Lecture 12

Question 1

Acute Blood Flow Control

Answer 1

Causes rapid changes in local vasodilation/vasoconstriction

Occurs in seconds to minutes

Question 2

Long-Term Blood Flow Control

Answer 2

Results in a increase in sizes/numbers of vessels

Occurs over a period of days, weeks, or months

Question 3

Vasodilator Theory

Answer 3

As metabolism increases, oxygen availability decreases; this results in the formation of vasodilators (adenosine, CO2, histamine, K+, H+, adenosine phosphate compunds)

Question 4

Oxygen (Nutrient) Lack Theory

Answer 4

As the concentration of oxygen decreases, blood vessels relax, which leads to vasodilation

Question 5

Vasomotion

Answer 5

Cyclical opening and closing of precapillary sphincters; # of precapillary sphincters open at any given time is roughly proportional to nutritional requirements of tissues; assumption is that smooth muscles require oxygen to remain contracted

Question 6

Reactive Hyperemia

Answer 6

Tissue blood flow is blocked from seconds to hours or more; when unblocked, blood flow increases 4-7 times normal

Question 7

Active Hyperemia

Answer 7

When any tissue becomes active, rate of blood flow increases

Question 8

Autoregulation

Answer 8

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

Question 9

Metabolic Theory

Answer 9

Increase in blood flow leads to too much oxygen or nutrients, which washes out vasodilators

Question 10

Myogenic Theory

Answer 10

Stretching of blood vessels leads to reactive vasculature constriction

Question 11

Kidney Blood Flow Control Mechanism

Answer 11

Tubuloglomerular feedback; involves the macula densa/juxtaglomerular appartus

Question 12

Brain Blood Flow Control Mechanism

Answer 12

Concentration of CO2 and/or H+ increases, which leads to cerebral vessel dilation, which washes out excess CO2 and/or H+

Question 13

Skin Blood Flow Regulation

Answer 13

Blood flow linked to body temperature and controlled by sympathetic nerves via CNS; 3mL/min/100g of tissue in COLD weather; 7-8 mL/min for entire body in HOT weather

Question 14

Vasoconstrictors under Humoral Circulation Control

Answer 14

Norepinephrine, epinephrine, angiotensin II (normally acts to increase total peripheral resistance), vasopressin (very powerful vasoconstrictor; major function is to control body fluid volume), catecholamines, endothelin

Question 15

Vasodilators under Humoral Circulation Control

Answer 15

Bradykinins (causes both vasodilation and increased capillary permeability), histamine (powerful vasodilator derived from mast cells and basophils), prostaglandins, nitric oxide

Question 16

Sympathetic System (What vessels it innervates and its function)

Answer 16

Innervates all vessels except capillaries and primarily results in vasoconstriction

Question 17

What secretes epinephrine and norepinephrine?

Answer 17

Adrenal medulla

Question 18

Vasoconstriction Area

Answer 18

Anterolateral portions of upper medulla; transmits continuous signals to blood vessels; continual firing results in sympathetic vasoconstrictor tone; partial state of contraction of blood vessels = vasomotor tone

Question 19

Vasodilator Area

Answer 19

Bilateral in the anterolateral portions of lower medulla; inhibits activity in vasoconstrictor area

Question 20

Sensory Area

Answer 20

Bilateral in tractus solitarius in posterolateral portion of medulla; receives signals via:
Vagus Nerves (CN X)
Glossopharyngeal Nerves (CN IX)

Question 21

Neural Rapid Control of Arterial Pressure

Answer 21

Simultaneous Changes: Constriction of most systemic arteries, constriction of veins, and increased heart rate

Rapid response, increased blood pressure during exercise (accompanied by vasodilation), and alarm reaction (fight or flight)

Question 22

Baroreceptors

Answer 22

Located in carotid sinuses and aortic sinus; stimulated by low arterial pressures; controlled by reticular substance (RAS), hypothalamus, and cerebral cortex

Question 23

At what pressure is carotid sinus baroreceptors stimulated?

Answer 23

> 60 mm Hg

Question 24

At what pressure is aortic sinus baroreceptors stimulated?

Answer 24

> 80 mm Hg

Question 25

Signals from baroreceptors do what?

Answer 25

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 26

Chemoreceptors

Answer 26

Located in carotid bodies in bifurcation of the common carotids and in aortic bodies; chemosensitive cells sensitive to lack of oxygen, carbon dioxide excess, and H+ excess; signals pass through Herring’s nerves and vagus nerves and play a more important role in respiratory control

Question 27

Atrial Reflexes

Answer 27

Low pressure receptors are located in the atria and pulmonary arteries and play an important role in minimizing arterial pressure changes in response to changes in blood volume

Question 28

Increase in Atrial Stretch results in:

Answer 28

Reflex dilation of kidney afferent arterioles (increases kidney fluid loss, decreases blood volume), increase in heart rate (via CN X to medulla), signals to hypothalamus (to decrease ADH), atrial natriuretic peptide, which goes to the kidneys to increase glomerular flow rate and decrease Na+ reabsorption

Question 29

How is arterial pressure calculated?

Answer 29

Cardiac output X total peripheral resistance