Lecture Notes: Blood Vessels and Blood Pressure Regulation

Announcements

• Discussion on blood vessels will continue and conclude on Wednesday.
• Blackboard outage led to an extension for pre-labs and in-class activities, now due tonight at midnight.
• Lab focus: Lymphatic vessels, blood pressure.
• Lab practical discussion upcoming; major portion on blood vessels.
• Dynamic study modules for blood vessels due on Friday.

Blood Pressure Regulation

Key Concepts

• Regulation involves short-term and long-term mechanisms.
• Factors affecting blood pressure:
  • Blood flow and resistance (Equation: Blood Flow = ΔPressure/Resistance)
  • Stroke volume, heart rate, cardiac output.
  • Vascular resistance (Vasoconstriction, blood viscosity, vessel length).

Short-term Regulation

• Neural Controls:

  • Baroreceptors (pressure sensors) in aortic arch and carotid sinus.
  • Cardiac center (affecting heart rate and stroke volume) and vasomotor center (affecting vessel diameter) in the medulla oblongata.
  • Sympathetic and parasympathetic influences.

• Hormonal Controls:

  • Hormones affecting cardiac output and vasoconstriction:
    • Epinephrine/Norepinephrine (increases cardiac output and BP).
    • Anti-diuretic hormone and Angiotensin (promote vasoconstriction and increase BP).
    • Atrial natriuretic peptide (promotes vasodilation, decreases BP).

Long-term Regulation

• Kidneys and Blood Volume:
  • Adjustments in blood volume can influence long-term BP regulation.
  • Renin-Angiotensin-Aldosterone system:
    • Renin release leads to Angiotensin production, causing vasoconstriction.
    • Increases aldosterone and anti-diuretic hormone release, promoting water reabsorption and increased blood volume.

Case Study: Diving Reflex

• Mechanism:

  • Increased BP due to vasoconstriction during breath-hold diving.
  • Baroreceptors trigger neural response to lower heart rate.

• Example Data:

  • Seals exhibit significant heart rate reduction during long dives.

Intrinsic and Extrinsic Regulation

Localized Control (Autoregulation)

• Intrinsic Control: Local tissue needs dictate blood flow changes.
  • Exercise: Increase in blood flow to skeletal muscles, decrease to digestive organs.
  • Heat: Vasodilation in skin to release heat.

Long-Term Adaptation

• Angiogenesis: Growth of blood vessels in response to prolonged increased demand (exercise).
  • Vascular endothelial growth factor (VEGF) stimulates new blood vessel formation.

Study Data Interpretation

• Birds Experiment: Seasonal variation in capillaries and water loss.
  • Summer birds exhibit more capillaries due to higher VEGF levels.

Conclusion

• Blood pressure and flow are regulated through a balance of neural, hormonal, and intrinsic mechanisms.
• Practical application in anticipating responses in different physiological states.