biology

• Homeostasis


  Maintenance of a constant internal environment.

  
• 3 examples of conditions that need to be controlled.

  Body temperature

  Blood glucose levels

  Water content
• Features of an automatic control system.

  Receptors

  Coordination centre

  Effector
• Negative Feedback


  A process that counteracts a change

  
• Nervous System


  A system that manages the body through negative feedback, hormones and effectors

  
• Central Nervous System


  The brain and spinal cord ; connected to the body by sensory neurones and motor neurones

  
• Sensory Neurones


  Carry signals from receptors to the CNS

  
• Motor Neurones


  Carry signals from the CNS to effectors

  
• Stimulus


  A change in the environment.

  
• Effectors


  Muscles or glands ; respond to receptors and bring about change

  
• Receptors


  Detect stimuli

  
• Synapse


  The gap between neurons. Information must be transmitted as a chemical message.

  
• Neurotransmitter


  Chemical messengers that cross the synaptic gaps between neurons.

  
• Reflexes


  Involuntary and often self-protective movements. Actions that do not require the CNS.

  
• Reflex arc


  A complete pathway through the nervous system from the stimulus to response.

  
• Pathway of a reflex arc

  stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> response

  
• Reaction time


  The time taken to respond to a stimulus.

  
• Endocrine system


  The collection of glands of an organism that secrete hormones into the blood.

  
• Hormones


  Chemical messages that are sent through the blood; produced by various glands.

  
• Pituitary gland


  Sometimes called the 'master gland' as it secretes many different hormones, some of which affect other glands.

  
• Ovaries


  Produce oestrogen (females only)

  
• Testes


  Produce testosterone (males only)
• Thyroid


  Produces thyroxine

  
• Adrenal gland


  Produces adrenaline

  
• Insulin


  Added if blood sugar levels are too high

  
• Glucagon


  Added if blood sugar levels are too low

  
• Pancreas


  The organ that monitors and controls blood glucose levels.

  
• Diabetes


  A condition that affects your ability to control your blood sugar levels

  
• Cause of type 1 diabetes

  The pancreas produces little or no insulin.

  
• Cause of type 2 diabetes

  The body is resistant to its own insulin. Being overweight can increase your chance of developing type 2 diabetes.

  
• Stages in the menstrual cycle

  Menstruation

  The uterus lining builds up

  An egg develops and is released

  The wall is maintained until day 28

  
• FSH (Follicle Stimulating Hormone)


  Produced by the pituitary gland.

  Causes the egg to mature

  Stimulates the ovaries to produce oestrogen

  
• Oestrogen


  Produced by the ovaries.

  Causes the uterus lining to regrow Stimulates the release of LH whilst inhibiting FSH

  
• LH (Luteinising Hormone)


  Produced by the pituitary gland.

  Stimulates the release of an egg at day 14

  
• Progesterone


  Produced by the ovaries.

  Maintains the lining of the uterus and inhibits the release of FSH and LH.

  
• Combined oral contraceptive pill

  An oral contraceptive that contains oestrogen and progesterone.

  
• Contraceptive patch


  A small patch containing oestrogen and progesterone worn on the skin.

  
• Contraceptive implant


  Inserted under the skin of the arm and releases a continuous amount of progesterone which stops the ovaries releasing eggs.

  
• Intrauterine device (IUD)


  A T-shaped device inserted into the uterus to kill sperm and prevent implantation of a fertilised egg.

  
• Barrier methods


  Non-hormonal forms of contraception that are designed to stop the sperm getting to the egg.

  Examples: condoms and a diaphragm.