Comparative AnatomyComparative AnatomyNervous SystemNervous System

Kardong Kardong Chapter 16Chapter 16

Part 15 Part 15

Primary Brain VesiclesPrimary Brain Vesicles

Prosencephalon (Forebrain)Prosencephalon (Forebrain) Smell Smell

Mesoncephalon (Midbrain)Mesoncephalon (Midbrain) VisionVision

Rhombencephalon (Hindbrain)Rhombencephalon (Hindbrain) Hearing Hearing

Figure 15.1. Primary brain vesicles (book figure 16.25).

Figure 15.2. Basic brain plan.

Primary Brain Vesicles Primary Brain Vesicles (cont’d.)(cont’d.)

Figure 15.3. Brain divisions.

HindbrainHindbrain MyelencephalonMyelencephalon

Medulla oblongataMedulla oblongata Involuntary reflexes Involuntary reflexes

Vagal lobeVagal lobe Metencephalon Metencephalon

CerebellumCerebellum Roof of metencephalonRoof of metencephalon Reflex control ofReflex control of

skeletal muscleskeletal muscle Pons - Floor of Pons - Floor of

metencephalon - relay metencephalon - relay station of sensory and motor station of sensory and motor tracts between spinal cord tracts between spinal cord and cerebrumand cerebrum

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

HindbrainHindbrain (cont’d.)(cont’d.)

4th ventricle4th ventricle Cavity of hindbrainCavity of hindbrain

Posterior choroid plexusPosterior choroid plexus Roof in hindbrainRoof in hindbrain 44thth ventricle tissue ventricle tissue Cerebrospinal fluidCerebrospinal fluid

Tela choroideaTela choroidea Roof of medullaRoof of medulla Thin membraneThin membrane

Figure 15.5. Choroid plexus shown in a larval anuran.

Brain Divisions/VesiclesBrain Divisions/Vesicles

Figure 15.6. Regions of the vertebrate brain (Fig. 16.32)

MidbrainMidbrain No subdivisionsNo subdivisions

Roof – tectum; floor - tegmentumRoof – tectum; floor - tegmentum Optic lobesOptic lobes

Optic reflex centersOptic reflex centers Well developed in birdsWell developed in birds

Auditory lobesAuditory lobes Caudal to optic lobesCaudal to optic lobes

Superior (optic) and inferior Superior (optic) and inferior (auditory) colliculi- when lobes occur (auditory) colliculi- when lobes occur togethertogether Corpora quadrigemina Corpora quadrigemina

collectivelycollectivelyFigure 15.7. Mesencephalon and tectum region.

MidbrainMidbrain (cont’d.)(cont’d.)

33rdrd ventricle ventricle Cavity of midbrainCavity of midbrain

Cerebral aqueduct Cerebral aqueduct Restricted passagewaysRestricted passageways Conducts between Conducts between 33rdrd and 4 and 4thth ventricle ventricle Aqueduct of Sylvius when Aqueduct of Sylvius when

restricted furtherrestricted further

Figure 15.8. Cerebral aqueduct and ventricles of brain.

Forebrain - DiencephalonForebrain - Diencephalon

Optic chiasmaOptic chiasma Two optic nerves crossTwo optic nerves cross

Pituitary glandPituitary gland Caudal to optic chiasmaCaudal to optic chiasma

Saccus vasculosus Saccus vasculosus Posterior to pituitary in Posterior to pituitary in

some fishsome fish Depth receptorDepth receptor

Figure 15.9. Regions of the diencephalon of a shark with third ventricle in red.

Forebrain- Diencephalon Forebrain- Diencephalon (cont’d.)(cont’d.)

HypothalamusHypothalamus Floor of diencephalonFloor of diencephalon

ThalamusThalamus Walls of diencephalonWalls of diencephalon 33rdrd ventricle cavity ventricle cavity

Communicates with lateral Communicates with lateral ventriclesventricles

Foramen of MonroForamen of MonroFigure 15.10. Medial view of the brain showing thalamus and hypothalamus of the diencephalon.

Forebrain- Diencephalon Forebrain- Diencephalon (cont.’d)(cont.’d)

EpithalamusEpithalamus Several evaginationsSeveral evaginations Roof of diencephalonRoof of diencephalon Paraphysis anteriorlyParaphysis anteriorly Epiphyseal complexEpiphyseal complex

PinealPineal PhotoreceptorsPhotoreceptors

ParapinealParapineal Pineal eye (3Pineal eye (3rdrd eye) eye)

Figure 15.11. Epithalamus; gross mid-sagittal section of the human brain.

