Comparative Anatomy
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.)
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.)



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.
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.)


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.
Forebrain - Diencephalon

Optic chiasma


Pituitary gland


Two optic nerves cross
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.)


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.
Forebrain- Diencephalon (cont.)

Epithalamus
Several evaginations
 Roof of diencephalon
 Paraphysis anteriorly
 Epiphyseal complex

Figure 15.11. Epithalamus; gross midsagittal section of the human brain.
 Pineal

Photoreceptors
 Parapineal

Pineal eye (3rd eye)
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.)
Figure 15.15. Dorsal view of vertebrate brains.
Telencephalon Terminology
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.
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.
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.
Mammalian Cerebrum

Lateral ventricles extremely expanded
 Neocortex
 Higher mental facilities
 Grooves (sulci)
 Folds (gyrae)
Figure 15.20. Neocortex of mammalian brain.
Mammalian Cerebrum (cont.)
Figure 15.21. Ventral view of human brain (see book Fig 16.36).
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
 Parkinson’s Disease
Figure 15.22. Globus pallidus of
human; left cerebral hemisphere
Mammalian Cerebrum (cont.)
Figure 15.23. Sagittal section of the human brain (book Fig. 16.37).
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.
Figure 15.25. Cranial nerve innervation
(book Fig. 16.15).
Figure 15.26. Cranial nerve innervation
(book Fig. 16.15).
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).
Cranial Nerves (cont.)
Cranial Nerves (cont.)