B5 Revision

• Homeostasis is maintaining a stable internal environment
• Reason for homeostasis:

  Cells need to work in the right conditions in order to function properly
• The automatic control systems include:

  x Nervous response

  x Chemical Response

  x Hormonal Response
• All automatic control systems have 3 main components:

  Receptors

  Coordination centres

  Effectors
• Receptors are cells that detect stimulus. examples are taste buds, and light receptors
• Coordination centre receives information from receptors and decides what to do with the information. Example is the brain and spinal cord
• Effectors produce a response which counteracts the change. Examples are muscles which contract and glands which produce hormones
• Negative feedback is what automatic control systems use to contradict any change in the environment
• The nervous system structure:

  Stimulus > Receptors > Sensory neurone > CNS ( relay neurones) > motor neurones > effector > Response
• Relay neurone connects the sensory neurone to the motor neurone
• Sensory neurones carry information as electrical impulses from the receptors to the CNS
• Motor neurone carry information as electrical impulses from CNS to the effectors
• CNS is a type of coordination centre which stands for Central nervous System. The role is to create a response to the change in environment. It is made up of the brain and spinal cord.
• The connection between two neurones is called a synapse which chemicals carry the nerve signal
• Reflexes help to prevent injury. They are automatic and rapid
• Reflex arc is the passage of information in a reflex from the receptors to effectors
• The endocrine system is a network of glands that secrete hormones into the bloodstream.
• Role of Hormones is to make changes in the cell that need constant adjustment
• Types of glands:

  
  

  Pituitary glands (master gland)

  Thyroid Gland

  Adrenal Gland

  Pancreas

  Testes

  Ovaries
• The pituitary Gland directs other glands to produce hormones and tells the body what to do.Attached to the the brain
• Pancreas produces insulin and glucagon to control glucose levels. Infront of kidneys
• Thyroid Glands produces thyroxine which regulates metabolism and growth. Found in neck
• Adrenal Glands produce adrenaline which "prepares for fight or flight" response. Increase heart rate

  Found on top of kidney
• Testes produce testosterone, which is responsible for the development of male characteristics and produces sperm
• Ovaries produces oestrogen responsible for female characteristics and produce egg cells
• Differences:

  Endocrine system: Very slow, effect last longer, around the entire body

  Nervous System: Very fast, doesn't last long, very precise
• If blood sugar levels are too High ^ :

  
  

  x Detected by Pancreas

  X Insulin is released into the bloodstream to alert Liver

  X glucose moves from bloodstream to liver and muscle cells.

  X Liver turns glucose in blood into glycogen
• If blood glucose levels are too low:

  X Glucagon is released into bloodstream from pancreas

  X Glucagon alerts liver to turn glycogen into glucose

  X Glucose is released into blood
• Diabetes affects the ability to control your blood glucose levels
• Type 2 Diabetes is when a person become resistant to their own insulin. They produce insulin but the bodies cells don't respond to it.
• Type 2 diabetes:

  When a person becomes resistant to their own insulin.

  Blood levels rise at a dangerous rate

  Obesity increase the risk

  Temporary

  Regular exercise and controlled diet
• Type 1 Diabetes:

  X Pancreas produces no insulin

  X Usually genetics and is life long

  X Insulin therapy - involves several injection throughout the day to remove glucose from the blood - very effective

  X Regular exercise
• Excess glucose can be stored as glycogen in the liver and muscles
• Adrenaline is released in response of stress, scary situations as the brain sends nervous impulses to the adrenal glands.
• 4 things that increase when you are in flight or fight mode:

  1. increased heart rates
  2. Increased blood pressure
  3. Increased blood flow
  4. Increased blood sugar levels
• Metablism is the speed at which chemical reactions occur
• the thyroxine regulate metabolism, help with growth and development and protein synthesis
• An example of a negative feedback system:

  If thyroxine levels are too low, the pituitary glands secrets TSH (Thyroid stimulating hormone) to stimulate thyroid gland to release more thyroxine
• Non hormonal forms of contraception - stop sperm from reaching egg

  • Condoms
  • Spermicides
  • Diaphragm
  • Sterilisaton
• Sterilisation - Cutting fallopian tubes or cutting sperm duct. Its permanent