Central Nervous System (CNS)Central Nervous System (CNS) CNS – composed of the brain and spinal cordCNS – composed of the brain and spinal cord CephalizationCephalization

Elaboration of the anterior portion of the CNSElaboration of the anterior portion of the CNS Increase in number of neurons in the headIncrease in number of neurons in the head Highest level is reached in the human brainHighest level is reached in the human brain

The BrainThe Brain Composed of wrinkled, pinkish gray tissueComposed of wrinkled, pinkish gray tissue Surface anatomy includes cerebral Surface anatomy includes cerebral

hemispheres, cerebellum, and brain stemhemispheres, cerebellum, and brain stem

Embryonic DevelopmentEmbryonic Development During the first 26 days of development: During the first 26 days of development:

Ectoderm thickens forming the neural plateEctoderm thickens forming the neural plate The neural plate invaginates, forming the neural The neural plate invaginates, forming the neural

groovegroove The neural groove fuses dorsally and forms the The neural groove fuses dorsally and forms the

neural tubeneural tube

Embryonic DevelopmentEmbryonic Development

Figure 12.1

Primary Brain VesiclesPrimary Brain Vesicles The anterior end of the neural tube expands The anterior end of the neural tube expands

and constricts to form the three primary brain and constricts to form the three primary brain vesiclesvesicles Prosencephalon – the forebrainProsencephalon – the forebrain Mesencephalon – the midbrainMesencephalon – the midbrain Rhombencephalon – hindbrainRhombencephalon – hindbrain

Neural Tube and Primary Brain Neural Tube and Primary Brain VesiclesVesicles

Figure 12.2a, b

Secondary Brain VesiclesSecondary Brain Vesicles In week 5 of embryonic development, In week 5 of embryonic development,

secondary brain vesicles formsecondary brain vesicles form Telencephalon and diencephalon arise from the Telencephalon and diencephalon arise from the

forebrainforebrain Mesencephalon remains undividedMesencephalon remains undivided Metencephalon and myelencephalon arise from the Metencephalon and myelencephalon arise from the

hindbrainhindbrain

Secondary Brain VesiclesSecondary Brain Vesicles

Figure 12.2c

Adult Brain StructuresAdult Brain Structures Fates of the secondary brain vesicles:Fates of the secondary brain vesicles:

Telencephalon – cerebrum: cortex, white matter, Telencephalon – cerebrum: cortex, white matter, and basal nucleiand basal nuclei

Diencephalon – thalamus, hypothalamus, and Diencephalon – thalamus, hypothalamus, and epithalamusepithalamus

Mesencephalon – brain stem: midbrainMesencephalon – brain stem: midbrain Metencephalon – brain stem: ponsMetencephalon – brain stem: pons Myelencephalon – brain stem: medulla oblongataMyelencephalon – brain stem: medulla oblongata

Adult Neural Canal RegionsAdult Neural Canal Regions

Figure 12.2c, d

Adult Neural Canal RegionsAdult Neural Canal Regions Adult structures derived from the neural canalAdult structures derived from the neural canal

Telencephalon – lateral ventriclesTelencephalon – lateral ventricles Diencephalon – third ventricleDiencephalon – third ventricle Mesencephalon – cerebral aqueductMesencephalon – cerebral aqueduct Metencephalon and myelencephalon – fourth Metencephalon and myelencephalon – fourth

ventricleventricle

Adult Neural Canal RegionsAdult Neural Canal Regions

Figure 12.2c, e

Basic Pattern of the Central Basic Pattern of the Central Nervous SystemNervous System

Spinal Cord Spinal Cord Central cavity surrounded by a gray matter core Central cavity surrounded by a gray matter core External is white matter composed of myelinated External is white matter composed of myelinated

fiber tractsfiber tracts BrainBrain

Similar to spinal cord but with additional areas of Similar to spinal cord but with additional areas of gray mattergray matter

