chapter 15 - homeostasis Flashcards
what is monitored in homeostasis
pH of blood
core body temperature
concentration of urea and sodium ions in blood
what is a negative feedback system
reverse initial stimulus
what is positive feedback
effectors reinforce and increase change detected by stimulus
what is an example of negative feedback system
production of insulin to lower blood glucose concentration when it increases
what is an example of a positive feedback system
oxytocin produced when head of baby presses againt cervix causing uterus to contract and push baby harder causing even more oxytocin to produce
what is an example of a positive feedback system
oxytocin produced when head of baby presses againt cervix causing uterus to contract and push baby harder causing even more oxytocin to produce
what is thermoregulation
maintenance of constant core body temperature to maintain optimum enzyme activity
what causes organisms to gain heat
waste heat from cellular respiration
conduction from surroundings
convection from surroundings
radiation from surroundings
what causes organisms to lose heat
evaporation of water
conduction to surroundings
convection to surroundings
radiation to surroundings
what are ectothermns
use mainly surroundings to warm their bodies
why do ectotherms live in water
high heat capacity of water means temperature of environment doesnt change much so they dont need to thermoregulate
what are endotherms
rely on metabolic processes to warm them up
why do endotherms need to eat more than ectotherms
they have higher rate of metabolism to stay warm so has higher metabolic needs
what are behavioural responses
bask in sun and orientate to maximise surface area exposed to radiation from sun
press against warm ground to gain heat by conduction
contract muscles to increase cellular metabolism to gain heat
shelter from sun to shade to get cold
hide in cracks in rocks
move to water or mud
orientate so minimum surface area is exposed to sun
minimise movements to decrease metabolic heat
what are physiological reponses
lizards living in colder climates have darker skin to absorb more heat
ectotherms can alter heart rate to increase or decrease metabolic rate
what receptors detect change in temperature of surface
peripheral receptors in skin
what receptors detect changes in temperature in blood
temperature receptors in hypothalamus
how do endotherms cool down
vasodilation- artierioles near skin dilate and vessels between arterioles and venules constrict forcing blood to surface of skin to cool
increased sweating
reducing insulating effect of hair by lying flat
how do endotherms warm up
arterioles near skin contrict so little blood flows through surface of skin so little radiation take place
decreases sweating
raising body hair
shivering
how is heat loss centre activated
when temperature of body flowing through hypothalamus increases it send impulses through autonomic motor neurones to effectors in skin and muscles
how is heat gain centre activated
when temperature of blood flowing through hypothalamus decreases
what are the main metabolic waste products in mammals
co2-waste product of cellular respiration
bile pigments - from breakdown of haemoglobin
nitrogenous waste - from breakdown of excess amino acids in liver
what does hepatic portal vein do
carries blood loaded with products of digestion straight from intestines to the liver for metabolic activities
what is the structure of hepatocytes
large nuclei
prominent golgi apparatus
lots of mitochondria as they are metabollically active
what do sinusoids do
mix blood from hepatic artery and hepatic portal vein increasing oxygen content of blood from hepatic portal vein supplying hepatocytes with enough oxygen for their needs
what do sinusoids contain
contain kupffer cells which act as macrophages and ingest pathogens
what is canaliculi
bile is stored here and drained into bile ductules which takes it to gall bladder
what are functions of liver
carbohydrate metabolism
deamination of excess amino acids
detoxification
what is transamination
conversion of one amino acid to another as diet does not always contain required balance of amino acids
what is deamination
removal of an amine group from a molecule converting it to ammonia and then to urea
where is urea excreted
excreted by kidneys
what can happen to remainder of amino acid
used in cellular respiration
converted into lipids for storage
how is ammonia converted to urea
placed into ornithine cycle
what are the 3 main areas of kidney
cortex - dark outer layer where filtering of blood takes place. Carries blood from renal artery to nephrons
Medulla - lighter in colour-contains tubules of nephrons that form kidney and collecting ducts
