hormonal coordination

• what is the endocrine system?

  a system of glands that produce and secrete hormones into the bloodstream to regulate various bodily functions.
• what is the pituitary gland?

  the master gland located at the brain that produces and releases hormones in the blood in response to body conditions. some of these hormones act on other glands and stimulate them to release hormones to bring about specific affects.
• what are some of the hormones do the pituitary gland release?

  ADH - affects the amount of urine produced in the kidney

  FSH - stimulates the ovaries to make oestrogen

  TSH - stimulates the thyroid gland to make thyroxine
• endocrine glands

  pituitary

  thyroid - controls the metabolic rate

  pancreas - controls the level of glucose

  adrenal - prepares the body for stressful situations

  ovaries - involved in the menstrual cycle and develops the female sexual characteristics

  testes - involved in the production of sperm and develops the male sexual characteristics
• glucagon

  a hormone secreted by the pancreas that makes the liver break down glycogen and release glucose into the blood
• control of blood glucose levels(if glucose in blood is low)

  1. pancreas secretes glucagon

  2. glucagon makes liver break down glycogen

  3. glycogen converted back into glucose

  4. glucose released into blood
• blood glucose control system

  • uses two hormones (insulin and glucagon)
  • involves negative feedback control
  • blood glucose is a tank with controlled and uncontrolled inlets and outlets
• the pancreas keeps blood glucose concentration fairly constant by using negative feedback control, which involves switching between the two hormones insulin and glucagon
• control of blood glucose levels (if glucose in blood is high)

  1. pancreas releases insulin
  2. glucose taken in by cells and converted to glycogen
  3. blood glucose falls
• what causes type 1 diabetes?

  the blood glucose may rise to fatally high levels because the pancreas does not secrete enough insulin. usually starts in young children and teenagers
• what causes type 2 diabetes?

  the body stops responding to its own insulin. it is often linked to obesity and lack of exercise. it can also be genetic.
• treating type 1 diabetes

  • inject insulin before meals.
  • people with type 1 need to be careful about the levels or carbohydrates they eat.
  • injections can treat diabetes but not cure it.
  • someone with type 1 diabetes have to take injections for their whole life
• treating type 2 diabetes

  • eating a balanced diet with carefully controlled amounts of carbs
  • losing weight
  • doing regular exercise
  • drugs that help insulin get produced more or reduce the amount of glucose you absorb
  • if none of these work, you would need injections (insulin)
• negative feedback

  systems that work to maintain a steady state. in negative feedback, the response causes the opposite of the initial change
• negative feedback systems

  1. if a factor in the internal environment increases, changes take place to reduce it and restore the original level

  2. if a factor in the internal environment decreases, changes take place to increase it and restore the original level
• negative feedback (thyroxine)

  if thyroxine levels rise, TSH levels fall - so thyroxine levels return to normal

  if thyroxine levels fall, TSH levels rise - so thyroxine levels return to normal
• thyroxine

  hormone produced by the thyroid gland that controls the basal metabolic rate, how quickly substances are broken down, and how much oxygen your tissues use
• thyroxine level

  relatively stable in adults due to negative feedback control involving the pituitary gland and thyroid stimulating hormone (TSH)
• adrenaline causes -

  • your heart and breathing rate to increase
  • stored glycogen in the liver to be converted to glucose for respiration
  • the pupils of your eyes to dilate to let in more light
  • your mental awareness to increase
  • blood to be diverted away from your digestive system to the muscles of the limbs
• hormones in negative feedback control

  many hormones are involved in negative feedback systems, including insulin and glucagon, most female sex hormones, and thyroxine
• puberty


  during puberty, the reproductive hormones control the development of the secondary sexual characteristics.
• male reproductive system

  
• the female reproductive system

  
• oestrogen

  the main female reproductive hormone is oestrogen, produced by the ovaries. they trigger the development of the female secondary sexual characteristics between ages of 8 and 14
• the menstrual cycle

  each month, eggs begin to mature in the ovary. every 28 days a mature egg is released. if the egg is not fertilised then after 14 days the lining of the uterus is shed along with the egg.
• hormones involved in the menstrual cycle

  • follicle stimulating hormone - causes the eggs in the ovary to mature
  • luteinising hormone - stimulates the release of the egg at ovulation
  • oestrogen and progesterone - stimulate the build up and maintenance of the uterus lining
• testosterone

  the main male reproductive hormone is testosterone, produced by the testes and stimulates sperm production.
• FSH

  • causes eggs to mature
  • stimulates the ovary to produce oestrogen
• LH

  triggers ovulation
• oestrogen

  • causes the lining of the uterus to develop
  • inhibits (stops) the release of FSH
  • stimulates the release of LH
• progesterone

  • maintains the lining of the uterus
  • inhibits the release of both FSH and LH
• what is contraception?

  preventing the egg and sperm meeting or a fertilised egg implanting in the uterus
• hormone based contraception

  • pill that inhibits the production of FSH by the pituitary gland, so no eggs mature, preventing pregnancy
  • pill that stops the uterus lining developing, preventing implantation
  • pill that makes the mucus in the cervix thick to prevent sperm getting through
  • these pills can have side effects
• chemical methods

  chemicals that kill or disable sperm are known as spermicides. they are not very effective at preventing pregnancy.
• barrier methods

  prevents the sperm reaching the egg.

  condoms offer protections against STDs however they can get damaged during intercourse and let sperm through
• intrauterine devices

  small structures inserted into the uterus by a doctor. they last for 3-5 years and can be removed anytime.

  they are effective but may cause period problems and infections
• abstinence

  if you don't have sex you won't get pregnant! some religious groups do not accept the artificial methods of contraception.
• surgical methods

  • in men, the sperm ducts can be cut and tied, preventing sperm getting in semen. this is called vasectomy
  • in women, the oviducts are cut or tied, preventing the egg reaching the uterus.
  • although this is effective, you would need surgery and can be expensive
• fertility drug treatment

  1. artificial FSH stimulates the eggs in the ovary to mature

  2. artificial LH triggers ovulation
• in vitro fertilisation (IVF)


  a form of fertility treatment used if the oviduct has been damaged or blocked by infection, if a donor egg has to be used, or if there is no obvious cause for infertility.