Figure 15.12. Pineal in detail (see book figure 16.37).

Forebrain- TelencephalonForebrain- Telencephalon

Cerebral hemispheres posteriorCerebral hemispheres posterior Rhinencephalon anterior Rhinencephalon anterior

OlfactionOlfaction Lower vertebratesLower vertebrates

Rhinencephalon prominentRhinencephalon prominent Hemisphere smallerHemisphere smaller

Higher vertebratesHigher vertebrates Hemispheres increase in sizeHemispheres increase in size Olfactory get smallerOlfactory get smaller

Figure 15.13. Frontal section of cerebral hemisphere formation.

Evolution of Vertebrate BrainEvolution of Vertebrate Brain

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

Vertebrate Brains Vertebrate Brains (cont’d.)(cont’d.)

Figure 15.15. Dorsal view of vertebrate brains .

Fish CerebrumFish Cerebrum

Primitive sensoryPrimitive sensory Pallium- dorsal areaPallium- dorsal area

Motor areaMotor area Subpallium- ventral areaSubpallium- ventral area

Globus pallidus (striatum)Globus pallidus (striatum)

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

Amphibian CerebrumAmphibian Cerebrum Similar pallium and globus pallidus Similar pallium and globus pallidus Split left and right hemispheresSplit left and right hemispheres

Figure 15.17. Globus pallidus of amphibian; left cerebral hemisphere.

Reptile CerebrumReptile Cerebrum Cerebrum is huge compared to Cerebrum is huge compared to

amphibiansamphibians Increase of lateral wallsIncrease of lateral walls Pushes into lateral ventriclePushes into lateral ventricle

Dorsal ventricular ridge formsDorsal ventricular ridge forms Receives visual, auditory, and Receives visual, auditory, and

sensory stimulisensory stimuli

Figure 15.18. Globus pallidus of reptile and bird; left cerebral hemisphere.

Bird CerebrumBird Cerebrum Similar to reptilesSimilar to reptiles Avian ridge (hyperstriatum)Avian ridge (hyperstriatum)

Stratum of neurons that capped ridgeStratum of neurons that capped ridge Processes visual informationProcesses visual information Important to instinctive stereotypic Important to instinctive stereotypic

behaviorbehavior Migration and courtshipMigration and courtship

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

Mammalian CerebrumMammalian Cerebrum

Lateral ventricles extremely expandedLateral ventricles extremely expanded NeocortexNeocortex

Higher mental facilitiesHigher mental facilities Grooves (sulci)Grooves (sulci) Folds (gyrae)Folds (gyrae)

Figure 15.20. Neocortex of mammalian brain.

Mammalian Cerebrum Mammalian Cerebrum (cont.’d)(cont.’d)

Figure 15.21. Ventral view of human brain (see book Fig 16.36).

Mammalian Cerebrum Mammalian Cerebrum (cont.’d)(cont.’d)

Portion of primitive brain retainedPortion of primitive brain retained Ventral mediallyVentral medially Hippocampus- ancient olfactory Hippocampus- ancient olfactory

palliumpallium Memory storage?Memory storage?

Globus pallidum pushed interiorlyGlobus pallidum pushed interiorly Basal gangliaBasal ganglia

Changes in basal ganglia Changes in basal ganglia motor motor dysfunctiondysfunction Parkinson’s DiseaseParkinson’s Disease

Figure 15.22. Globus pallidus of human; left cerebral hemisphere

Mammalian Cerebrum Mammalian Cerebrum (cont.’d)(cont.’d)

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

Cranial NervesCranial Nerves Amniotes have 12Amniotes have 12 Anamniotes have 10Anamniotes have 10 Terminal nerve (Nerve 0)- uncommon in humansTerminal nerve (Nerve 0)- uncommon in humans

Associated with pheromone receptorsAssociated 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 Cranial Nerves (cont.’d)(cont.’d)

Figure 15.27. Cranial nerves in 6th week embryo.

Figure 15.28. Head organization in 4th week embryo (book figure 16.39).

Cranial Nerves Cranial Nerves (cont.’d)(cont.’d)

Cranial Nerves Cranial Nerves (cont.’d)(cont.’d)