M5 C15: homeostasis Flashcards
what is homeostasis?
maintaining a dynamic equilibrium with fluctuations over a narrow range
why does homeostasis include fluctuations over a narrow range?
impossible to be completely stable within the body
what are some factors controlled by homeostasis?
temperature
urea concentration
blood glucose conc
blood ph
what is negative feedback?
when a increase or decrease in conditions is detected the body will either have a response so the body goes back to ideal conditions
what are some examples of negative feedback?
insulin- lowers blood glucose conc by converting glucose to glycogen
glucagon- increases blood glucose conc by converting glycogen to glucose
what is positive feedback?
when a change is detected in conditions, a response reinforces the change.
what are some example of positive feedback?
blood clotting
depolarisation
contractions
thermoregulation
maintenance of a relatively constant core body temp
why is maintaining a constant core body temp good?
maintains optimum enzyme activity
what is an ectotherm?
animals that use their surroundings to warm their bodies
what is an endotherm?
animals that rely on metabolic processes to warm up and maintain a stable temp
what are behavioral responses?
change in how organisms behaves to different stimuli
what are physiological responses?
automatic responses to stimulus due to physiological features of an organism
what is conduction?
heating due to collision of particles/molecules
are gases, solids or liquids good conductors?
gases- poor due to low freq of collisions
liquids + solids - good due to particles being close together
what is convection?
heating and cooling due to currents of air.
e.g. warm air rises, but cools down the higher it is. this then sinks and warms up again as it is closer to the ground.
what is radiation?
heating and cooling by transmission of electromagnetic waves to and from a source
what type of organisms are ectotherms?
fish
amphibians
reptiles
invertebrate animals
why are most aquatic animals ectotherms?
they live in water, which has a high heat capacity. this means it doesn’t change temperature easily so they don’t need to thermoregulate themselves
what are some behavioural responses a ectotherm could do to warm up?
increasing SA towards sun
vibrating
pressing body against warm ground
bating in sun
what are some physiological responses a ectotherm could do to warm up?
increase heart rate
darker colour
what are some behavioural responses a ectotherm could do to cool down?
hide in cracks
reduce movements
face body away from sun
what are some physiological responses a ectotherm could do to cool down?
decrease metabolic rate
why can ectotherms live in environments with limited food?
because they need less energy to maintain a constant core body temp to regulate temp
what is a disadvantage of ectotherms?
affected by fluctuations in the environment
what is vasodilation?
when arterioles near the surface of the skin dilate and the vessels between the arterioles and venules constrict, forcing blood through capilaries close to the skin
what does vasodilation do to an organsism?
cools it down due to radiation of heat from blood to skin
what does increased sweating do?
cools an organism down as heat is lost due to evaporation which cools the blood below the skin
what is vasoconstriction?
arterioles near the surface of the skin constrict and the vessels that connect them to the venules dilate so less blood goes close to the surface of the skin
what does vasoconstriction do?
warms up the organism as there is little radiation taking place
what does decreased sweating do?
decreasing cooling as there is little evaporation happening from water on the surface of the skin
what is hypothermia?
core body temperature falls below 36 degrees
what is a fever?
core body temperature rises above 38 degrees
what does the hypothalamus do in regards to temperature reception?
monitors temperature by thermoreceptors in skin
what do receptors in the hypothalamus detect?
temperature changes in the brain and blood
how is the heat loss centre in the hypothalamus activated?
when blood temperature flowing through increases. It sends impulses through autonomic motor neurons to effectors in the skin and muscles, triggering responses that act to lower core temperature.
how is the heat gain centre in the hypothalamus activated?
when blood temperature flowing through decreases. It sends impulses through autonomic motor neurones to effectors in the skin and muscles, triggering responses that act to raise core temperature.
what are the 3 main roles of the liver?
carbohydrate metabolism
detoxification
deamination
what is deamination?
the amino group (NH2) is removed from an amino acid … converted to ammonia … and then the less toxic urea, to be excreted. The remainder of the amino acid is then used in cellular respiration or converted into lipids for storage.
why is deamination needed?
the body cannot store proteins or amino acids,
How are bile pigments produced in the body?
