Renal system Flashcards
hypothalamic control of the posterior pituitary - water balance
- ADH stimulates an increase in water permeability of the collecting duct in the kidneys, allowing water to be reabsorbed
ADH secretion as a response to osmolality
- ADH secretion is stimulated by osmoreceptor neurone in the hypothalamus as a response to a rise in plasma osmolality and osmotic pressure (cell shrinks)
what do osmoreceptors stimulate
- thirst
- a greater AP frequency of ADH-producing neurone in the hypothalamus, leading to a greater release of ADH
stretch receptors and blood volume
- low blood volume is sensed by stretch receptors in the left atrium of the heart - increases ADH secretion
negative feedback loop fincreased blood osmolality
- blood osmolality increases
- thirst and increased ADH secretion by posterior pituitary
- drinking and water retention by the kidneys
- increased blood volume (and decreased osmolality)
what happens upon release of ADH into the blood stream
- helps to increase H2O reabsorption in the kidneys
- allows water to be reabsorbed in the collecting ducts of the kidney (returned to the blood)
- concentrated urine is secreted
what are the plasma osmolality htresholds
- for stimulating ADH secretion = 280mOsm/kg
- for stimulating thirst secretion = 290mOsm/kg
- changes in plasma osmolality are greatly affected by Na+, Cl- and K+ cocentrations
what happens to osmolality when you are overhydrated
- rise in blood volume stimulates stretch receptors in the left atrium and decreased plasma osmolality sensed by osmoreceptors
- leads to inhibited ADH secretion
- water is less effectively reabsorbed in the collecting duct of the kidneys (not returned to blood)
- dilute urine is secreted
ADH secretion: effects and stimulus
increased osmolality = increased ADH = urine vol decreased
decreased osmolality = decreased ADH = urine vol increased
increased blood vol = decreased ADH = urine vol increased
decreased blood vol = increased ADH = urine vol decreased
what happens If you don’t pee
- can possibly die from acute water intoxication
what happens if the ADH gene is mutated: rat model
- a frame shift mutation in Avp gene leads to deficient synthesis and release of ADH
- rats exhibit polyuria, excessive thirst and polydipsia
diabetes insipidus
central: caused by inadequate secretion of ADH
nephrogenic: caused by an inability of the kidneys to report to ADH
distinguished by…
- measuring plasma ADH levels
- diving a desmopressin challenge
the patients don’t take insulin
ADH and nocturnal enuresis (bedwetting)
- in healthy children: increased ADH secretion at night, increased reabsorption of water and decreased nocturnal production of urine
- with nocturnal enuresis these patters are messed up
- may be because of insufficient ADH production, insufficient response to ADH or impaired sensory input from the bladder
- treatment = desmopressin
body water contents: male vs female
male: more water than women because testosterone is anabolic
female: less water than men because they typically have more body fat
where is water stored in the body
- 2/3 intracellular
- 1/3 extracellular
- of the extracellular water 80% is in interstitial fluid and 20% is in blood plasma
if we take in 1.5-2.5L of water everyday how is most of it excreted
- majority from kidneys
- lungs
- skin (sweat glands)
- feces
what is water balance
water intake = water loss
water regulation in the Arabian camel: lipid humps
- lipid is stored In the hump of camels
- lipid metabolism can provide significant metabolic water
- > 1g water per 1g lipid
- much of the water produced is evaporated from the lungs during respiration = net loss of water
what was observed with suppression of cholesterol biosynthesis in the kidneys of the Arabian camel
- it facilitates their ability to retain water
- a decrease in cholesterol showed an increase in ion channel and transporter expression in the kidneys which increases water reabsorption
- includes aquaporin 2
water regulation in the Arabian camel: RBCs
- camel RBCs are able to withstand dehydration
- RBCs are oval shaped , smaller and circulate in larger numbers
- their Hb has a greater affinity for O2
- RBC properties allows passage through small blood vessels even hewn blood viscosity is high during dehydration
- RBCs can expand up to 240% original volume - prevents hemolysis when camels drink lots of water
water regulation in the kangaroo rat: adaptations
- can survive without any intake of water
- avoid harsh desert environment
- live in colonies underground - moist air in the burrows reduces respiratory water loss
- obtain water from seeds
- produce very dry feces
- kidneys concentrate urine to lose almost no water through it
salt content in water vs humans
fresh water = 0.1% dissolved salt
human body = 0.9% dissolved salt
seawater = 3.5% dissolved salt (4x more than blood)
what happens if we drink sea water?
