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• Homeostasis


  The maintenance of a constant internal environment (temp, water and glucose levels) i.e. controlling body conditions
• Homeostasis is to keep optimum (i.e. best) conditions for enzymes and cell functions
• We lose more water on hot days


  As we sweat to cool ourselves down
• Control systems

  • Include receptors, coordination centres and effectors
• Receptors

  Cells that detect stimuli. Stimuli are changes in the environment e.g. increasing light, increasing temp etc.
• Receptors


  • Eyes have light receptors
  • Skin has pressure receptors
• Coordination centres


  e.g. brain, spinal cord, & pancreas. Receive and process information from receptors
• Effectors


  Muscles or glands. Bring about responses that restore optimum levels
• Hormonal system (endocrine system)

  Uses hormones- chemical messengers that travel in the blood and affect a target organ. Slow acting, but longer effect. Hormones are released from glands.
• Nervous system

  Uses nerves that carry electrical impulses. Very quick acting. Usually short effects.
• Nerve cells


  • Animal cells (have nucleus, cytoplasm etc). Are long to communicate with distant parts of body. Most have a covering called a myelin sheath, which speeds up the impulse.

  
• Reflex arc

  Quick responses that protect the body from harm. Don't involve conscious part of brain.

  
• Order


  Not reflex actions, as they involve conscious part of brain. Are voluntary.
• Information is passed along neurones quicker than synapses.- chemical must diffuse across the synapse (gap between 2 neurones)
• Instructions for ruler experiment

  1. Use your weaker hand

  2. Your partner will hold a ruler vertically with the bottom end (the end with the 0 cm) in between your thumb and first finger

  3. Your partner will then drop the ruler without telling you. You must catch it as quickly as possible

  4. After catching the ruler, look at the number level with the top of your thumb. Use a conversion table to convert your ruler measurements into reaction times

  5. Repeat at least 3 times and do with stronger hand

  6. Repeat with at least 3 people

  7. Remove anomalous results and then calculate a mean for both hands
• Pituitary gland

  In the brain is a 'master gland' which secretes several hormones into the blood in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects
• Blood glucose concentration

  Is monitored and controlled by the pancreas
• If blood glucose concentration is too high
• Diabetes


  • Often inherited
  • Risk factors= obesity/lack of exercise
  • Treated with daily insulin injections
  • Treated with a carefully controlled carbohydrate diet and exercise regime.
• Testosterone


  The main male reproductive hormone. Made by testes. Stimulates sperm to be made.
• Hormones in menstrual cycle (females)

  • FSH – -in pituitary- causes eggs to mature in ovary and stimulates oestrogen/progesterone release
  • Oestrogen/progesterone – makes uterus lining thicker , stimulates LH release and inhibits FSH from pituitary
  • LH stimulates the eggs to be released (on day 14 of cycle)
  • Progesterone released from empty follicle after day 14. Maintains uterus lining for 2nd half of cycle. It eventually starts to fall and uterus lining is released as period.
• Oestrogen

  The main female reproductive hormone. Made in the ovary. At puberty eggs begin to mature and one is released approximately every 28 days. The release of eggs is called ovulation
• Hormones


  • LH/oestrogen/progesterone - Pituitary - Ovary
  • Adrenaline - Adrenal - Heart/lungs/liver
  • Glucagon - Pancreas - Liver/muscle
  • Insulin - Pancreas - N/A (any cell with an insulin receptor)
• Contraception (to prevent pregnancy)

  • Either hormonal or non hormonal
  • Hormonal uses chemicals to prevent an egg being released
  • Non-hormonal has a barrier which prevents the sperm reaching an egg or prevents implantation
• Contraception (to prevent pregnancy). You need to be able to name the main methods and evaluate these (i.e. give good and bad points). Some suggestions of evaluation points have been given, but be prepared to do for all methods. Think physical, emotional, medical. If given data, comment on figures etc. E.g. don't just say 95% effective compared to 100% effective. Say that it is more effective.
• Oral contraceptives


  Uses hormones. Contain oestrogen (& sometimes progesterone). This inhibits FSH production, so no eggs mature.
• Injection, implant or skin patch of slow release progesterone


  To stop eggs maturing for a number of months or years
• Biotic factors


  Availability of food/new predators/new pathogens/competition between animals
• Abiotic factors


  Light intensity, temperature, moisture, soil pH, wind intensity, CO2 levels (for plants), O2 levels (for animals living in water)
• Ecosystem


  The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of an environment
• Habitat


  The place where an organism lives
• Community


  Populations of different species living in the same habitat
• Population


  A group of interbreeding organisms of one species in a habitat
• Always too many animals –they compete for food, territory & mates
• Plants compete for light, space, water and minerals from the soil
• Interdependence


  How each species depends on another (e.g. for food, shelter, pollination etc). If 1 species is taken away, it can affect lots of the others
• Stable community


  All the species and environmental factors are in balance so that the population stays fairly constant
• Adaptations


  • Structural (physical feature), behavioural (things they do) or functional (body process that help them survive)
• Plant adaptations for dry conditions

  • Long roots near surface (to get as much water), leaves with small surface area, ability to store water (e.g. cactus)
• Extremophiles


  Organisms that live in extreme conditions (e.g. v. hot, v. acidic) and may have specific adaptations. E.g. bacteria living in deep sea vents.