animal coordination, control and homeostasis

• what are hormones

  • are chemical messages sent in the blood.
  • they are carried in the blood to parts of the body but only affect target organs
• what sends hormones around the body

  • the endocrine system
• what is the endocrine system made up of

  • it is made up of glands which secrete hormones into the bloodstream:
  • pituitary gland
  • pancreas
  • thyroid
  • adrenal gland
  • ovary
  • testes
• what does the pituitary gland do

  • secretes the hormones: ACTH, FSH, LH and growth hormone
  • it regulates body conditions
• what does the pancreas do

  • secretes insulin
  • controls blood glucose levels
• what does the thyroid do

  • secretes thyroxine
  • controls metabolic rate, heart rate and temperature
• what do the adrenal gland do

  • secretes adrenalin
  • involved in the 'fight or flight' response
• what do the ovaries do

  • secretes oestrogen
  • is involved in the menstrual cycle
• what do the testes do

  • secretes testosterone
  • is involved in the production of sperm and controls puberty
• what is the difference between hormones and neurons

  • hormones are slower but acts for longer
• what is a 'fight or flight' response

  • is the body's response to a dangerous / stressful situation
• what do aspects of the 'fight or flight' response include

  • increased heart rate and blood pressure:
  • adrenaline binds to specific receptors in the heart
  • causes the heart muscles to contract more frequently and with more force
  • this increased blood flows allows more oxygen to reach the muscles quickly, so we can move out of the path of danger
  • increased blood flow to muscles
  • blood vessels leading to vessels dilate to allow more blood to reach them, this allows them to contract with greater strength and quicker
  • increased blood sugar levels
  • adrenaline binds to receptors in the liver causing the liver to break down glucagon into glucose which muscles can use to contract
• what does thyroxine regulate

  • metabolic rate
• how is thyroxine controlling metabolic rate an example of negative feedback

  • it keeps the amount of thyroxine in the blood at the right level
• how does thyroxine regulate metabolic rate when the blood thyroxine level is lower than normal

  • low levels of thyroxine stimulate the production of a hormone TRH in the hypothalamus
  • TRH cause the release of TSH from the pituitary gland
  • TSH acts on the thyroid to produce thyroxine
  • when thyroxine levels have reached the normal level, thyroxine inhibits the release of TRH which stops the production of TSH
• how does thyroxine regulate metabolic rate when the blood thyroxine level starts to increase

  • when the levels increase, it is detected by receptors in the brain
  • this inhibits the release of TSH
  • this inhibits the release of thyroxine so levels of thyroxine fall
• what are the stages of the menstrual cycle

  • stage 1: menstruation day 0-4
  • the lining of the uterus breaks down
  • bleeding
  • stage 2: proliferation 4-14days
  • lining starts to build up due to the release of oestrogen from ovaries
  • this lining becomes a thick spongy layer full of blood vessels
  • prepares for fertilised egg to implant there
  • stage 3: ovulation day 14
  • FSH is released by pituitary gland, causing an egg to mature in the ovaries
  • an egg develops and is released
  • LH released by pituitary gland, to help control the menstrual cycle
  • stage 4: maintenance 14-28day
  • oestrogen falls as lining is developed
  • lining is maintained by the release of progesterone until day 28
  • on day 28 the lining starts to break down(LH decreases)
  • if the egg is fertilised it develops into a foetus
• what are the interactions between FSH, LH, progesterone and oestrogen

  • FSH stimulates oestrogen production( as lining no longer needs to increase)
  • progesterone inhibits release of FSH and LH
• how does hormone contraception influence the menstrual cycle and prevent pregnancy

  • the contraceptive pill contains oestrogen and progesterone
  • this means oestrogen levels are constantly high, inhibiting FSH so no eggs mature
  • the lining also stops developing and the mucus in the cervix becomes thick so sperm cannot move through
• what are the different methods of hormonal and barrier methods of contraception

  • the contraceptive pill:
  • side effects such as mood changes, depression, breast pain, increased blood pressure
  • the contraceptive patch:
  • small and is stuck on the skin
  • lasts for 1 week
  • the contraceptive injection
  • releases progesterone so ovaries cannot release egg
  • lasts 2 or 3 weeks
  • the contraceptive implant
  • releases progesterone so ovaries cannot release egg
  • lasts for 3 years
  • the plastic intrauterine device(IUD)
  • releases progesterone so ovaries cannot release egg
  • lasts 5 to 10 years
  • use condoms
  • may tear so may not be as effective
  • use diaphragms
  • prevents sperm entering the cervix
• Explain the use of hormones in Assisted Reproductive Technology (ART)