Breakdown of haemoglobin from old red blood cells in the liver
how is the blood supplied to the liver?
by hepatic artery
how is blood taken away from the liver to the heart?
by the hepatic vein
what does the hepatic portal vein do?
take digestion products from the intestines to the liver
what are hepatocytes?
liver cells
what are some key features of hepatocytes?
have large nuclei
prominent golgi apparatus
lots of mitochondria
will replicate even if around 65% is lost
what it the name of the place where the blood from the hepatic portal vein and artery mix?
Blood is mixed in sinusoids which are surrounded by hepatocytes
this is to supply blood with enough oxygen to hepatocytes
where are kufper cells located?
in the sinusoids. they digest foreign particles
where is bile drained to from the hepatocytes?
canaliculi then it drains into the bile ductules and is taken to the gall bladder.
how are hepatocytes involved in carbohydrate metabolism?
they convert glucose to glycogen when levels rise and then back to glucose when levels fall.
what is transamination?
the conversion of one amino acid into another.
what is detoxification + an example?
the Conversion of toxic substances into harmless ones. e.g. hydrogen peroxide into oxygen and water using the enzyme catalase.
what are some amino acids used for?
some amino acids that are absorbed from the small intestine go into the amino acid pool to build new proteins
what happens to excess amino acids?
sent to liver for deamination where the amino group combines wth CO2 to form urea and sent to kidneys
what is the rest of the amino acid used for? (apart from the amino group)
used as a respiratory substrate
what is the ornithine cycle?
where the ammonia group produced in deamination combines with CO2 to make citrulline and water
what happens in the ornithine cycle after citrulline and water is made?
ammonia is added again to make arginine and water. this is combined with water to make urea and what is left is ornithine
bowmans capsule?
Cup-shaped structure that contains the glomerulus, a tangle of capillaries. Where ultrafiltration takes place.
proximal convoluted tubule?
First coiled region of the tubule after the Bowman’s capsule. Where reabsorption takes place.
loop of Henle?
Long loop of tubule that creates a region with a very high solute concentration in the tissue fluid deep in the kidney medulla.
distal convoluted tubule?
Second twisted tubule where the fine-tuning of the water balance takes place.
collecting duct?
Urine passes down here through the medulla to the pelvis. More fine tuning of water balanced takes place.
what is the role of the kidneys?
excretion and osmoregulation
how are the kidneys supplied with blood?
by the renal arteries that branch off from the abdominal aorta
how does blood leave the kidneys?
via the renal vein that drains into the inferior vena cava.
where does urea go to after the kidneys?
it passes out of the kidneys down tubes called ureters. It is collected in the bladder, and then passes out of the body via the urethra.
what is the cortex of the kidney?
the dark outer layer where filtering of blood takes place.
what is the medulla of the kidney?
lighter in colour than the cortex and contains tubules of the nephrons that form pyramids of the kidney and the collected ducts.
what is the pelvis of the kidney?
the central chamber where urine
collects before being passed out the ureter.
what happens to the blood in the nephrons?
Blood is filtered
the majority of the filtrate is returned to blood
removing nitrogenous wastes
balancing the mineral ions and water.
what is the difference between the afferent and the efferent arteriole?
afferent is thicker and the efferent is narrower
what happens in the bowmans capsule?
Ultrafiltration occurs in the Bowman’s capsule.
what happens in the proximal convoluted tubule?
selective reabsorption
what is reabsorbed in selective reabsorption?
all of the glucose, amino acids, hormones and vitamins are reabsorbed and about 85% of the sodium chloride and water.
what happens in the ascending limb in the loop of henle?
sodium and chloride ions are pumped out into the medulla tissue fluid.as it is H20 impermeable
what happens in the descending limb in the loop of henle?
Water moves out of the descending limb of the loop of Henle, by osmosis down a concentration gradient. as this is permeable to water
what happens in the distal convoluted tubule?
