homeostasis

• what is homeostasis and why is it important?

  • body maintains dynamic equilibrium with small fluctuations over a narrow range of conditions
  • receptors and effectors are key for the body to maintain this equilibrium
• why are receptors important in homeostasis?

  detect changes in internal and external stimuli
• what is positive feedback? state 2 examples

  • a change in the internal environment is detected by sensory receptors
  • effectors are stimulated to reinforce that change and initiate a response
  • blood clotting cascade- platelets form at the site of injury, release chemicals which causes more platelets to accumulate
  • pregnancy- the head of the foetus pushes against the cervix, releases hormones which causes the uterus to contract more, which pushes the baby's head harder against the cervix
• what is positive feedback? state two examples

  • a change in the internal environment is detected by sensory receptors
  • effectors are stimulated to reinforce that change and initiate a response
  • blood clotting cascade- platelets form at the site of injury, release chemicals which causes more platelets to accumulate
  • pregnancy- the head of the foetus pushes against the cervix, releases hormones which causes the uterus to contract more, which pushes the baby's head harder against the cervix

  
• what are ectotherms?

  use their surroundings to maintain their core body temperature

  • eg invertebrates
• what are endotherms?

  require metabolic processes to maintain their core body temperature
• true or false? ectotherms in water need to thermoregulate

  FALSE- water has high heat capacity so temperatures don't fluctuate often
• describe how ectotherms maintain body temperature

  BEHAVIOURAL:

  • bask in the sun- orientate body towards sunlight to maximise surface area for increased radiation absorption/ seek shade from sun to cool down/reduce SA exposed to sun
  • press bodies against warm ground- through conduction. /cool ground- to cool down, or move in mud/water.
  • contraction of muscles and vibration to warm up/ Minimise movement to cool down.
  • huddling together

  PHYSIOLOGICAL-

  • darker colours if living in colder climates as they absorb radiation/converse for lighter colors
  • alter heart rate to increase/decrease metabolic rate and cool/warm the body
• true or false? ectotherms require more energy regulating body temperature than endotherms

  FALSE- therefore their movements are limited as they also need less food
• what receptors in the skin of endotherms detect changes in surface temperature/temperature of the environment?

  peripheral temperature receptors in the skin
• what receptors in the body detect temperature changes deep in the body, within the blood?

  thermoreceptors in the hypothalamus
• True or false? temperature of the skin is more likely to be affected BY external conditions than temperature of the hypothalamus

  TRUE
• what is an advantage of having thermoreceptors in the skin and hypothalamus?

  provide the body with great sensitivity
• describe how endotherms maintain body temperature

  BEHAVIOURAL:

  • basking in sun/pressing to warm surfaces/wallowing in water and mud/digging in burrows (similar to ectotherms)
  • clothes are worn
  • houses are built and heating installed