THE CENTRAL NERVOUS SYSTEM Human Anatomy Sonya Schuh-Huerta, Ph.D

THE CENTRAL NERVOUS THE CENTRAL NERVOUS SYSTEMSYSTEM

Human AnatomyHuman Anatomy

Sonya Schuh-Huerta, Ph.D.Sonya Schuh-Huerta, Ph.D.

The Central Nervous System

• Central nervous system – The brain & spinal cord

• Directional terms unique to the CNS– Rostral toward the nose– Caudal toward the tail

The Spinal Cord

• Functions of the spinal cord– Spinal nerves attach to it– Provides 2-way conduction pathway– Major center for reflexes

• Location of the spinal cord– Runs through the vertebral canal– Extends from the foramen magnum to the

level of vertebra L1 or L2

The Spinal Cord

• Conus medullaris– The inferior end of the spinal cord

• Filum terminale– Long filament of connective tissue– Attaches to the coccyx inferiorly

• Cervical & lumbar enlargements – Where nerves for upper & lower limbs arise

• Cauda equina– Collection of spinal nerve roots

The Spinal Cord

Cervicalspinal nervesCervical

enlargement

Lumbarspinal nerves

Sacralspinal nerves

Thoracicspinal nerves

Dura andarachnoidmater

LumbarenlargementConusmedullaris

Caudaequina

Filumterminale

(a) The spinal cord and its nerve roots, with the bony vertebral arches removed. The dura mater and arachnoid mater are cut open and reflected laterally.

The Spinal Cord

• Spinal cord segments– Indicate the region of the spinal cord from

which spinal nerves emerge– Designated by the spinal nerve that issues

from it• T1 is the region where the first thoracic nerve

emerges

Spinal Cord SegmentsSpinal cordsegment C1

Dorsal (posterior) Ventral (anterior)

Spinal nerve C8Spinal nerve T1

Spinal nerve T5

Spinal nerve L1

Spinal nerve S1

Spinal cordsegment T1

Spinal cordsegment T5

Spinal cordsegment L1

Spinousprocess T1

Spinal nerve C1

The Spinal Cord

• 2 deep grooves run the length of the cord– Dorsal median sulcus– Ventral median fissure

– Remember seeing these in lab on the spinal cord cross section?....

White Matter of the Spinal Cord

• White matter– Outer region of the spinal cord– Composed of myelinated & unmyelinated

axons• Allow communication between spinal cord & brain

– Fibers classified by type• Ascending fibers• Descending fibers• Commissural fibers

Gray Matter of the Spinal Cord & Spinal Roots

• Shaped like butterfly!– Gray commissure contains the central

canal

• Dorsal horns– Consist of interneurons

• Ventral & lateral horns– Contain cell bodies of motor neurons

Anatomy of the Spinal Cord

(a) Cross section of spinal cord and vertebra

Epidural space(contains fat)

Pia materSpinalmeninges

Arachnoid materDura materSubdural space

Subarachnoidspace(contains CSF)

Dorsalrootganglion

Body of vertebra

Anatomy of the Spinal Cord

(b) The spinal cord and its meningeal coverings

Dorsal funiculus

Dorsal median sulcus

Central canalVentral median fissure

Pia mater

Arachnoid mater

Spinal dura mater

Gray commissureDorsal horn

Graymatter

Lateral hornVentral hornVentral funiculus

Lateral funiculus

Whitematter

Dorsal rootganglion

Dorsal root (fansout into dorsal rootlets)

Ventral root(derived from severalventral rootlets)

Spinal nerve

Organization of the Gray Matter of the Spinal Cord

• Gray matter– Divided according to somatic & visceral

regions• SS somatic sensory• VS visceral sensory• VM visceral motor• SM somatic motor

Gray Matter of the Spinal Cord & Spinal Roots

Somatic sensoryneuron

Dorsal root(sensory)

Dorsal rootganglion

Visceralsensory neuron

Somatic motorneuron

Spinal nerve

Ventral root(motor)

Ventral horn(motor neurons)

Dorsal horn (interneurons)

Visceralmotorneuron

SS

VS

VM

SM

Interneurons receiving input from somatic sensory neurons

Interneurons receiving input from visceral sensory neurons

Visceral motor (autonomic) neurons

Somatic motor neurons

Protection of the Spinal Cord

• Protected by vertebrae, meninges, & CSF– Meninges

• Dura mater a single layer surrounding spinal cord

• Arachnoid mater lies deep to the dura mater• Pia mater innermost layer

– Delicate layer of connective tissue– Extends to the coccyx – Denticulate ligaments lateral extensions of pia mater

