Physio renal clearance, blood flow etc

What is the equation for renal clearance?

C= (U x V)/Px

Define the variables of renal clearance

U= urine conc of substance

V= urine flow per minute

Px= plasma conc of a substance

Filtered means a substance is filtered at

the glomerulus

rebasorption means that

solutes/water leave from tubule to blood

secretion is when

solutes move from blood/water to the tubule

excretion is when

solutes/water are ultimately eliminated through urine

Glomerular filtration rate is

the process by which kidneys filter blood to remove waste and excess fluids

Renal plasma flow is

the volume of plasma delivered to kidneys per a unit of time, Renal plasma flow effects GFR

What is used to estimate Renal Plasma Flow?

PAH (para-aminohippurate)

What is used to estimate Glomerular Filtration Rate?

Inulin

Sodium, calcium, Mg, and phosphate should all be

filtered and reabsorbed

Potassium should typically be

filtered and reabsorbed, also secreted

Albumin should typically be

unfiltered due to protein nature

Glucose should typically be

filtered and completely reabsorbed

How do you calculate the clearance ration

Clearance of substance x/ C inulin

What substance exactly equals glomerular filtration rate?

inulin

Why is inulin equal to GFR?

it is freely filtered and not absorbed or secreted

If clearance ration is 1

filtered, but not reabsorbed or secreted

If clearance ratio is greater than 1

the substance is filtered and secreted

If clearance ratio is less than 1

the substance is not filtered or it is filtered and reabsorbed

Renal blood flow is proportional to what

pressure gradient between the renal artery and renal vein

What is the major mechanism for changing renal blood flow?

changing arteriolar resistance

What receptors are more prevalent on afferent than efferent arterioles?

a1 receptors

When sympathetic nervous system activity is increased what happens to the renal system?

decreased renal blood flow and glomerular filtration rate

What is most sensitive to angiotensin 2?

efferent arterioles

Why would angiotensin 2 levels be high?

RAAS system is activated

How do low levels of angiotensin II effect GFR?

Low levels increase GFR because main effect is on efferent arterioles, so blood leaves glomerulus slower

What is the effect of high levels of angiotensin 2 on RBF and GFR?

Decrease GFR and RBF because afferent is constricted decreasing blood flow

What arteriole has the smallest diameter?

Efferent arterioles

What is the effect of ANP?

dilation of afferent arterioles and constriction of efferent arterioles, RBF and GFR both increase, resistance decrease

What are the effects of prostoglandins E2 and I2 in the kidneys?

vasodilation of afferent arterioles to protect renal blood flow by modulating vasoconstriction of SNS

What is the effect of dopamine on the kidneys?

dilates renal arterioles, used in hemmorhage to protect by counteracting SNS vasoconstriction

Which renal vessel is mainly effected by low levels of angiotensin 2?

efferent arterioles

Increased arterial blood pressure leads to

stretched blood vessels, which cause reflex contraction in smooth muscle in BV walls and increases resistance to BF

What is the role of the macula densa?

senses increased load and responds by secreting vasoactive substances to constrict afferent arteriole

Why is PAH the gold standard for the estimate of clearance from the kidneys?

it is removed only by the kidneys, all PAH enters the urine without altering RBF

In tubuloglomerular feedback, how does the afferent arteriole react to an increase in delivery of solute and water to the macula dense?

vasoconstriction