Endotherms and ectotherms
Ectotherms --> use their surroundings to warm their bodies (reptiles and amphibians)
behavioural responses --> they bask in the sun, orientating as much surface area toward the sun to absorb the most head by radiation or they can increase their body heat by conduction by pressing their bodies against warm ground or can use some exothermic metabolic reactions
they shelter from the sun or dig burrows to cool down or they press their bodies against cool rocks or stones or they orientate their bodies so that a small surface area is in the sun
physiological responses --> they use the fact that dark colours absorb more heat radiation than light and some increase or decrease their heart rate to effect their metabolic activity
Endotherms --> rely on metabolic processes to heat themselves, usually maintain a steady body temperature regardless of their environment (mammals and birds)
behavioural responses --> basking in the sun, pressing themselves to warm surfaces, wallowing in water and mud or digging burrows --> humans wear clothes and build houses
physiological responses --> peripheral temperature receptors, thermoregulatory centres in the hypothalamus, the skin and muscles
anatomical adaptations --> animals in hot climates have large SA:Vol to increase heat loss (big ears) and pale fur or feathers to reflect the sun but animals in cold climates do the opposite often having a thick insulating layer of blubber
cooling down
vasodilation --> vessels near the skin dilate so more heat is lost via radiation through the skin
increased sweating --> as sweat evaporates from the surface of the skin, heat is lost and the blood below is cooled
reducing the insulating effect of hair --> erector pili muscles in the skin relax and hairs lay flat to remove the insulating layer of air
warming up
vasoconstriction --> vessels near the skin constrict so less heat is lost via radiation through the skin
decreased sweating --> reduces the cooling provided by the evaporation of water from the surface of the skin
raising of body hairs or feathers --> erector pili muscles contract to lift the hairs or feathers which traps a layer of air to insulate the body and reduce heat loss
shivering --> rapid and ivoluntary contracting and relaxing od the large voluntary muscles to increase respiration which releases heat
Changes to the temperature of the blood are detected in the hypothalamus which sends impulses along motor neurones and the autonomic nervous system to effectors in the skin and muscles to create these ^^^^ responses
The Liver
Has a very rich blood supply
Blood supplied by hepatic artery
Blood removed by hepatic vein
Blood loaded with products from digestion supplied by the hepatic portal vein
Hepatocytes (liver cells) have large nuclei, prominent Golgi apparatus and lots of mitochondria
Blood from hepatic artery and portal vein mixed together in spaces aka sinusoids which are surrounded by hepatocytes
Mixing increases the oxygen content to satisfy the needs of the hepatocytes
Sinusoids contain Kupffer cells which act as macrophages
Hepatocytes secrete bile which drain into the canaliculi that drain into the bile duct to the gall bladder
Functions of the liver
carbohydrate metabolism
hepatocytes are particularly responsive to insulin and glucagon
they convert glucose to glycogen and store it and reverse this when glucagon is about
deamination of excess amino acids
hepatocytes synthesise most of the plasma proteins
hepatocytes carry out transamination where one amino acid is converted to another
hepatocytes carry out deamination where the amine group is removed from the molecule
the amine group is converted to ammonia and then to urea to be removed
the rest of the amino acid can be used in respiration or the formation of lipids
ammonia is converted to urea through the ornithine cycle (ornithine --> ammonia added, CO2 added, water produced --> citruline --> ammonia added, water produced --> arginine --> water added, urea produced --> ornithine)
detoxificiation
hydrogen peroxide --> by-product of metabolic pathways --> hepatocytes contain catalase which splits it into oxygen and water
ethanol --> hepatocytes contain alcohol dehydrogenase --> ethanol converted to ethanal --> ethanal converted to ethanoate which can be used to make fatty acids
The kidneys
Made of millions of nephrons
Ultimately, urine is made which is taken to the bladder by the ureters and it then leaves the body via the urethra
Medulla --> contains the tubules of the nephrons and the collecting ducts
Cortex --> where the blood is filtered through the dense capillary network
Pelvis --> central chamber where the urine collects before going to the bladder
Nephrons
Bowman's capsule --> contains the glomerulus with its afferent and efferent arteriole
Proximal convoluted tubule --> in the cortex, many of the substances are reabsorbed into the blood
Loop of Henle --> creates a region of high solute concentration in the medulla to increase water reabsorption
