Renin-Angiotensin Mechanism And Its Role In Blood Pressure

Renin-Angiotensin Mechanism And Its Role In Blood Pressure

Question 1. Reninangiotensin mechanism.
Answer:

Reninsecretion:

• Renin is a glycoprotein with 340 amino acids.

Stimuli for rennin secretion:

• Low blood pressure.
• Low ECF volume.
• Sympathetic stimulation.
• Low plasma sodium.

Reninangiotensin system:

Actions:

1. Angiotension II.

• Regulates GFR.
• Increases blood pressure
• Increases water intake.
• Increases ADH secretion.
• Increases aldosterone secretion
• Cause vasoconstriction.

2. Angiotensin III and IV.

• Increases aldosterone secretion.
• Causes vasoconstriction.

Question 2. Effective filtration pressure.
Answer:

1. Glomerular hydrostatic pressure (HP)

2. Colloidal osmotic pressure (OP)

3. Intracapsular pressure (ICP)

• HP provides the driving force for the filtration.
• OP and ICP opposes the process of filtration.
• The resultant of these factors is termed as the effective filtration pressure.
• Therefore, for each nephron, effective filtration pressure is.
  EFP = HP-[OP+ ICP]= 60 – (25+15)= 20 mm Hg

Value:

• It is about 20 mm Hg, varies between 15 and 20 mm Hg.

Significance:

• It is essential for maintenance of GFR.
• It is based on starling’s hypothesis.
• It states that the net filtration through capillary membrane is proportional to the hydrostatic pressure difference across the membrane minus the oncotic pressure difference.