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Central Nervous System (CNS)

• CNS consists of brain and spinal cord

• Cephalization– Evolutionary development of rostral (anterior)

portion of CNS– Increased number of neurons in head– Highest level reached in human brain

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Regions and Organization

• Adult brain regions1. Cerebral hemispheres

2. Diencephalon

3. Brain stem (midbrain, pons, and medulla)

4. Cerebellum

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Figure 12.2c Brain development.

Cerebralhemisphere

Diencephalon

Cerebellum

Brain stem• Midbrain• Pons• Medulla oblongata

Birth: Shows adult pattern of structures and convolutions.

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Regions and Organization of the CNS

• Spinal cord – Central cavity surrounded by gray matter – External white matter composed of myelinated

fiber tracts

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Regions and Organization of the CNS

• Brain– Similar pattern– Additional areas of gray matter in brain– Cerebral hemispheres and cerebellum

• Outer gray matter called cortex

– Cortex disappears in brain stem• Scattered gray matter nuclei amid white matter

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Ventricles of the Brain

• Filled with cerebrospinal fluid (CSF)

• Connected to one another and to central canal of spinal cord– Lateral ventricles third ventricle via

interventricular foramen– Third ventricle fourth ventricle via cerebral

aqueduct

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Ventricles of the Brain

• Paired, C-shaped lateral ventricles in cerebral hemispheres– Separated anteriorly by septum pellucidum

• Third ventricle in diencephalon

• Fourth ventricle in hindbrain– Three openings: paired lateral apertures in

side walls; median aperture in roof• Connect ventricles to subarachnoid space

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Figure 12.3 Ventricles of the brain.

Septumpellucidum

Inferiorhorn

Lateralaperture

Lateralventricle

Anteriorhorn

Interventricularforamen

Thirdventricle

Cerebral aqueduct

Fourth ventricle

Central canal

Posteriorhorn

InferiorhornMedianaperture

Lateralaperture

Anterior view Left lateral view

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Cerebral Hemispheres

• Surface markings– Ridges (gyri), shallow grooves (sulci), and

deep grooves (fissures)– Longitudinal fissure

• Separates two hemispheres

– Transverse cerebral fissure• Separates cerebrum and cerebellum

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PLAYPLAY Animation: Rotatable brain

Cerebral Hemispheres

• Five lobes– Frontal– Parietal – Temporal – Occipital– Insula

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Cerebral Hemispheres

• Central sulcus– Separates precentral gyrus of frontal lobe

and postcentral gyrus of parietal lobe

• Parieto-occipital sulcus– Separates occipital and parietal lobes

• Lateral sulcus outlines temporal lobes

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Cerebral Hemispheres

• Three basic regions– Cerebral cortex of gray matter superficially– White matter internally– Basal nuclei deep within white matter

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Figure 12.4c Lobes, sulci, and fissures of the cerebral hemispheres.

Frontal lobe

Postcentralgyrus

Parietal lobe

CentralsulcusPrecentral

gyrus

Parieto-occipital sulcus(on medial surfaceof hemisphere)

Lateral sulcus

Temporal lobeOccipital lobe

Transversecerebral fissure

Pons

Spinal cordFissure(a deepsulcus)

Gyrus

Cortex (gray matter)

Sulcus

White matter

Lobes and sulci of the cerebrum

Medulla oblongata

Cerebellum

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Frontal lobeCentralsulcus

Gyri of insula

Temporal lobe(pulled down)

Location of the insula lobe

Figure 12.4d Lobes, sulci, and fissures of the cerebral hemispheres.

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Figure 12.4a Lobes, sulci, and fissures of the cerebral hemispheres.

Anterior

Longitudinalfissure

Frontal lobe

Cerebral veinsand arteriescovered byarachnoidmater

Left cerebralhemisphere

Parietal lobe

Right cerebralhemisphere

Occipitallobe

Superior view

Posterior

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Figure 12.4b Lobes, sulci, and fissures of the cerebral hemispheres.

Left cerebralhemisphere

Transversecerebralfissure

Cerebellum

Brain stem

Left lateral view

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Cerebral Cortex

• Thin (2–4 mm) superficial layer of gray matter

• 40% mass of brain

• Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding

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4 General Considerations of Cerebral Cortex

1. Three types of functional areas– Motor areas—control voluntary movement– Sensory areas—conscious awareness of

sensation– Association areas—integrate diverse

information

2. Each hemisphere concerned with contralateral side of body

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4 General Considerations of Cerebral Cortex

3. Lateralization of cortical function in hemispheres

4. Conscious behavior involves entire cortex in some way

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Motor Areas of Cerebral Cortex

• In frontal lobe; control voluntary movement

• Primary (somatic) motor cortex in precentral gyrus

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Figure 12.6a Functional and structural areas of the cerebral cortex.

