Question

The Renin-Angiotensin-Aldosterone Pathway and the roles that the kidney plays in the human body and how it works to keep the body in balance. Include what happens if there is a homeostatic imbalance as it plays this role.

Answer 1

ANSWER: THE KIDNEYS PLAY SOME MAJOR ROLES IN HUMAN BODY.

1. ROLE IN HOMEOSTASIS.

• EXCRETION OF WASTE PRODUCTS SUCH AS UREA, URIC ACID, CREATININE AND BILIRUBIN. (HOMEOSTATIC IMBALANCE- RETENTION OF THESE TOXIC WASTE PRODUCTS FORMED DURING METABOLIC ACTIVITIES IN THE BODY LEADING TO AN UNHEALTHY CONDITION)
• MAINTAINING WATER AND ELECTROLYTE BALANCE IN THE BODY (HOMEOSTATIC IMBALANCE- WATER IMBALANCE IN THE BODY)
• MAINTAINING ACID BASE BALANCE IN THE BODY ( HOMEOSTATIC IMBALANCE - DISTURBANCE IN OSMOLARITY OF BODY WATER)

2. HEMOPOIETIC FUNCTIONS ( PRODUCTION OF ERYTHROPOIETIN WHICH STIMULATES ERYTHROPOIESIS).

3. SECRETION OF SOME HORMONES SUCH AS ERYTHROPOIETIN, THROMBOPOIETIN, RENIN, CALCITRIOL, PROSTAGLANDINS.

4. REGULATES BLOOD CALCIUM LEVELS BY ACTIVATING 1,25 DIHYDROXYCHOLECALCIFEROL INTO VITAMIN D.

HOMEOSTASIS IS MAINTAINING THE CONSTANT INTERNAL ENVIRONMENT OF THE BODY.

THE KIDNEYS MAINTAIN THE BLOOD PRESSURE IN THE BODY THROUGH RENIN- ANGIOTENSIN-ALDOSTERON MECHANISM.

FALL IN BLOOD PRESSURE STIMULATES THE JUXTAGLOMERULAR APPARATUS------------- SECRETION OF RENIN FROM THE KIDNEYS------------ RENIN CONVERTS ANGIOTENSINOGEN INTO ANGIOTENSIN I ( ACTS AS A PRECURSOR OF ANGIOTENSIN II AND DOES NOT HAVE ANY OTHER ROLE) ------------- ANGIOTENSIN I IS CONVERTED INTO ANGIOTENSIN II BY THE ANGIOTENSIN-CONVERTING ENZYME.

NOW THIS ANGIOTENSIN II ACTS IN TWO DIFFERENT WAYS:

1. IT CONSTRICTS THE ARTERIOLES IN THE BODY TO INCREASE THE PERIPHERAL RESISTANCE WHICH IN TURN INCREASES THE BLOOD PRESSURE. ALSO , IT CONSTRICTS THE AFFERENT ARTERIOLES IN THE KIDNEYS SO THAT THE GFR FALLS LEADING TO RETENTION OF SALT AND WATER IN THE BODY. THIS IN TURN RESTORES THE NORMAL EXTRA CELLULAR FLUID VOLUME.
2. SIMULTANEOUSLY, IT ALSO STIMULATES THE SECRETION OF ALDOSTERON FROM ADRENAL CORTEX OF THE KIDNEY, WHICH FACILITATES THE REABSORBTION OF SODIUM AND WATER FROM THE RENAL TUBULES. HENCE RESTORING THE NORMAL ECF VOLUME.