Cerebrospinal Fluid

• Fills the hollow cavities of brain & spinal cord

• Provides a liquid cushion for spinal cord & brain

• Other functions:– Nourishes brain & spinal cord– Removes wastes– Carries chemical signals between parts of CNS

Diagram of Lumbar Puncture

Ligamentumflavum

Supra-spinousligament

Lumbar punctureneedle enteringsubarachnoidspace

Filumterminale

Intervertebraldisc

T12

L5

Cauda equina insubarachnoid space

Duramater

L5

L4

S1

Arachnoidmater

The Brain

• Performs the most complex

neural functions:– Intelligence– Consciousness– Memory– Sensory-motor integration– Involved in innervation of the head

• Brain also controls:– Heart rate, respiratory rate, blood pressure– Autonomic nervous system (ANS)– Endocrine system

Embryonic Development of the Brain

• Brain arises from rostral part of the?...

neural tube

• 3 primary brain vesicles in 4-week-old embryo– Prosencephalon the forebrain – Mesencephalon the midbrain– Rhombencephalon the hindbrain


• Structures of the adult brain– Develop from secondary brain vesicles

• Telencephalon the cerebral hemispheres • Diencephalon thalamus, hypothalamus, &

epithalamus • Metencephalon pons & cerebellum • Myelencephalon medulla oblongata


• Brain stem includes:– The midbrain, pons, & medulla oblongata

• Ventricles – Central cavity of the neural tube enlarges


(e) Adult neural canal regions

(d) Adult brain structures

(a) Neural tube

(c) Secondary brain vesicles Week 5

(b) Primary brain vesicles Week 4

Anterior(rostral)

Posterior(caudal)

Spinal cord

Cerebellum

Brain stem: medullaoblongata

Brain stem: pons

Brain stem: midbrain

Diencephalon(thalamus, hypothalamus,epithalamus), retina

Cerebrum: cerebralhemispheres (cortex,white matter, basal nuclei)

Myelencephalon

Metencephalon

Mesencephalon

Diencephalon

Telencephalon

Rhombencephalon(hindbrain)

Mesencephalon(midbrain)

Prosencephalon(forebrain)

Central canal

Fourth ventricle

Cerebralaqueduct

Third ventricle

Lateral ventricles


• Brain grows rapidly

• Changes occur in the relative position of its parts– Cerebral hemispheres envelop the diencephalon

& midbrain – Wrinkling of the cerebral hemispheres

• Fit many more neurons within the limited space!

Brain Development from Week 5 - Birth

Midbrain

Cerebellum

Pons

Medullaoblongata

Spinal cord

Cerebralhemisphere

Outline ofdiencephalon

(b) Week 13

Metencephalon

Anterior (rostral) Posterior (caudal)

MesencephalonDiencephalon Midbrain

Cervical

Spinal cord

Flexures

Telencephalon

Myelencephalon

(a) Week 5

Cerebellum

PonsMedullaoblongata

Spinal cord

Cerebralhemisphere

(c) Week 26

Cerebellum

Diencephalon

Cerebrum

(d) Birth

Brain stem Midbrain Pons Medulla oblongata

Basic Parts & Organization of the Brain

• Divided into 4 regions:– Cerebral hemispheres– Diencephalon– Brain stem:

• Midbrain, pons, & medulla oblongata

– Cerebellum

Basic Parts & Organization of the Brain

• Organization – Centrally located gray matter– Externally located white matter– Additional layer of gray matter external to

white matter• Due to groups of neurons migrating externally

– Cortex outer layer of gray matter• Formed from neuronal cell bodies• Located in cerebrum & cerebellum

Basic Parts & Organization of the BrainCortex ofgray matter

Inner graymatter

Gray matter

Outer whitematter

Centralcavity

Inner graymatter

Gray matter

Outer whitematter

Centralcavity

Inner graymatter

Outer whitematter

CerebrumCerebellum

Migratorypattern ofneurons

Central cavity

Region of cerebellum

Brain stem

Spinal cord

Ventricles of the Brain

• Expansions of the brain’s central cavity

• Filled with cerebrospinal fluid

• Lined with ependymal cells

• Continuous with each other

• Continuous with the central canal of spinal cord


• Lateral ventricles located in cerebral hemispheres– Horseshoe-shaped from bending of the

cerebral hemispheres

• Third ventricle lies in diencephalon – Connected with lateral ventricles by

interventricular foramen


• Cerebral aqueduct connects 3rd & 4th ventricles

• Fourth ventricle lies in hindbrain– Connects to the central canal of spinal cord