pelvis - central chamber where urine collects before passing down ureter
what is structure of nephron
bowmans capsule - contains glomerulus
proximal convulated tubule - where substance needed are reabsorbed into blood. Found in cortex
loop of henle - creates a region of high solute concentration in tissue fluid in medulla
distal convulated tubule - where tuning of water balance takes place
collecting duct - urine passes down collecting duct through medulla to pelvis
what is ultrafiltration
removal of nitrogenous waste and osmoregulation of blood
how is proximal convulated tubule adapted
covered with microvili to increase SA
have many mitochondria to provide ATP for active transport
where is ADH produced
produced by hypothalamus and secreted into posterior pituitary gland
what does ADH do
increase permeability of distal convulated tubule
what is the mechanism for ADH action
1)ADH is released from pituitary gland to the collecting duct which binds to receptors on cell membrane to form CAMP which causes events
2) vesicles lining collecting duct fuse with cell surface membrane on the side of the cell in contact with tissue fluid of medulla
3) membranes of these vesicles contain aquaporins which are inserted into cell surface membrane making it more permeable to water
4) this provides a route for water to move out of tubule cells into tissue fluid of medulla and blood capillaries by osmosis
what do osmoreceptors do
controls permeability of collecting duct by sending nerve impulse to posterior pituitary gland which releases ADH
how do osmoreceptors detect short water supply
when water is slow, osmoreceptors detect high concentration of inorganic ions making water potential more negative
what hormone is found in urine which shows your pregnant
hcG produced by uterus 6 days after conception
what are monoclonal antibodies
antibodies from a single clone of cells that are produced to target particular cells or chemicals in the body
how are monoclonal antibodies created
hcG in injected into mouse and B-cells that make specific antibody are removed from spleen and fused with cancer cell called myeloma forming hybridoma. This divides very rapidly
what are the stages of pregnancy test
1) wick is soaked in the first urine passed in morning as it has highest level of hcG
2) test contains mobile monoclonal antibodies that have coloured beads that only attach to hcG forming hcG/antibody complex
3) urine carries on along test structure until it reaches a window containing immobilised monoclonal antibodies that only binds to hcG/antibody complex forming a line
4) urine continues up through test to a second window
5) there is a line of immobilised monoclonal antibodies that bind to mobile antibodies whether they have hcG or not showing that test works
what are anabolic steroids
mimick the male sex hormone testosterone that stimulates growth of muscles
how is urine used to test for anabolic steriods
urine is vaporised with known solvent and passed along a tube. The lining of tube absorbs the gases and is analysed to give a chromatogram that can be read to show presence of the drugs
what are reasons why kidney fail
kidney infections where pedocytes and tubules are damaged
raised blood pressure that can damage epithelial cells and basement membrane of bowmans capsule,
and genetic conditions such as polycystic kidney disease where healthy tissue is replaced by fluid-filled cysts
what happens if kidneys are affected by high blood pressure
proteins present in urine as basement membrane are damaged and no longer filters
blood in urine as filtering system isnt working
what happens if kidney fails completely
concentration of urea and mineral ions build up in body causing:
- loss of electrolyte balance causing osmotic balance
- build of toxic urea in blood
- high blood pressure
- weakened bones as calcium balance in blood is lost
- pain and stiffness in joints as abnormal proteins build up in blood
- anaemia - reduces production of red blood cells
how is health of kidney measured
glomerular filtration rate by measuring level of creatinine in blood
how are kidney diseases treated
renal dialysis- function of kidney is carried out artificially
kidney transplant
what is haemodialysis
uses dialysis machine
blood leaves patient body from artery and flows into dialysis machine between partially permeable dialysis membranes mimicking basement membrane of bowmans capsule
no active transport
how does haemodialysis make sure glucose isnt removed
dialysis fluid has normal plasma levels of glucose so glucose doenst leave blood
what is peritoneal dialysis
used natural dialysis membrane formed by lining of abdomen, peritoneum
dialysis fluid is introduced into abdomen for dialysis to take place
dialysis fluid is then drained off
