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Urinary System/Fluids&Electrolytes (Electrolyte Functions (Conditions,…
Urinary System/Fluids&Electrolytes
Nephron Physiology
Reabsorption
Glucose
PCT
~100% reabsorped
secondary active transport w/ Na+
Oligopeptides, proteins, amino acids
PCT
~100% reabsorped
symport w/ Na+
Vitamins
PCT
Lactate
PCT
Creatinine
PCT
Urea
PCT
50% reab by diffusion, also secreted
LOH
Secretion, diffusion in descending limb
collecting ducts
reab in medullary cavity
Sodium
PCT
65% actively reab
LOH
25% reab in thick ascending limb, AT
DCT
5% reab, active
collecting ducts
5% reab, stimulated by aldosterone, active
Chloride
PCT
Reab, symport w Na+, diffusion
LOH
Reab in thick and thin ascending limb
diffusion in ascending limb
DCT
reab, diffusion
collecting ducts
reab, symport
Water
PCT
67% reab, osmotically w solutes
LOH
15% rreab in descending limb, osmosis
DCT
8% reab, if ADH, osmosis
collecting ducts
variable amts reab, controlled by ADH, osmosis
Bicarbonate
PCT
80-90% symport reab with Na
LOH
reab, symport with Na+ and antiport w Cl-, in ascending limb
collecting ducts
reab antiport w Cl-
H+
PCT
secreted, diffusion
DCT
secreted, active
collecting ducts
secreted, active
Nh4+
PCT
secreted , diffusion
DCT
secreted, diffusion
collecting ducts
secreted, diffusion
HCO3-
PCT
reab, diffusion
LOH
reab, diffusion in ascending limb
DCT
reab, diffusion
collecting duct
reab, antiport w Na+
Potassium
PCT
65% reab, diffusion
LOH
20% reab in thick ascending limn, symport
DCT
secreted, active
collecting ducts
secretion controlled by aldosterone, active
Calcium
PCT
reab, diffusion
LOH
reab in thick ascending limn, diffusion
collecting ducts
reab if PTH present, active
Magnesium
PCT
reab, diffusion
LOH
reab in thick ascending limb, diffusion
DCT
reab
Phosphate
PCT
85% reab, inhibited by PTH, diffusion
DCT
reab, diffusion
Water is most reab, then Cl-, than Na+
Secretion
mvmt of solutes usually by active transport
move from the blood within peritubular and vasa recta capillaries into tubular fluid
materials moved selectively into tubules to be excreted
secreted for removal: potassium, ammonium, urea, hydrogen ions, creatinine
Tubular secretion occurs from epithelial cells that line renal tubules
Filtration
glomerular filtration rate
volume of filtrate formed by both kidneys per minute
105-125 mL per min produced on average
99% of filtrate returned to circulation by reabsorption
only 1-2 lts of urine produced per day
inulin determines GFR
Net filtration pressure
pressure of fluid across glomerulus
hydrostatic pressureof csapillary-colloid osmotic pressure of blood
also minus pressure of bowman's capsule
Excretion
process of eliminating or expelling waste matter
majority of metabolic waste removed due to kidneys
metabolic wastes cannot be used by the organism
nitrogen compounds, CO2, nitrates, sulfates
Electrolyte Functions
Sodium
Na+
Plasma: 136-146mM
CSF:138-150mM
Urine: 40-220 mM
Cation of extracellular fluid
responsible for 1/2 of osmotic pg btw inside/outside of cells
Chloride
Cl-
Plasma: 98-107mM
CSF: 118-132mM
Urine: 110-250mM
Predominant extracellular anion
Major contributor to osmostic pressure gradient btw ICF & ECF
maintains proper hydration
balances cations in ECF
maintains electrical neutrality of ECF
Potassium
K+
Plasma 3.5-5mM
CSF: .35-3.5mM
Urine: 25-125 mM
major intracellular cation
established resting membrane potention in neurons and muscle fibers
after membrane depolarization and action potentials
Very little effect on osmotic pressure
Phosphate
(HPO^2)4
Plasma:.81-1.45mmol/day
Urine: 12.90-42mmol/day
mostly in bone and teeth
found in phospholipids
makes up cell membranes, in ATP, nucleotides, and buffers
Calcium
Ca+
Plasma:2.15-2.55mmol/day
Urine: up to 7.49 mmol/day
Mostly bound up in bone
used for muscle contraction, enzyme activity, blood coagulation
stabilize membranes
essential for release of neurotransmitters from neurons/hormones from endoglands
Conditions
Hypokalemia
Low potassium blood level
can be involving blood or whole body
can be caused by decreased intake, vomiting, diarrhea, alkalosis
Insulin can cause hyperpolarization of cell membranes of neurons by increasing potassium uptake
Hyperkalemia
Elevated potassium blood level
impairs function of skeletal muscles, nervous system, and heart
potassium in blood ends up in ECF
causes partial depolarization and inability to repolarize
Hypernatremia
Increase of blood sodium levels
caused by water loss from blood
hemoconcentration of blood constituents
can be caused by imbalance of ADH or aldosterone
Hypocalcimia
low calcium blood levels
hypoparathyroidism
may follow removal of thyroid gland
Hyponatremia
low concentration of salt
usually associated w excess water accumulation in body
caused by: excessive sweating, vomiting, diarrhea, use of diuertics
swelling of RBCs
decrease in oxygen carrying ability
can lead to brain damage
Hypercalcemia
high calcium blood level
primary hyperparathyroidism
some malignancies may result in hypercalcimia
Acidosis/acidemia
Excessive acidity of the blood
ineffective breathing causes build up of CO2 in bloodstream
other causes: metabolic problems affecting buffers
overproduction of acid
Alkalosis/alkalemia
Blood is too basic.
caused by breathing disorders
CO2 levels fall too low
lung disease, aspirin overdose, shock, ordinary anxiety
reduces normal concentration of H+
Major Fluid Compartments
Intracellular fluid
fluid within our cells
2/3 of total body fluid
enclosed by plasma membrane
Has more K, Mg2, PO43, and negatively charged proteins
differences due to processes within cell and transport proteins
Extrecellular Fluid
Fluid outside our cells
includes interstitial fluid, lymph, and blood plasma
Lymph
Interstitial Fluid
Extercellular fluid surrounding cells
composes 2/3 of extracellular fluid
Blood Plasma
extracellular fluid within blood vessels
separated from interstitial fluid by capillary vessel wall
more permeable than plasma membrane
interstitial fluid and blood plasma similar in composition
protein is in blood plasma
both high in na, ca2, cl, hco3
fluid mvmt is continuous btw the compartment
due to changes in osmolarity
concentration in compartment
hypotoinic or hypertonic
Drinking water decreases plasma osmolarity
water moves into interstitial fluid, then into cells
reverse mvmt if water lost from body