Anterior horn

Interventricularforamen

Inferiorhorn

Lateralaperture

(b) Left lateral view

Lateral ventricle

Septumpellucidum

Third ventricle

Cerebral aqueduct

(a) Anterior view

Fourth ventricle

Central canal

Inferiorhorn

Posteriorhorn

Medianaperture

Lateralaperture

The Brain Stem

• Several general functions:– Produces automatic behaviors necessary for

survival– Passageway for all fiber tracts running

between cerebrum & spinal cord– Heavily involved with the innervation of the

face & head• 10 of the 12 pairs of cranial nerves attach to it

Ventral View of the Human Brain

Frontal lobe

Olfactory bulb(synapse point ofcranial nerve I)

Optic chiasma

Optic nerve (II)Optic tract

Mammillary body

Pons

Medullaoblongata

Cerebellum

Temporal lobe

Spinal cord

Midbrain

The Brain Stem – The Medulla Oblongata

• Cranial nerves VIII–XII attach to the medulla– VIII vestibulocochlear– IX glossopharyngeal nerve– X vagus nerve – XI accessory nerve – XII hypoglossal nerve

The Brain Stem – Medulla Oblongata & Cranial Nerves

Optic chiasma

View(a)

View(c)

View(b)

Optic nerve (II)

Mammillary body

Oculomotor nerve (III)Crus cerebri of cerebralpeduncles (midbrain)

Trigeminal nerve (V)

Abducens nerve (VI) Facial nerve (VII)

Vagus nerve (X)

Accessorynerve (XI)

Hypoglossal nerve (XII)

Ventral root of firstcervical nerve

Trochlear nerve (IV)

PonsMiddle cerebellarpeduncle

Pyramid

Decussation ofpyramids

(a) Ventral view

Spinal cord

Vestibulocochlearnerve (VIII)

Glossopharyngeal nerve (IX)

Diencephalon Thalamus Hypothalamus

Diencephalon

Brainstem

ThalamusHypothalamusMidbrain PonsMedullaoblongata

Optic tract

The Brain Stem – The Medulla Oblongata

• The core of the medulla contains– Much of the reticular formation

• Nuclei influence autonomic functions

– Visceral centers of the reticular formation include

• Cardiac center• Vasomotor center• The medullary respiratory center• Centers for hiccupping, sneezing, swallowing, &

coughing

Brain Stem – The Medulla Oblongata

View(a)

View(c)

View(b)

Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medullaoblongata

Pineal gland

Diencephalon

Anterior wall offourth ventricle

(c) Dorsal view

Thalamus

Dorsal root offirst cervical nerve

Midbrain Superior colliculus Inferior colliculus

Trochlear nerve (IV) Superior cerebellar peduncle

Corporaquadrigemina

Medulla oblongata Inferior cerebellar peduncle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI)

Pons Middle cerebellar peduncle


Choroid plexus(fourth ventricle)

The Brain Stem – The Pons

• A “bridge” between the midbrain & medulla oblongata

• Pons contains the nuclei of cranial nerves: – V trigeminal nerve– VI abducens nerve– VII facial nerve


• The pons contains: – Motor tracts coming from the cerebral cortex– Pontine nuclei

• Connect portions of the cerebral cortex & cerebellum

• Send axons to cerebellum through the middle cerebellar peduncles


Reticularformation

Trigeminalnerve (V)

Pontinenuclei

Fibers ofpyramidal tract

Middlecerebellarpeduncle

Trigeminalmain sensorynucleus

Trigeminalmotor nucleus

Superior cerebellarpeduncle

Medial lemniscus

Fourthventricle

The Brain Stem – The Midbrain

• Lies between the diencephalon & the pons

• Cerebral aqueduct– The central cavity of the midbrain

• Cerebral peduncles located on the ventral surface of the brain– Contain pyramidal (corticospinal) tracts

• Superior cerebellar peduncles– Connect midbrain to the cerebellum; dorsal surface


• Periaqueductal gray matter surrounds the cerebral aqueduct– Involved in 2 related functions

• Fight-or-flight reaction• Mediates response to visceral pain


• Corpora quadrigemina– The largest nuclei

• Divided into the superior & inferior colliculi – Superior colliculi nuclei that act in visual

reflexes– Inferior colliculi nuclei that act in reflexive

response to sound

The Brain Stem – Dorsal View

View(a)

View(c)

View(b)

Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medullaoblongata

Pineal gland

Diencephalon

Anterior wall offourth ventricle

(c) Dorsal view

Thalamus

Dorsal root offirst cervical nerve

Midbrain Superior colliculus

Inferior colliculus

Trochlear nerve (IV) Superior cerebellar peduncle

Corporaquadrigeminaof tectum

Medulla oblongata Inferior cerebellar peduncle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI)

Pons Middle cerebellar peduncle


Choroid plexus(fourth ventricle)


