Renal System

How do we move water, salts, glucose, waste products?

Through filtration through membranes

passive transport

no energy required, no ATP

active transport

needs energy, ATP

Tasks membrane proteins perform

transport, receptors for signal transduction, enzymatic activity, cell-cell recognition, attachment to the cytoskeleton and ECM, cell-to-cell joining

cell junctions

some cells are not bound to any other cells (ex. blood cells, sperm cells, lymphatic fluid)

tight junctions

integral proteins on adjacent cells fuse to form an impermeable junction that encircles the whole cell; prevent fluids and most molecules from moving in between cells (ex. bladder)

desmosomes

rivet-like cell junction formed when linker proteins (cadherins) of neighboring cells interlock like the teeth of a zipper (ex. ligament or tendon, places where you need flexibility/elasticity, nose, ears)

gap junctions

transmembrane proteins (connexions) form tunnels that allow small molecules to pass from cell to cell; allows electrical signals to be passed from 1 cell to the next (ex. used in cardiac and smooth muscle cells)

diffusion

greater conc., smaller molecules, higher temps. —> faster diffusion

simple diffusion

nonpolar lipid-soluble (hydrophobic) substances diffuse directly through phospholipid bilayer (ex. O2, CO2)

facilitated diffusion

larger or non-lipid soluble or polar molecules can cross membrane but only with assistance of carrier molecules (ex. glucose, a.a.s, ions)

osmosis

movement of water actoss a selectively permeable membrane from high solvent (low solute) to low solvent (high solute)

tonicity

ability of a solution to change the shape or tone of cells by altering cells’ internal water volume

isotonic

same osmolarity as inside the cell, so the volume remains unchanged

hypertonic

solution has higher osmolarity than inside cell, so water flows out of cell, shrinking/crenation

hypotonic

solution has lower osmolarity than inside cell, so water flows in cell, swelling/bursting hemolysis

antiporters

transport 1 substance into cell while transporting a different substance out of cell

symporters

transport 2 different substances in the SAME direction

primary active transport

energy from hydrolysis of ATP causes change in shape of protein, shape change causes ions bound to protein to be pumped across membrane (ex. calcium, Na-K pumps)

Na-K Pumps

pumps 3 Na out of cell and 2 K into cell

secondary active transport

required energy is obtained indirectly from ionic gradients created by primary active transport, something sneaks a ride in when channel opens

vesicular transport

transport of large particles, macromolecules, and fluids across membrane in vesicles

endocytosis

transport into cell, formation of vesicles

phagocytosis

cell engulfs large particle by forming pseudopod around it and enclosing it within a membranous sac called a phagosome

pinocytosis

cell “gulps” a drop of extracellular fluid containing solutes into tiny vesicles (main way where absorption of nutrients occur in SI)

receptor-mediated endocytosis

extracellular substances bind to specific receptor proteins, enabling the cell to ingest and concentrate specific substances in protein-coated vesicles

exocytosis

process where material is ejected from cell, activated by cell-surface signals or changes in membrane volume (ex. Ca, hormones, neurotransmitters)

kidney

filters 180L of blood daily, regulates volume and chemical makeup of blood, maintain proper balance between water, salts, acids, and bases

Urine formation and adjustment of blood comp. involves

glomerular filtration, tubular reabsoption, secretion

fenestrated capillaries

found wherever active capillary absorption or filtrate formation occurs

glomerulus filtration

membrane is more permeable; 10 mmHg

Increase in BP?

Increase in NFP and GFR

Increase in NFP and GFR?

Increase in urine production

glomerular filtration rate

total amount of filtrate formed per minute by kidneys (MEN 125 mL/min; WOMEN 120 mL/min - 7.5 L/hr, 180L/day, 45 gallons/day)

Total Blood Volume is filtered into glomerulus

every 40 minutes

GFR too high?

needed substances cannot be reabsorbed quickly enough and are lost in urine

GFR too low?

everything is reabsorbed, including wastes that are normally disposed of

Renal autoregulation

vasoconstriction/dilation of afferent arterioles

low bp? (means vasodilation)

back to homeostasis:

greater blood flow —> increased GFR

• pee less, more conc. urine

• ADH released by pituitary gland

  • thirsty

• aldosterone

• vasoconstrict

under normal conditions, renal autoregulation

maintains a nearly constant GFR for subtle changes in bp

high bp? (means vasoconstriction)

back to homeostasis:

reduced blood flow —> decreased GFR

tubularglomerular

responds to chronic low/high BP, detects NaCl directly, not P

high NaCl/GFR? (high bp)

• chemical released

• Vasoconstricts afferent arteriole

• decrease in bp and GFR

low NaCl/GFR? (low bp)

• less chemical released

• vasodilates afferent arterioles

• increase in bp and GFR

extrinsic controls

when sympathetic NS is at rest:

renal BVs are maximally dilated

autoregulation mechanisms prevail

decrease in bp?

