Posterior pituitary stores and releases what two hormones?
- ADH
- Oxytocin
- released when needed
ADH is significant why?
- primary role is to stimulate water retention by kidneys
- secondary role is to cause a rise in blood pressure via vasoconstriction
Osmolality
- concentration of solution (how “substancey” something is)
Brattleboro rats
Mutated ADH gene
- exhibit excessive thirst and frequent urination
- kidneys can’t retain water
Human water content varies with age and gender - give some examples
- babies ~75% water
- women ~50%
- men ~60%
- elderly ~45%
What happens when blood osmolality goes up?
- osmoreceptors in hypothalamus signal to posterior pituitary to release ADH into blood stream
- ADH tells kidneys to resorb water (pee less)
- Blood volume goes up and blood osmolality decreases
Sources of water intake
- fluids and food (2250 mL)
- metabolism (250 mL)
Sources of water loss
- urine (1500 mL)
- lungs (700 mL)
- sweat (200 mL)
- feces (100 mL)
Where is all the water in our bodies?
2/3 is intracellular
1/3 is extracellular
* interstitial fluid
* blood plasma
Human urine is ___ times more ______ than blood
4.6; concentrated
Arabian camel water regulation
Can’t avoid hot dry dessert and could go days without water - even active
- can’t close kidneys down! so instead
- lipid stored in hump because lipid metabolism provides lots of energy
- dry food provides some water
- kidney is very efficient
- thermoregulates by panting but shuts down when dehydrated
- urine to blood ratio is 7
Kangaroo rat water regulation
Never drinks water and has high respiratory water loss!
- obtains water from dry food and metabolic water
- moist air in burrows
- nocturnal
- very dry fees
- urine to blood ratio is 14
Marine mammal water regulation
No access to fresh water and seawater has a salt concentration of 3.5%
- obtain water from food (krill)
- produce very concentrated urine
- ratio of 5 to 6
Water regulation hibernating bears
Hibernate at half the year without eating drinking or excreting
- reduce BT
- reduce heart rate
- metabolic water from lipids balances respiratory water loss
- special mechanism for eliminating urea without urinating
3 main functions of the kidney
- excrete metabolic waste products
- involved in water and electrolyte regulation
- balance pH
Functional unit of kidney
NEPHRON
- 80% cortisol
- 20% dip into medulla
4 regions of nephron
- Bowman’s capsule
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
Bowman’s capsule
Contains glomerulus
- porous epithelial lining allows for filtration
- podocytes (holey cells)
PCT
Located in renal cortex
- lots of mitochondria to make ATP to power pumps that pull lots of sodium ions from filtrate
- large surface area
Loop of Henle
Starts in cortex, dips into medulla, and comes back up
- Drives reabsorption by creating a salt concentration gradient
- actively pumps out salt in ascending limb
- passively pumps out water in defending limb
DCT
Renal cortex
- filtrate runs out of loop and into collecting duct
Urine is formed by 3 basic steps
- Filtration
- Reabsorption
- Secretion
Glomerulus
Tangle of capillaries (like a ball of yarn)
- blood flows in afferent arteriole
- blood exits efferent arteriole
- filtering occurs thanks to hydrostatic blood pressure
Glomerular filtration rate
Myogenic autoregulation of filtration so that nothing changes with blood pressure
- increase in bp causes afferent to constrict and efferent to dilate
- decrease in bp causes afferent to dilate and efferent to restrict