• Imbedded in the white matter of the midbrain– 2 pigmented nuclei:

• Substantia nigra neuronal cell bodies contain melanin (degenerates in people with Parkinson’s)

– Functionally linked to the basal nuclei

• Red nucleus lies deep to the substantia nigra– Largest nucleus of the reticular formation

The Cerebellum

• Located dorsal to the pons & medulla

• Looks like “mini-brain” behind the real brain– Smoothes & coordinates body movements – Helps maintain equilibrium– Involved in motor learning &

motor memories

The Cerebellum

• Consists of 2 cerebellar hemispheres

• Surface folded into ridges called folia– Separated by fissures

• Hemispheres each subdivided into– Anterior lobe– Posterior lobe– Flocculonodular lobe (tiny)

The Cerebellum

(b) Illustration of parasagittal section

Medullaoblongata

Flocculonodular lobe

Choroidplexus offourth ventricle

Posteriorlobe

Arborvitae

Cerebellar cortex

Anterior lobe

Cerebellarpeduncles

SuperiorMiddleInferior

(a) Midsagittal section

Medullaoblongata


Fourthventricle

Arbor vitaeCerebellarcortex

Folia

Anterior lobe

Choroid plexus

Pons

Posteriorlobe

The Cerebellum

• Composed of 3 regions:– Cortex gray matter– Arbor vitae

• Internal white matter

– Deep cerebellar nuclei deeply situated gray matter

The Cerebellum

• To coordinate body movements, the cerebellar cortex receives 3 types of information: – On equilibrium – On current movements of the limbs, neck, &

trunk– From the cerebral cortex

The Cerebellum

• Coordinating movement1. The Cerebellum receives info on movement

from the motor cortex of the cerebrum

2. The cerebellum compares intended movement with body position

3. The cerebellum sends instructions back to the cerebral cortex to continuously adjust & fine tune motor commands

The Cerebellum

• Higher cognitive functions of the cerebellum– Learning a new motor skill– Participates in cognition

• Language, problem-solving, task planning

The Cerebellum – Cerebellar Peduncles

• Thick tracts connecting the cerebellum to the brain stem are:– Superior cerebellar peduncles– Middle cerebellar peduncles– Inferior cerebellar peduncles

• Fibers to & from the cerebellum are ipsilateral

The Cerebellum

(b) Illustration of parasagittal section

Medullaoblongata


Choroidplexus offourth ventricle

Posteriorlobe

Arborvitae

Cerebellar cortex

Anterior lobe

Cerebellarpeduncles

SuperiorMiddleInferior

(a) Midsagittal section

Medullaoblongata


Fourthventricle

Arbor vitaeCerebellarcortex

Folia

Anterior lobe

Choroid plexus

Pons

Posteriorlobe

The Diencephalon

• Forms the center core of the forebrain

• Surrounded by the cerebral hemispheres

• Composed of 3 paired structures:– Thalamus– Hypothalamus– Epithalamus

• Border the 3rd ventricle

• Primarily composed of gray matter

The Diencephalon & Brainstem

Corpus callosum

Choroid plexus

Thalamus(encloses third ventricle)

Pineal gland(part of epithalamus)

Posterior commissure

CorporaquadrigeminaCerebralaqueduct

Arbor vitae (of cerebellum)Fourth ventricleChoroid plexusCerebellum

Septum pellucidum

Interthalamicadhesion(massa intermedia)

InterventricularforamenAnteriorcommissureHypothalamus

Optic chiasma

Pituitary gland

Cerebral hemisphere

Mammillary body

PonsMedulla oblongata

Spinal cord

Midbrain

Fornix

The Diencephalon – The Thalamus

• Makes up 80% of diencephalon

• Contains approximately a dozen major nuclei– Act as relay stations for incoming sensory

messages– Every part of brain communicating with

cerebral cortex relays signals through thalamic nuclei!!!

• Send axons to regions of the cerebral cortex

The Diencephalon – The Thalamus

• Afferent impulses converge on the thalamus– Synapse in at least one of its nuclei

• Is the “gateway” to the cerebral cortex

• Nuclei organize & amplify or tone down signals

The Thalamus (Nuclei)Dorsal nuclei

Ventral nuclei

Medial

Anteriornucleargroup

Reticularnucleus

Ventralanterior

Ventrallateral

Ventralpostero-lateral

Lateralgeniculatebody

Medialgeniculatebody

Pulvinar

Lateraldorsal

Lateralposterior

(a) The main thalamic nuclei. (The reticular nuclei that “cap” the thalamus laterally are depicted as curving translucent structures.)

