I first covered the fast and moderate control mechanisms which I think are

Fast control: Baroreceptive reflex (tonus), Chemoreceptive reflex (CO$_2$). Moderate control: Bicarbonate (ECF), Phosphate buffer (ECF), Proteins (ICF).

then late control mechanisms about which I am unsure

  • Capillary fluid shift mechanisms
  • Stress-relaxation of the vasculature
  • RAA

What are the late control mechanisms of blood pressure?


Capillary fluid shift mechanisms

If the pressure of the blood is high, there is high hydrostatic pressure. Simply put, this means fluid exits the capillaries at the arterial side due to this pressure, and less fluid returns at the venous side. With less fluid in the circulation, blood pressure falls.

Stress-relaxation of the vasculature

Imagine the arteries are like springs. The more you pull them the stronger the recoil force. However if you stretch them too much for too long, they stay stretched.

Renin-Angiotensin-Aldosterone system

When the blood pressure is high, there is less release of renin from the kidneys. This means less angiotensin II production. Angiotensin acts to increase blood pressure by increasing vasoconstriction and increasing retention of fluid and salt (via aldosterone). With less RAA system activation, the blood pressure drops.

  • $\begingroup$ Can you say about the stress-relaxation of vasculature that high ICF leads to increased diameter and length of arteries? $\endgroup$ – Léo Léopold Hertz 준영 Feb 17 '14 at 5:59

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