Homeostasis & Kidneys Flashcards
What is Homeostasis?
maintaining a stable internal environment despite external factors
What are some of the conditions that are controlled by homeostasis?
temperature, water levels, sugar levels, pH
What does the maintaining of a stable internal environment allow for?
allows for organisms to function at optimal levels even when challenged by internal and external changes
What is a stimulus?
what causes a reaction to occur
What is a receptor?
sensory neurone, sends signal in response to stimulus
what is the CNS?
Central Nervous System - contains hypothalamus, transfers signal to receptors and sends signal to effectors
WHat is the effector?
the actual cell that responds to the signal. Brings change back to the normal.
What is positive feedback? and example
something of small quantity increased (e.g. hormone oxytocin produced in large quantity for cervix contraction) a lot rarer
WHat is negative feedback? and example
something in a large quantity regulated to normal (insulin is released, removing glucose from blood, blood glucose level drops and insulin production stops/decreases)
When is ADH released?
when you are dehydrated
Where is ADH secreted from?
the pituitary gland
What detects the osmolarity to send message for ADH release?
the Hypothalamus has osmoreceptors which detects an increase in osmolarity
What does ADH do?
causes production of urine to decrease (less water lost)
makes the walls of the collecting duct more permeable (more aquaporins) to water, so that more is reabsorbed from the filtrate back into the blood
What is the urine produced when there is a low water potential / increased osmolarity?
relatively concentrated
What does osmolarity mean?
number of particles of solute per litre of solution (solute concentration)
What is Diuresis?
production increase result in large volume of urine
What is anti-diuresis?
production decrease result in little/controlled urine
What is the hypothalamus?
coordinates the nervous system, controls homeostasis systems contains receptors for homeostasis (osmoreceptors)
What is the anterior pituitary gland?
endocrine gland, secretes hormones, epithelial cells
WHat is the collecting duct?
collects urine from the kidneys (nephrons), reabsorbs water
WHat are aquaporins?
transmembrane proteins that regulate the flow of water into and out of cells/allow water to move across cell membrane
What does permeability mean?
ability of water to move across cell membrane
What is excretion?
getting rid of the waste products of metabolism (CO2, Urea)
What is secretion?
movement of products out of the cell tobe used elsewhere like enzymes
What is egestion?
removal of stuff that cannot be digested (undigested material)
What is the process which happens in the liver to do with excess proteins?
deamination
What happens to excess proteins in deamination?
proteins are metabolised for ATP
What group is removed from a protein in deamination?
AMine group is removed which forms ammonia which is toxic
ammonia is converted to Urea which is transported in the blood and removed
What is ultrafilitration?
blood comes into the nephron in the afferent arteriole into glomerulus under high hydrostatic pressure, filtrate forced out through the pores in the basement membrane. Podocytes absorb filtrate and passes it through to the bowman’s capsule filtrate then to proximal convoluted tubule. blood carries on through the glomerulus through the efferent arteriole
Why does the efferent arteriole have a smaller diameter?
to create pressure in the glomerulus to filter the waste materials
What 3 things cannot pass from the blood through the bowman’s capsule (pores in basement membrane)?
large molecules - platelets, large plasma proteins, and red blood cells
What do podocytes do?
create a large surface area for absorption
What happens to glucose and amino acids in filtrate in proximal convoluted tubule?
glucose and amino acids will be reabsorbed
Describe the structure of the proximal convoluted tubule
Long, Highly folded so has a large surface area lots of cuboidal epithelial cells with microvilli
What is the function of the proximal convoluted tubule?
selective reabsorption - so that glucose, amino acids, water, some salts are not lost in urine
Describe the structure of the Loop of Henle
Long U shaped portion of the tubule
thin descending limb which is permeable thick ascending limb which is impermeable
surrounded by capillaries
What is the function of the Loop of Henle?
low water potential of the medulla allows for reabsorption of water
What is the structure of the distal convoluted tubule?
twisted region between loop of Henle and collecting duct
What is the function of the distal convoluted tubule?
alters the concentration of water and salts reabsorbed
permeability to water is altered by ADH
What is the structure of the collecting duct?
The final region connects distal convoluted tubule to the renal pelvis
WHat is the function of the collecting duct?
transports urine from the distal convoluted tubules to the renal pelvis
permeability to water is altered by ADH
How do ions move through the membrane of the cuboidal epithelial cells of the proximal convoluted tubule?
facilitated diffusion, as they are charged so cannot pass through the phospholipid bilayer
How do amino acids move through the membrane of the cuboidal epithelial cells of the proximal convoluted tubule?
cotransport, through symport (2 molecules the same way), binding to cotransporter with sodium ions. Therefore antiport active transports potassium and sodium ions in.