The Diencephalon – The Hypothalamus

• Lies between the optic chiasm & the mammillary bodies

• Pituitary gland projects inferiorly

• Contains approximately a dozen nuclei

• Main visceral control center of the body– The master gland’s master!!

The Diencephalon – The Hypothalamus

• Functions include:– Control of the ANS– Control of emotional responses– Regulation of body temperature– Regulation of hunger & thirst sensations– Control of behavior– Regulation of sleep-wake cycles– Control of the endocrine & reproductive sys– Formation of memory

Nuclei of the Hypothalamus

Preopticnucleus

SupraopticnucleusSuprachiasmaticnucleus

Anteriorhypothalamicnucleus

Dorsomedialnucleus

Paraventricularnucleus

FornixAnteriorcommissure

PosteriorhypothalamicnucleusLateralhypothalamicareaVentromedialnucleus

Opticchiasma

Infundibulum(stalk of thepituitary gland)

Pituitarygland

Arcuatenucleus

Mammillarybody

The Diencephalon – The Epithalamus

• Forms part of “roof” (top) of the 3rd ventricle

• Consists of a tiny group of nuclei

• Includes the pineal gland (pineal body)– Secretes the hormone melatonin – Under influence of the hypothalamus– Aids in control of circadian rhythms

The Cerebral Hemispheres

• Account for ~83% of brain mass!!!– Fissures deep grooves, which separate

major regions of brain• Transverse fissure separates cerebrum &

cerebellum

• Longitudinal fissure separates cerebral hemispheres

transverse fissure


• Sulci– Grooves on the surface of the cerebral

hemispheres

• Gyri– Twisted ridges between sulci

• Prominent gyri & sulci are similar in all people


• Deeper sulci divide cerebrum into lobes

• Lobes are named for the skull bones overlying them

• Central sulcus separates frontal & parietal lobes– Bordered by 2 gyri:

• Precentral gyrus • Postcentral gyrus

The Cerebral HemispheresPostcentralgyrus

CentralsulcusPrecentral

gyrusFrontal lobe

(c) Lobes and sulci of the cerebrum

Parietal lobeParieto-occipital sulcus(on medial surfaceof hemisphere)

Lateral fissure

Transversecerebral fissure

Occipital lobeTemporal lobe

CerebellumPonsMedulla oblongataSpinal cord

Cortex (gray matter)

Fissure(a deepsulcus)

Gyrus

Sulcus

White matter


• Parieto-occipital sulcus – Separates the occipital from the parietal lobe

• Lateral fissure/sulcus – Separates temporal lobe from parietal &

frontal lobes

• Insula deep within the lateral sulcus

The Cerebral HemispheresCentral sulcus

(d) Location of the insula lobe

Frontal lobe

Temporal lobe(pulled down)

Gyri of insula


• Frontal section through forebrain– Cerebral cortex– Cerebral white matter– Deep gray matter of the cerebrum (basal

ganglia)

The Cerebral Cortex

• Home of our conscious mind

• Enables us to:– Be aware of ourselves & our sensations– Initiate & control voluntary movements– Communicate,

remember, & understand

– Process info on both conscious & unconscious levels

The Human Mind

• To prove to you that your brain is constantly processing information, that you are not always aware of, and also selecting your attention to specific things, I have a set of activities….

The McGurk Effect

(McGurk & MacDonald, 1976)

Attention Experiment

(Neisser & Becklen, 1975)

Stroop Effect

(Stroop, 1935)

Visual illusions – The Power & Stubborness of the Mind

The Human Mind

• All of these illustrate how powerful the unconscious processing of our mind is – based on experience & memory our minds create biases that actually shape how we view the world around us, other people, & other things. They shape our “reality.” These unconscious biases are also at the root of prejudice & discrimination.

• But we can be aware of this fact – & truly keep an open mind!

The Cerebral Cortex

• Is composed of gray matter– Neuronal cell bodies, dendrites, & short axons

• Folds in cortex triples its size!!!

• Approximately 40% of brain’s mass

• “Brodmann areas”– 47 structurally distinct areas

The Cerebral Cortex

• Functional regions– Traditionally studied in brain-injured people &

animals• Many new discoveries by PET & fMRI

– Regions of the cerebral cortex • Perform distinct motor & sensory functions

– Memory & language spread over wide area

The Cerebral Cortex

• 3 general kinds of functional areas– Sensory areas– Association areas– Motor areas

The Cerebral Cortex

• There is a sensory area for each of the major senses– A “primary sensory cortex”

• Each primary sensory cortex– Has an association area that processes

sensory information• Sensory association areas

Functional & Structural Areas of Cerebral Cortex

Primary motor cortex

Premotor cortexFrontaleye field

Working memoryfor spatial tasks

Executive area fortask management

Working memory for object-recall tasks

Broca’s area(outlined by dashes)

