Adult Brain Regions Cerebral hemispheres Cerebral cortex Basal

Adult Brain Regions – Cerebral hemispheres • Cerebral cortex • Basal nuclei – Diencephalon • Thalamus • Epithalamus • Hypothalamus – Cerebellum – Brain stem • Midbrain • Pons • Medulla oblongata © 2013 Pearson Education, Inc.

Brain Regions Cerebral hemisphere Diencephalon Cerebellum Brain stem • Midbrain • Pons • Medulla

Regions and Organization of the CNS • Spinal cord – Central Canal surrounded by

Ventricles of the Brain • Lateral ventricles (2) – Cerebral hemispheres • Separated by septum pellucidum – Interventricular foramen • Third ventricle – Diencephalon – Cerebral aquaduct • Fourth ventricle – Continuous with Central Canal • Spinal cord © 2013 Pearson Education, Inc.

Ventricles of the Brain • Filled with cerebrospinal fluid (CSF) • Lined by ependymal cells – Circulate CSF • Apertures connect to Subarachnoid space – Cerebrospinal fluid covers brain surface • Brain floats © 2013 Pearson Education, Inc.

Ventricles of the brain. Lateral ventricle Septum pellucidum Interventricular foramen Third ventricle Cerebral aqueduct Lateral aperture Median aperture Fourth ventricle Lateral aperture Central canal Anterior view © 2013 Pearson Education, Inc. Left lateral view

Cerebral Hemispheres • Three basic regions – Cerebral cortex of gray matter superficially –

Cerebral Cortex: Surface markings • Gyri – raised ridges of gray matter • Sulci – shallow broves between gyri • Fissures – wide, deep grooves – Transverse fissure • Separates cerebrum & cerebellum – Longitudinal fissure Gyri • Separates 2 hemispheres Sulci © 2013 Pearson Education, Inc. Longitudinal fissure

Lobes of the Cerebrum Central sulcus Frontal Parietal Insula Occipital Lateral sulcus Temporal

Cerebral Cortex: 5 Lobes • Frontal – Somatic motor output • Parietal – Somatosensory (general sensations) input • Temporal – Hearing – Olfaction (smell) • Occipital – Vision • Insula – Gustation (taste) – Balance – Visceral sensations Discrete functional domains © 2013 Pearson Education, Inc.

Cerebral Cortex: gray matter • 40% mass of brain • Conscious mind: – Awareness – Sensory perception – Voluntary motor initiation – Communication – Memory storage – Understanding © 2013 Pearson Education, Inc.

4 General Considerations of Cerebral Cortex 1. Three types of functional areas – Motor areas: control voluntary movement – Sensory areas: conscious awareness – Association areas: highest form of integration • Specialized memory banks 2. Hemispheres regulation is contralateral 3. Lateralization (specialization) of cortical function 4. Conscious behavior involves entire cortex © 2013 Pearson Education, Inc.

Frontal Lobe: Motor Areas • Primary (somatic) motor cortex • Motor Association Area – Premotor cortex – Broca's area – Frontal eye field Primary motor cortex Premotor cortex Frontal Eye Field Broca’s Area © 2013 Pearson Education, Inc.

Primary Motor Cortex: Conscious control • Large pyramidal neurons (upper motor neurons) – Pyramidal tracts (axons) spinal cord • Corticospinal tracts • Synapse with lower motor neurons • Control skilled, skeletal muscle movements – Most neurons dedicated to precise skills • Face, tongue, hands • Contralateral motor innervation © 2013 Pearson Education, Inc.

Motor Association: Premotor Cortex • Helps plan movements – Staging area for skilled motor activities • Memories to control – Learned, repetitious, or patterned motor skills • Select & sequence basic motor movements into more complex tasks • Coordinates actions that depend on sensory feedback © 2013 Pearson Education, Inc.

Motor Association: Broca's Area • In one hemisphere (left) • Special motor speech area – Muscles of speech production • Active in planning speech • Active in planning other motor activities Motor Association: Frontal Eye Field • Controls voluntary eye movements © 2013 Pearson Education, Inc.

Parietal Lobe: General Sensory input Primary Somatosensory cortex Somatosensory association area © 2013 Pearson

Primary Somatosensory Cortex • Receives general sensory information from – Skin (touch, pressure, vibration, itch, pain, etc) – Proprioceptors of skeletal muscle, joints, and tendons • Map of body surface – Spatial discrimination: identify location stimulated • No identification for stimulus • Contralateral reception – Most sensitive areas have most neurons • Face, lips, fingertips © 2013 Pearson Education, Inc.

Somatosensory Association Cortex • Integrates sensory input – From primary somatosensory cortex – Compares with “touch memories” • Determines – Size, texture, and relationship of parts • Perception of the object’s significance © 2013 Pearson Education, Inc.

Primary Visual Cortex • Contralateral reception from retinas • Perceive only – Shape –

Visual Association Areas • Receives output from primary visual cortex – Compares with “vision memories” • Past visual experiences • Complex process – Entire posterior half of hemisphere – 2 visual streams • Spatial relationships, object location • Recognize faces, written words, objects – Interpret what is seen © 2013 Pearson Education, Inc.

Temporal Lobe: Hearing Primary Auditory Cortex Auditory Association Area © 2013 Pearson Education, Inc.

