UR2 (pt. 1)

Define GFR

vol. fluid filtered from glomeruli to Bowmans space per unit time

3 layers of corpuscular membrane:

1. 1 cell capillary endothelium

2. basement membrane

3. podocytes

When would NFP be ‘-’

severe dehydration or blood loss

NET filt. P. effects:

GFR

impact of high BP:

increased; P. GC, NFP, GFR

impact of low BP:

decreased; P. GC, NFP, GFR

What in kidneys keeps GFR within tolerance despite what BP is doing?

intrinsic mechanisms (renal autoregulation)- GFR Homeostasis

What do mesangial cells constrict?

Glom. Capillaries (bc they alter capillary SA available for filtration)

T or F: GFR is solely reliant on BP

FALSE (renal auto regulation)

What keeps GFR within tolerance despite what BP is doing?

intrinsic mechanisms (renal auto regulation)

What are the methods of renal autoregulation / intrinsic mechanisms?

• myogenic mechanisms

• tubuloglomerular feedback

if low GFR, low BP, ____ generates response

renal autoregulation

what mechanism happens in seconds, which if LOW BP, causes smooth muscle to dilate aff art and constrict eff art?

Myogenic mechanism

what would happen if u did not have myogenic mechanism?

vessels could not contract or relax

what do macula densa cells measure?

NaCl lvls in filtrate

what happens if NaCl lvls are too high?

Macula densa cells detect → release Nitric Oxide → lowers GFR

What structure releases nitric oxide?

Macula densa cells

What does Nitric Oxide do?

decreases GFR

if NaCl too low you want to reabsorb salt by

slowing filtration, constrict eff art, increase GFR

If NaCl too low you want to

increase GFR, dilate aff art.

If NaCl too high you want to :

• constrict aff art.

• decrease GFR

What does not pass from glom → B.C.?

Proteins

you reabsorb 99% of

H20, Na, and 100% of glucose

What is the waste product you excrete most of?

H2O

2 ways of reabsorption, and their definitions:

1. Paracellular

• diffusion

• across tight junctions

• conc gradient (not selective)

2. Transcellular

• mediated transport

• req. participation of prot.s in plasma membrane of tubular cells

Pathway of reabsorption

tubule → interstitial fluid → peritubular capillaries

What type of reabsorption happens at the gap junctions

Paracellular reabsorbtion! - diffusion, conc gradient

The 5 types of transporters:

1. Ion channels

2. Uniporters

3. Symporters

4. Antiporters

5. Primary Active transporters

Define ‘ion channels’

• permits specific molecules

• aquaporins (1/4 hormonally regulated)

Define ‘Uniporter’

permits molecules w/ prot. carrier

• ex. GLUCOSE!

What transport is glucose?

uniporter

aquaporin transport:

ion channels

Define ‘Symporter’

permits 2 molecules, same direction

• 1 MUST be conc. gradient (Na)

ex. Na and Gluc into cell

what transporter permits 2 molecules in the same direction?

symporter

Define ‘Antiporter’

permits 2 molecules, opposite direction

• 1 must move w/ conc gradient

ex. Na and H+

What transporter permits 2 molecules in opposing direction?

Antiporters

ex. Na and H+ antiporter

Define ‘Primary Active Transporters’

against conc gradient

• REQUIRE ATP
  ex. 3Na/2K+ pump

What is 3Na/2K transporter an example of?

Primary Active Transporter

why do we need to pump Na out of cell against gradient?

to keep the conc gradient