Local and Humeral Control of Tissue Blood Flow

Question 1

Active Hyperemia vs Reactive Hyperemia

Answer 1

Increase in blood flow associated with increase in tissue or organ metabolism

Increase in blood flow after a period of decrease

Question 2

Mechanism of Local Control

Answer 2

2 Different Theories:

1) Vasodilators released from cells during increased metabolism
Exs - Adenosine, CO2, adenosine phosphate compounds, histamine, potassium ions, and hydrogen ions
Vasodilators can be released due to decrease in oxygen levels as well

2) Decrease in tissue oxygen levels causes a direct increase in flow due to dilation of vessels

Question 3

Humeral Regulation of Blood Flow

Answer 3

Vasoconstrictors and vasodilators traveling through blood t

Question 4

Vasoconstrictors

Answer 4

1) Norepinephrine (more intense) and Epinephrine are produced initially by the sympathetic nervous system in order to excite heart and contract blood vessels THEN they signal the adrenal medullae to secrete more of these substance to circulate in the blood providing prolonged effects
2) Angiotensin II - very strong; constricts small arterioles = increase total peripheral resistance = inc in arterial P
3) Vasopressin (Antidiuretic Hormone) - Body’s most potent vascular constrictor

Question 5

Angiotensin II Mechanism

Answer 5

1) Dec in arterial P stimulates release of Renin from kidneys
2) Renin stimulates conversion of Angiotensin to Angiotensin I
3) Angiotensin I is then converted to Angiotension II through the activation of the Angiotensin Converting Enzyme
4) Angiotensin II causes constriction of arterioles
5) Angiotensin II ALSO causes an increase in aldosterone release and sodium reabsorption

Question 6

Vasodilators

Answer 6

1) Histamine - Increases dilation of arterioles and pores in capillaries allowing fluid and plasma proteins to leave to vessels = can cause issues if not controlled
2) Nitric Oxide

Question 7

Vasopressin

Answer 7

Antidiuretic Hormone

Body’s most potent vascular constrictor

Created in the hypothalamus and secreted form the posterior pituitary gland into the blood

Responds to dec in arterial P AND inc in plasma osmolarity

Causes inc in arterial pressure after hemorrhaging (mainly controls renal reabsorption in kidney = small role in vascular control

Release is inhibited by alcohol consumption