topic b5- homeostasis and response

• homeostasis

  the maintenance of a constant internal environment
• negative feedback

  • stimulus detected as too high
  • response is co-ordinated
  • stimulus is decreased
• negative feedback

  • stimulus detected as too low
  • response is co-ordinated
  • stimulus is increased
• the nervous system

  • start
  • stimulus
  • receptors
  • sensory neurones
  • central nervous system (CNS)
  • motor neurones
  • effectors
  • response
  • end
• stimulus- the nervous system

  change is detected
• receptors- the nervous system

  electrical impulses generated
• sensory neurones- the nervous system

  • synapses used to travel across neurones +
  • impulses carried to CNS
• central nervous system (CNS)- the nervous system

  • brain or spinal cord +
  • decision is made
• motor neurones- the nervous system

  • carries impulses to effectors +
  • synapses used to travel across neurones
• effectors- the nervous system

  muscles/ glands take action
• response- the nervous system

  stimulus has been dealt with
• reflex arc

  • relay neurone
  • spinal cord
  • effector
  • brain is skipped out
• reflex arc

  • for stimuli that could cause harm or injury for example a bright line shining in your eye
  • an unconscious action is made, without using the brain or decision making
  • impulses are sent back to effectors faster
  • which reduces the time you could get injured or hurt
• the endocrine system- (for hormones)

  • thyroid gland
  • pancreas
  • ovaries (females)
  • pituitary gland
  • adrenal gland
  • testes (male)
• thyroid gland- the endocrine system

  produces thyroxine, regulates heart rate, metabolism and temperature
• pancreas- the endocrine system

  produces insulin, regulates blood glucose
• ovaries (females)- the endocrine system

  produces oestrogen, involved in menstrual cycle
• pituitary gland- the endocrine system

  'master gland', controls other glands to release hormones
• adrenal gland- the endocrine system

  releases adrenaline to prepare for 'fight or flight' response
• testes (males)- the endocrine system

  releases testosterone, controls puberty and sperm production
• blood glucose maintenance

  • insulin produced when sugar (glucose) goes in
  • this reduces the blood-glucose if it gets too high
• blood glucose maintenance

  • glucagon released when the sugar (glucose) is gone
  • this increases the blood glucose if it gets too low
• how many types of diabetes are there

  2
• type 1 diabetes

  • pancreas doesn't produce enough insulin, treatment involves injecting insulin into body
• type 2 diabetes

  • where a person becomes immune to their bodies insulin, obesity can increase risk, staying fit and healthy diet can fix
• the menstrual cycle

  • stage 1- uterus lining breaks down
  • stage 2- lining builds up
  • stage 3- egg released
  • stage 4- lining maintained
  • next cycle
• how many days is a menstrual cycle

  28
• the menstrual cycle

  
• hormones

  • FSH
  • oestrogen
  • LH
  • progesterone
• FSH

  • produced in the pituitary gland
  • function:
  • causes egg to mature
  • stimulates ovaries to produce oestrogen
• oestrogen

  • produced in the ovaries
  • function
  • grows uterus lining
  • stimulates LH and egg to release
• LH

  • produced in the pituitary gland
  • function
  • stimulates release of egg
• progesterone

  • produced in the ovaries
  • function
  • maintains uterus lining
  • inhibits release of LH and FSH
• reaction time and caffeine

  • reaction time- speed of response, affected by age, gender, drugs (e.g., caffeine)
  • test- drop ruler, catch, record number, repeat
  • caffeine effect- drink, wait 10 min, repeat test
  • control variables- same person, hand, height, no prior caffeine
  • computer tests- more precise, no anticipation, measured in milliseconds
• fertility control- hormonal methods

  • oestrogen- stops FSH- no egg release
  • progesterone- thick mucus- blocks sperm
  • methods
  • pill- combine/ progesterone only
  • patch (1 week), implant (3 years), injection (2-3 months), IVD (plastic- progesterone, copper- kills sperm)
• fertility control- barrier methods

  • condoms- only methods protecting against STDs
  • diaphragm- covers cervix, used with spermicide
  • spermicide alone- 70%-80% effective
• fertility control- other methods

  • sterilisation- permanent (fallopian tubes/ sperm duct cut)
  • natural methods- avoid fertile days (not reliable)
  • abstinence- 100% effective
• increasing fertility- fertility drugs (FSH + LH : stimulates ovulation)

  • pros- help pregnancy
  • cons- expensive, multiple attempts, risk of multiple births
• increasing fertility- IVF (In Vitro Fertilisation)

  • process- egg collection- lab fertilisation- embryo transfer
  • pros- helps infertile couples
  • cons- low success (26% UK), stress, multiple births risk
  • advances- micro-tools, genetic testing, time-lapse imaging
• increasing fertility- ethical issues

  • unused embryos destroyed
  • risk of genetic selection