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THE CENTRAL NERVOUS SYSTEM Human Anatomy 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 Cervical enlargement Dura and arachnoid mater Lumbar enlargement Conus medullaris Cauda equina Filum terminale Cervical spinal nerves Thoracic spinal nerves Lumbar spinal nerves Sacral spinal nerves (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 Segments Dorsal (posterior) Ventral (anterior) Spinal cord segment C1 Spinal nerve C1 Spinal cord segment T1 Spinous process T1 Spinal cord segment T5 Spinal nerve C8 Spinal nerve T1 Spinal nerve T5 Spinal cord segment L1 Spinal nerve L1 Spinal nerve S1 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 Epidural space (contains fat) Subdural space Pia mater Arachnoid mater Dura mater Spinal meninges Subarachnoid space (contains CSF) Dorsal root ganglion Body of vertebra (a) Cross section of spinal cord and vertebra Anatomy of the Spinal Cord Dorsal median sulcus Dorsal funiculus White matter Ventral funiculus Lateral funiculus Gray commissure Dorsal horn Ventral horn Lateral horn Gray matter Dorsal root ganglion Spinal nerve Dorsal root (fans out into dorsal rootlets) Ventral root (derived from several ventral rootlets) Central canal Ventral median fissure Pia mater Arachnoid mater Spinal dura mater (b) The spinal cord and its meningeal coverings 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 Dorsal root (sensory) Dorsal horn (interneurons) Dorsal root ganglion SS Somatic sensory neuron Visceral sensory neuron Visceral motor neuron Somatic motor neuron VS VM SM Spinal nerve Ventral root (motor) Ventral horn (motor neurons) 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 T12 L5 Ligamentum flavum Lumbar puncture needle entering subarachnoid space L4 Supraspinous ligament Filum terminale L5 S1 Intervertebral disc Arachnoid mater Dura mater Cauda equina in subarachnoid space 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 (a) Neural tube Anterior (rostral) (b) Primary brain vesicles Week 4 Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (hindbrain) (c) Secondary brain vesicles Week 5 (e) Adult neural canal regions Telencephalon Cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei) Lateral ventricles Diencephalon (thalamus, hypothalamus, epithalamus), retina Third ventricle Diencephalon Mesencephalon Brain stem: midbrain Metencephalon Brain stem: pons Cerebellum Myelencephalon Posterior (caudal) (d) Adult brain structures Cerebral aqueduct Fourth ventricle Brain stem: medulla oblongata Spinal cord Central canal 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 Anterior (rostral) Metencephalon Mesencephalon Diencephalon Telencephalon Myelencephalon Posterior (caudal) Midbrain Cervical Cerebral hemisphere Flexures Cerebellum Pons Medulla oblongata Spinal cord (a) Week 5 Cerebral hemisphere (c) Week 26 Outline of diencephalon Spinal cord Cerebrum Midbrain Cerebellum Diencephalon Pons Cerebellum Medulla oblongata Spinal cord (b) Week 13 (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 Brain Cortex of gray matter Central cavity Migratory pattern of neurons Inner gray matter Outer white matter Cerebrum Cerebellum Region of cerebellum Gray matter Central cavity Inner gray matter Outer white matter Brain stem Gray matter Central cavity Outer white matter Spinal cord Inner gray matter 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 Lateral ventricle Septum pellucidum Anterior horn Posterior horn Interventricular foramen Inferior horn Third ventricle Inferior horn Cerebral aqueduct Lateral aperture (a) Anterior view Fourth ventricle Median aperture Central canal Lateral aperture (b) Left lateral view 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 of cranial nerve I) Optic chiasma Optic nerve (II) Optic tract Mammillary body Midbrain Pons Temporal lobe Medulla oblongata Cerebellum Spinal cord 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 View (a) Diencephalon Thalamus Hypothalamus View (c) Optic chiasma Optic nerve (II) View (b) Optic tract Mammillary body Oculomotor nerve (III) Crus cerebri of cerebral peduncles (midbrain) Trochlear nerve (IV) Trigeminal nerve (V) Pons Facial nerve (VII) Middle cerebellar peduncle Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Hypoglossal nerve (XII) Pyramid Vagus nerve (X) Ventral root of first cervical nerve Accessory nerve (XI) Decussation of pyramids Spinal cord (a) Ventral view Thalamus Hypothalamus Midbrain Pons Medulla oblongata Diencephalon Brainstem 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 Diencephalon Pineal gland Anterior wall of fourth ventricle Choroid plexus (fourth ventricle) Dorsal median sulcus Thalamus (a) Midbrain Superior colliculus Corpora Inferior quadrigemina colliculus View (c) View (b) Trochlear nerve (IV) Superior cerebellar peduncle Pons Middle cerebellar peduncle Medulla oblongata Inferior cerebellar peduncle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Thalamus Dorsal root of first cervical nerve (c) Dorsal view Hypothalamus Diencephalon Midbrain Pons Medulla oblongata Brainstem 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 Superior cerebellar peduncle Fourth ventricle Trigeminal main sensory nucleus Reticular formation Trigeminal motor nucleus Middle cerebellar peduncle Trigeminal nerve (V) Medial lemniscus Pontine nuclei Fibers of pyramidal tract 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 Diencephalon Pineal gland Anterior wall of fourth ventricle Choroid plexus (fourth ventricle) Dorsal median sulcus Thalamus Midbrain Superior colliculus Inferior colliculus View (a) Corpora quadrigemina of tectum View (c) View (b) Trochlear nerve (IV) Superior cerebellar peduncle Pons Middle cerebellar peduncle Medulla oblongata Inferior cerebellar peduncle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Thalamus Hypothalamus Dorsal root of first cervical nerve Midbrain Pons Medulla oblongata (c) Dorsal view Diencephalon Brainstem 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 Anterior lobe Cerebellar cortex Arbor vitae Anterior lobe Arbor vitae Cerebellar cortex Folia Cerebellar peduncles Superior Middle Inferior Medulla oblongata Pons Fourth ventricle Medulla oblongata (a) Midsagittal section Posterior lobe Flocculonodular lobe Choroid plexus of fourth ventricle Posterior lobe Flocculonodular lobe Choroid plexus (b) Illustration of parasagittal section 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 movement 1. 