• baroreceptors in aorta

• increased sympathetic nerve activity

  • 1. Vasoconstriction of GI tract and skin

  • 2. HR increases

• raises systemic bp

increase in bp?

• baroreceptors in aorta

• decreased sympathetic nerve activity

  • 1. Vasodilation of GI tract and skin

  • 2. HR decreases

• lowers systemic bp

renin release (low bp)

renin release is triggered by:

1. reduced stretch of granular JG cells

2. direct stimulation of JG granuluar cells via nor/epinephrine by renal nerves

• stimulates cells in JGA

• release renin

• travels to liver

• release angiotensinogen

• travels in blood to lungs

• converts angiotensin I to angiotensin II

Angiotensin II

hypothalamus activates thirst center

• increases blood volume —> increases P

posterior pituitary gland activates ADH

• pee less —> increase blood volume —> increases P

systemic arterioles vasoconstriction

adrenal cortex relase aldosterone

• increase water and salt reabsorption

• increase blood volume —> increases P

ADH

promotes water retention in the collecting duct; pees less

renin release (high bp)

atrial natriuretic peptide

• stretching of cells due to increase blood volume and increase bp

• promotes excretion of water and sodium

dilates afferent arterioles

• increases GFR

increases permeability of glomerulus

• increases GFR

decrease ADH

decrease aldosterone

decrease renin

decrease blood volume

site of most reabsorption

proximal convoluted tubule

transport maximum

when carriers for solute (glucose) are saturated, excess is excreted in urine

countercurrent mechanism

interaction between flow of filtrate through Loop of Henle (countercurrent multiplier) and flow of blood through vasa recta BVs (countercurrent exchanger)

Establishes and maintains an osmotic gradient extending from the cortex through the depths of the medulla that allows the kidneys to vary urine concentrate dramatically

descending Loop of Henle

impermeable to solutes, permeable to water

ascending Loop of Henle

permeable to solutes, impermeable to water

Renal clearance

Volume of plasma that is cleared of a particular substance in a given time

• used to determine GFR

• detect glomerular damage

• follow progress of renal disease

Renal Clearance Equation

GFR x P = U x V

GFR = (U x V) / P

chronic renal disease

GFR less than 60 mL/min for 3 months

filtrate formation decreases, nitrogenous wastes accumulate in blood, pH acidic

Renal failure

GFR less than 15 mL/min

causes uremia, metabolic abnormalities, toxic molecules accumulate

hemodialysis or transplant

uremia

Build up of urea in blood, RBCs shrink and cannot carry oxygen

Urine composition

95% water 5% solutes

Urea

Uric acid

Creatinine

Glucose in urine

Glycosuria

Seen in diabetes

Proteins in urine

Proteinuria/albuminuria

Seen in glomerulonephritis

Ketones in urine

Ketonuria

Seen in diabetes

Smells like nail polish remover, bananas/fruity

warmer lung tissue?

Less O2 and increase in vapor pressure

surfactant

body’s detergent-like liquid and protein complex that helps reduce surface tension of alveolar fluid

• prevents alveolar collapse

• produced by type II alveolar cells

vasa recta

involved in urine concentration

peritubular capillaries

blood supply that directly receives substances from tubular cells, low-pressure and reabsorbs water and solutes

glomerular capillaries

fenestrated vessels that allow the passage of all plasma elements but no blood cells

afferent arteriole

high P vessel forces fluid and solutes into glomerulus

Vasodilation/increase diameter increases GFR

efferent arteriole

form meandering vessels or bundles of long straight vessels

vasoconstriction/decrease diameter increases GFR

solute concentration in the interstitial space increases?

urine volume and urine concentration decreases

glucose carrier proteins are located where?

PCT

as glucose carriers are added to the proximal tubule

The glucose concentration in the urinary bladder decreases

which hormone has a greater effect on urine volume

ADH

can urine concentration still vary if ADH is not available?

NO!

Raise bp?

Urine volume increases