Renin-Angiotensin-Aldosterone System (RAAS)

Overview

• RAAS: A system of hormones, proteins, enzymes, and reactions for long-term regulation of blood pressure and blood volume.
• Primary Function: Increases sodium reabsorption, water retention, and vascular tone.

Key Components

• Renin: An enzyme.
• Angiotensin II: A hormone.
• Aldosterone: A hormone.

Definitions

• Enzymes: Proteins that trigger chemical reactions.
• Hormones: Chemicals that coordinate body functions by sending signals through blood.

Blood Pressure

• Definition: Measurement of force inside arteries with each heartbeat.
• Factors Influencing: Blood volume pumped by heart, artery diameter, medications, cholesterol, smoking.

RAAS vs. Baroreceptor Reflex

• RAAS: Long-term regulator of blood volume and systemic vascular resistance.
• Baroreceptor Reflex: Short-term response to blood pressure changes through autonomic nervous system.

Organs and Systems Involved in RAAS

• Kidneys
• Liver
• Blood Vessels
• Lungs
• Adrenal Glands: Endocrine glands on top of kidneys.
• Pituitary Gland: Base of brain.
• Hypothalamus: Coordinates autonomic nervous system and pituitary activity.

Steps of RAAS

1. Renin Release: Triggered by low blood pressure, released by kidneys.
2. Angiotensin I Formation: Renin converts angiotensinogen from liver to angiotensin I.
3. Angiotensin II Formation: Angiotensin-converting enzyme (ACE) converts angiotensin I to II.
4. Effects of Angiotensin II: Causes arteries to constrict, adrenal glands to release aldosterone, and pituitary gland to release ADH.
5. Retention of Sodium and Water: Leads to increased blood volume and pressure.
6. Hormonal Activation: Also influenced by corticosteroids, estrogen, and thyroid hormones.

RAAS and Heart Failure

• Heart Failure: RAAS adaptations occur due to inadequate heart blood flow.
• Angiotensin II Excess: Worsens heart failure by increasing heart size.
• Medications: Beta-blockers, ACE inhibitors, angiotensin receptor blockers, MRAs.

Conclusion

• Importance: RAAS is crucial for blood pressure regulation, though other factors can affect it.
• Healthcare Guidance: Consult providers for blood pressure issues.