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The Brain

The Brain. Origins and Diversity. The Generalised Vertebrate Brain. The Generalised Vertebrate Brain. All chordates: Front end of notochord thickened – Brain All vertebrates: Tripartite brain structure Forebrain Midbrain Hindbrain Most primitive condition:

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The Brain

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  1. The Brain Origins and Diversity

  2. The Generalised Vertebrate Brain

  3. The Generalised Vertebrate Brain • All chordates: Front end of notochord thickened – Brain • All vertebrates: Tripartite brain structure • Forebrain • Midbrain • Hindbrain • Most primitive condition: • F – Smell; M – Vision; H – Balance, vibration detection

  4. The Generalised Vertebrate Brain

  5. The Generalised Vertebrate Brain

  6. Brain Development

  7. Brain Development

  8. Petromyzontida - Lampreys

  9. Petromyzontida- Lampreys • Small cerebellum • simple mode of locomotion • Rest of hind-brain highly developed • To control powerful sucking structures – med. obl. • Pineal eye • Affect expansion of melanophores – skin colour

  10. Chondrichthyes – e.g. Catsharks

  11. Chondrichthyes – e.g. Catsharks • Pineal organ • Non-secretory, no visual function • Hypothalamus well-developed • Regulation of unconditioned reflexes • ‘Higher’ vertebrates • Large mid-brain • Vision

  12. Amphibia – e.g. Frogs • Large optic lobes • Hippocampalcommissure • Link to reptiles, mammals • Pineal body • Vestigial in adults • Cerebellum v. small • Inactive animal, moves principally in 1 plane

  13. Reptilia – e.g. Lizards • Small brain • 0.5% of body weight in lizards, several inches in dinosaurs weighing 20 tons • Cerebral hemispheres • Bigger than amphibians’ • Olfactory bulbs – linked to Jacobson’s organs

  14. Aves – e.g. Pigeons • Second in brain size to Mammalia • Med. obl. ventral flexure • Similar to Reptilia • Cerebellum large • Flight, equilibrium control

  15. Aves – e.g. Pigeons • Cerebral hemispheres large • Massive corpora striata • For control of reflex behaviours governing lives of birds • Diencephalon hidden

  16. Mammalia – e.g. Rabbits • Hemispheres united via corpus callosum • Commissural fibres • Cerebral hemispheres more extensively developed • Cerebellum large, complex

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