animal coordination, control and homeostasis

• Endocrine system

  Sends hormones (chemical messengers) around the body to produce a response when they reach a target tissue
• Fight or flight response


  Body's response to a dangerous situation, involving aspects like increased heart rate, blood pressure, blood flow to muscles, and blood sugar levels
• Adrenal gland

  Secretes adrenaline, involved in the 'fight or flight' response
• Testes

  Secretes testosterone, involved in the production of sperm and development of male secondary sexual characteristics
• Adrenaline

  Hormone produced by the adrenal glands to prepare the body for a 'fight or flight response'
• Low levels of thyroxine

  Stimulate production of TRH in the hypothalamus, which causes the release of TSH
• Pituitary gland


  The master gland that secretes hormones into the blood to have an effect on the body or stimulate other glands
• Thyroid

  Secretes thyroxine, controls metabolic rate, heart rate, and temperature
• Components of the endocrine system

  • Pituitary gland
  • Pancreas
  • Thyroid
  • Adrenal gland
  • Ovary
  • Testes
• Ovary

  Secretes oestrogen, involved in the menstrual cycle and development of female secondary sexual characteristics
• Pancreas

  Secretes insulin and controls blood glucose levels
• Endocrine system compared to the nervous system

  Hormonal system is slower but acts for longer
• Thyroxine

  Regulates metabolic rate, important in growth and development
• Follicle stimulating hormone (FSH)


  • Causes the maturation of an egg in the ovary, within a structure called a follicle
  • Produced in the pituitary gland
  • Stimulates the ovaries to produce oestrogen
• Progesterone

  • Produced in the ovaries and secreted from the egg follicle
  • Maintains the lining of the uterus and supports a pregnancy if the egg is fertilised
  • Inhibits the release of both FSH and LH
• Control of Thyroxine levels

  1. Low levels of thyroxine stimulate production of TRH in the hypothalamus

  2. TRH causes the release of TSH from the pituitary gland

  3. TSH acts on the thyroid to produce thyroxine

  4. When thyroxine levels have reached the normal level, thyroxine inhibits the release of TRH, which stops the production of TSH

  5. Levels of thyroxine are controlled by negative feedback

  6. When levels increase, it is detected by receptors in the brain

  7. This inhibits the release of TSH

  8. This inhibits the release of thyroxine, so levels of thyroxine fall
• The Menstrual Cycle

  1. The menstrual cycle is the process the body undergoes each month to prepare for a potential pregnancy

  2. It begins with the lining of the uterus breaking down, and the woman has her period

  3. The layer then builds up again until ovulation (day 14) occurs - an egg is released from the ovary and moves to the uterus via the fallopian tube

  4. If a fertilised egg has not been embedded in the lining after 28 days, it begins to break down and the cycle continues
• Oestrogen


  • Causes the lining of the uterus to grow again
  • Produced in the ovaries
  • Secreted as a result of FSH
  • Stimulates the production of LH and inhibits the secretion of more FSH
• Hormonal Contraception

  1. The contraceptive pill must be taken regularly or the body's own hormones will be released, leading to an egg maturing

  2. The mixed pill contains oestrogen and progesterone which inhibits FSH so no eggs mature, stops the lining from developing, and thickens the mucus in the cervix so sperm cannot move through

  3. The progesterone only pill has less side effects compared to the mixed pill

  4. The contraceptive patch contains oestrogen and progesterone, is small, stuck on the skin, and lasts for 1 week

  5. The contraceptive implant releases a continuous amount of progesterone, preventing the ovaries from releasing the egg, thickening the mucus in the cervix, and stopping fertilised eggs from embedding in the uterus, lasting for 3 years

  6. The contraceptive injection is made up of progesterone, has the same effect as the implant, and lasts for 2 to 3 months

  7. The plastic intrauterine device (IUD) releases progesterone, has the same effect as the implant, is T-shaped, inserted into the uterus, and lasts for 5 - 10 years

  8. Non-hormonal methods of contraception stop sperm fertilising the egg, chemical methods involve spermicides which kill or disable sperm but are only 70% to 80% effective, barrier methods include condoms and diaphragms
• Thyroxine and Metabolic Rate

  1. Thyroxine regulates metabolic rate (how quickly reactions occur)

  2. Thyroxine is important in growth and development
• Hormones controlling the events of the menstrual cycle

  • Follicle stimulating hormone (FSH)
  • Oestrogen
  • Luteinising hormone (LH)
  • Progesterone
• Luteinising hormone (LH)


  • Produced in the pituitary gland
  • Produced as a result of the hormone oestrogen
  • Its release results in ovulation
• Copper intrauterine device


  Works by killing sperm in the uterus and stopping fertilised embryos from implanting in the uterus lining
• Fertility drugs are used to increase the chance of pregnancy
• Main hormones used in fertility drugs

  • FSH and LH, stimulate the maturation and release of the egg
• Homeostasis is the maintenance of a constant internal environment
• In Vitro Fertilisation (IVF)

  Mother is given FSH and LH to encourage the release and maturation of eggs, extracted eggs are fertilised in the lab using sperm, fertilised eggs develop into embryos and one or two are inserted in the uterus
• Barrier methods


  Include condoms and diaphragms
• Aspects controlled by homeostasis in the human body

  • Blood glucose concentration
  • Body temperature
  • Water levels
• Nervous and hormonal communication is involved in the automatic control systems for homeostasis
• If the blood concentration changes, cells cannot perform their function, so it is vital that the blood remains at a constant level via osmoregulation
• Thermoregulation is the act of keeping internal body temperature constant
• Surgical methods of male and female sterilisation

  Involve cutting and tying the fallopian tubes or sperm duct, often permanent procedures but can be reversed in some cases
• Condoms

  • Worn over the penis or placed inside the vagina, help prevent contracting sexually transmitted diseases, can tear and let sperm through
• Clomiphene


  Increases the amount of FSH and LH released from the hypothalamus, increasing the chance that a woman will ovulate
• Diaphragm


  • A plastic cup positioned over the cervix, used with spermicide
• Abstaining from intercourse

  Ensures that an egg is not fertilised, some may only abstain during ovulation
• Chemical methods

  Involve spermicides which kill or disable sperm, but are only 70% to 80% effective
• Homeostasis is important to maintain enzyme action and all cell functions including growth, replication, and controlled cell death
• Components of control systems for homeostasis

  • Receptors - cells that detect stimuli
  • Coordination centres - process the information received from the receptors
  • Effectors - bring about responses to bring the conditions in the body back to optimum levels