Anatomy of the Brain and Cranial

Nerves

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The Nervous System can be divided in:

Central Nervous System (CNS)Brain and Spinal Cord

Peripheral Nervous System (PNS)Cranial and spinal nerves, ganglia, sensory

receptors

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Division of the Peripheral Nervous System

Sensory or afferentSomaticVisceral

Motor or efferentSomatic - voluntaryVisceral or Autonomic Nervous System

(ANS) - involuntarySympatheticParasympathetic

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Six regions in the adult brainCerebrumDiencephalonMesencephalonPonsCerebellumMedulla oblongata

Brain contains extensive areas of neural cortexLayer of gray matter on the surface of the

cerebellum and cerebrum

Major regions and landmarks

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The Cerebrum

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Surface contains gyri, sulci, fissuresFissures

Longitudinal fissure separates two cerebral hemispheres

Transverse fissure separates cerebellum from cerebrum

The cerebral hemispheres

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The Cerebrum

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The cerebral hemispheres

SulciParieto-occipital sulcus separates parietal

from occipital lobeLateral sulcus separates temporal from

parietal lobeCentral sulcus separates frontal and parietal

lobe

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The cerebral hemispheres

GyriPrecentral gyrusPoscentral gyrus

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The cerebral lobes Frontal

Precentral gyrusPrimary motor area – conscious

control of voluntary movements. Premotor cortex – memory bank for

skilled motor activities or of patterned and repetitious nature.

Broca’s areaLocated on the left hemisphere.

Controls speech.

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The cerebral lobesPrefrontal cortex – responsible for

personality, cognition, intellect. Lesion cause mental and personality disorder

ParietalPrimary Somatosensory Area – touch,

pressure, temperature, vibration, and pain from body wall

Somatosensory association area – interprets stimulus sent by the above area. Ex: recognizes objects by touch.

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The cerebral lobesTemporal

Primary Auditory area – temporal lobe. Primary association auditory area – interprets

the sound heard by above areaWernicke’s area – only on left hemisphere,

between parietal and temporal lobes. Area responsible for understanding spoken language

Olfactory area –uncus. Smell area.

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The cerebral lobes

OccipitalPrimary visual area – perception of lightVisual association area – interprets the

images seen on the area aboveInsula

Gustatory cortex

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Cerebral hemispheres - internal structures

Gray matterCell bodies of the neuronsDendrites Small unmyelinated axonsNeuroglias

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Cerebral hemispheres - internal structures

White matterTracts

Association – connects 2 areas of the same hemisphere

Projection – connects upper and lower brain. Ex: internal capsule

Commissure – connects the 2 hemispheres.

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Tracts

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Sagittal Section

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Cerebral hemispheres - internal structures

Corpus callosumConnects the 2 hemispheres

FornixConnects limbic system areas

Septum pellucidumSeparates the 2 lateral ventricles

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Cerebral hemispheres - internal structures

Basal Nuclei – regulation of voluntary motor activities. Allows smooth movements.Caudate NucleusPutamen Globus pallidus

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The Diencephalon

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Diencephalon: external view

Olfactory tractOlfactory bulbOptic nerveChiasma opticPituitary gland or hypophysis Mammilary bodies – relay for olfaction

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EpithalamusHypothalamusThalamus

The diencephalon is composed of

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Figure 14.12b

Sagittal Section

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The Epithalamus

Roof of the third ventricleContains choroid plexus Contains pineal gland

Regulates sleep-awake cycle

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Relay area for impulses Two large lobes of gray matterInterthalamic adhesion or intermediate mass

The thalamus

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Autonomic center for regulation of body temperature, water balance, etc

Secretes hormonesMammilary bodies – relay station for olfactionPituitary glands – secretes hormonesOptic chiasm

The hypothalamus

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The Brain Stem

MidbrainCerebral Aqueduct – connects third and forth

ventriclesCerebral peduncles – connects pons to

cerebrumCorpora quadrigemina

Superior colliculi – visual reflex centerInferior colliculi – auditory reflex center

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The Brain Stem Pons

Consists of tracts and nucleiConnects brain to lower CNS

• Medulla Oblongata• Tracts• Decussation of the pyramids• Autonomic reflex centers – heart rate, blood

pressure, vomiting, swallowing, respiratory rhythm

• Olives30

PART 2

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Cerebellum

Two hemispheres connected by the vermisArbor vitae – white matterCortex of gray matter

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The Cerebellum

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The Cerebellum

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Dura mater Falx cerebri-formed by dura mater that

dips into the longitudinal fissure and separates the 2 hemispheres

Falx cerebelli – separate the two cerebellar hemispheres

The cranial meninges

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The cranial meninges – dura mater

Superior sagittal Sinus – collects blood from the brain

Tentorium cerebelli – separates the cerebrum from the cerebellum

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The cranial meninges

Arachnoid Subarachnoid space

Filled with CSF Arachnoid villi – projections of the mater

that protrude through the dura For the CSF to drain back to the venous

circulation

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The cranial meninges

Pia mater Highly vascular Covers the entire brain

Meningites

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The Relationship among the Brain, Cranium, and Meninges

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Filled with cerebrospinal fluid (CSF)Lateral ventricles

Septum pellucidumInterventricular foramina or foramen of

Monro

Ventricles of the brain

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Ventricles of the brain

Third ventricleCerebral aqueduct

Forth ventricle3 Apertures

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Ventricles of the Brain

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CSF cushions delicate neural structuresSupports the brainPathway of CSF

Produced at the Choroid plexusTravels through the apertures on the 4th

ventricle to the subarachnoid space Diffuses across the arachnoid villus

(granulation) into the superior sagittal sinus

Cerebrospinal fluid (CSF)

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The Circulation of CSF

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12 pairs of cranial nervesTo help to remember“Old Opie Occasionally Tries Trigonometry And

Fells Very Gloomy Vague And Hypoactive”

Cranial Nerves

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The Cranial Nerves

PLAY

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Cranial Nerves

Number Name Major FunctionsI Olfactory (sens) SmellII Optic (sens) VisionIII Oculomotor

(mot)Eye movement

IV Trochlear (mot) Eye movement

V Trigeminal (mix) Chewing muscles, head and face sensation

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Cranial nerves

VI Abducens (mot) Eye movement

VII Facial (mix) Face expression, taste

VIII Vestibulocochlear(sen)

Vestibular: posture and balanceCochlear: hearing

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Cranial NervesIX Glossopharingeal

(mix)Swallowing, taste, general sensation for pharynx

X Vagus (mix) Visceral muscle movement and taste sensation

XI Accessory (mot) Swallowing, and head movement

XII Hypoglossal (mot)

Movement of tongue for speaking, swallowing and mixing food

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Brain Dissection

Whole BrainPia-Arachnoid GyrusSulcusFissure

TransverseLongitudinal

Cerebrum50

Brain Dissection

PonsMedulla OblongataCerebellumCranial nerves: I (bulb, tract) II (nerve, chiasma) III

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Brain Dissection

ColliculiSuperiorInferior

Pineal Gland

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Brain Dissection

Sagittal CutDiencephalon

EpithalamusThalamusHypothalamus

VentriclesLateral, third, forth

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Brain Dissection

Septum pellucidumCorpus callosumFornixArbor vitae (cerebellum)

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