Glomerular Filtration

Glomerular filtration is driven by

Hydrostatic pressure

What is the primary characteristic of the filtration membrane regarding solute size?

Smaller solutes pass through

Larger solutes cannot

Three components of the glomerulus membrane

Fenestrated endothelium

Basement membrane

Foot processes of podocytes

Glomerular capillaries enothelium

Fenestrated with small pores

Glomerular capillaries prevent the passage of ___

Blood cells

Glomerular capillaries allow the diffusion of ___

Solutes (not the big ones), including plasma proteins

Glomerular basement membrane allows passage of

Only small plasma proteins, nutrients, and ions

Glomerular filtration is governed by balance between

Hydrostatic pressure (fluid pressure) - pushing pressure into capsule and

Colloid osmotic pressure (of materials in solution) on each side of capillary walls - pulling pressure into or keeping into the capillaries

GHP is __ than hydrostatic pressure in peripheral capillaries

Higher

GHP tends to push water and solutes out of ___ and into ___

Bloodstream

Filtrate

What is CsHP

Capillary Hydrostatic Pressure

CsHp tends to push water and solutes out of ___ and into ___

Filtrate

Bloodstream

Net Hydrostatic Pressure (NHP) is the sum of what equation

GHP (50) - CsHP (15) = 35

Net Filtration Pressure (NFP) is the sum of what equation

NHP (35) - BCOP (25) = 10

Glomerular filtration rate (GFR) is the

Amount of filtrate kidneys produce each minute

About 10 percent of fluid delivered to kidneys leaves the ___ and enters the ___

Bloodstream

Capsular spaces

Glomeruli generate about ___ liters of filtrate per day

180

Three interacting levels of control of GFR are

1. Autoregulation (local level)

2. Hormonal regulation (initiated by kidneys)

3. Autonomic regulation (by sympathetic division of ANS)

How does autoregulation of GFR work

It maintains adequate GFR despite changes in local blood pressure and blood flow

Autoregulation of GFR involves changing luminal diameters of

Afferent arterioles

Efferent arterioles

Glomerular capillaries

Hormonal regulation of GFR

Renin-angiotensin-aldosterone system (RAAS)

What are the three stimuli that cause the juxtaglomerular complex (JGC) to release renin in the Renin-Angiotensin-Aldosterone System (RAAS)?

Decrease in BP at glomerulus due to decrease in blood volume, decrease in systemic pressures, or blockage in renal artery or its branches

Stimulation of juxtaglomerular cells by sympathetic innervation

Decrease in osmotic concentration of tubular fluid at macula densa

Renin converts inactive ___ to inactive ___

Angiotensinogen

Angiotensin I

Angiotensin I is converted to angiotensin II by

Angiotensin-converting enzyme (ACE)

Where is angiotensin I primarily changed to angiotensin II

Capillaries in the lungs

Does angiotensin II constrict or dilate? And what does it constrict OR dilate?

Constricts

Smooth muscle in the peripheral capillary beds

Angiotensin II leads to increased ___ secretion by ___

Aldosterone

Adrenal glands

The overall effect of angiotensin II is an (increase/decrease) in systemic ___ and ___ and restoration of normal GFR

Increase

Blood pressure

Blood volume

Explain the auto-regulatory mechanism where increased blood volume affects the Glomerular Filtration Rate (GFR) and what is the ultimate result of this change?

With an increase in blood volume, blood pressure increases, automatically causing the GFR to increase. The result of this change is fluid loss and decrease in blood volume and restore normal blood pressure (fluid homeostasis).

What the heart releases due to increased BV or increased BP

Natriuretic peptides

Atrial natriuretic peptide (ANP) is released by

Atria

Natriuretic peptides trigger dilation of ___ and constriction of ___

Afferent glomerular arterioles

Efferent glomerular arterioles

Natriuretic peptides increase ___ and increase ___

Glomerular pressures

GFR

Autonomic regulation of GFR mostly consists of

Sympathetic postganglionic fibers

Sympathetic activation in the autonomic regulation of the GFR causes what 3 things?

Constricts afferent glomerular arterioles

Decreases GFR

Slows filtrate production