homeostasis & response

• what is homeostasis?

  the regulation of the internal conditions in a cell or organism to maintain optimum conditions for function in response to internal and external changes
• what key 3 factors does homeostasis in humans control?

  1. blood glucose concentration

  2. body temperature

  3. water levels
• what does the nervous system do in humans?

  enable humans to react to their surroundings and to coordinate their behaviour
• what is the central nervous system (cns)?

  brain and spinal cord
• what does the cns do?

  coordinates the response of effectors, which may be muscles or glands secreting hormones
• what is the cns sequence?

  stimulus -> receptor -> coordinator -> effector -> response
• what is the endocrine system?

  a system composed of glands which secrete chemicals called hormones directly into the bloodstream
• what is the pituitary gland?

  the "master gland" in the brain which secretes hormones into the blood in response to body conditions
• what do the pancreas do?

  monitor and control blood glucose concentration
• what happens when blood glucose levels are too high?

  the pancreas produce the hormone insulin that causes glucose to move from the blood into the cells
• what happens when the blood glucose concentration is too low?

  the pancreas produce the hormone glucagon that causes glycogen to be converted into glucose and release into the blood
• what is glucose converted to in liver and muscle cells?

  glycogen
• what is type 1 diabetes?

  a disorder where the pancreas fail to produce sufficient insulin
• what is type 2 diabetes?

  where body cells no longer respond to insulin produced by the pancreas
• how can t1 diabetes be treated?

  through insulin injections
• how can t2 diabetes be treated?

  through a carbohydrate controlled diet and exercise regime
• what is oestrogen?


  main female reproductive hormone produced in the ovaries
• what is ovulation?

  when a mature egg is released from the ovaries
• what is testosterone?


  main male reproductive hormone produced by the testes. it stimulates sperm production
• name the hormones involved in the menstrual cycle

  • follicle stimulating hormone (FSH)
  • luteinizing hormone (LH)
  • oestrogen
  • progesterone
• what does the follicle stimulating hormone cause?

  maturation of an egg in the ovaries
• what does the luteinizing hormone do?

  stimulates release of an egg
• what is the role of oestrogen and progesterone?

  involved in maintaining the uterus lining
• what do oral contraceptives do?

  contain hormones to inhibit FSH production so that no eggs mature
• how do injection, implant or skin patch contraceptives work?

  by slowly releasing progesterone to inhibit the maturation and release of eggs for a number of months of years
• name one barrier method of contraception

  condom
• what is an intrauterine device?

  a device that prevents the implantation of an embryo or releases a hormone
• what do spermicidal agents do?

  kill/disable sperm
• what are the 4 steps of in vitro fertilisation (IVF) treatment?

  1. mother is given FSH and LH to stimulate maturation of several eggs
  2. eggs are collected from the mother and fertilised by sperm from the father in the laboratory
  3. the fertilised eggs develop into embryos
  4. one or two of the developed embryos are inserted into the mothers uterus
• give 3 negatives of IVF treatment

  1. emotionally and physically stressful
  2. success rates are not high
  3. can lead to multiple births, which are a risk to both fetuses and the mother
• what is adrenaline?

  a hormone produced by the adrenal gland in times of fear or stress
• what are the effects of adrenaline?

  • increases heart rate
  • boosts delivery of oxygen and glucose to the brain and muscles
• what is thyroxine?

  a hormone produced by the thyroid gland that stimulates basal metabolic rate
• how are thyroxine levels controlled?

  by negative feedback