Glomerular Filtration Rate (GFR) Regulation

Principles of GFR Regulation

Renal Autoregulation
- Maintains GFR despite changes in systemic blood pressure.
- Mechanisms:
  - Tubuloglomerular Feedback:
    - Disruption in homeostasis increases GFR.
    - Macula densa cells detect increased delivery of NaCl and water.
    - Decrease in nitric oxide secretion (a vasodilator) causing vasoconstriction of afferent arterioles, reducing pressure and slowing filtration.
  - Myogenic Mechanism:
    - Responds to increased blood pressure by constricting smooth muscle in the afferent arteriole, returning GFR to normal.
Neural Regulation
- Sympathetic Nervous System: The kidney has only sympathetic innervation.
- Effects on GFR:
  - High sympathetic stimulation (fight or flight) decreases GFR by vasoconstriction of afferent arterioles, reducing urine output.
  - Low sympathetic stimulation (rest) increases GFR by vasodilation.
Hormonal Regulation
- Atrial Natriuretic Peptide (ANP):
  - Released due to atrial stretch from high blood volume.
  - Increases GFR by relaxing mesangial cells to increase filtration surface area.
- Angiotensin II:
  - Strong vasoconstrictor reducing GFR by narrowing afferent and efferent arterioles.

List the three processes involved in forming urine and identify their locations.
Features of Renal Corpuscle: Enhance filtration.
Three Filters at the Glomerulus: Describe the substances each blocks.
Three Forces of Net Filtration Pressure (NFP):
- Glomerular Blood Hydrostatic Pressure
- Capsular Hydrostatic Pressure
- Blood Colloidal Osmotic Pressure
Causes and Directions of Forces: How each affects blood movement into/out of filtrate.
Formula and Normal Values for NFP.
Effect of Reduced Plasma Proteins: Due to kidney/liver disease on NFP.
GFR Explained: Consequences of high or low GFR.
Mechanisms of GFR Regulation: Detailed descriptions.
Hormonal Effects: Which hormones directly affect GFR.
Define Filtration Fraction.