Cerebellum has gray matter in nucleiCerebellum has gray matter in nuclei Cerebrum has nuclei and additional gray matter in Cerebrum has nuclei and additional gray matter in

the cortexthe cortex

Basic Pattern of the Central Nervous Basic Pattern of the Central Nervous SystemSystem

Figure 12.4

Ventricles of the BrainVentricles of the Brain Arise from expansion of the lumen of the Arise from expansion of the lumen of the

neural tubeneural tube The ventricles are:The ventricles are:

The paired C-shaped lateral ventricles The paired C-shaped lateral ventricles The third ventricle found in the diencephalonThe third ventricle found in the diencephalon The fourth ventricle found in the hindbrain dorsal The fourth ventricle found in the hindbrain dorsal

to the ponsto the pons

Ventricles of the BrainVentricles of the Brain

Figure 12.5

Cerebral HemispheresCerebral Hemispheres Form the superior part of the brain and make Form the superior part of the brain and make

up 83% of its massup 83% of its mass Contain ridges (gyri) and shallow grooves Contain ridges (gyri) and shallow grooves

(sulci)(sulci) Contain deep grooves called fissuresContain deep grooves called fissures Are separated by the longitudinal fissureAre separated by the longitudinal fissure Have three basic regions: cortex, white matter, Have three basic regions: cortex, white matter,

and basal nucleiand basal nuclei

Major Lobes, Gyri, and Sulci of Major Lobes, Gyri, and Sulci of the Cerebral Hemispherethe Cerebral Hemisphere

Deep sulci divide the hemispheres into five Deep sulci divide the hemispheres into five lobes:lobes: Frontal, parietal, temporal, occipital, and insulaFrontal, parietal, temporal, occipital, and insula

Central sulcus – separates the frontal and Central sulcus – separates the frontal and parietal lobesparietal lobes

Brain LobesBrain Lobes

Figure 12.6a–b

Major Lobes, Gyri, and Sulci of Major Lobes, Gyri, and Sulci of the Cerebral Hemispherethe Cerebral Hemisphere

Parieto-occipital sulcus – separates the parietal Parieto-occipital sulcus – separates the parietal and occipital lobesand occipital lobes

Lateral sulcus – separates the parietal and Lateral sulcus – separates the parietal and temporal lobestemporal lobes

The precentral and postcentral gyri border the The precentral and postcentral gyri border the central sulcuscentral sulcus

Cerebral CortexCerebral Cortex The cortex – superficial gray matter; accounts The cortex – superficial gray matter; accounts

for 40% of the mass of the brainfor 40% of the mass of the brain It enables sensation, communication, memory, It enables sensation, communication, memory,

understanding, and voluntary movementsunderstanding, and voluntary movements Each hemisphere acts contralaterally (controls Each hemisphere acts contralaterally (controls

the opposite side of the body)the opposite side of the body) Hemispheres are not equal in functionHemispheres are not equal in function No functional area acts alone; conscious No functional area acts alone; conscious

behavior involves the entire cortexbehavior involves the entire cortex

Functional Areas of the Cerebral Functional Areas of the Cerebral CortexCortex

The three types of functional areas are:The three types of functional areas are: Motor areas – control voluntary movementMotor areas – control voluntary movement Sensory areas – conscious awareness of sensationSensory areas – conscious awareness of sensation Association areas – integrate diverse informationAssociation areas – integrate diverse information

Functional Areas of the Cerebral Functional Areas of the Cerebral CortexCortex

Figure 12.8a

Functional Areas of the Cerebral Functional Areas of the Cerebral CortexCortex

Figure 12.8b

Cerebral Cortex: Motor AreasCerebral Cortex: Motor Areas Primary (somatic) motor cortexPrimary (somatic) motor cortex Premotor cortexPremotor cortex Broca’s areaBroca’s area Frontal eye fieldFrontal eye field

