bio 2 module 11

intracellular fluid (ICF)

enclosed in cells, cytoplasm, 60% of water in the body

extracellular fluid (ECF)

surrounds cells; plasma (blood) and interstitial fluid

osmolarity

ratio of solutes to solvent in a solution

plasma osmolarity

ratio of solutes to water in blood plsama, measure of hydration

hyperosmotic

higher solute

hypoosmotic

lower solute

isoosmotic

equal solute

fluid movement

moves from high pressure to low pressure; from low solute concentration to high solute concentration; balance of hydrostatic and osmotic pressure

solute movement

depends on size, polarity, membrane permeability, and concentration gradient; can be active or passive

osmoreceptors

in hypothalamus detect changes in blood osmolarity and trigger thirst

digestive system regulates

water and solute input; water absorbed in large intestine

urinary system regulates

water and solute output with help from endocrine and cardiovascular systems

characteristics of healthy urine

pale yellow to deep amber, clear; odorless; slightly acidic; 750-2000mL/day; should be denser than waterc

characteristics of unhealthy urine

red (blood) brown (liver failure) cloudy (infection; sweet smell (diabetes); below 500ml means dehydration; pH changed by diet

kidneys

form urine; partially protected by rib cage

ureters

transport urine from kidney to bladder

bladder

storage reservoir for urine

urethra

connectes bladder to outside

kidneys inner medulla

contains pyramids and collecting ducts

renal pelvis

collects urine and transports to ureter

nephron

functional units in the kidney, cleans blood and solute concentration

glomerulus

arterioles form tuft to increase pressure

renal corpuscle

glomerulus + Bowman’s capsule

proximal convoluted tubule (PCT)

brush border for SA: maximize absorption and secretion; high concentration of mitochondria beause of active transport

distal convoluted tubule (DCT)

similar to PCT but shorter and less active

collecting ducts

not part of nephron, but continuous with it; each duct collects from several nephrons; lined with simple squamous epithelium with receptors for ADH; insert aquaporin protein channels

function of nephrons

take in, fultrate and modify into urine; primary goals: balance homeostatic set points of plasma and remove potential toxins; secondary goals regulate blood pressure, red blood cell production, and Ca2+ homeostasis

3 steps of nephrons

1. filtration

2. reabsorption (back into blood)

3. secretion (into nephron)

glomerular filtration rate (GFR)

the volume of filtrate by both kidneys per minute; 1L of blood enters kidneys per min an dproduces 80-140 mL/filtrate = 150-180L/day

hydrostatic pressure

fluid against a surface; fluid on both sides oppose each other

osmotic pressure

water wants to flow to high solute concentrations

net filtration pressure (NFP)

sum of all pressures

reabsorption and secretion

necessary to prevent rapid dehydration; can be passive (water, urea, most ions), active (Na+), or secondary active (glucose and amino acids)

secondary active transport

Na+ is actively pumped from the PCT to the interstitial space and diffuses into the capillary, water follows; 3 membranes causes interesting sodium gradient which carries molecules, like glucose through membrane

descending loop of Henle

aquaporins, for water reabsorption; almost no protein channels for salt or other molecules; uncoupled reabsorption of water and Na+

ascending loop of Henle

no aquaporins; Na+/K+Cl- symporter drives most reabsorptions

vasa recta

flow is the opposite the flow of filtrate

juxtaglomerular cells

release renin when high osmolarity is detected in filtrate

renin-angiotensin-aldosterone system (RAAS)

renin converts angiotensinogen into angiotensin I; lungs convert angiotensin I into angiotensin II using angiotensin-converting enzyme (ACE)

angiotensin II

causes vasoconstriction, stimulates release of ADH and aldosterone, triggers thirst

aldoesterone

stimulate synthesis and insertion of Na+/K+ pumps on the basolateral side; stimulate synthesis and opening of Na+ and K+ channels on the apical membrane

role of ADH

increase permeability to water to increase water retention in kidney; constrict blood vessels to increase blood pressure and reduce flow to extremities

diuretics

oppose ADH function and increase urine outputl

alcohol

inhibits ADH which leads to dehydration

atrial natriuretic peptide

opposes RAAS; releases by walls of atria when blood volume and blood pressure increase (baroreceptors); inhibits release of renin and aldosterone; inhibits NaCl reabsorption by collecting ducts; decreases ADH and angiotensin II; decreases blood pressure