SF: Chapter 26pt3

what are the 3 general steps in urine formation

1. filtration

2. reabsorption

3. secretion

filtration def.

removal of unwanted substances from blood

Where does the initial formation of ultrafiltrate occur?

glomerulus

reabsorption def.

moving water and nutrients back into the bloodstream

reabsorption occurs where?

renal tubule

secretion def.

last chance to remove waste ions by bringing blood into the renal tubule

When is the complete formation of urine done?

during secretion

renal corpuscle is responsible for?

filtration

PCT, loop of henle, MINIMAL DCT, and the collecting duct are responsible for?

reabsorption

DCT and MINIMAL PCT are responsible for?

secretion

filtration is based on?

size and charge of molecules

Do blood cells and most proteins pass through when filtering?

NO

What type of substances are able to fit through the filtration membrane

small molecules

How much filtrate is produced daily?

180L

How much filtrate becomes urine

<1%

How much filtrate is reabsorbed into the blood

~99%

we use GFR to asses the severity of?

renal disease

What are the 2 ways to regulate GFR

intrinsic and extrinsic mechanisms

intrinsic regulation of GFR is (general)

autoregulation due to renal corpuscle structures

What is the myogenic mechanism

intrinsic regulation of the afferent arteriole diameter in response to change in BP

What is tubuloglomerular feedback?

-negative feedback by macula densa cells that responds to changes in Na+ and Cl- in filtrate

What is the purpose of tubuloglomerular feedback?

keep filtration and reabsorption in balance so we don't lose too much fluid or retain too much waste

tubuloglomerular feedback does what when there is increased flow to the afferent arteriole?

juxtaglomerular cells constrict the afferent arteriole

How does GFR respond to less glomerular capillary pressure

decreases

extrinsic regulation of GFR is controlled by?

ANS and hormones

During severe conditions such as a hemorrhage or dehydration, what happens to mean arterial pressure?

drops <90mmHg

During severe conditions such as a hemorrhage or dehydration, what does the SNS do

significantly decreases renal blood flow and GFR to keep BP stable

During intense stimulation with shock or vigorous exercise, what happens to rate of filtration?

decreases

During intense stimulation with shock or vigorous exercise, what happens if there is excess shock

vasoconstriction of afferent arterioles and renal damage. Need to treat quickly

If there is low blood pressure readings, what do juxtaglomerular cells do?

secrete Renin to keep GFR stable

Where does 70% of tubular reabsorption occur

PCT

Why do we require tubular reabsorption

its necessary to prevent excessive dehydration

How many solutes are returned during reabsorption

99% of solutes and water

What is happening concurrently while solutes and water are being put back into the blood

quickly removing toxic waste

99% of filtrate volume moves ??

out of the renal tubule into the IF-> peritubular capillaries and into renal veins

examples of solutes that are reabsorbed

amino acids, glycogen, fructose, sodium, potassium, calcium

tubular secretion is the last ditch for?

additional solutes to be moved from the blood to filtrate

Where is tubular secretion most active?

PCT

What solute is moved during tubular secretion

potassium

What is an example of something that is moved from blood to filtrate in tubular secretion

toxic by-products of metabolism and drugs/molecules that are NOT normally made in the body

What is an example of a toxic by product of protein metabolism

ammonia, K+, ACh, epi, bile pigments, urea, uric acid, drugs, toxins and morphine

What is antiport

kidney secretes H+, regulating pH

If the blood is too acidic, what does the kidney do

secrete H+

Hormonal mechanisms for controlling urinary concentrations

renin-angiotensin- aldosterone hormone

renin and angiotensinogen becomes

angiotensin I

angiotensin i and ACE becomes

angiotensin II

angiotensin II leads to

vasoconstriction and aldosterone secretion from the adrenal cortex

ADH is made by

hypothalamus

ADH is stored in the

posterior pituitary

When the osmolality of blood and IF increases, what happens ??

ADH is stimulated and released to conserve water

ANF stands for

atrial natriuretic factor

ANF is secreted by

right atrial cells when stretched more than normal

When does ANF secretion occur

when there is an increased stretch of the right atrium, when BV is high

ANF inhibits?

ADH secretion and increases urine volume which lowers BV and BP

ANF dilates the arteries to??

decrease peripheral resistance and lower BP

What elevates BV and BP?

ADH

What decreases BV and BP?

ANF

What is the urine concentration with ADH release?

urine is much more concentrated

What is the urine concentration with ANF release

urine is much more diluted