Motor areas

Primary motor cortex

Premotor cortexFrontaleye fieldBroca's area(outlined by dashes)

Working memoryfor spatial tasks

Executive area fortask management

Working memory for object-recall tasksSolving complex,multitask problems

Prefrontal cortex

Lateral view, left cerebral hemisphere

Sensory areas and relatedassociation areasPrimary somatosensorycortexSomatosensoryassociation cortex

Gustatory cortex(in insula)

Somatic sensation

Taste

Wernicke's area(outlined by dashes)

Primary visualcortexVisualassociation area

Auditoryassociation area

Primary auditory cortex

Vision

Hearing

Central sulcus

Primary motorcortex

Motor associationcortex

Primary sensorycortex

Sensoryassociation cortex

Multimodal associationcortex

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Primary Motor Cortex

• Large pyramidal cells of precentral gyri

• Long axons pyramidal (corticospinal) tracts of spinal cord

• Allows conscious control of precise, skilled, skeletal muscle movements

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Figure 12.7 Body maps in the primary motor cortex and somatosensory cortex of the cerebrum.

Posterior

Motor SensoryAnterior

Primary motorcortex(precentral gyrus)

Primary somato-sensory cortex(postcentral gyrus)

Motor map inprecentral gyrus

Sensory map inpostcentral gyrus

Swallowing

Tongue

Jaw

Lips

Face

Eye

Brow

Neck

Thumb

Fingers

Hand

Elb

ow

Wrist

Toes

Genitals

Arm

Sh

ou

lder

Tru

nk

Hip

Fo

ot

Kn

ee

Kn

ee

Leg Hip

Tru

nk

Ne

ck

Hea

dA

rmE

lbow

Fore

arm

Han

d

Fing

ers

Thum

b

Eye

Nose

Face

Lips

Teeth

JawGums

Tongue

Pharynx

Intra-abdominal

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Premotor Cortex

• Helps plan movements; staging area for skilled motor activities

• Controls learned, repetitious, or patterned motor skills

• Coordinates simultaneous or sequential actions

• Controls voluntary actions that depend on sensory feedback

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Broca's Area

• Present in one hemisphere (usually the left)

• Motor speech area that directs muscles of speech production

• Active in planning speech and voluntary motor activities

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Frontal Eye Field

• Controls voluntary eye movements

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Figure 12.6a Functional and structural areas of the cerebral cortex.

Motor areas

Primary motor cortex

Premotor cortexFrontaleye fieldBroca's area(outlined by dashes)

Working memoryfor spatial tasks

Executive area fortask management

Working memory for object-recall tasksSolving complex,multitask problems

Prefrontal cortex

Lateral view, left cerebral hemisphere

Sensory areas and relatedassociation areasPrimary somatosensorycortexSomatosensoryassociation cortex

Gustatory cortex(in insula)

Somatic sensation

Taste

Wernicke's area(outlined by dashes)

Primary visualcortexVisualassociation area

Auditoryassociation area

Primary auditory cortex

Vision

Hearing

Central sulcus

Primary motorcortex

Motor associationcortex

Primary sensorycortex

Sensoryassociation cortex

Multimodal associationcortex

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Figure 12.6b Functional and structural areas of the cerebral cortex.

Corpuscallosum

Frontal eye field

Prefrontalcortex

Processes emotionsrelated to personaland social interactions

Orbitofrontalcortex

Olfactory bulb

Olfactory tract

FornixTemporallobe

Primaryolfactorycortex

Uncus

Calcarine sulcus

Parahippocampalgyrus

Parietal lobe

Somatosensoryassociation cortex

Parieto-occipitalsulcus

Occipitallobe

Visual associationarea

Primaryvisual cortex

Primary somatosensorycortex

Central sulcusPrimarymotor cortex

Cingulategyrus

Premotorcortex

Parasagittal view, right cerebral hemisphere

Primary motorcortex

Motor associationcortex

Primary sensorycortex

Sensoryassociation cortex

Multimodal associationcortex

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• Vestibular cortex

• Olfactory cortex

• Gustatory cortex

• Visceral sensory area

Sensory Areas of Cerebral Cortex

• Primary somatosensory cortex

• Somatosensory association cortex

• Visual areas

• Auditory areas

• Conscious awareness of sensation• Occur in parietal, insular, temporal, and

occipital lobes

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Figure 12.7b Body maps in the primary motor cortex and somatosensory cortex of the cerebrum.

Posterior

SensoryAnterior

Primary somato-sensory cortex(postcentral gyrus)

Sensory map inpostcentral gyrus

Genitals

Fo

ot

Kn

ee

Leg Hip

Tru

nk

Ne

ck

Hea

dA

rmE

lbow

Fore

arm

Han

d

Fing

ers

Thum

b

Eye

Nose

Face

Lips

Teeth

JawGums

Tongue

Pharynx

Intra-abdominal