homeostasis

• endotherms- rely on heat from metabolic processes to maintain heat

  too hot

  • sweating
  • vasodilation
  • metabolic rate decreases

  too cold

  • shivering
  • vasoconstriction
  • metabolic rate increases
• ectotherms- rely on external sources of heat to maintain temperature

  too hot

  • avoid sunlight
  • decrease surface area by absorbing heat
  • avoid activity during hot parts of the day

  too cold

  • bask in the sun
  • increase surface area exposed to heat
  • decrease in breathing rate
• hepatic artery- supplies oxygenated blood

  hepatic vein- returns deoxygenated blood

  hepatic portal vein- products of the digestive system carried to the liver
• structure of the liver

  • blood from HA and HPV mixes in spaces called sinusoids
  • sinusoids are surrounded by hepatocytes
  • sinusoids contain kuppfer cells
  • kuppfer cells ingest foreign particles
  • hepatocytes secrete bile from the breakdown of blood into canaliculis
  • bile from canaliculi drain into gall bladder to be stored
• carbohydrate metabolism

  • insulin stimulates conversion of glucose into glycogen
  • glucagon stimulates conversion of glycogen into glucose
• transamination

  • conversion of amino acid into another
  • transamination provides what the diet does not
• deamination

  • removal of an amine group from a molecule

  1. removed amino group converted into ammonia
  2. ammonia converted into urea
  3. urea excreted by the kidney

  • remander of amino acid converted to lipid for storage
• ornithine cycle

  • converting ammonia into urea with the addition of carbon dioxide
• detoxification

  • poisenous substances are detoxified and made harmless
  • hepatocytes contain alcohol dehydrogenase

  1. ethanol converted to ethanal
  2. ethanal converted to ethanote
• alcohol liver damage

  fatty liver fat- vesicles displace hepatocytes nuclei

  hepatitis- sinusoids and HV narrowed

  cirrhosis- hepatocytes die and are replaced by fibrous tissue
• bowmans capsule- surrounds glomerulus
• proximal convoluted tubule- series of loops surrounded by capillaries
• loop of Henle- loop that extends from the context to the medulla, surrounded by capillaries
• distil convoluted tubule- fewer capillaries surrounding it than PCT
• collecting duct- distal convoluted drain into it
• ultafiltration

  1. blood from renal artery enters smaller arterioles in the cortex
  2. arterioles split into glomerulus
  3. afferent arteriole wider than efferent so a build up of hydrostatic pressure squeezes water, glucose ions out
  4. proteins too large to be forced out
• selective reabsorbtion

  1. Na+ actively transported out of cells to PCT
  2. Na+ enter through facilitated diffusion
  3. Na+ cotransport other substances
• adaptations of PCT

  • microvilli
  • infoldings
  • mitochondria
• distal convoluted tubule

  • water balancing process takes place
  • permeability affected by ADH
  • mitochondria present for active transport
  • if the body lacks salt, Na+ pumped out, Cl- following down electrochemical gradient
• Decending limb

  1. water moves out of filtrate down a concentration gradient
  2. concentration of Na+, Cl- in the tissue fluidof medulla increases as it moves from pyramids to cortex
  3. filtrate starts as isotonic with the blood
  4. as filtrate passes down the limb, water moves into tissue fluid by osmosis
  5. then moves into the blood of surrounding capillaries
  6. fluid reaching hairpin is highly concentrated, hypertonic to capillaries
• ascending limb
• Ascending limb

  1. very permeable to Na+, Cl- so ions diffuse out of concentrated filtrate
  2. ions actively pumped out of limb and into medulla tissue fluid
  3. creates a high concentration in medulla tissue and fluid left in limb is very dilute.
  4. ascending limb is impermeable so water cannot leave, at the top of the limb the solution is hypotonic
  5. solution enters distil convoluted tubule
• collecting duct

  • where urine concentration and volume is determined

  1. water moves out by diffusion as it moves through renal medulla
  2. as a result, urine is more concentrated
  3. level of Na+ increases from the cortex to pelvis so water can be removed throughout its length
• Glomerular filtration rate

  GFR- used to indicate kidney disease

  Creatinine- breakdown product of muscles

  1. blood test measures level of creatinine in blood
  2. if levels increase- kidney works properly

  factors taken into consideration

  • age
  • gender
• osmoregulation

  • controls water potential of the blood
  • ADH- increases permeability of the distal convoluted tuble and collecting duct to water
  • produced by hypothalamus
• mechanism of ADH

  • ADH binds to receptors on cell membrane
  • triggers cAMP
• cAMP causes a cascade of events

  1. vesicles in collecting duct fuse with tissue fluid in medulla
  2. when inserted into cell surface membrane, it becomes permeable due to aquaporins
  3. provides a route for water to move out of tubules cells and into medulla tissue fluid and capillaries by osmosis
• negative feedback loop

  1. normal solute concentration of blood
  2. water potential rises
  3. detected by osmoreceptors
  4. less ADH produces
  5. less water reabsorbed from nephron
  6. larger volume of dilute urine produces
  7. water potential falls
• negative feedback loop

  1. normal solute concentration of blood
  2. water potential falls
  3. detected by osmoreceptors
  4. more ADH produced
  5. more water reabsorbed from nephron
  6. smaller volume of concentrated urine produced
  7. water potential rises
• anabolic steroids- drugs that stimulate muscle growth
• gas chromotography

  1. urine sample is vapourised with a known solvent and passed along a tube
  2. the linng of the tube absorbs the gases to give a chromatogram
  3. chromatogram read and compared to show presence of drugs
• monoclonal antibodies- from a single clone of cells
• stages of pregnancy testing

  1. wick is soaked in urine
  2. mobile antibodies (attached to beads) bind to HCG
  3. first window- HCG/mobile antibody complex binds to immobilised antibodies to form coloured line.
  4. second window- Excess antibodies bind to immobilised antibodies to form coloured line
• haemodialysis

  dialysis fluid

  • normal plasma level of glucose
  • normal plasma level of mineral ions
  • no urea
  • blood and dialysis fluid flow in opposite direction to miantain countercurrent exchange system
• peritoneal dialysis

  1. dialysis fluid introduced into abdomen using a catheter
  2. dialysis takes place for several hours across peritoneal membrane
  3. fluid drained off and decanted- leaves the blood balanced and urea, excess mineral ions removed
• dialysis

  advantages

  • more readily available

  disadvantages

  • monitor diet carefully
  • regular sessions on machines
  • carried out in hospital
• transplant

  advantages

  • normal functioning kidney for years
  • drugs suppress immune response
  • free from restrictions

  disadvantages

  • risk of rejection
  • immunosuppressant drugs taken for the rest of life
  • drugs prevent patient from efficiently responding to disease
  • lasts 9-10years