Comparative Anatomy Nervous System

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Comparative AnatomyNervous System

• Kardong
• Chapter 16
• Part 15

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Primary Brain Vesicles

• Prosencephalon (Forebrain)
• Smell
• Mesoncephalon (Midbrain)
• Vision
• Rhombencephalon (Hindbrain)
• Hearing

Figure 15.1. Primary brain vesicles (book figure
16.25).
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Primary Brain Vesicles (cont.)
Figure 15.2. Basic brain plan.
Figure 15.3. Brain divisions.
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Hindbrain

• Myelencephalon
• Medulla oblongata
• Involuntary reflexes
• Vagal lobe
• Metencephalon
• Cerebellum
• Roof of metencephalon
• Reflex control of
• skeletal muscle
• Pons - Floor of metencephalon - relay station
  of sensory and motor tracts between spinal cord
  and cerebrum

Figure 15.4. Regional divisions of the brain
(book figure 16.25).
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Hindbrain (cont.)

• 4th ventricle
• Cavity of hindbrain
• Posterior choroid plexus
• Roof in hindbrain
• 4th ventricle tissue
• Cerebrospinal fluid
• Tela choroidea
• Roof of medulla
• Thin membrane

Figure 15.5. Choroid plexus shown in a larval
anuran.
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Brain Divisions/Vesicles
Figure 15.6. Regions of the vertebrate brain
(Fig. 16.32)
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Midbrain

• No subdivisions
• Roof tectum floor - tegmentum
• 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. Mesencephalon and tectum region.
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Midbrain (cont.)

• 3rd ventricle
• Cavity of midbrain
• Cerebral aqueduct
• Restricted passageways
• Conduit between
• 3rd and 4th ventricle
• Aqueduct of Sylvius when restricted further

Figure 15.8. Cerebral aqueduct and ventricles of
brain.
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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.
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Forebrain- Diencephalon (cont.)

• Hypothalamus
• Floor of diencephalon
• Thalamus
• Walls of diencephalon
• 3rd ventricle cavity
• Communicates with lateral ventricles
• Foramen of Monro
• (actually 2 foramina)

Figure 15.10. Medial view of the brain showing
thalamus and hypothalamus of the diencephalon.
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Forebrain- Diencephalon (cont.)

• 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 (see book figure
16.37).
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Forebrain- Telencephalon

• Cerebral hemispheres posterior
• Rhinencephalon anterior
• Olfaction
• Lower vertebrates
• Rhinencephalon prominent
• Hemisphere smaller
• Higher vertebrates
• Hemispheres increase in size
• Olfactory get smaller

Figure 15.13. Frontal section of cerebral
hemisphere formation.
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Evolution of Vertebrate Brain
Figure 15.14. Phylogenetic enlargement of
vertebrate brains (see Fig. 16.33).
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Vertebrate Brains (cont.)
Figure 15.15. Dorsal view of vertebrate brains.
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Telencephalon Terminology
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Fish Cerebrum

• Primitive sensory
• Pallium- dorsal area
• Motor area
• Subpallium- ventral area
• Globus pallidus (striatum)

Figure 15.16. Embryonic development of the
telencephalon (Book figure 16.42.
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Amphibian Cerebrum

• Similar pallium and globus pallidus
• Split left and right hemispheres

Figure 15.17. Globus pallidus of amphibian left
cerebral hemisphere.
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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.
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Bird Cerebrum

• Similar to reptiles
• Avian ridge (hyperstriatum)
• Stratum of neurons that capped ridge
• Processes visual information
• Important to instinctive stereotypic
• behavior
• Migration and courtship

Figure 15.19. Globus pallidus of reptile and
bird left cerebral hemisphere.
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Mammalian Cerebrum

• Lateral ventricles extremely expanded
• Neocortex
• Higher mental facilities
• Grooves (sulci)
• Folds (gyrae)

Figure 15.20. Neocortex of mammalian brain.
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Mammalian Cerebrum (cont.)
Figure 15.21. Ventral view of human brain (see
book Fig 16.36).
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Mammalian Cerebrum (cont.)

• 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
• Parkinsons Disease

Figure 15.22. Globus pallidus of human left
cerebral hemisphere
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Mammalian Cerebrum (cont.)
Figure 15.23. Sagittal section of the human brain
(book Fig. 16.37).
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Cranial Nerves

• Amniotes have 12
• Anamniotes have 10
• Terminal nerve (Nerve 0)- uncommon in humans
• Associated with pheromone receptors

Figure 15.24. Cranial nerve locations on the
brain.
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Figure 15.25. Cranial nerve innervation (book
Fig. 16.15).
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Figure 15.26. Cranial nerve innervation (book
Fig. 16.15).
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Cranial Nerves (cont.)
Figure 15.27. Cranial nerves in 6th week embryo.
Figure 15.28. Head organization in 4th week
embryo (book figure 16.39).
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Cranial Nerves (cont.)
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Cranial Nerves (cont.)