  • use a drug called clomiphene
  • which increases the amount of FSH and LH released from hypothalamus
  • this increases chance that a woman will ovulate
  • In Vitro Fertilisation: IVF
  • given FSH and LH to encourage the release and maturation of eggs
  • these are extracted from the mother and fertilised in the lab using sperm
  • the fertilised eggs develop into embryos which are then inserted in the uterus
• what are the benefits and cons of using hormones in Assisted Reproductive Technology (ART)

  • provides a way for an infertile couple to have a child
  • physically stressful as women may have side effects such as feeling sick
  • emotionally stressful as may not work
  • can lead to multiple births
  • can be expensive if the process needs to be repeated
• what is homeostasis

  • maintaining the right conditions inside your body, so that everything works properly
• why is homeostasis important

  • it is important to maintain enzyme action and all cell function - including growth, replication and controlled cell death
• in the human body what does homeostasis control

  • blood glucose concentration
  • body temperature
  • water levels
• how do nervous and hormonal communication detect changes

  • they are involved in the automatic control systems
  • all control system have:
  • receptors - cells that detect stimuli (changes to environment)
  • coordination centres - process the information received from receptors e.g. brain, spinal cord
  • effectors - bring about responses to bring the conditions in the body back to optimum levels
• what is thermoregulation

  • is the act of keeping internal body temperature constant
  • this is important because if the temperature exceeds the optimum level of 37 degrees the enzymes will gradually become less effective and will eventually denature
• what happens when the body temperature becomes too high

  • the hypothalamus in the brain has receptors that monitor the temperature
  • if the temperature becomes too high the receptors in the skin that send impulses to the thermoregulatory centre
  • sweat evaporates from the dermis layer of skin surface and is produced from sweat glands.
  • the sweat is then released onto the surface of the epidermis
  • vasodilation means more blood flows closer to the surface of the skin resulting in increased energy transfer from the body
• what happens when the body temperature becomes too low

  • the hypothalamus in the brain has receptors that monitor the temperature
  • if the temperature becomes too low the receptors in the skin that send impulses to the thermoregulatory centre
  • sweating stops
  • skeletal muscles contract rapidly (shivering) to generate heat from respiration
  • hairs stand on end to create an insulating, trapping warm air
  • vasoconstriction means blood does not flow so close to the surface, resulting in less heat lost
• what is osmoregulation

  • the act of keeping the concentration of the blood at a constant level.
  • this is important because if the blood becomes too dilute, water will move into cells by osmosis and they will swell, eventually bursting under pressure
  • also if the blood becomes too concentrated, water will move out of cells and they will shrink.
  • this means the cells cannot preform their function
• how does osmoregulation maintain water content when there is an increase in water potential of blood

  • detected by osmoreceptors in hypothalamus
  • less ADH is released from pituitary gland
  • makes the collecting duct walls less permeable
  • less water is reabsorbed into blood and more urine produced
  • this causes decrease in water potential of blood
• how does osmoregulation maintain water content when there is a decrease in water potential of blood

  • detected by osmoreceptors in the hypothalamus
  • more ADH released from pituitary gland
  • collecting duct walls is more permeable
  • more water is reabsorbed into blood and less urine is produced
  • increase in water potential of blood
• how does insulin control blood glucose concentration

  • insulin binds to cell in target organs(muscles and liver) causing:

  1. glucose to move from the blood into muscle cells for respiration
  2. excess glucose to be converted into glycogen which is stored in the liver
• how is blood glucose regulated when the blood glucose concentration is too high

  • detected by pancreas
  • insulin is secreted by pancreas into blood
  • causes the liver and muscle cells to take in glucose
  • it then converts it to glycogen to be stored
  • this lowers blood glucose concentration
• how is blood glucose regulated when the blood glucose concentration is too low

  • detected by pancreas
  • glucagon is released by pancreas
  • causes glucagon to enter the liver and convert glycogen into glucose
  • glucose is released into the blood by liver
  • increases blood glucose concentration
• what is the cause and symptoms of type 1 diabetes

  • caused: when pancreas produces little or no insulin, this causes a rise in blood glucose concentration
  • symptoms: tired, thirsty, glucose in urine, high blood glucose levels
• how is type 1 diabetes controlled

  • have insulin therapy: inject insulin before meals into the subcutaneous tissue(fatty layer below skin) to enter the blood stream
  • the amount injected depends on the [persons diet and how active they are
  • take regular exercise
  • reduce intake of foods containing carbohydrates
• what is the cause of type 2 diabetes

  • when body cells become resistant to insulin
• how is type 2 diabetes controlled

  • reducing number of simple carbohydrates in diet
  • losing weight
  • increasing exercise
• what is the correlation between type 2 diabetes and body mass

  • the greater your BMI and waist : hip ratio the greater the risk of developing type 2 diabetes