Local blood flow is controlled through both acute and long-term mechanisms. Acute control involves rapid changes in vasodilation and vasoconstriction in response to tissue metabolism and oxygen availability, mediated by vasodilator and vasoconstrictor substances. Long-term control involves changes in tissue vascularity through growth factors to meet metabolic needs over time. Both humoral factors and ion concentrations also regulate blood flow through vasoactive effects. Precise control of local blood flow is crucial for efficiently delivering nutrients and oxygen to tissues while minimizing cardiac workload.

1. Local Control of Blood
Flow
By:
M. Rasjad Indra
Lab. Ilmu Faal FK UNIBRAW

2. Introduction
 The greater the metabolism  the greater
its blood flow
– Liver: 95 ml/min/100 g of liver tissue.
– Kidneys: 1100 ml/min  cleansing the blood.
 The importance of blood flow control 
effective & efficient
– Serving metabolic need
– Efficient heart workload.

3. Mechanism of Blood Flow Control
 Acute control (rapid changes in local vasodilatation /
vasoconstriction):
– Effect of tissue metabolism
– The availability of oxygen changes.
– Two basic theories:
 Vasodilator theory: adenosine; CO2; histamine; K+ & H+
 Oxygen lack theory: vasomotion in metarterioles & precapillary
sphincters.
– Other nutrients besides Oxygen:
– Lack of glucose  vasodilatation
– Vitamin B deficiency  vasodilatation

5. The examples of acute metabolic
control of local blood flow
1. Reactive hyperemia
• Blocked (seconds – hours)  unblocked
• Blood flow increases to 4 – 7 times normal
• Depends on how long it is blocked.
2. Active hyperemia
• Tissue activity lack of nutrient & release
vasodilator substances.
• Local blood flow increases 20 times in
muscle during heavy exercise.

6. Blood flow control & The arterial
pressure changes
 Acute autoregulation theory:
1. The metabolic theory
2. The myogenic theory (still doubtful !!)
 Endothelial-Derived Relaxing Factor
“EDRF” (NO):
– Rapid flow of blood  shear stress NO
release  relaxes the local arterial wall.

8. Long Term Blood Flow Regulation
1. Change in Tissue Vascularity
– Reconstruction to meet the needs of the
tissues
– Role of Oxygen in Long-Term Regulation.
– Vascular Endothelial Growth Factors:
1. VEGF
2. FGF
3. Angiogenin
2. Collateral Circulation:

9. Humoral Regulation of The Circulation
1. Vasoconstrictor Agents:
1. Norepinephrine & Epinephrine
2. Angiotensin
3. Vasopressin
4. Endothelin
2. Vasodilator Agents:
1. Bradikynin
2. Histamin
3. Effects of Ion & Other Chemical Factors
1. Calcium  vasoconstriction
2. Potasium  Vasodilatation
3. Magnesium  powerful vasodilatation
4. Hydrogen  vasodilatation
5. Acetate & Citrate  mild degree vasodilatation

10. Humoral Regulation of The Circulation
1. Vasoconstrictor Agents:
1. Norepinephrine & Epinephrine
2. Angiotensin
3. Vasopressin
4. Endothelin
2. Vasodilator Agents:
1. Bradikynin
2. Histamin
3. Effects of Ion & Other Chemical Factors
1. Calcium  vasoconstriction
2. Potasium  Vasodilatation
3. Magnesium  powerful vasodilatation
4. Hydrogen  vasodilatation
5. Acetate & Citrate  mild degree vasodilatation