Homeostasis and Response

• What is homeostasis?

  an organism's ability to regulate/ control its internal conditions so crucial reactions can happen.
• What needs to be regulated

  blood glucose concentration

  internal temperature

  water levels
• what is the CNS

  central Nervous System ( brain & spinal cord)
• What is the PNS

  Peripheral Nervous System ( all other nerves)
• What is the role of a receptor

  detect changes in the environment (stimuli) and convert them into electrical signals, triggering a response.
• what is the role of a sensory neuron

  transmit nerve impulses from sensory receptors in the body to the central nervous system.
• what is the role of the effector?

  Executes response
• examples of effectors

  muscles and glands
• what is the reflex arc

  signal bypasses brain - much quicker!
• what is the role of a relay neurone

  acts as a bridge between sensory and motor neurons, enabling communication within the CNS.
• what is the role of a motor neuron

  transmit signals from the brain and spinal cord to muscles, causing them to contract and enabling movement.
• what is the role of a synapse

  to facilitate communication between neurons
• Practical - Reaction Time - Independent Variables

  e.g. energy drink increase neurotransmission
• Practical - Reaction Time - Dependent Variable

  e.g. alcohol decreases neurotransmission
• Method for Reaction Time Practical

  drop ruler between finger and thumb

  measure distance fallen before caught, repeat, calculate mean
• why are glands effectors

  they secrete chemicals
• endocrine system

  system of glands that secrete hormones to send signals to effectors, transported via blood ( slower than nervous system)
• Thyroid

  controls growth, metabolism and more
• Pituitary Gland

  'Master Gland' : sends signals to other glands
• Pancreas

  secretes insulin ( and glucagon) to control blood sugar
• Testes


  produce sperm
• Ovaries

  release eggs and secrete hormones.
• what happened to the pancreas if the blood glucose is to high

  pancreas secretes insulin
• what does that mean for the insulin in the pancreas for high blood glucose

  causes glucose to move from bloodstream into cells to be used for respiration.

  excess glucose converted into glycogen as energy store.
• what happen to the pancreas if the blood glucose is too low

  pancreas secretes glucagon
• what does that mean for the insulin in the pancreas for low blood glucose

  causes liver and muscles glycogen back into glucose. This is an example of negative feedback.
• Type 1 Diabetes

  Pancreas cannot produce (enough) insulin

  injections needed.
• Type 2 Diabetes

  cells do not absorb glucose as they should

  obesity increases risk of developing
• menstrual cycle

  females are born with eggs, which start to mature at puberty
• FSH

  (Follicle stimulating hormone) from pituitary gland causes an egg to mature and the ovaries to produce oestrogen.
• What does oestrogen do?

  causes uterus lining to thicken and it inhibits FSH so no more eggs mature until the next cycle. It also causes the pituitary gland to secrete LH.
• What is LH?

  Luteinising hormone causes egg to be released, which starts to travel towards the uterus. A sperm cell can fertilise it while in the oviduct
• FSH - inhibiting pills

  no egg mature
• Progesterone injection / implant

  ( convenient) to stop eggs being released
• Condom / Diaphragm

  stops sperm entering vagina
• IUD ( copper coil)

  stop egg embedding in lining
• Different types of fertility treatments

  FSH / LH injections

  IVF
• What is IVF

  it is hard/ expensive.

  Egg collected after inducing release with LH to be fertilised in a lab.

  Viable embryos inserted back into woman's uterus
• Negatives about IVF

  success rate very low

  can potentially cause more than one embryos to develop.
• Adrenal Glands

  (attached to top of kidneys) release adrenaline into your body, which increases blood flow and breathing rate to prepare you for 'fight' or 'flight'