biology 2

• homeostasis


  maintaining optimum conditions within the body
• negative feedback in the body

  1. receptor detects stimulus is too high
  2. coordination centre receives and processes info, organises response
  3. effector produces a response which counteracts the change and restores optimum conditions
• central nervous system (CNS)


  in vertebrates it consists of the brain and the spinal chord

  in mammals the CNS is connected to the body by sensory neutrons and motor neurones
• sensory neurones


  neurones carry information as electrical impulses from the receptors to the CNS
• motor neurones


  neurones carry electrical impulses from cns to effectors
• effectors


  all your muscles and glands, which response to nervous impulses
• receptors

  receptors are cells that detect stimuli

  taste receptors on the tongue

  sound receptors on ears
• effectors


  respond to nervous impulses and bring change

  muscles and glands

  muscles contract in response to a nervous impulse whereas glands make hormones
• CNS


  receives info from receptors then coordinates a response, response is then carried out by effectors
• synapse


  connection between two neurones

  caused by chemicals that diffuse across the gap
• reflex


  rapid automatic response that doesn't involve the conscious part of the brain
• reaction time


  time it takes to respond to a stimulus

  affected by age gender or drugs
• measuring reaction time


  person sits with arm resting on edge of table

  hold ruler vertically between thumb and forefinger

  let go with no warning

  reaction time is the number on the ruler where it is caught

  repeat and find mean distance that the ruler fell
• hormones


  chemical molecules released into the blood

  control things in organs and cells that need ajustments
• pituitary gland


  produces hormones that regulate body conditions

  direct other glands to release hormones that bring change
• ovaries


  produce oestrogen which is involved in the menstrual cycle
• testes


  where testosterone is produced, controls puberty and sperm production
• thyroid


  produces thyroxine

  regulates rate of metabolism and heart rate
• adrenal gland


  produces adrenaline which is used to prepare fight or flight response
• pancreas


  produces insulin

  used to regulate blood glucose levels
• nerves


  FAST action

  act for a short time

  act on very precise area
• hormones


  slower action

  act for a long time

  act in a more general way
• eating foods containing carbohydrates puts glucose into the blood
• what is added when glucose levels are too high

  insulin
• what is added when glucose levels are too low

  glucagon
• type 1 diabetes


  pancreas produces little to no insulin

  insulin therapy = injecting insulin during the day removing glucose from the body as it enters

  must take regular exercise to remove excess glucose
• menstrual cycle

  uterus lining breaks down for about 4 days

  uterus lining builds up again from day 4 to 14 ready to receive egg

  egg develops and is released from the ovary on day 14=ovulation

  wall is maintained from day 14 to 28, if no fertilised off has landed the lining breaks down and the cycle starts again
• oestrogen

  produced in the ovaries

  causes uterus lining to grow

  stimulates release of LH which causes release of an eg and releases FSH
• progesterone

  produced in ovaries

  maintains lining of the uterus in the second half of the cycle

  inhibits release of LH and FSH
• FSH (FOLLICLE STIMULATING HORMONE)


  produced in pituatry gland

  causes egg to mature in the follicle

  stimulates ovaries to produce oestrogen
• LH (LUTENISING HORMONE)


  produced by pituatry gland

  stimulates release of an egg at day 14
• types of contraception


  patch

  implant

  injection

  iud
• pros and cons of FSH and LH to stimulate ovulation


  pros: helps woman get pregnant

  cons: doesn't always work, expensive, too many eggs=twins/triplets
• pros and cons of IVF

  pros: gives infertile couple a child

  cons: low success rate=upsetting and discouraging, side effects such as vomiting and abdominal pain
• adrenaline


  triggers fight or flight

  released by adrenal glands

  brain detects fear and sends nervous impulses

  increases heart rate
• thyroxine regulates metabolism


  released in thyroid gland in the neck

  released in response to TSH
• cystic fibrosis is caused by

  a recessive allele
• polydactyly


  caused by dominant allele
• selective breeding


  humans artificially selecting plants and animals that will breed
• abiotic factors in an ecosystem

  moisture level

  light intensity

  temperature

  carbon dioxide level

  wind intensity

  oxygen level