Biology topic 2

• Structure of the nervous sytem ?


  sight smell taste touch hear
• Stimulus ?


  change in the environment
• Reflex action ?


  Automatic and rapid responses to the nervous system to a stimulus.
• Reflexes ?


  Rapid responses to a stimulus for protection.
• Reflex arc ?


  A chain of 3 neurones
• Structure of skin (5)

  Hair, Erector muscles, sweat duct, sweat pore, sweat gland, capillary network
• Negative feedback ?


  reduces the stimulus and balances the system.
• Homoestasis

  Regulates blood glucose
• Insulin

  Causes liver to take up excess glucose from the blood and stores it
• Glucagon

  Responses to low blood glucose
• Human nervous system

  Made of the brain, spinal cord and nerves. Information gets travelled through the nervous system as electrical impulses along neurones.
• Central nervous system

  Brain + spinal cord
• Neurone

  Cells which carry electrical impulses.
• Types of neurones

  1. Sensory
  2. Motor
  3. Relay
• Synapse

  A gap between neurones.
• Reaction time

  Time taken to react to a stimulus.
• 4 factors needed to keep constant levels inside the body

  1. Temperature
  2. Blood glucose
  3. water levels
  4. salts and ions
• What happens when your skin is too hot ?

  Hair goes flat

  Goes red

  Sweat

  Blood vessels expand
• What happens to skin when too cold?

  Hair goes up

  Goes blue

  Goosebumps

  Blood vessels tighten
• Glucose?


  Type of sugar
• Hormones

  Send chemical messengers around the body
• Two types of hormones

  1. Insulin
  2. Glucagon
• When blood glucose is too high what is added ?

  Insulin
• When blood glucose is too low what is added ?

  Glucagon
• What does the pancreas do ?


  Monitors blood glucose levels and makes insulin
• Diabetes?

  Unable to control their blood glucose levels
• Sensory neurones

  Carry nerve impulses towards the CNS
• Motor neurones

  Carry nerve impulses away from the CNS
• Relay neurones

  Carry nerve impulses within the CNS
• Nervous system stages

  Stimulus - Receptor - Sensory neurone - relay neurone - motor neurone - effector - response
• Homozygous

  Genotype in which the two alleles are identical
• Heterozygous

  Genotype in which the two alleles are different