Distal convoluted tubule --> in the cortex, fine-tuning of water balance, ions and pH, permeability of walls to water controlled by ADH
Collecting duct --> more fine-tuning of water balance and also controlled by ADH
Ultrafiltration
wide afferent arteriole of glomerulus but narrower efferent arteriole
this means the glomerulus has a high pressure which forces blood out through the capillary wall
the fluid then pushes through the basement membrane AND podocytes with pedicels into the Bowman's capsule
the fluid in the Bowman's capsule contains water, ions, glucose and other substances
Reabsorption
PCT
all the glucose, amino acids, vitamins and hormones moved back into the blood via active transport
Na ions move by active transport and Cl ions follow passively
PCT cells covered in microvilli and have many mitochondria
once removed from the nephron, the substances diffuse into the capillary network down steep concentration gradients
Loop of Henle
ascending limb is very permeable to sodium and chloride ions
in the early limb they just diffuse out but further up they are actively transported out
this makes the region hypertonic compared to the descending limb
descending limb is very permeable to water and due to the hypertonic region created by the ascending limb the water moves out passively by osmosis
DCT
permeability of tubule controlled by ADH
have many mitochondria for active transport
if the body lacks salt, the ions are pumped out
water can also leave if there's ADH and aquaporins
Collecting duct
main site that's effected by ADH
the ion concentration in the surrounding solution increases as you go down meaning water can move at any point --> produced hypertonic urine
Osmoregulation
ADH in produced in the hypothalamus and secreted by the posterior pituitary gland
ADH increases the permeability of the CD and DCT to water
The hormone is released into the bloodstream
It binds to the receptors on the cells and triggers the formation of cAMP
cAMP causes the vesicles lining the collecting duct to fuse to the surface membranes and insert the aquaporins into these membranes
This provides a route for water to move via osmosis out of the CD and into the capillaries
more ADH = more aquaporins so more water is reabsorbed
When ADH levels fall, the process is reversed --> cAMP levels fall so the aqauporins are removed from the membranes and they are made less permeable
When water levels are low, the osmoreceptors detect that ion concentration of the blood is high and the water potential of the blood and tissue fluid is more negative --> ADH released
When water levels are high the blood becomes more dilute and the water potential of the blood and tissue fluid becomes less negative --> the release of ADH is inhibited
Kidney failure
Shown by protein or blood in the urine
Results in loss of electrolyte balance, build up of urea, high blood pressure, weakened bones, pain and stiffness in joints and anaemia
If the levels of creatinine in the blood increase it is a sign that the kidneys are damaged
Dialysis
Haemodialysis --> blood taken from an artery, blood thinners are added, it passes over a semi-permeable membrane where nutrients either diffuse in or out to the optimum levels then returns to the body (uses a countercurrent system to maintain the concentration gradients)
Peritoneal dialysis --> inside the body, used the peritoneum as the membrane, dialysis fluid is introduced through a catheter --> excess urea and ions pass out of the capillaries, into the tissue fluid across the membrane and into the dialysis fluid where its drained off
Transplants
risk of rejection --> match between antigens is made as closely as possible
recipient is treated with immunosuppressants for the rest of their lives --> can't respond effectively to any infections
transplant doesn't last forever
waiting lists can be very long
Pregnancy tests
Work using monoclonal antibodies that complement hCG (human chorionic gonadotrophin) which is made by the development of the placenta
Main stages:
Wick is soaked in the first urine passed in the morning
Test contains mobile monoclonal antibodies that have dye attached that will only bind to hCG
If she's pregnant, the hCG binds to the antibody making a hCG-antibody complex (with the dye)
The urine moves up the test by capillary action
1st window has immobilised antibodies that only bind to hCG-antibody complex (if they do the dye attached will show the positive shape)
2nd window has immobilised antibodies that will bind to the mobilised ones regardless of whether they have a hCG attached --> this proves that the test has worked
Other urine tests
Anabolic steroids
tested with gas chromatography and mass spectrometry
sample is vapourised with a known solvent and passed along a tube
a lining of the tube absorbs the gases and is analysed to give an image that can be read to show the presence of drugs
Drug testing
immunoassay which uses monoclonal antibodies that bind to the drug or its breakdown product
^ if this is positive, they use gas chromatography and mass spectrometry to confirm the presence of a drug