Homeostasis and response

• The Brain

  • Cerebral cortex - consciousness, intelligence, memory and language
  • Medulla - unconscious activities like breathing
  • Cerebellum - muscle coordination
• Body has to keep its insides at 37°C to prevent enzymes from denaturing
• Body Too Hot

  • Sweat is produced from the sweat glands and evaporates form the skin - this transfers energy to the environment
  • blood vessels dilate (vasodilation) so more blood flows to the surface of the skin - this helps to transfer energy from the skin to the environment
• Body Too Cold

  • Hairs stand up to trap insulating layer of air
  • no sweat produced
  • blood vessels constrict (vasoconstriction) to close off the skins blood supply
  • shiver (muscle coordination) - requires respiration which transfers energy to warm the body
• Hormones are chemical molecules that travel through the blood
• Pituitary gland

  • Produces many hormones
  • known as the master gland - the hormones can act in any other gland
• Thyroid gland

  • Produces thyroxine
  • controls rate of metabolism, heart rate and temperature
• Adrenal glands

  • Produces adrenaline
  • fight or flight
• Pancreas

  • Produces insulin
  • controls blood glucose levels
• Ovaries

  • Produces oestrogen
  • involved in menstrual cycle
• Testes

  • Produce testosterone
  • involved in puberty and sperm production
• Nerves

  • Fast acting
  • shot time
  • precise area
• Hormones

  • Slower acting
  • long time
  • general way
• Blood glucose too high

  • Insulin secreted by pancreas
  • glucose moves from blood to liver and muscle cells
  • blood glucose levels decrease
  • insulin makes liver turn glucose into glycogen
• Blood glucose too low

  • Glucagon secreted by pancreas
  • glucose released into blood by liver
  • blood glucose levels increased
  • glucagon makes liver turn glycogen into glucose
• Type 1 diabetes = little to no insulin
• Type 2 diabetes = resistant to their own insulin
• Hormonal contraception

  • Oestrogen - prevents the release of an egg, inhibits FSH production
  • progesterone - thick mucus prevents sperm
  • the pill - oestrogen and progesterone
  • 99% effective, but can cause side effects and doesn’t protect against STDs
• Barriers to pregnancy:

  • Condoms and diaphragms - prevent the sperm from reaching the egg
  • spermicide - kills or disables the sperm, only 70-80% effective
• Other ways to avoid pregnancy:

  • Sterilisation - cutting or tying the fallopian tubes or the sperm duct
  • avoiding sexual intercourse when women is most fertile, not very effective
  • not having intercourse