- osmolality increases
- ADH secretion increases
- thirst increases
- kidneys increase water reabsorption to get rid of saline in blood plasma (Na+ bad for osmolality)
- cells will shrivel
- dehydration
water regulation in marine mammals
- obtains water from metabolism of food
- produce very concentrated urine
water regulation in baleen whales
- baleen whales don’t have teeth, they have baleen made of keratin
- baleen are arranged like the teeth of a comb
- whales open their mouth to fill it with water, then force the water out
- the mat on the inside of the baleen teeth catches plankton
water regulation in hibernating bears
- live completely off of stored fat reserves from the summer and fall
- burn 8000 calories a day
- do not eat defecate, drink or urinate
water regulation in hibernating bears: adaptations
- metabolic rate is but by 50-60% as the loss of body heat is slowed
- high insulating pelt - lower surface to mass ration
- metabolic water from lipid balances respiratory water loss
- decreased respiratory and heart rates
- urea produced from fat metabolism is broken down, resulting in nitrogen being used to build protein (sustained muscle mass)
what are the 4 main structures of the urinary system
- kidney
- ureters
- urinary bladder
- urethra
what do the kidneys regulate by forming urine
- the volume of blood plasma
- the concentration of waste products
- the concentration of electrolytes in plasma
- the pH of the plasma
- also secrete EPO to stimulate RBC production
basic pathway of urine from kidneys to the urethra
- urine produced in the kidneys is drained into the renal pelvis
- the urine is then channelled from the ureters to the urinary bladder by peristalsis
- the urinary bladder is a storage sac for urine
- the bladder is drained by the tubular urethra
shape of the bladder
empty = pyramid shaped
full = ovoid, bulges up into abdominal cavity
anatomy of the kidney: 2 zones of the renal parenchyma
renal cortex: outer part, contains many capillaries
renal medulla: inner part, contains microscopic tubules
anatomy of the kidney: moving from renal cortex to the renal pelvis
- extensions of the renal cortex form renal columns which divide the renal medulla into renal pyramids
- the boat face of the pyramids faces the cortex, the blunt point is called the renal papilla
- the papilla of each pyramid is nestled in a cup called a minor calyx (collects urine from each renal pyramid)
- 2 or 3 minor calyces converge into a major calyx
- 2 or 3 major calyces converge to form the funnel-like renal pelvis (one)
what is the renal pelvis
the renal pelvis is part of the kidney that is in continuation with the ureter to allow urine from the kidneys to get into them
what is included in one lobe of the kidney
one renal pyramid and overlying cortex
- about 6-10 lobes per kidney
what is the purpose of kidney circulation
filter out products from blood into the urine
how cardiac output is delivered to the kidneys
- kidneys receive about 21% of CO
- each kidney is supplied by the renal artery
- the renal artery divides into interlobar arteries that pass between the pyramids through the columns
- interloper arteries branch into arcuate arteries at the divide between the cortex and medulla
- interlobular arteries branch off the arcuate arteries into the cortex
- interlobular arteries subdivide into a series of afferent arterioles
order of arteries leading to the kidney (specifically nephron)
renal - interlobar - arcuate - interlobular - afferent arterioles
what happens when blood arrives at the afferent arterioles of the kidney (until efferent arterioles)
- each afferent arteriole supplies one nephron
- the afferent arteriole delivers blood into the glomerulus which is then drained by an efferent arteriole
how does blood get back to the heart after getting to the efferent arteriole
- efferent arterioles deliver blood into the peritubular capillaries (which surround the renal tubules)
- blood from the peritubular capillaries - interlobular vein - arcuate vein - interlobar vein - renal vein - inferior vena cava
brief events that happen when filtering blood at the kidneys
- blood enters at the glomerulus
- blood is filtered through the nephron
- a) urine leaves out the collecting duct (whatever remains in filtrate)
- b) blood leavers out the renal vein (anything filtered out of filtrate)
lobulated bovine kidney
- present in cattle (don’t have the simple kidney)
reticulate kidneys
- in hibernating and marine mammals
- has increased surface area (more renal pyramids and release more toxins/absorb more water)
what is the nephron
the functional unit of the kidney which is responsible for the formation of urine
- each kidney contains over a million nephrons
- made up of tubules and associated small blood vessels
- fluid formed by capillary filtration enters the tubules and the resulting fluid that leaves is urine
what are the 2 types of nephrons
- Juxtamedullary nephrons (20%)
- originate in the inner 1/3 of the cortex
- longer nephron loop
- important for producing concentrated urine - cortical nephrons (80%)
- originate in the outer 2/3 of the cortex
- shorter loops - don’t extend as deep into adrenal medulla
what are the 4 regions of the nephron
- Bowmans/ glomerular capsule
- proximal convoluted tubule (PCT)
- loop of Henle (consists of a descending and ascending limb)
- distal convoluted tubule (DCT)
how does filtrate leave the DCT
- the DCT is in direct contact with the glomerulus and arterioles
- filtrate drains from the DCT into the collecting ducts where we have secretion of ADH for water reabsorption
true or false: all regions of the nephron are associated with networks of peritubular capillary vessels
true