homeostasis Flashcards
describe the difference between negative and positive feedback
negative= reverse change positive= reinforce change
name some behavioural and physiological responses of ectotherms
behavioural
- increase/ reduce radiation absorbed from sun
- press bodies against warm ground
- contract + vibrate muscles
- shelter from sun
- move into water/ mud
physiological
- change colour
- alter heart rate
how do endotherms detect temp change
peripheral temperature receptors in skin
temp receptors in hypothalamus detect blood temp
name and describe the 2 control centres in endotherms (physiological responses)
heat gain centre
- activated when blood temp in hypothalamus decreases
- effectors raise body temp
heat loss centre
- blood temp in hypothalamus increases
- sends impulses through motor neurones to effectors in skin + muscles
name methods of warming up + cooling down in endotherms
warming up
- vasoconstriction (reduce radiation of heat from capillaries close to ski surface)
- raising body hairs (traps insulating layer of air)
- shivering
cooling down
- vasodilation
- increased sweating
- hair erector muscles relax
name the blood vessels linked to the liver
hepatic artery- supplies oxygenated blood
hepatic vein- takes blood away to heart
hepatic portal vein- supplies blood loaded with products of digestion
describe the structure and function of the liver
detoxifies potentially poisonous substances
made up of hepatocytes
-many mitochondria
-secrete bile from breakdown of blood into spaces called canaliculi
blood from hepatic artery + hepatic portal vein mix in spaces called sinusoids
how to hepatocytes control carbohydrate metabolism
blood glucose levels rise - so do insulin levels
stimulates hepatocytes to convert glucose to glycogen
vise versa
controlled by hormone glucagon
what is transamination and deamination
transamination= conversion of an amino acid into another deamination= removal of amine group from a mol
what happens to excess amino acids
deaminated by hepatocytes into ammonia then into urea (excreted by kidneys)
others used for cellular respiration/ converted to lipids as body can’t store amino acids
how is blood supplied to/ removed from kidneys
renal arteries + veins
how is urine removed from the body
passed down tubes called ureters
exits through urethra
name and describe the 3 main structural components of the kidney
cortex
- dark outer layer
- dense capillary network
- where filtering of blood occurs
medulla
-contains tubules of nephrons (filtering units) which form collecting ducts
pelvis
-central chamber where urine collects
describe the structure of nephrons
bowman capsule
- cup shapes structure
- contains tangle of capillaries (glamorous)
- ultrafiltration occurs
proximal convoluted tubule
- in cortex
- coiled region after capsule
- many substances reabsorbed
loop of henle
- down context through medulla and back up
- high solute conc
distal convoluted tubule
- fine tuning of water balance occurs
- permeability of walls varies due to levels of ADH in blood
collecting duct
-urine passes down through medusa to pelvis
describe ultrafiltration in nephrons
results in formation of tissue fluid in capillary beds
glomorous supplied with blood by arterial fro renal artery
blood leaves through narrower arteriole
resulting in presssure in capillaries of glomerous- forces blood out capillary walls
bowman capsule has special cells called podocytes
- act as additional filter
what is reabsorption
after bowman capsule
nephron returns most of filtered substances back to blood
mainly in proximal convoluted tubule
-cells covered in microfilm to increase SA for reabsorption
-many mitochondria provide ATP for active transport
what is ADH
produced in hypothalamus and released by pituitary gland
increased permeability of distal convoluted tubule
describe mechanism of ADH
carries in blod to cels of collecting duct
doesn’t cross membrane- binds to receptors
triggers formation of cyclic AMP which acts as secondary messenger
-relays signal received as cell surface
cAMP causes vesicles in cels lining collecting duct to fuse with plasma membrane on side of cell in contact with tissue fluid
these vesicles contain protein based water channels making cell membrane permeable to water
how is urine used to diagnose pregnancy
developing placenta produces chemical hCG
rely on monoclonal antibodies
describe the stages in a pregnancy test
1-wick soaked in first urine of the day (highest hCG levels)
2-test contains mobile monoclonal antibodies with colours beads attached- will only bind to hCG forming hCG/ antibody complex
3-urine reaches window- immobilised antibodies arranged in plus sign and will only bind to hCG/ antibody complex so coloured plus appears
4- urine continues to second window- immobilised monoclonal antibodies that only bind to mobile antibodies-coloured line always forms to indicate test works
name causes and effects of kidney failure
infection -podocytes + tubules damaged/ destroyed high blood pressure protein in urine -both damage membranes of bowman capsule so can no longer act as filter
name some effects of complete kidney failure
loss of electrolyte balance- osmotic imbalances in tissues leads to death
build up of toxic urea in blood can damage cells
high blood pressure= heart problems
calcium/phosphorous balance lost weakens bones