Solving complex,multitask problems

(a) Lateral view, left cerebral hemisphere

Motor areas

Prefrontal cortex

Sensory areas & relatedassociation areas

Central sulcus

Primary somatosensorycortexSomatosensoryassociation cortex

Somatic sensation

Gustatory cortex(in insula) Taste

Wernicke’s area(recognizing & understandingspeech)

Primary visualcortex

Visualassociation area

Vision

Auditoryassociation area

Primary auditory cortex

Hearing

Primary motor cortex Motor association cortex

Primary sensory cortex Sensory association cortex

Multimodal association cortex

Sensory Areas

• Cortical areas involved in conscious awareness of sensation– Located in:

• Parietal lobes• Temporal lobes • Occipital lobes

• Distinct regions of each lobe interpret each of the major senses

Sensory Areas – Primary Somatosensory Cortex

• Located along the postcentral gyrus

• Involved with conscious awareness of general somatic senses

• Spatial discrimination – Precisely locates a stimulus– Certain regions are more adept at distinguishing

precise stimuli


• Projection is contralateral – Cerebral hemispheres:

• Receive sensory input from the opposite side of the body!!!

• Sensory homunculus – somatotopy (map)

– A body map of the sensory cortex


MotorMotor map inprecentral gyrus

SensorySensory map inpostcentral gyrus

Posterior

Anterior

Genitals

Toes

Swallowing

Tongue

Jaw Primary motorcortex(precentral gyrus)

Primarysomato-sensory cortex(postcentral gyrus)

Lips

Face

Eye

Brow

Neck

Thumb

Fingers

Hand

Wrist

Elb

ow

Sh

ou

lder

Tru

nk

Hip

Kn

ee Fo

ot

Kn

ee Leg Hip

Tru

nk

Nec

kH

ead

Arm

Elb

owFo

rear

mH

and

Fing

ers

Thum

bEye

Nose

Face

Lips

TeethGums

Tongue

Pharynx

Sensory Areas – Somatosensory Association Cortex

• Lies posterior to the primary somatosensory cortex

• Integrates different sensory inputs– Touch– Pressure

• Draws upon stored memories of past sensory experiences – You are able to recognize keys or coins in your

pocket without looking at them

Sensory Areas – Visual Areas

• Primary visual cortex – Location is deep within the calcarine sulcus

• On medial part of the occipital lobe

– Largest of all sensory areas • Receives visual information that originates on the

retina• Exhibits contralateral function

– First of a series of areas processing visual input

Sensory Areas – Visual Areas

• Visual association areas– Approximately 30 cortical areas have been

identified– Visual information proceeds in two streams

The Ventral & Dorsal StreamsPost central gyrusCentral sulcus

Frontal lobe Temporal lobe

Parietal lobe

Dorsal stream(“where” pathway)

Visualassociationarea

Primaryvisualcortex

Ventral stream(“what” pathway)

Sensory Areas – Auditory Areas

• Primary auditory cortex– Function

• Conscious awareness of sound• Sound waves excite receptors in the inner ear

– Impulses transmitted to primary auditory cortex

– Location• Superior edge of the temporal lobe

Sensory Areas – Auditory PathwaysCentral sulcus

Temporal lobe

Parietal lobePosterolateral(“where” pathway)

Prefrontalcortex

Primaryauditorycortex

Auditoryassociationarea

Anterolateral(“what” pathway)

Sensory Areas – Vestibular Cortex

• Responsible for– Conscious awareness of sense of balance

• Located in the posterior part of the insula– Deep to the lateral sulcus

Sensory Areas – Gustatory Cortex

• Function– Involved in the conscious awareness of taste

stimuli

• Location– On the “roof” of the lateral sulcus – insula

Sensory Areas – Olfactory Cortex

• Lies on the medial aspect of the cerebrum– Located in the piriform lobe

• Olfactory nerves transmit impulses to the olfactory cortex– Provides conscious awareness of smells

Sensory Areas – Olfactory Cortex

• Part of the rhinencephalon “nose brain”

• Includes: – The piriform lobe, olfactory tracts, &

olfactory bulbs

• Connects the brain to the limbic system– Explains why smells trigger emotions

• Involved with consciously identifying & recalling specific smells

Visceral Sensory Areas

• Location– Within the lateral sulcus– On the insula lobe

• Receives general sensory input– Pain– Pressure– Hunger

Multimodal Association Areas

• Large areas of the cerebral cortex– Receive sensory input from

• Multiple sensory modalities • Sensory association areas

– Make associations between different kinds of sensory information

Posterior Association AreaA type of Multimodal Assoc Area

• Multiple language areas in left cerebral cortex– Wernicke’s area functions in:

