Dr. Sullivant - Renal Physiology

What is GFR?

The rate at which the glomerular capillaries filter plasma

What are the determinants of GFR?

Net filtration pressure and Capillary filtration coefficient (Kf)

What is the balance of hydrostatic and colloid osmotic forces acting across capillary membrane?

Net filtration pressure

What are the 3 layers of the glomerular capillary membrane?

The basement membrane, The Podocytes, and The endothelium

What charge does the components of the glomerular capillary membrane have?

negative

What does the negative charge of the glomerular capillary membrane help with?

prevent the loss of proteins

What is the relative filterability of albumin?

0.005

What is the relative filterability of water/glucose/Na?

0.1

What is more relative filterabilable: water/glucose/Na or albumin?

water/glucose/Na

What are the forces favoring filtration in the glomerulus?

 Glomerular hydrostatic pressure (60) and Bowman’s capsule colloid osmotic pressure (0)

What are the forces opposing filtration in the glomerulus?

Bowman’s capsule hydrostatic pressure (18) and Glomerular capillary colloid osmotic pressure (32)

Increased hydrostatic pressure in Bowman’s capsule ______ GFR

reduces

What is he primary physiological means by which  GFR is regulated?

 changes in glomerular hydrostatic pressure

Increases in glomerular hydrostatic pressure _______ GFR

Increases

Decreases in glomerular hydrostatic pressure _______ GFR

Decreases

What is a specialized portion of the peritubular capillary system that supplies blood to the renal medulla?

vasa recta

What does the vasa recta do?

plays an important role in the kidneys ability to form concentrated urine

 What factors influence glomerular capillary pressure the most?

Systemic arterial pressure, Afferent arteriolar resistance, Efferent arteriolar resistance, and Interlobular artery resistance

What systemic systolic arterial pressures does auto regulation maintain?

80-170 mmHg

What prevents large changes in GFR and renal excretion of water and solutes that would otherwise occur with changes in blood pressure/vascular resistance?

auto regulation

What maintains the pressure range over which is works and maintains GFR?

auto regulation

What hormones constrict renal arterioles?

epinephrine, norepinephrine, and endothelin

What hormones dilate renal arterioles?

NO, PGF, and bradykinin

What hormones is the efferent arteriole very sensitive to?

angiotensin II

What does angiotensin do to efferent arterioles in states of hypovolemia or hypotension?

increase glomerular hydrostatic pressure to increase/preserve GFR

What decrease renal blood flow through peritubular capillaries and thus increase resorption of sodium and water to restore blood volume and blood pressure?

angiotensin II

What is a special feedback mechanism that senses changes in NaCl concentration reaching the distal tubule?

tubuloglomerular feedback

What are the components of the tubuloglomerular feedback?

macula densa and juxtaglomerular cells

What does the tubuloglomerular feedback system sense changes in?

NaCl

Where can macula densa cells be found?

 initial portion of the distal tubule

What are specialized epithelial cells that come into close contact with afferent and efferent arterioles?

Macula densa cells

Where can Juxtaglomerular cells be found?

in the walls of the afferent and efferent arterioles

What do Juxtaglomerular cells do?

 store and release renin

What converts angiotensin I to angiotensin II?

renin

What release renin?

 juxtaglomerular cells

Is tubular resorption highly selective?

Yes

How does the tubular reabsorption of solutes occur?

 passive diffusion or active transport

How does the diffusion of tubular reabsorption of solutes occur?

paracellularly

How does the diffusion/active transport of tubular reabsorption of solutes occur?

transcellularly

What is use to co-transport or counter-transport lots of things?

Na

Where is sodium reabsorption is greatest?

Proximal tubule

What % of waste nitrogen is excreted by the kidneys of urea?

90%

How is urea resorbed?

passively down a concentration gradient

What is a highly metabolic area with large numbers of mitochondria and extensive brush border and channels?

Proximal tubule

Is the proximal tubule permeable to water?

very

What % of filter Na and water is resorbed in the proximal tubule?

65%

What % of NaCl reabsorbed via the NaCl co-transporter in the sital tubule?

5%

Is the distal tubule permeable to water?

No

What stimulates principle cells in the distal tubule?

aldosterone

What is the primary site of action of K sparing diuretics such as spironolactone?

principal cells in the distal tubule

What do the principle cells of the distal tubule do?

Reabsorb Na and Secrete K via NaK ATPase pump in basolateral membrane

What are the two types of cells in the distal tubule?

principal cells and intercalated cells

What are the two types of intercalated cells?

Type A and type B

What do type A intercalated cells do?

secrete H via H/ATPase transporter and a H/K/ATPase transporter

What do intercalated type B cells do?

secretes HCO3 and resorbs H during alkalosis

What do intercalated cells play a major role in?

acid base regulation

What do type A intercalulated cells secrete during acidosis?

H

What do type A intercalulated cells resorb during acidosis?

HCO3

What counter-transporter are Type B intercalated cells apart of?

Cl/HCO3

Where are intercalated cells?

collecting ducts and collecting tubules

What controls the water permeability of the late distal tubule and cortical collecting duct and medullary collecting duct?

aldosterone (and other hormones)

How much of the filtered water and sodium is reabsorbed in medullary collecting ducts and that this area secretes H?

less than 5%

What do High levels of ADH do to urine concentration?

concentrates it

What does the absence of ADH do to urine concentration?

dilutes it

What are the 4 pressures that govern reabsorption of solutes into the peritubular capillary?

Hydrostatic pressure,Osmotic pressure,Renal interstitial fluid hydrostatic pressure, Renal interstitial colloid osmotic pressure

What pressure which one favors reabsorption the most?

Osmotic pressure

What is the net reabsorption pressure?

10 mmHg

What cleaves angiotensin into angiotensin I?

renin

What is the most powerful Na retaining hormone?

Angiotensin II

What activates the RAAS system?

low blood volume/low pressure

What does low blood volume/low pressure stimulate the secretion of in the RAAS system?

aldosterone

What directly stimulates Na resorption in proximal tubules, loops of Henle, distal tubules and collecting tubules in the RAAS syste,?

aldosterone

What is the end result of the RAAS system?

water and salt reabsorption, increasing circulatory volume and blood perfusion to the kidneys

What is the net effect of Angiotensin II Blockade?

Decrease aldosterone, Directly inhibit Na+ reabsorption, Decrease efferent arteriolar resistance

What does aldosterone cause principal cells do to?

increase Na reabsorption and K secretion

What does aldosterone cause intercalated cells to do?

increase H secretion

What acts on principal cells of collecting duct and tubules to increase Na/H20 resorption and increase K secretion and also causes H secretion?

aldosterone

What is increased in states of fluid overload, such as in congestive heart failure, and works to minimize blood volume expansion?

atrial natriuretic peptide