ENT 104 Lecture 9

• Neurons


  Structure and function

  
• Reflexes


  Sensory input / behavioral output
• Dendrite


  Receive information from sensory structure, tissue, or another neuron
• Axons


  Send information away from neuron to another neuron or glandular structure
• Synapses


  • Where axons and dendrites meet
  • Neurotransmitters trigger the next neuron to fire
  • Neuromodulators change the likelihood of the neuron firing
• Effector


  Receives input and does something (a muscle or a gland that changes function in response to a signal from a brain center)
• Simplest behaviors


  • Walking, jumping, flying, etc
• Insect gaits can be simple (classic tripod gait) or complex (roaches can sprint on their hind legs alone or gallop like a horse)
• Other stereotyped insect behaviors


  • Flight
  • Digging
  • Eating
  • Reproduction
  • Predation
  • Anti-predation
  • Signaling
• Central pattern generators


  • Nerves are organized into fixed circuits that control stereotyped periodic behavior like walking
  • Can function independent of sensory inputs
  • Neuron A connects to B to C to D, etc in a clock like fashion
  • Circuit repeats with the period of the behavior to create a rhythm
• Physical models


  Can highlight real world problems difficult to imagine with a theoretical model alone
• Reflexes


  • A sensory structure receives information
  • Information is relayed by neurons to a ganglion (or spinal cord in vertebrates)
  • CNS sends signal to effector such as a muscle to jump or run
  • Connections are fixed
  • Response time is the time the signal takes to propagate along path from sensory structure to effector
• Insect nervous systems are distributed, with many ganglia acting as mini brains handling more tasks than in vertebrates with bigger brains
• Decisions


  1. Information is received via sensory structure

  2. Information is filtered

  3. Signal is sent to the brain (afferent)

  4. Information is again filtered and integrated in brain centers of interneurons

  5. Animal status is factored in

  6. Signal is sent out to one or more effectors to change behavior (efferent)
• Social insects recognize colony mates by odor
• Neuroethology

  • How the central nervous system compares the smell to a template in the brain and makes a decision
  • Habituation to the odors of nestmates in the peripheral nervous system