• Speech comprehension• Coordination of auditory & visual aspects of

language• Initiation of word articulation• Recognition of sound sequences

Functional Neuroimaging (fMRI)Central sulcus

Longitudinalfissure

Left frontallobe

Left temporallobe

Areas activein speech & hearing

Anterior Association Areas• Prefrontal Cortex

• More complex functions include all aspects of– Thinking, perceiving,

intentionally remembering– Processing abstract ideas, reasoning,

judgment– Impulse control, mental flexibility, social skills– Humor, empathy, conscience– Has 3 working memory areas

Limbic Association Areas

• Located on medial side of frontal lobe– Involved with memory & emotions– Integrates sensory & motor behaviors– Aids in the formation of memory– Processes emotions

Motor Areas

• Cortical areas controlling motor function– Premotor cortex– Primary motor cortex– Frontal eye field– Broca’s area

• All localized in posterior frontal lobe

• Motor cortex– Plans & initiates voluntary motor functions

Motor Areas – Primary Motor Cortex

• Controls motor functions– Primary motor cortex (somatic motor area)– Located in precentral gyrus

• Pyramidal cells– Large neurons of primary motor cortex

Motor Areas – Primary Motor Cortex

• Corticospinal tracts descend through brain stem & spinal cord– Axons signal motor neurons to control skilled

movements – Contralateral

• Pyramidal axons cross over to opposite side of brain

Motor Areas

• Specific pyramidal cells control specific areas of the body– Face & hand muscles are controlled by many

pyramidal cells

• Somatotopy– Body is represented spatially in the primary

motor cortex (just like somatosensory cortex)– Humunculus of motor cortex

Motor Areas

MotorMotor map inprecentral gyrus

Posterior

Anterior

Genitals

Toes

Swallowing

Tongue

Jaw Primary motorcortex(precentral gyrus)

Lips

Face

Eye

Brow

Neck

Thumb

Fingers

Hand

Wrist

Elb

ow

Sh

ou

lder

Tru

nk

Hip

Kn

ee Fo

ot

Motor Areas – Broca’s Area

• Located in left cerebral hemisphere– Manages speech production– Connected to language comprehension areas

in posterior association area

• A corresponding region in the right cerebral hemisphere controls emotional overtones to spoken words

Lateralization of Cortical Functioning

• The 2 hemispheres control opposite sides of the body– Contralateral = opposite side

• Hemispheres are specialized for different cognitive functions

Lateralization of Cortical Functioning

• Left cerebral hemisphere control over:– Language abilities, math, logic

• Right cerebral hemisphere involved with:– Visual-spatial skills– Reading facial expressions– Intuition, emotion, artistic, & musical skills

– Where the terms “left-” & “right-brained” come from

Cerebral White Matter

• Types of tracts– Commissures composed of commissural

fibers• Allows communication between cerebral

hemispheres• Corpus callosum the largest commissure!

– Association fibers • Connect different parts of the same hemisphere

– Parts of Wernike’s & Broca’s areas are connected by association fibers

Cerebral White Matter

Coronaradiata

Projectionfibers

Longitudinal fissure

Gray matter

White matter

Association fibers

Lateralventricle

Fornix

Thirdventricle

Thalamus

Pons

Medulla oblongata Decussationof pyramids

Commissural fibers(corpus callosum)

Internalcapsule

Superior

Basal ganglia Caudate Putamen Globus pallidus

(a) Frontal section

Deep Gray Matter of Cerebrum

• Consists of:– Basal ganglia

• Involved in motor control• Dysfunction in Parkinson’s

– Basal forebrain nuclei• Associated with memory

• Amygdala– Located in cerebrum, but is considered

part of the of limbic system!

Basal Ganglia

• A group of nuclei deep within the cerebral white matter

• Formed from– Caudate nucleus– Putamen– Globus pallidus

Basal Ganglia

• Complex neural calculators– Cooperate with the cerebral cortex in controlling

movement

• Receive input from many cortical areas• Substantia nigra also influences basal

ganglia (this degenerates in Parkinson’s Disease)

Basal Ganglia

Striatum

Substantia nigraof midbrain

Caudatenucleus Thalamus

Tail of caudatenucleus

Putamen

Basal Ganglia

Corpus callosumAnterior hornof lateral ventricle

Head of caudatenucleus Putamen

(b)

