increase or decrease in arterial pressure

Question 32

What is the primary function of a baroreceptor?

Answer 32

reduce the minute by minute variation in arterial pressure

Question 33

Where are chemoreceptors located?

Answer 33

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

Question 34

What do chemosensitive cells do?

Answer 34

sense lack of oxygen, carbon dioxide excess, and hydrogen ion excess

Question 35

Where do chemoreceptor signals pass through?

Answer 35

Herring’s nerve and vagus nerves

Question 36

Chemoreceptors play a important role in ______

Answer 36

respiratory control

Question 37

Low pressure receptors are located in the ____ and _____ arteries and play an important role in minimizing _______ in response to changes in blood volume

Answer 37

atria; pulmonary; pressure changes

Question 38

What does increase in atrial stress result in?

Answer 38

reflex dilation of kidney afferent arterioles
increase in heart rate
signals to hypothalamus to decrease ADH
atrial natriurteric peptide signals kidneys to increase GFR and decrease sodium reabsorption

Question 39

What happens when the kidney afferent arterioles are reflex dilated?

Answer 39

increase in kidney fluid loss

decreases blood volume

Question 40

What is arterial pressure?

Answer 40

cardiac output x total peripheral resistance

Question 41

Arterial pressure rises when total peripheral resistance is ______

Answer 41

acutely increased