1. Comparative Chordate Anatomy: II Nervous System (T.Y.B.Sc.)
Dr. Rahul B. Patil,
Department of Zoology,
Veer Wajekar A.S.C. College, Phunde

2. Primary Brain Vesicles
Prosencephalon (Forebrain)
Smell
Mesoncephalon (Midbrain)
Vision
Rhombencephalon (Hindbrain)
Hearing
Figure 15.1: Primary brain vesicles

3. Primary Brain Vesicles (con’t)
Figure 15.2: Basic brain plan.
Figure 15.3: Brain divisions.

4. Hindbrain Myelencephalon Metencephalon Medulla oblongata Vagal lobe
Involuntary reflexes
Vagal lobe
Metencephalon
Cerebellum
Roof of metencephalon
Reflex control of skel. muscle
Pons
Figure 15.4: Neural tube development.

5. Hindbrain (con’t) Lateral ventricles Posterior choroid plexus
Two cerebral hemispheres
Posterior choroid plexus
Roof in hindbrain
4th ventricle tissue
Cerebral spinal fluid
Tela choroidea
Roof of medulla
Thin membrane
Figure 15.5: Choroid plexus shown of larval anuran.

6. Divisions and Vesicles
Figure 15.6: Divisions of the brain and ventricles numbered.

7. Midbrain No subdivisions Optic lobes Auditory lobes
Optic reflex centers
Well developed in birds
Auditory lobes
Caudal to optic lobes
Superior (optic) and inferior (auditory) colliculi- when lobes occur together
Corpora quadrigemina collectively
Figure 15.7: Mesoncephalon and tectum region.

8. Midbrain (con’t) 3rd ventricle
Optic ventricles- extension to optic lobe
Ventricles disappear in higher phylogeny
Cerebral aqueduct
Restricted passageways
Conducts 3rd and 4th ventricle
Aqueduct of Sylvius when restricted further
Figure 15.8: Cerebral aqueduct and ventricles of brain.

9. Forebrain- Diencephalon
Optic chiasma
Two optic nerves cross
Pituitary gland
Caudal to optic chiasma
Saccus vasculosus
Posterior to pituitary in some fish
Depth receptor
Figure 15.9: Regions of the diencephalon of a shark with third ventricle in red

10. Forebrain- Diencephalon (con’t)
Hypothalamus
Floor of diencephalon
Autonomic nervous system
Thalamus
Walls of diencephalon
3rd ventricle cavity
Communicates with lateral ventricles
Foramen of Monro
Figure 15.10: Medial view of the brain showing thalamus and hypothalamus of the diencephalon.

11. Forebrain- Diencephalon (con’t)
Epithalamus
Several evaginations
Roof of diencephalon
Paraphysis anteriorly
Epiphyseal complex
Pineal
Photoreceptors
Parapineal
Pineal eye (3rd eye)
Figure 15.11: Epithalamus; gross mid-sagittal section of the human brain.
Figure 15.12: Pineal in detail

12. Forebrain- Telencephalon
Cerebral hemispheres posterior
Rhinencephalon anterior
Olfaction
Lower vertebrates
Rhinencephalon prominent
Hemispheres smaller
Higher vertebrates
Hemispheres increase in size
Olfactory get smaller
Figure 15.13: Front section of cerebral hemisphere formation

13. Craniate Brains
Figure 15.14: Craniate brains.

14. Craniate Brains (con’t)
Figure 15.15: Dorsal view of craniate brains

15. Fish Cerebrum Primitive sensory Motor area Pallium- dorsal area
Subpallium- ventral area
Globus pallidus (Striatum)
Figure 15.16: Globus pallidus of fish; left cerebral hemisphere

16. Amphibian Cerebrum Similar pallium and globus pallidus
Split left and right hemispheres
Figure 15.17: Globus pallidus of amphibian; left cerebral hemisphere

17. Reptile Cerebrum Cerebrum is huge compared to amphibians
Increase of lateral walls
Pushes into lateral ventricle
Dorsal ventricular ridge forms
Receives visual, auditory, and sensory stimuli
Figure 15.18: Globus pallidus of reptile and bird; left cerebral hemisphere

18. Bird Cerebrum Similar to reptiles Avian ridge (hyperstiatum)
Stratum of neurons that capped ridge
Processes visual information
Important to instinctive stereotypic behavior
Migration and courtship

19. Mammal Cerebrum Lateral ventricles extremely expanded Neocortex
Higher mental facilities
Grooves (sulci)
Folds (gyrae)
Figure 15.19: Neocortex of mammalian brain.

20. Mammal Cerebrum (con’t)
Figure 15.20: Ventral view of human brain

21. Mammal Cerebrum (con’t)
Portion of primitive brain retained
Ventral medially
Hippocampus- ancient olfactory pallium
Memory storage?
Globus pallidum pushed interiorly
Basal ganglia
Changes in basal ganglia  motor dysfunction
Parkinson’s Disease
Figure 15.21: Globus pallidus of human; left cerebral hemisphere

22. Mammal Cerebrum (con’t)
Figure 15.22: Sagittal section of the human brain

23. Cranial Nerves Amniotes have 12 Anamniotes have 10
Terminal nerve (Nerve 0)- uncommon in humans
Associated with pheromone receptors
Figure 15.23: Cranial nerve locations on the brain.

24. Figure 15.24: Cranial nerve innervation.

25. Figure 15.25: Cranial nerve innervation.

26. Cranial Nerves (con’t)
Figure 15.27: Cranial nerves in 6th week embryo.
Figure 15.26: Head organization in 4th week embryo

27. Cranial Nerves (con’t)

28. Cranial Nerves (con’t)

29. THANK YOU