Globuspallidus

Thalamus

Tail of caudatenucleus

Third ventricle

Cerebral cortex

Cerebral white matter

Anterior

Posterior

Posterior hornof lateral ventricle

Basal Ganglia

• Evidence shows that they:– Start, stop, & regulate intensity of voluntary

movements– Select appropriate muscles for a task & inhibit

others– In some way estimate the passage of time

Structures & Functions of the Cerebrum



Functional Brain Systems

• Networks of neurons functioning together– Limbic system

• Spread widely in the forebrain

– The reticular formation• Spans the brain stem

Functional Brain Systems –The Limbic System

• Location – Medial aspect of cerebral hemispheres– Also within the diencephalon

• Composed of:– Septal nuclei, cingulate gyrus, hippocampus, olfactory bulb & tracts– Part of the amygdala

• The fornix & other tracts link the limbic system together

Functional Brain Systems –The Limbic System

Functional Brain Systems – The Limbic System

• The “emotional brain”– Cingulate gyrus

• Allows us to shift between thoughts• Interprets pain as unpleasant

• Hippocampal formation (memory) – Hippocampus & the parahippocampal gyrus

Functional Brain Systems – The Limbic System

Corpus callosum

Septum pellucidum

Olfactory bulb

Diencephalic structuresof the limbic system

Anterior thalamicnuclei (flanking3rd ventricle)

HypothalamusMammillary body

Fiber tracts connectinglimbic system structures

FornixAnterior commissure

Cerebral structures of the limbic system

Cingulate gyrusSeptal nucleiAmygdalaHippocampusDentate gyrusParahippocampalgyrus

Protection of the Brain

• The brain is protected from injury by– The skull– Meninges– Cerebrospinal fluid– Blood-brain barrier

Protection of the Brain –Meninges

• Functions of meninges– Cover & protect the CNS– Enclose & protect the vessels that supply the

CNS– Contain the CSF

• Between pia & arachnoid maters

The Meninges

Skin of scalpPeriosteum

Falx cerebri(in longitudinalfissure only)

Blood vesselArachnoid villus

Pia materArachnoid mater

Dura materMeningeal

Periosteal

Bone of skull

Superior sagittalsinus

Subdural space

Subarachnoidspace

Protection of the Brain –Cerebrospinal Fluid (CSF)

• Formed in choroid plexuses in the brain ventricles– Choroid plexus is

• Located in all 4 ventricles• Composed of ependymal cells & capillaries

• Arises from blood– 500 ml/day

Protection of the Brain – Blood-Brain Barrier

• Prevents most blood-borne toxins from entering the brain– Impermeable capillaries!

• Not an absolute barrier– Nutrients such as glucose & oxygen pass

through– Allows alcohol, nicotine, & anesthetics

through

Disorders of the CNS

• Spinal cord damage– Paralysis loss of motor function– Parasthesia loss of sensation– Paraplegia injury to the spinal cord is

between T1 and L2

• Paralysis of the lower limbs

– Quadriplegia injury to

spinal cord in cervical region• Paralysis of all 4 limbs!


• Brain disorders• Schizophrenia• Autism (Austism spectrum disorder)

http://en.wikipedia.org/wiki/File:Autism-stacking-cans_2nd_edit.jpg


• Brain dysfunction– Degenerative brain diseases

• Cerebrovascular accident (= stroke)– Blockage or interruption of blood flow to a brain region

• Alzheimer’s disease – Progressive degenerative disease leading to dementia &

memory loss (characterized by abnormal accumulations of proteins in the brain)

• Parkinson’s Disease – Progressive degenerative disease leading to impaired

motor skills, speech & other functions (loss of normal functioning of basal ganglia & substantia nigra – where are these?)


• Congenital malformations – Hydrocephalus – “water on the brain”– Neural tube defects

• Anencephaly cerebrum & cerebellum absent• Spina bifida incomplete closing of neural tube

during development (some vertebrae not surrounding spinal cord - exposed)

– Cerebral palsy voluntary muscles are poorly controlled

• Results from damage to motor cortex of brain• Common in multiple-baby pregnancies!

Hydrocephalus

Baby with hydrocephalus

AJ Rizzo, 6 years old Born with hydrocephalus(Now doing very good!)

Postnatal Changes in the Brain• Brain structures complete development at

different times– Critical periods in learning

• Language

– Some development occurs into early 20s!– Decline with age attributed to changes in:

• Neural circuitry• Amount of neurotransmitters being released

Remember – in general, no regeneration of neurons throughout life! Exercise your brain! “Use it or lose it.”

Questions…?

What’s Next?Lab: Brain, & other modelsMon Lecture: CNS / PNS & ANS Mon Lab: Sheep Brain Dissection!

Additional images

Documents

THE CENTRAL NERVOUS SYSTEM Human Anatomy Sonya Schuh-Huerta, Ph.D