Nervous System Overall Structure

• Nervous System


  A network of electro-chemically active cells specialised to communicate with each other, enabling flexible interaction with the environment
• Nervous System


  • Registers ('senses') the environment
  • Transforms (interprets, 'makes sense of') those signals
  • Generates an appropriate response
• Uncentralised Nervous System


  • No 'nerve centre' that controls activity of groups of other neurons or actions of distant body parts
• Centralised Nervous System


  • Has separate Central Nervous System ("proto-brain" & nerve cord) and Peripheral Nervous System
• Vertebrate Nervous System


  • Central and Peripheral Nervous System more clearly separated
  • More hierarchically organised, with brain specialized to organize & direct communication between neurons and control actions of distant body parts
• Monosynaptic Reflex Arc


  1. Sensory neuron activated by muscle spindle

  2. Sensory neuron connects directly with motor neuron

  3. Motor neuron activates same muscle to contract
• Monosynaptic Reflex


  • Works to 'resist' or 'dampen' quick stretching of skeletal muscles, enabling smooth, stable movement
  • Can have additional synaptic connections
• Polysynaptic Reflex Arc


  1. Sensory and motor neurons connected via one or more interneurons

  2. Sensor and effector in different locations

  3. More flexible arrangement, can show simple forms of learning
• Synapse


  Signalling link between a neuron and another cell (e.g., another neuron)
• Monosynaptic


  Functionally, only one synapse linking sensory and motor neuron
• Polysynaptic


  Functionally, several synapses between sensory and motor neuron
• Learning


  Modifying links between inputs and responses
• Central Pattern Generators


  • Spinal cord neurons can generate complex movement patterns (e.g., walking) but cannot voluntarily initiate movements - patterns are only elicited in response to appropriate stimulation
• Every type of behavioural control that is more complicated than this NEEDS A BRAIN