How does glucose move through the membrane of the cuboidal epithelial cells of the proximal convoluted tubule?
cotransport, through symport (2 molecules the same way), binding to cotransporter with sodium ions. Therefore antiport active transports potassium and sodium ions in.
How does water move through the membrane of the cuboidal epithelial cells of the proximal convoluted tubule?
osmosis
what does length and number of tubules in proximal convoluted tubule allow?
lots of diffusion/active transport/ cotransport/osmosis due to increased surface area (more selective reabsorption)
what do the cuboidal epithelial cells with lots of microvilli in proximal convoluted tubule allow?
increase surface area, allow for more absorption and lots of carrier proteins in the phospholipid bilayer
What do the channel proteins in proximal convoluted tubule allow?
to allow for movement of large molecules like glucose and amino acids through the membrane
What are 2 of the major roles of the Kidney?
excretion and osmoregulation
What are the consequences if excretion and osmoregulation fail?
body is unable to remove urea, so concentration increases to toxic levels
body is unable to remove excess water, so bodily fluids increase in volume and are diluted, compromising metabolic reactions
What are the common causes of kidney failure?
diabetes, high blood pressure, auto-immune disease, infection, crushing injuries
How can diabetes cause kidney failure?
high glucose concentration in the plasma results in the glomeruli losing protein into the filtrate and causes some proteins to link together, triggering scarring in a condition called glomerulosclerosis
How can high blood pressure cause kidney failure?
cause damage to the capillaries of the glomerulus preventing ultrafiltration
What are some treatments for kidney failure?
reducing intake of certain nutrients (mainly proteins) to release urea formation and ions
using drugs to reduce blood pressure
insulin/glucose for potassium
bisphosphates for calcium
dialysis
kidney transplant
What drugs are used to reduce blood pressure?
angiotensin-converting enzyme inhibitors and angiotensin receptor blockers
Calcium channel blockers
beta blockers
What do angiotensin-converting enzyme inhibitors and angiotensin receptor blockers do?
reduce effect of angiotensin, (a hormone that constricts blood vessels, increasing the pressure of the blood within.)
What do calcium channel blockers do?
dilate blood vessels and reduce blood pressure
What are bisphosphates used for?
treating calcium in the blood - which is correlated with increased risk of heart disease, kidney stones and osteoporosis. Bisphosphates decrease the activity of the osteoclast (cells that break down bone in its constant recycling) Calcium therefore accumulates in the bone and less circulates in the blood
What does dialysis do?
enables blood to be cleaned, without the kidneys
How does dialysis work?
blood and dialysis fluid are separated by a selectively permeable membrane the dialysis fluid has the same water potential as the blood, but a low ion concentration and no urea. Inorganic ions, water and urea diffuse out of the blood across the membrane, down their concentration gradients. No glucose diffuse out as dialysis machine contains same concentration of glucose
What are the pros of dialysis?
readily available, no wait time
no chance of rejection
no need for major surgery
no need to take drugs like immuno-suppressants
What are the cons of dialysis?
requires expensive machinery
time consuming 2-3 days a week 4-6 hours at a time
must monitor diet very carefully
painful for patient
can cause infections
more expensive for NHS
can cause blood clots
What are the pros of a kidney transplant?
live longer
better quality of life
no longer need dialysis
What are the cons of a kidney transplant?
infections are common
can be rejected
kidney disease may return n transplanted kidney
What are the 3 types of excretory products?
ammonia, urea, uric acid
What types of animals excrete ammonia? and why?
fish, crocodiles and alligators - as they do not need to conserve water as much, it requires little energy
What animals excrete urea? and why?
humans - as its less toxic so can be stored and less water required, but still some for urine.
What animals excrete uric acid? and why?
lizards, snakes, birds and insects - to conserve water (as its insoluble in water) if water used may cause dehydration.
Allows for the laying of terrestrial eggs as uric acid can be stored as solid waste in the shell (which is left behind when hatched)
what is the function of the loop of henle?
management of fluids - selective reabsorption of water and sodium ions
In the loop of Henle where are ions pumped out?
in the thick ascending limb
In the loop of Henle where is water pumped out?
in the thin descending limb
What happens to the water potential in the interstitial space when ions are pumped out?
it lowers
Where is the water pumped out the thin descending limb absorbed by?
vasa recta
As water is pumped out of the thin descending limb what happens to the filtrate in the loop of henle?
filtrate becomes more concentrated
