WEEK 5: CH 17--Tissue Blood Flow & CH 18: Nervous Regulation of Circulation and Rapid Control of Arterial Pressure

Question 1

Chapter 17 Local and Humoral Control of Tissue Blood Flow

1. Blood flow to tissues is________ between the tissues metabolic needs and the total volume of blood the heart can handle.
2. “Experiments have shown that the blood flow to each tissue usually is regulated at the ________ level that will supply the tissue’s requirements—no more, no less”
3. With this level of control, the tissues are able to meet their needs and the workload on the heart is kept to a _______

Answer 1

balanced

minimal

minimum.

Question 2

Mechanisms of Blood Flow

1. ———— Control—occurs within seconds to a few
   minutes.
2. _____-________ Control—takes days, weeks, months
   for this level of control to be established. These
   changes are a result of an increase or decrease
   in physical size and the number of blood vessels
   supplying these tissues.

Answer 2

Acute

Long-Term

Question 3

Reasons for ↓ O2 availability :

1. high altitude
2. Pneumonia
3. Carbon Monoxide (CO) poisoning (Hb has higher affinity for CO than O2)
4. Cyanide poisoning (tissues are poisoned and unable to use O2)

Answer 3

know theses 4

Question 4

Many physiologists believe that_________ is a powerful
vasodilator for coronary and skeletal muscle blood
flow.

Answer 4

adenosine

Question 5

Regulation of local blood flow when either metabolism ↑ or the concentration (availability) of O2 ↓.

(1) Vasodilator Theory—when tissue metabolism ↑ or
O2 concentration ↓

(2) Oxygen Lack (Oxygen Demand) Theory—oxygen is needed for the ________ muscle in the arterioles and pre-capillary sphincter to contract.

Therefore, if oxygen supply is NOT adequate, the smooth muscles simply relaxes and naturally dilate (local vasodilation) . This ___________ local blood flow.

Answer 5

smooth

increases

Question 6

____________ of arterioles which increases tissue blood flow = Adenosine and other ADP compounds, CO2, histamines, K+, H+.

Answer 6

Vasodilators

Question 7

Other nutrients that may assist in local blood flow:

1. __________of glucose, amino acids or fatty acids in perfusing blood can cause local vasodilation—don’t have the nutrients to make ATP.
2. Vitamin B substances—thiamine, niacin, and riboflavin are needed for the oxygen-induce phosphorylation of ATP so if they are NOT present (as in the disease called beriberi), then ______ cannot be made.
3. Without the nutrients listed above, adequate levels of ATP cannot be made therefore, the smooth muscles of the arterioles and pre-capillary sphincters cannot contract effectively thus vasodilation occurs

Answer 7

Deficiency

ATP

Question 8

Two additional examples of metabolic control

1. _________ Hyperemia—an increase in blood flow after a
   temporary blockage (occlusion or interruption). During the hyperemia, the tissue becomes re-oxygenated and
   vasodilator metabolites are washed out of the tissue. This
   causes the blood vessels to regain their normal tone.
2. ______ Hyperemia –increased flow of blood to a tissue
   associated with increased metabolism. Blood flow increases because of increased oxygen consumption during muscular contractions which stimulates the production of vasodilator substances which then dilate the blood vessels in the skeletal muscles.

Answer 8

Reactive

Active

Question 9

_____________ –is the process where tissues adjust blood flow over a wide range of arterial pressure changes. While most systems of the body show some degree of autoregulation, it is most clearly observed in the kidneys, the heart, and the brain.

Answer 9

Autoregulation

Question 10

Metabolic Theory suggests that as arterial pressure
decreases, O2 and nutrient delivery decreases resulting
in the release of ______substances.

Answer 10

vasodilator

Question 11

______ Theory suggests that as arterial pressure falls, the arterioles vasodilate as a result of an intrinsic property that responds to a decrease in blood vessel wall tension.

Answer 11

Myogenic

Question 12

Control of Tissue Blood Flow by Endothelial Factors

Nitric Oxide (NO)—as a vasodilator:

As blood flows through the blood vessels, the
viscous nature of blood creates “shear stress”
because of the drag against the _________ walls.

