Page 175 - Physiology and Pathophysiology MNU 2024-2025 نظرى

Clinical pharmacy 2024/2025 Level 2 Pharm D Physiology and Pathophysiology (MD303)
Regulation of blood pressure

Baroreceptor Reflex Renin - Angiotensin - Aldosterone System (RAAS)

Characters fast neural mechanism Slow hormonal mechanism
Used for Minute-to-minute regulation of blood pressure (-Ve feedback system) Long-term regulation of blood pressure regulation
Occur through Baroreceptor  Stretch receptor located within the walls of Occur through adjustment of blood volume (through
Mechanism
the carotid sinuses & aortic arch kidney)

Steps 1.  ABP   Stretch on the receptor of the carotid sinus. 1.  ABP   in renal perfusion  Juxtaglomerular
2.  Stretch   firing rate of the carotid sinus nerve (which carries cells secretes  Renin.
information to the vasomotor center in the brain stem [Medulla Oblongata] 2. Renin ➔ catalyzes the conversion of
3. The set point for mean arterial pressure (Pa) in the vasomotor center Angiotensinogen to Angiotensin I in plasma.
[Medulla Oblongata] ➔ 100 mm Hg. 3. Angiotensin converting enzyme (ACE) ➔ catalyzes
 If Pa > 100mm Hg  response occur   ABP toward normal. the conversion of Angiotensin I (inactive) to
4. The main responses are : Angiotensin II (active).

  Parasympathetic outflow to the heart. 4.. Angiotensin II has the following effects:
  Sympathetic outflow to the heart and blood vessels: four effects: 1. VC of arterioles  TPR & ABP.
1.  Heart rate. 2.  Contractility & Stroke volume   COP   2. Stimulates Secretion of Aldosterone  Salt & Water
ABP. retention   Na+ reabsorption   ECF & ABP.
3.  VD of arterioles   TPR   ABP.
4.  VD of veins   unstressed volume   VR   COP.
The reverse responses occur in the case of  ABP

| P a g e 115