15. Blood Flow

Each tissue controls its own...

blood flow in proportion to it's needs

Why does the body not give all the tissue all the blood flow it needs?

It would require many times more blood flow than the heart can pump

Increase in tissue metabolism and reduced oxygen availability lead to...

Increased tissue blood flow

Active Hyperemia

Increase in tissue blood flow due to an increase in metabolism

Reactive Hyperemia

Increase in blood flow after flow has been stopped for a short period.

Vasodilator Theory

the greater the rate of metabolism or the less the availability of oxygen or some other nutrients to a tissue, the greater the rate of formation of vasodilator substances in the tissue cells.

Vasodilators are released from cells during...

Increased metaobolism

Examples of vasodilator substances

Adenosine, CO2, adenine phosphate compounds, histamine, K+, H+

Oxygen is one of the metabolic nutrients required to cause...

Vascular muscle contraction

In the absence of oxygen...

Blood vessels would relax and dilate

Increased utilization of oxygen in tissues from metabolism...

Could decrease the availability of oxygen to smooth muscle fibers in local blood vessels, causing vasodilation

In the left ventricle during systole, the increase in ventricular pressure partially occludes some of the blood vessels supplying the heart, causing...

Reactive Hyperemia

In any tissue of the body, a rapid increase in arterial pressure causes an immediate...

Rise in blood flow

The return of flow toward the normal rate is called....

Autoregulation

Nitric Oxide

A vasodilator released from healthy endothelial cells

Endothelin

A powerful vasoconstrictor released from damaged endothelium

Norepinephrine

-activates a1-, a2-, b1-adrenergic receptors
-Released from sympathetic nerves and adrenal medulla

Activation of alpha receptors on the smooth muscle cells of blood vessels causes...

an increase in intracellular calcium concentration and which initiates a cascade that causes smooth muscle to contract.

When epinephrine binds to a1 and a2 adrenergic receptors in blood vessels, it will cause...

Vasoconstriction

When epinephrine binds to B2 adrenergic receptors in blood vessels, it will cause...

Vasodilation

Two dogs are anesthetized. One dog is infused intravenously with norepinephrine and the other with an equal dose of epinephrine. In which dog will there be a greater increase in peripheral vascular resistance and why?

Norepinephrine: Will increase peripheral vascular resistance more than epinephrine

Angiotensin II (Ang II)

causes vasoconstriction in arterioles but no in veins

Ang II acts in the kidneys to increase...

Absorption of salt and at the adrenal glands to case increase in aldosterone release.

ACE inhibitors prevent the formation of...

Ang II

How is Angiotensin II formed?

-Renin is released by the kidneys when a decrease in arterial pressure occurs.
-Renin acts on Angiotensinogen which is released from the liver, converting it to Angiotensin I
-Ang I is converted to Ang II in the lungs by ACE

Ace Inhibitors are used for patients with...

Hypertension and Congestive Heart Failure

Vasopressin (Antidiuretic)

Formed in hypothalamus, transported down to posterior pituitary where it is secreted into blood.

Vasopressin is released in response to...

1. Decrease in arterial pressure
2. Increase in plasma osmolarity

Actions of Vasopressin

1. Potent vasoconstrictor
2. Increases renal reabsorption of water

Histamine

Contained in mast cells in tissues and basophils in blood that are released in response to tissue damage, inflammation, or allergic reaction

Histamine is a powerful...

Vasodilator

Histamine will also increase...

Capillary permeability