Answer 12

endothelial

**This increase in NO release protects against excessive
vasoconstriction.

Question 13

____________—a powerful vasoconstrictor substance derived from damaged endothelial cells. When blood vessels have been severed, release of endothelin and the subsequent blood vessel vasoconstriction, prevents extensive bleeding from the major arteries

Answer 13

Endothelin

Question 14

If metabolism of a tissue is increased over a
prolonged period of time, such as starting a
regular exercise program, then the number
and size of blood vessels to those muscles will
increase.
• The growth of new blood vessels is called
________________

Answer 14

angiogenesis.

Question 15

three peptides have been identified as “angiogenic factors” that lead to the formation of new blood vessels.

1. Vascular endothelial growth factor (VEGF)
2. fibroblast growth factor (FGF)
3. angiogen

are the three angiogenic factors.

**They cause new vessels to sprout and then develop
from other small vessels.

Answer 15

KNOW

Question 16

___________ Circulation—occurs when an artery or
vein is blocked so a new vascular channel
develops around the blockage.

Answer 16

Collateral

Question 17

Humoral Control of Circulation

Humoral control is by means of hormones or locally
produced factors that are absorbed into the body
fluids.

Answer 17

KNOW

Question 18

Vasoconstrictor Agents X5

1 • Norepinpherine and epinephrine— are secreted from the adrenal medulla as a response to sympathetic nerve stimulation during times of stress or exercise—”Fight or
Flight mechanism.”

2 • Angiotensin II—– plays a significant role in regulating arterial pressure by vasoconstriction of small arterioles to increase total peripheral resistance, thereby increasing arterial pressure.

3 • Vasopressin (also called antidiuretic hormone)—- plays a similar role as Angiotensin II in increasing arterial
pressure.

Answer 18

KNOW

4..5…Histamine is released due to tissue damage or
inflammation. Like bradykinin, it causes a powerful
arteriole vasodialtion and increases capillary
permeability allowing leakage of fluid and plasma
proteins into the interstitial fluid for the tissues.

Question 19

Other Chemical Agents that have Vascular Control

1. Ca2+–vasoconstrictor; stimulates smooth
   muscle contraction.
2. K+–vasodilator; inhibit smooth muscle
   contraction.
3. Mg+– vasodilator; inhibit smooth muscle
   contraction.
4. ↑H+–vasodilator; ↓H+–vasoconstrictor
5. CO2—vasodilator

Answer 19

KNOW

Question 20

All blood vessels except
the capillaries are
innervated by sympathetic
nerves.

Answer 20

Innervations of the veins 
decreases the volume in 
these vessels to return 
more blood to the heart 
(increase venous return ).

Question 21

sympathetic vasoconstrictor tone.

These constant impulses
maintain a partial state of
contraction of the blood
vessels called _________ tone.

Answer 21

vasomotor

Question 22

There are reflex mechanisms that operate on a NEGATIVE feedback system to maintain normal pressure.

These reflex mechanisms include:

1. Baroreceptor Reflex
2. Chemoreceptor Reflex
3. Atrial Reflexes
4. CNS Ischemic Response

Answer 22

KNOW

Question 23

The baroreceptors oppose both increases and
decreases in arterial pressure, thus they are
referred to as “_______ __________.” Feedback
signals are sent via the ANS to the circulation to reduce
arterial pressure back to normal.

Answer 23

pressure buffers

Question 24

Both the atria and the pulmonary artery have stretch

receptors in their walls called low-pressure receptors

Answer 24

KNOW

Question 25

LOW BLOOD FLOW to the brain increases CO2 levels
dramatically which has a potent effect of stimulating
the sympathetic VMC in the medulla to increase arterial pressure.

CNS Ischemic Response— is one of the most powerful of all activators of the sympathetic VASOCONSTRICTOR system.

Answer 25

The CNS ischemic response is often called the “last ditch” stance to control arterial BP because it only operates under emergency situations where blood flow to the brain is dangerously diminished.

***It doesn’t do it’s significant work until BP falls to 15-20
mmHg.