Primary Motor CortexPrimary Motor Cortex Located in the precentral gyrusLocated in the precentral gyrus Pyramidal cells whose axons make up the Pyramidal cells whose axons make up the

corticospinal tracts corticospinal tracts Allows conscious control of precise, skilled, Allows conscious control of precise, skilled,

voluntary movementsvoluntary movements

Premotor CortexPremotor Cortex Located anterior to the precentral gyrusLocated anterior to the precentral gyrus Controls learned, repetitious, or patterned Controls learned, repetitious, or patterned

motor skillsmotor skills Coordinates simultaneous or sequential actions Coordinates simultaneous or sequential actions

Involved in the planning of movementsInvolved in the planning of movements

Broca’s AreaBroca’s Area Broca’s areaBroca’s area

Located anterior to the inferior region of the Located anterior to the inferior region of the premotor areapremotor area

Present in one hemisphere (usually the left)Present in one hemisphere (usually the left) A motor speech area that directs muscles of the A motor speech area that directs muscles of the

tonguetongue Is active as one prepares to speakIs active as one prepares to speak

Frontal Eye FieldFrontal Eye Field Frontal eye fieldFrontal eye field

Located anterior to the premotor cortex and Located anterior to the premotor cortex and superior to Broca’s areasuperior to Broca’s area

Controls voluntary eye movementControls voluntary eye movement

Sensory AreasSensory Areas Primary somatosensory cortexPrimary somatosensory cortex Somatosensory association cortexSomatosensory association cortex Visual and auditory areas Visual and auditory areas Olfactory, gustatory, and vestibular corticesOlfactory, gustatory, and vestibular cortices

Sensory AreasSensory Areas

Figure 12.8a

Primary Somatosensory CortexPrimary Somatosensory Cortex Located in the postcentral gyrus, this area:Located in the postcentral gyrus, this area:

Receives information from the skin and skeletal Receives information from the skin and skeletal musclesmuscles

Exhibits spatial discriminationExhibits spatial discrimination

Somatosensory Association Somatosensory Association CortexCortex

Located posterior to the primary Located posterior to the primary somatosensory cortexsomatosensory cortex

Integrates sensory informationIntegrates sensory information Forms comprehensive understanding of the Forms comprehensive understanding of the

stimulusstimulus Determines size, texture, and relationship of Determines size, texture, and relationship of

partsparts

Visual AreasVisual Areas Primary visual (striate) cortexPrimary visual (striate) cortex

Seen on the extreme posterior tip of the occipital Seen on the extreme posterior tip of the occipital lobelobe

Most of it is buried in the calcarine sulcusMost of it is buried in the calcarine sulcus Receives visual information from the retinasReceives visual information from the retinas

Visual association areaVisual association area Surrounds the primary visual cortexSurrounds the primary visual cortex Interprets visual stimuli (e.g., color, form, and Interprets visual stimuli (e.g., color, form, and

movement)movement)

Auditory AreasAuditory Areas Primary auditory cortexPrimary auditory cortex

Located at the superior margin of the temporal lobeLocated at the superior margin of the temporal lobe Receives information related to pitch, rhythm, and Receives information related to pitch, rhythm, and

loudnessloudness Auditory association areaAuditory association area

Located posterior to the primary auditory cortexLocated posterior to the primary auditory cortex Stores memories of sounds and permits perception Stores memories of sounds and permits perception

of soundsof sounds Wernicke’s area (understanding of words)Wernicke’s area (understanding of words)

Association AreasAssociation Areas Prefrontal cortexPrefrontal cortex Language areasLanguage areas General (common) interpretation areaGeneral (common) interpretation area Visceral association areaVisceral association area

Association AreasAssociation Areas

Figure 12.8a

Prefrontal CortexPrefrontal Cortex Located in the anterior portion of the frontal Located in the anterior portion of the frontal

lobelobe Involved with intellect, cognition, recall, and Involved with intellect, cognition, recall, and

personalitypersonality Necessary for judgment, reasoning, Necessary for judgment, reasoning,

persistence, and consciencepersistence, and conscience Closely linked to the limbic system (emotional Closely linked to the limbic system (emotional

part of the brain)part of the brain)