homeostasis

• What is homeostasis?


  the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes
• what does homeostasis help the body control?

  blood glucose concentration

  body temperature

  water levels
• what do all control systems include?

  Receptors, coordination centres and effectors
• what do receptors do?

  detect stimuli
• What does the coordination centre do?

  Receives and processes information from receptor cells
• what do effectors do?

  bring responses which restore optimum levels
• what are the first two steps of IVF?

  give a mother FSH and LH to stimulate maturation of eggs

  eggs collected from mother and fertilised in a lab
• what are the second two steps of IVF?

  fertilised eggs develop into embryos

  when they are tiny balls of cells one or two embryos are inserted into the womb
• what are the downsides to IVF?

  very stressful

  success rates are low

  can lead to multiple births which are high risk for mother and baby
• What does adrenaline do?

  It increases the heart rate, boosting the delivery of oxygen and glucose to the brain and muscles
• What does thyroxine do?

  Regulates metabolism, heart rate and temperature
• what happens in negative feedback?

  A change in a system cause a response that tends to return that system to its original state
• what is controlled by negative feedback?

  thyroxine

  body temperature
• Why do plants produce hormones?

  To coordinate and control growth and responses to light and gravity
• what causes unequal growth rates in plant roots and shoots?

  unequal distributions of auxin
• why're gibberellins important?


  important in initiating seed germination
• what ethene control?


  call division and ripening fruits
• name 3 plant hormones

  auxins

  gibberellins

  ethene
• what does the digestion of proteins in a diet result in?

  excess amino acids which need to be excreted

  these amino acids are deaminated to form ammonia in the liver

  ammonia is toxic and immediately excreted by urea
• what is the function of the kidney in maintaining water balance?

  urinary system blood us transported to kidney via renal artery

  this blood is filtered at high pressure and kidney selectively reabsorbs
• what effect does ADH have on permeability of kidney tubules?

  ADH is released when blood is too concentrated

  travels to target organ via bloodstream and cause kidney tubules to become more permeable
• how can kidney failure be treated?

  organ transplant

  dialysis
• what happens if blood glucose concentration is too low?

  pancreas produces glucagon that cause glycogen to be converted to glucose and released into blood
• how do the kidneys produce urine?


  By filtration of the blood and selective reabsorption of useful substances such as glucose, some ions and water
• what effect does osmotic changes in body fluid have on cells?

  water leaves the body via lungs during exhalation

  water, ions and urea are lost through skin in sweat

  no control over water, ion or urea loss by lungs or skin

  if body cells lose or gain too much water by osmosis they do not function effectively
• how does insulin control blood glucose levels in the body?

  glucagon breaks down glycogen to glucose in liver while insulin enables blood glucose to enter cells
• What is type 1 diabetes?

  the body's immune system destroys cells in the pancreas that produce insulin.
• what is type 2 diabetes?

  It occurs when the body does not properly use insulin.
• how does FSH interact in control of the menstrual cycle?

  causes maturation of the egg
• how does oestrogen interact in control of the menstrual cycle?

  repairs and thickens uterus lining
• how does LH interact in control of the menstrual cycle?

  stimulates release of egg
• how does progesterone interact in control of the menstrual cycle?

  maintains uterus lining
• how are auxins used?

  weed killers

  rooting powders

  promoting growth in tissue culture
• how is ethene used?

  In the food industry to control ripening of fruit during storage and transport
• what are the forms of hormonal contraception?

  oral contraceptives

  injection/patch

  IUD
• what are the forms of non hormonal contraception?

  condoms

  spermicidal agents

  surgical methods
• how are gibberellins used?

  end seed dormancy

  promote flowering

  increase fruit size
• what does the pancreas do?

  produce insulin to regulate blood glucose levels
• what does the thyroid do?

  produce thyroxine to regulate rate of metabolism, heart rate and temperature
• what does the adrenal gland do?

  Produce adrenaline which is used to prepare the body for a fight or flight response