homeostasis

Question 1

describe the difference between negative and positive feedback

Answer 1

negative= reverse change
positive= reinforce change

Question 2

name some behavioural and physiological responses of ectotherms

Answer 2

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

Question 3

how do endotherms detect temp change

Answer 3

peripheral temperature receptors in skin

temp receptors in hypothalamus detect blood temp

Question 4

name and describe the 2 control centres in endotherms (physiological responses)

Answer 4

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

Question 5

name methods of warming up + cooling down in endotherms

Answer 5

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

Question 6

name the blood vessels linked to the liver

Answer 6

hepatic artery- supplies oxygenated blood
hepatic vein- takes blood away to heart
hepatic portal vein- supplies blood loaded with products of digestion

Question 7

describe the structure and function of the liver

Answer 7

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

Question 8

how to hepatocytes control carbohydrate metabolism

Answer 8

blood glucose levels rise - so do insulin levels
stimulates hepatocytes to convert glucose to glycogen
vise versa
controlled by hormone glucagon

Question 9

what is transamination and deamination

Answer 9

transamination= conversion of an amino acid into another 
deamination= removal of amine group from a mol

Question 10

what happens to excess amino acids

Answer 10

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

Question 11

how is blood supplied to/ removed from kidneys

Answer 11

renal arteries + veins

Question 12

how is urine removed from the body

Answer 12

passed down tubes called ureters

exits through urethra

Question 13

name and describe the 3 main structural components of the kidney

Answer 13

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

Question 14

describe the structure of nephrons

Answer 14

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

Question 15

describe ultrafiltration in nephrons

Answer 15

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

Question 16

what is reabsorption

Answer 16

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

Question 17

what is ADH

Answer 17

produced in hypothalamus and released by pituitary gland

increased permeability of distal convoluted tubule

Question 18

describe mechanism of ADH

Answer 18

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

Question 19

how is urine used to diagnose pregnancy

Answer 19

developing placenta produces chemical hCG

rely on monoclonal antibodies

Question 20

describe the stages in a pregnancy test

Answer 20

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

Question 21

name causes and effects of kidney failure

Answer 21

infection
-podocytes + tubules damaged/ destroyed
high blood pressure
protein in urine
-both damage membranes of bowman capsule so can no longer act as filter

Question 22

name some effects of complete kidney failure

Answer 22

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