Nervous System
Kardong
Chapter 16
Part 15

Primary Brain Vesicles



Prosencephalon (Forebrain)
 Smell
Mesoncephalon (Midbrain)
 Vision
Rhombencephalon (Hindbrain)
 Hearing
Figure 15.1. Primary brain vesicles (book figure 16.25).

Primary Brain Vesicles (cont’d.)
Figure 15.2. Basic brain plan.
Figure 15.3. Brain divisions.



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).

Hindbrain (cont’d.)



4th ventricle
 Cavity of hindbrain
Posterior choroid plexus


Roof in hindbrain
4 th ventricle tissue
 Cerebrospinal fluid
Tela choroidea
 Roof of medulla
 Thin membrane
Figure 15.5. Choroid plexus shown in a larval anuran.

Brain Divisions/Vesicles
Figure 15.6. Regions of the vertebrate brain (Fig. 16.32)





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.

Midbrain
(cont’d.)


3 rd ventricle
 Cavity of midbrain
Cerebral aqueduct
 Restricted passageways
 Conducts between
3 rd and 4 th ventricle
 Aqueduct of Sylvius when restricted further
Figure 15.8. Cerebral aqueduct and ventricles of brain.

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.

Forebrain- Diencephalon (cont’d.)


Hypothalamus
 Floor of diencephalon
Thalamus


Walls of diencephalon
3 rd ventricle cavity
 Communicates with lateral ventricles
 Foramen of Monro
Figure 15.10. Medial view of the brain showing thalamus and hypothalamus of the diencephalon.

Forebrain- Diencephalon (cont.’d)
 Epithalamus
 Several evaginations
 Roof of diencephalon
 Paraphysis anteriorly
 Epiphyseal complex
 Pineal
 Photoreceptors
 Parapineal
 Pineal eye (3 rd eye)
Figure 15.11. Epithalamus; gross midsagittal section of the human brain.
Figure 15.12. Pineal in detail
(see book figure 16.37).

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.

Evolution of Vertebrate Brain
Figure 15.14. Phylogenetic enlargement of vertebrate brains (see Fig. 16.33).

Vertebrate Brains (cont’d.)
Figure 15.15. Dorsal view of vertebrate brains .

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.

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

 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.



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.

Mammalian Cerebrum
 Lateral ventricles extremely expanded
 Neocortex
 Higher mental facilities
 Grooves (sulci)
 Folds (gyrae)
Figure 15.20. Neocortex of mammalian brain.

Mammalian Cerebrum (cont.’d)
Figure 15.21. Ventral view of human brain (see book Fig 16.36).

(cont.’d)
 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 15.22. Globus pallidus of human; left cerebral hemisphere

(cont.’d)
Figure 15.23. Sagittal section of the human brain (book Fig. 16.37).




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.

Figure 15.25. Cranial nerve innervation
(book Fig. 16.15).

Figure 15.26. Cranial nerve innervation
(book Fig. 16.15).

(cont.’d)
Figure 15.28. Head organization in 4 th week embryo (book figure 16.39).
Figure 15.27. Cranial nerves in 6 th week embryo.

(cont.’d)

(cont.’d)