Mechanisms of Blood Flow Control

Oct 9, 2024

Cardiovascular Network: Control of Blood Flow

Introduction

  • Focus: Control of blood flow to the system.
  • Previous discussions: Structures of arteries, veins, capillaries, and fluid movement.
  • Current topic: How arteries and veins regulate flow to capillaries.

Blood Flow Control Mechanism

  • Local Control: Similar to local governance.

    • Capillaries communicate with nearby arterials and arteries.
    • Governed by direct interaction in small areas.

  • Hierarchy of Control:

    • Local capillaries manage immediate needs.
    • Larger scale oversight from broader system (e.g., hormones).

Local Control

  • Acute Control:

    • Short-term regulation involving molecule release affecting smooth muscle cells.
    • Can dramatically change local fluid movement (up to sevenfold changes).

  • Long-term Control:

    • Adjustments based on continuous needs leading to structural changes (e.g., angiogenesis).
    • Example: Increased blood flow to muscles with regular exercise.

Hormonal Control

  • Hormones and neurotransmitters signal vessels to adjust.

Key Features of Local Control

  • Sensitivity to Oxygen:
    • Capillary beds respond to oxygen levels.

Vasodilator Theory

  • Cells release adenosine in response to high activity and ATP breakdown.
  • Adenosine signals for increased blood flow to meet oxygen demands.
  • Represents acute regulation.

Myogenic Response

  • Smooth muscles in capillaries react to oxygen levels, influencing contraction.
  • Oxygen-deficient areas cause dilation and increased blood flow.

CO2 and Oxygen Regulation

  • CO2 Increase:
    • Indicates high cellular activity, leading to vasodilation and increased blood flow.

Oxygen Demand Theory

  • High Blood Pressure Response:
    • Excess oxygen causes smooth muscle contraction to protect capillaries.
    • Can lead to backed-up pressure, a sign of inadequate mechanism.

Myogenic Theory

  • Stretch Response:
    • Stretch in capillaries enhances contraction ability, causing vasoconstriction.

Conclusion

  • Study Importance:

    • Mechanisms crucial for understanding and will be tested.

  • Next Steps:

    • Review and discuss in lab sessions.

  • Exam Preparation: Key topics will be included in the midterm.