Comparative Chordate Anatomy II Nervous System T Y

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

Primary Brain Vesicles n Prosencephalon (Forebrain) n n Mesoncephalon (Midbrain) n n Smell Vision Rhombencephalon (Hindbrain) n Hearing Figure 15. 1: Primary brain vesicles 2

Primary Brain Vesicles (con’t) Figure 15. 2: Basic brain plan. Figure 15. 3: Brain divisions. 3

Hindbrain n Myelencephalon n Medulla oblongata n Involuntary reflexes n n Vagal lobe Metencephalon n Cerebellum n Roof of metencephalon Figure 15. 4: Neural tube development. n Reflex control of skel. muscle n Pons 4

Hindbrain (con’t) n Lateral ventricles n n Two cerebral hemispheres Posterior choroid plexus Roof in hindbrain n 4 th ventricle tissue n Cerebral spinal fluid n n Tela choroidea Roof of medulla n Thin membrane n Figure 15. 5: Choroid plexus shown of larval anuran. 5

Divisions and Vesicles Figure 15. 6: Divisions of the brain and ventricles numbered. 6

Midbrain No subdivisions n Optic lobes n Optic reflex centers n Well developed in birds n n Auditory lobes n n Caudal to optic lobes Superior (optic) and inferior (auditory) colliculi- when lobes occur together n Corpora quadrigemina collectively Figure 15. 7: Mesoncephalon and tectum region. 7

Midbrain (con’t) n 3 rd ventricle n n n Optic ventricles- extension to optic lobe Ventricles disappear in higher phylogeny Cerebral aqueduct n n n Restricted passageways Conducts 3 rd and 4 th ventricle Aqueduct of Sylvius when restricted further Figure 15. 8: Cerebral aqueduct and ventricles of brain. 8

Forebrain- Diencephalon n Optic chiasma n n Pituitary gland n n Two optic nerves cross Caudal to optic chiasma Saccus vasculosus Posterior to pituitary in some fish n Depth receptor n Figure 15. 9: Regions of the diencephalon of a shark with third ventricle in red 9

Forebrain- Diencephalon (con’t) n Hypothalamus Floor of diencephalon n Autonomic nervous system n n Thalamus Walls of diencephalon n 3 rd ventricle cavity n n Communicates with lateral ventricles n Foramen of Monro Figure 15. 10: Medial view of the brain showing thalamus and hypothalamus of the diencephalon. 10

Forebrain- Diencephalon (con’t) n Epithalamus Several evaginations n Roof of diencephalon n Paraphysis anteriorly n Epiphyseal complex n n Pineal n Figure 15. 11: Epithalamus; gross mid -sagittal section of the human brain. Photoreceptors n Parapineal n Pineal eye (3 rd eye) Figure 15. 12: Pineal in detail 11

Forebrain- Telencephalon n n Cerebral hemispheres posterior Rhinencephalon anterior n n Lower vertebrates n n n Olfaction Rhinencephalon prominent Hemispheres smaller Higher vertebrates n n Hemispheres increase in size Olfactory get smaller Figure 15. 13: Front section of cerebral hemisphere formation 12

Craniate Brains Figure 15. 14: Craniate brains. 13

Craniate Brains (con’t) Figure 15. 15: Dorsal view of craniate brains 14

Fish Cerebrum n Primitive sensory n n Pallium- dorsal area Motor area n Subpallium- ventral area n Globus pallidus (Striatum) Figure 15. 16: Globus pallidus of fish; left cerebral hemisphere 15

Amphibian Cerebrum Similar pallium and globus pallidus n Split left and right hemispheres n Figure 15. 17: Globus pallidus of amphibian; left cerebral hemisphere 16

Reptile Cerebrum n Cerebrum is huge compared to amphibians Increase of lateral walls n Pushes into lateral ventricle n n Dorsal ventricular ridge forms n Receives visual, auditory, and sensory stimuli Figure 15. 18: Globus pallidus of reptile and bird; left cerebral hemisphere 17

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

Mammal Cerebrum n Lateral ventricles extremely expanded n Neocortex n Higher mental facilities Grooves (sulci) n Folds (gyrae) n Figure 15. 19: Neocortex of mammalian brain. 19

Mammal Cerebrum (con’t) Figure 15. 20: Ventral view of human brain 20

Mammal Cerebrum (con’t) n Portion of primitive brain retained n n Ventral medially Hippocampus- ancient olfactory pallium n n Globus pallidum pushed interiorly n n Memory storage? Basal ganglia Changes in basal ganglia motor dysfunction n Figure 15. 21: Globus pallidus of human; left cerebral hemisphere Parkinson’s Disease 21

Mammal Cerebrum (con’t) Figure 15. 22: Sagittal section of the human brain 22

Cranial Nerves n n n Amniotes have 12 Anamniotes have 10 Terminal nerve (Nerve 0)- uncommon in humans n Associated with pheromone receptors Figure 15. 23: Cranial nerve locations on the brain. 23

Figure 15. 24: Cranial nerve innervation. 24

Figure 15. 25: Cranial nerve innervation. 25

Cranial Nerves (con’t) Figure 15. 27: Cranial nerves in 6 th week embryo. Figure 15. 26: Head organization in 4 th week embryo 26

Cranial Nerves (con’t) 27

Cranial Nerves (con’t) 28

THANK YOU 29