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Comparative Chordate Anatomy: II Nervous System ( T.Y.B.Sc .)

Comparative Chordate Anatomy: II Nervous System ( T.Y.B.Sc .). Dr. Rahul B. Patil , Department of Zoology, Veer Wajekar A.S.C. College, Phunde. Primary Brain Vesicles. Prosencephalon (Forebrain) Smell Mesoncephalon (Midbrain) Vision Rhombencephalon (Hindbrain) Hearing.

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Comparative Chordate Anatomy: II Nervous System ( T.Y.B.Sc .)

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  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 • Medulla oblongata • 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 • 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 • 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 • Saccusvasculosus • 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 • Pallium- dorsal area • Motor area • Subpallium- ventral area • Globus pallidus (Striatum) Figure 15.16: Globus pallidus of fish; left cerebral hemisphere

  16. Amphibian Cerebrum • Similar pallium and globuspallidus • 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

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