CPGs

Question 1

What is a fixed action pattern

Answer 1

an instinctive behavioural sequence that is relatively invariant within the species and almost inevitably runs to completion.

Question 2

What are the important properties of CPGs?

Answer 2

1. intrinsic properties of neurones
2. Synaptic properties
3. Patterns of neuronal connectivity

Question 3

What is a network oscillator?

Answer 3

None of the neurones in the CPG have endogenous bursting properties (pacemaker like activity).

Question 4

Describe the tritonia escape swimming CPG.

Answer 4

• Network oscillator
  • sensory input triggers command gating neurones ( trigger-type command neurone tr1 and dorsal ramp interneurone DRI)
  • DRI excites dorsal swim interneurone DSI
  • DSI excites cerebral neurone 2 C2, and itself.
  • C2 have have high thresholds so it takes about 1-4 seconds for firing.
  • C2 then excites DRI (positive feedback loop), keeping it firing.
  • C2 excites ventral swim interneurone VSI (this is delayed slightly due to an A current), which inhibits DSI and eventually C2. When VSI stops, the cycle repeats.

Question 5

Briefly outline the sea angel swimming CPG.

Answer 5

CPG creates permanent rhythmic activity, it is constantly swimming.
It does this through a very strongly connected bursting system at the heart of the CPG.
Uses reciprocal and recurrent inhibition.

Question 6

Briefly outline the Lymnaea feeding CPG.

Answer 6

A network oscillator generating 3 phase rhythm
involves 3 types of CPG neurone
Driven by sensory inputs and higher order modulators
includes the behaviours of protraction, rasp and swallow