THE CENTRAL NERVOUS SYSTEM Human Anatomy Sonya Schuh-Huerta, Ph.D.
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Transcript of 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
Embryonic Development of the Brain
• Structures of the adult brain– Develop from secondary brain vesicles
• Telencephalon the cerebral hemispheres • Diencephalon thalamus, hypothalamus, &
epithalamus • Metencephalon pons & cerebellum • Myelencephalon medulla oblongata
Embryonic Development of the Brain
• Brain stem includes:– The midbrain, pons, & medulla oblongata
• Ventricles – Central cavity of the neural tube enlarges
Embryonic Development of the Brain
(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
Embryonic Development of the Brain
• 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
Ventricles of the Brain
• 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
Ventricles of the Brain
• Cerebral aqueduct connects 3rd & 4th ventricles
• Fourth ventricle lies in hindbrain– Connects to the central canal of spinal cord
Ventricles of the Brain
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
Dorsal median sulcus
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 Brain Stem – The Pons
• 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
The Brain Stem – The Pons
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
The Brain Stem – The Midbrain
• Periaqueductal gray matter surrounds the cerebral aqueduct– Involved in 2 related functions
• Fight-or-flight reaction• Mediates response to visceral pain
The Brain Stem – The Midbrain
• 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
Dorsal median sulcus
Choroid plexus(fourth ventricle)
The Brain Stem – The Midbrain
• 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
Flocculonodular lobe
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
Flocculonodular lobe
Choroidplexus offourth ventricle
Posteriorlobe
Arborvitae
Cerebellar cortex
Anterior lobe
Cerebellarpeduncles
SuperiorMiddleInferior
(a) Midsagittal section
Medullaoblongata
Flocculonodular lobe
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
The Cerebral Hemispheres
• Sulci– Grooves on the surface of the cerebral
hemispheres
• Gyri– Twisted ridges between sulci
• Prominent gyri & sulci are similar in all people
The Cerebral Hemispheres
• 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
The Cerebral Hemispheres
• 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
The Cerebral Hemispheres
• 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
Sensory Areas – Primary Somatosensory Cortex
• 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
Sensory Areas – Primary Somatosensory 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
Structures & Functions of the Cerebrum
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!
Disorders of the CNS
• Brain disorders• Schizophrenia• Autism (Austism spectrum disorder)
Disorders of the CNS
• 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?)
Disorders of the CNS
• 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