3.1

• Antagonistic


  Acting in opposition
• Effectors


  Parts of the body, such as muscles and glands, that produce a response to a detected stimulus
• Excitatory signal


  Causes the signal to propagate more action potentials are triggered
• Hormone


  Chemical messenger produced in glands and carried by the blood to specific organs in the body
• Inhibitory signal


  Works to cancel the signal
• Motor neurons


  Take impulses from the CNS to muscles and glands
• Parasympathetic system


  Also known as rest and digest, the body enters a calm state and decreases the rate of energy expenditure
• Receptors


  Group of specialised cells that detect a change in the environment (stimulus) and produce electrical impulses in response
• Sense organs


  Contain groups of receptors that respond to stimuli
• Sensory neurons


  Take impulses from sense organs to the CNS
• Stimulus


  Any change in the environment that can be detected by receptors in an organism
• Sympathetic system


  Also known as fight or flight, prepares the body for action and increases the rate of energy expenditure
• Structure of the central nervous system (CNS) and the peripheral nervous system (PNS)

  • The central nervous system (CNS) consists of the brain and the spinal cord
  • The peripheral nervous system (PNS) consists of nerve cells that carry information to or from the CNS
• How the nervous system works

  1. Receptors detect stimulus

  2. Sensory neurons take impulses from receptors to CNS

  3. CNS processes information

  4. Motor neurons take impulses from CNS to effectors

  5. Effectors produce response
• Receptor examples


  • Sense organ
  • Skin
  • Eye
  • Ear
• Effector examples


  • A muscle contracting to move an arm
  • A gland releasing a hormone into the blood
• Divisions of the peripheral nervous system (PNS)

  • Somatic nervous system (SNS) contains sensory and motor neurons
  • Autonomic nervous system (ANS) consists of sympathetic and parasympathetic systems
• Sympathetic system


  Speeds up heart rate and breathing rate while slowing down peristalsis and production of intestinal secretions
• Parasympathetic system


  Slows down heart rate and breathing rate and increases peristalsis and intestinal secretions
• Forms of neural pathways

  • Converging
  • Diverging
  • Reverberating
• Converging neural pathway


  • Impulses from several neurons travel to one neuron, increasing the sensitivity to excitatory or inhibitory signals
• Diverging neural pathway


  • Impulses from one neuron travel to several neurons, affecting more than one destination at the same time
• Reverberating pathway


  • Neurons later in the pathway link with earlier neurons, sending the impulse back through the pathway, allowing repeated stimulation