B3

• stimulus = change in environment

  sensory receptor = what detects a stimulus

  effectors = muscles or glands that response to stimulus

  muscles contract for movement

  glands = produce hormones
• dendron = receive signal

  axon = transmit / sends signal
• relay neuron

  
• reflex actions = automatic and involuntary (have to do it) reactions to the stimulus

  stimulus are usually dangerous eg too hot , too cold , too bright for eyes
• normal voluntary action arc/ reflex involuntary action arc

  stimulus ➡️ receptor cells ➡️ sensory neuron ➡️ spinal cord ➡️ brain ➡️ spinal cord ➡️ relay neuron ➡️ motor neuron ➡️ effectors ➡️ respond

  stimulus ➡️ receptor cells ➡️ sensory neuron ➡️ spinal cord➡️ motor neuron ➡️ effectors ➡️ respond
• sensory neuron

  
• motor neuron

  
• bright light reflex arc

  stimulus = bright light hits eyes

  receptor cells in your eyes detect stimulus and send signal to sensory neuron

  nerve impulse travels from sensory neuron to spinal cord to motor neuron to effector

  impulse travels to effector cells in eyelid (muscle)

  muscle in eye lid contract and eye closes
• hormones are chemical messengers that control the functions of the cells hormones produced in endocrine glands
• hypothalamus and pituitary gland (brain) produce hormones that control production of other hormones

  thyroid gland (neck) produce thyroxine

  adrenal gland produce adrenaline (above kidney)

  pancreas produce insulin

  ovaries produce oestrogen and progesterone

  testes produce testosterone
• nerves vs hormones

  nervous system = very fast , method = electrical impulse , response is short acting , very precise area

  endocrine system = slower , method = in the blood , response is longer acting , larger area targeted
• thyroxine control your metabolic rate (speed in which energy is used)

  pituitary gland produces thyroid stimulating hormones (TSH) which stimulates the thyroid gland to produce thyroxine

  pituitary gland stops producing TSH which stops stimulating thyroid gland to produce thyroxine so now thyroxine is produced
• negative feedback = a way hormones level get back to normal

  
• adrenaline = prepares body for extreme action (fight or flight)

  body response to adrenaline = respiration rate ⬆️ - ATP production ⬆️ (more glucose converted to atp) , breathing rate ⬆️(body needs more oxygen to respire), heart rate ⬆️ (oxygen needs to be pumped faster to cells - cells needs oxygen to respire)

  once all stress/ danger removed adrenal gland stop producing adrenaline - H levels go back to normal
• menstrual cycle:

  follicle-stimulating hormone (FSH) in pituitary gland causes egg to mature and stimulates ovaries to produce oestrogen

  oestrogen - produce in ovaries - causes lining of uterus to build and thicken , stimulate production of LH , inhibits production of FSH

  LH - pituitary gland - ovulation is trigger when levels at peak

  progesterone - maintains uterus lining - inhibits production of LH & FSH
• changing levels of menstrual cycle hormones

  
• contraception

  non hormonal - barrier method for sperm not come in contact with egg

  hormonal - disrupt normal menstrual cycle
• types of contraception 


  condom = non hormonal / barrier

  cervical cap = non hormonal / barrier

  IUD copper coil - non hormonal - prevents sperm surviving in uterus and fallopian tube - copper toxic to sperm - kills it

  progesterone pill - hormonal - thickens mucus from cervix stopping sperm from reaching egg

  oestrogen & progesterone pill (combined pill) - hormonal - thickens mucus from cervix stopping sperm from reaching egg - prevents ovulation

  IUS / hormonal coil - same effect as progesterone pill

  hormonal contraception more effective then non hormonal
• insulin = hormone produce in the pancreas that is used to control sugar levels

  insulin stimulates the liver to turn glucose into glycogen

  glycogen stored in liver - lowers blood sugar levels - less glucose in blood
• glucagon = hormone produce in the pancreas that is used to control sugar levels

  converts glycogen into glucose - increase blood sugar levels
• negative feedback of controlling blood sugar levels

  
• type 1 diabetes = can’t produce insulin , pancreas produces little on low insulin - blood sugar levels increases dangerously

  overcome this = inject insulin so that blood sugar levels not severely high
• type 2 diabetes = when a person body / cells become unresponsive to insulin

  blood sugar levels have to be maintained more carefully - eating balanced diet & checking levels throughout day

  being overweight = increases likelihood of type 2 diabetes

  type 2 diabetes usually occurs in later life - cells are dying
• cons of contraceptions

  side effects to hormonal contraception - headaches , acne heavy / irregular periods , mood changes , length of action some contraception can last for weeks months or years while others are one time use

  medical imput - some contraception require doctors to insert IUD / IUS - uncomfortable for women

  STD - can still happen if u have contraception
• causes of infertility

  blocked sperm ducts / fallopian tube

  low sperm count

  lack of mature eggs

  failure to release egg

  women’s = use hormones to counter

  • FSH used to stimulate lack matured egg - FSH also stimulates oestrogen production - increases chance of more then one egg released
• IVF - in vitro fertilisation

  eggs taken out from ovary and sperm taken out from man and fertilised outside both body

  • FSH and LH injected to make as many eggs mature as possible
  • cons of IVF = sometimes no pregnancy occurs & sometimes multiple pregnancy occur
• issues of IVF

  • not natural process
  • people that can’t have babies now can (same sex / single)
  • older parents can have children
  • expensive
  • younger women can focus on career and have kids later