A balancing of the water needs of the body takes place in the distal convoluted tubule.
what happens in the collecting duct?
Water moves out of the collecting duct by diffusion and this is where ADH makes it more permeable to water
what does adh stand for?
anti diuretic hormone
where is adh produced?
the hypothalamus
where is adh stored?
posterior pituaitry gland
what does adh do?
affects peremability of the collecting duct and distal convuluted tubule
how does adh work?
when it binds to receptos of collecting duct mebrane it triggers the formation of cAMP this causes vesucles in the cells lining the membrane to fuse with the cell surface membrane on the side near the tissue fluid they then release aquaporins into the membranes
what is cAMP called in the action of ADH/
a secondary messenger
what do aquaporins in the collecting duct membrane do/
allows water to move out via osmosis so more water is reabosrbed from the nephron
what happens when water potential increases in regards to ADH?
this is detected by osmoreceptors in the hypothalamus, less ADH is released so less water is reabsorbed as there are no aquaporins, a large vol of dilute urine is produced
what does urea contain?
brealdown of products that have been in the body such as hormones, drugs,
what is hCG?
human chorionic gonadotrophin
a hormone only found in pregnant women
what are monoclonal antibodies?
identical copies of antibodies
how are monoclonal antibodies made?
hormone injected into mouse which makes antibodies for the hormone. these are removed and then fused with a myeloma cell that divides rapidly making hybridoma cells. these antibodies are then collected and purified from the cells
what happens at the reaction site on a pregnancy test?
urine is added to the stick hcg binds to mobilised antibodies which then form a hcg antibody complexw
hat happens at the test site on a pregnancy test?
the hcg antibody complexes bind to imobilised antibodies this causes a colour change due to the dye on the antibody being activated this produces a line showing that someone is pregnant
what happens at the control site on a pregnancy test?
excess mobilized antibodies bind to more immobilized antibodies which causes a second line to appear.
what are anabolic steroids?
used by sports athletes to increase testosterone (strength and muscle mass)
how are athleets tested for steroids?
urine test is done where gas chromatography i used where the urine is vaporized with a solvent the lining on a tube then absorbs gases and is analyzed with mass spectrometry for drugs
what are some symptoms of kidney failure?
blood in urine
high blood pressure
anemia
weak bones
low glucose concentration
Loss of electrolyte balance
urea in blood
what can cause blood pressure?
infections
genetics
raised blood pressure
what is GFR?
glomerular filtration rate
Uses levels of creatinine in blood to estimate the glomerular filtration rate.
why are levels of creatine used to estimate GFR?
Creatine is a breakdown product of muscles. If creatine levels go up, its an indication that the kidneys are not working properly – they aren’t effectively filtering creatine out.
what GFR indicates kidney failure?
below 60- chronic kidney disease
below 15- severe failure of the kidneys
what can affect GFR?
age
ethnicity
gender
exercise
body mass
what happens in haemodialysis?
Blood flows between partially permeable dialysis membranes. These membranes mimic the basement membranes of the Bowman’s capsule in a counter current flow. During dialysis, patient lose the excess urea and mineral ions that have built up in the blood – but not the glucose and some mineral ions.
what does dialysis fluid consist of?
normal levels of glucose found in blood
normal concentration of mineral ions … so excess mineral ions move out
No urea in dialysis fluid
why is it good that the blood and dialysis fluid flow in different directions?
counter current flow maintains a steep concentration gradient so increases diffusion rate.
what happens in peritoneal dialysis?
occurs inside the body making use of membranes formed by the abdomen lining, the peritoneum.The dialysis fluid is introduced into the abdomen using a catheter. You may need 3 to 5 exchanges during the day
what happens during a kidney transplant?
a single healthy kidney from a donor is placed in the body
what are pros of having a kidney transplant?
no need for regular sessions
less expensive
long term dialysis can have side effects and cause damage to body
no diet restrictions
what are cons of having a kidney transplant?
less readily available
transplants have a limited lifespan
risk of rejection
immuno- suppressants can lead to a chance of infection