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 Anterior lobe Cerebellar cortex Arbor vitae Anterior lobe Arbor vitae Cerebellar cortex Folia Cerebellar peduncles Superior Middle Inferior Medulla oblongata Pons Fourth ventricle Medulla oblongata (a) Midsagittal section Posterior lobe Flocculonodular lobe Choroid plexus of fourth ventricle Posterior lobe Flocculonodular lobe Choroid plexus (b) Illustration of parasagittal section 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 Cerebral hemisphere Septum pellucidum Interthalamic adhesion (massa intermedia) Interventricular foramen Anterior commissure Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord Corpus callosum Fornix Choroid plexus Thalamus (encloses third ventricle) Posterior commissure Pineal gland (part of epithalamus) Corpora quadrigemina Cerebral aqueduct Midbrain Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum 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 Medial Lateral Lateral dorsal posterior Anterior nuclear group Pulvinar Medial geniculate body Reticular nucleus Ventral Ventral Ventral posteroanterior lateral lateral Ventral nuclei (a) The main thalamic nuclei. (The reticular nuclei that “cap” the thalamus laterally are depicted as curving translucent structures.) Lateral geniculate body 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 Paraventricular nucleus Anterior commissure Preoptic nucleus Anterior hypothalamic nucleus Supraoptic nucleus Suprachiasmatic nucleus Optic chiasma Infundibulum (stalk of the pituitary gland) Fornix Dorsomedial nucleus Arcuate nucleus Posterior hypothalamic nucleus Lateral hypothalamic area Ventromedial nucleus Mammillary body Pituitary gland 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 Hemispheres Precentral gyrus Frontal lobe Central sulcus Postcentral gyrus Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral fissure Occipital lobe Temporal lobe Transverse cerebral fissure Cerebellum Pons Medulla oblongata Spinal cord Fissure (a deep sulcus) Gyrus Cortex (gray matter) Sulcus White matter (c) Lobes and sulci of the cerebrum 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 Hemispheres Frontal lobe Gyri of insula Temporal lobe (pulled down) (d) Location of the insula lobe Central sulcus 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 information 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, and other things. They shape our “reality.” These unconscious biases are also at the root of discrimination. • But we can be aware of this – and 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 Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Sensory areas & related association areas Primary somatosensory cortex Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Prefrontal cortex Working memory for spatial tasks Somatic sensation Taste Wernicke’s area (recognizing & understanding speech) Executive area for task management Primary visual cortex Working memory for object-recall tasks Solving complex, multitask problems Visual association area Auditory association area Primary auditory cortex Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex (a) Lateral view, left cerebral hemisphere Vision Hearing 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 Posterior Sensory Anterior Hip Trunk Motor map in precentral gyrus Motor Foot Toes Genitals Jaw Tongue Swallowing Primary motor cortex (precentral gyrus) Primary somatosensory cortex (postcentral gyrus) Sensory map in postcentral gyrus 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 Streams Central sulcus Post central gyrus Parietal lobe Dorsal stream (“where” pathway) Visual association area Primary visual cortex Ventral stream (“what” pathway) Frontal lobe Temporal lobe 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 Pathways Central sulcus Posterolateral (“where” pathway) Parietal lobe Prefrontal cortex Primary auditory cortex Anterolateral (“what” pathway) Temporal lobe Auditory association area 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 Area A 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 Longitudinal fissure Left frontal lobe Left temporal lobe Areas active in 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 Posterior Motor map in precentral gyrus Motor Anterior Foot Toes Genitals Jaw Tongue Swallowing Primary motor cortex (precentral gyrus) 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 Longitudinal fissure Lateral ventricle Basal ganglia Caudate Putamen Globus pallidus Thalamus Third ventricle Pons Medulla oblongata (a) Frontal section Superior Association fibers Commissural fibers (corpus callosum) Corona radiata Fornix Internal capsule Gray matter White matter Projection fibers Decussation of pyramids Deep Gray Matter of Cerebrum • Consists of: – Basal ganglia • Involved in motor control • Disfunction in Parkinson’s Disease – 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 arches over thalamus – 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 Caudate nucleus Thalamus Putamen Tail of caudate nucleus Substantia nigra of midbrain Basal Ganglia Anterior Cerebral cortex Cerebral white matter Corpus callosum Anterior horn of lateral ventricle Head of caudate nucleus Putamen Globus pallidus Thalamus Tail of caudate nucleus Third ventricle Posterior horn of lateral ventricle (b) Posterior 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, & hippocampal formation – Part of the amygdala • The fornix & other tracts link the limbic system together 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 Septum pellucidum Diencephalic structures of the limbic system Anterior thalamic nuclei (flanking 3rd ventricle) Corpus callosum Fiber tracts connecting limbic system structures Fornix Anterior commissure Cerebral structures of the limbic system Hypothalamus Mammillary body Cingulate gyrus Septal nuclei Amygdala Hippocampus Dentate gyrus Parahippocampal gyrus Olfactory bulb 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 scalp Periosteum Bone of skull Superior sagittal sinus Subdural space Subarachnoid space Periosteal Dura mater Meningeal Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) 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 – BloodBrain 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 models Wed Lecture: PNS & ANS Wed Lab: PNS & ANS / Review!
