reflex actions

• reflex actions are not controlled by the brain -> quicker
• what is a reflex?

  a rapid, involuntary response to a stimulus
• properties of a reflex action?

  fast, automatic, protective (usually)
• reflex actions limit the harm you recieve
• withdrawal reflex

  
• reflex arc = withdrawal reflex
• reflex arc QER:

  1. stimulus received by receptor
  2. electrical impulse sent along sensory neurone to spinal cord (coordinator)
  3. electrical impulse moves across tiny gap (synapse) to relay neurone
  4. relay neurone transmits signal (via another synapse) to motor neurone
  5. motor neurone stimulates effector (the muscle) to carry out response -> muscle contracts
• stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response (contracts)
• effector is usually a muscle or gland
• receptor cells detects stimulus
• label:

  A) vertebrae

  
• synapse = gap between neurones
• explain how a message travels through the nervous system

  along neurones in the form of electrical impulses