Auditory Areas • Primary auditory cortex – Interprets input from inner ear • Pitch, loudness, and location • Auditory association area – Receives output from primary auditory cortex – Compares with memories of sounds • Wernicke’s area – spoken word – Perception of sound • Speech, scream, music, thunder, etc. © 2013 Pearson Education, Inc.

Primary Olfactory Cortex: Smell • Region of conscious awareness of odors • Part of primitive rhinencephalon evolved – Limbic system (emotional brain) Olfactory bulb & tract Olfactory cortex © 2013 Pearson Education, Inc.

Insula Gustatory cortex Visceral sensory cortex Vestibular cortex © 2013 Pearson Education, Inc.

Gustatory Cortex • Involved in perception of primary tastes – Sweet – Sour –

Vestibular Cortex • Conscious awareness of balance – Position of head in space – Loss of balance Visceral Sensory Area • Conscious perception of visceral sensations – Upset stomach – Full bladder © 2013 Pearson Education, Inc.

Multimodal Association Areas Wernicke’s Area Broca’s area Anterior Association Area (Prefrontal Cortex) Posterior Association Area Information flow: Sensory receptors primary sensory cortex Sensory Association area Multimodal Association area © 2013 Pearson Education, Inc.

Multimodal Association Areas • • • Give meaning to information received Store it in memory Tie it to previous experience & knowledge Decide what action to take Outputs to multiple areas – Premotor cortex Primary motor cortex • Conscious awareness • Sensations • Thoughts • Emotions © 2013 Pearson Education, Inc.

Multimodal Association Areas: 3 parts • Anterior Association area (prefrontal Cortex) • Posterior Association

Anterior Association Area (Prefrontal Cortex) • Intellect, cognition, recall, and personality • Contains working memory necessary for: – Abstract ideas – Judgment – Reasoning – Persistence – Planning • Development depends social feedback (+/-) – Develops slowly © 2013 Pearson Education, Inc.

Posterior Association Area • Recognizing patterns and faces • Localizing us in space – Aware of our body within location and time • Understanding written, spoken language – Wernicke's area © 2013 Pearson Education, Inc.

Limbic Association Area • Provides emotional impact – Makes scene important – Helps establish

Lateralization of Cortical Function • Division of labor between hemispheres – 1 or the other dominates each task – Instant communication between hemispheres • Cerebral dominance for language – Math, logic • 90% left hemisphere; right-handed • 10% reversed – Bilateral dominance; ambidextrous © 2013 Pearson Education, Inc.

Cerebral White Matter • Myelinated fibers and tracts • Communication – Between cortical areas – Between cortex and lower CNS – Association fibers • Horizontal within same hemisphere – Commissural fibers • Transverse between two hemispheres – Projection fibers • Connect hemispheres with lower brain or spinal cord © 2013 Pearson Education, Inc.

White Matter - Tracts Corona radiata Projection tracts Association fibers Anterior Commissural fibers Corpus callosum, Fornix Cerebral cortex Internal capsule

Basal Nuclei (Ganglia) • Subcortical nuclei – Caudate nucleus – Putamen – Globus pallidus • Caudate nucleus + putamen = striatum • Functional association with – Subthalamic nuclei (diencephalon) – Substantia nigra (midbrain) © 2013 Pearson Education, Inc.

Basal nuclei. Thalamus Head of caudate nucleus Tail of caudate nucleus Putamen Anterior Head

Proposed Functions of Basal Nuclei • • • Initiate & terminate movements Regulate intensity of slow movements Filter out incorrect/inappropriate responses Inhibit antagonistic/unnecessary movements Disorders result in – Too little movement – Too much movement © 2013 Pearson Education, Inc.

Diencephalon: 3 components Interthalamic adhesion Fornix intermediate mass Thalamus Pineal Epithalamus Gland Hypothalamus Pituitary

Thalamus • 80% of diencephalon • Bilateral egg-shaped nuclei; functioning specialty – Projects fibers to specific region of cerebral cortex Medial Lateral dorsal posterior nucleus Pulvinar Anterior nuclei Reticular nucleus Ventral posteroanterior lateral Ventral nuclei © 2013 Pearson Education, Inc. Medial geniculate body Lateral geniculate body

Thalamic Function – the relay station • Gateway to cerebral cortex • Sorts, edits, and relays all ascending input – All senses, all body parts – Impulses from hypothalamus • For regulation of emotion and visceral function – Impulses from cerebellum and basal nuclei • Help direct motor cortices – Impulses for memory or sensory integration © 2013 Pearson Education, Inc.

Hypothalamus • Contains many nuclei • Mammillary bodies Olfactory relay stations Fornix The main hypothalamic nuclei. Optic chiasma Infundibulum © 2013 Pearson Education, Inc. Mammillary body Pituitary gland

Hypothalamic Function • Major homeostatic control center – Main visceral control center • Controls ANS – Cardiac muscle, smooth muscle, glands • Blood pressure, rate and force of heartbeat, digestive tract motility, pupil size • Initiates physical responses of emotions – Limbic system • Perception of pleasure, fear, and rage • Biological rhythms and drives © 2013 Pearson Education, Inc.

Hypothalamic Function • Regulates body temperature – Heat promoting, heat loss centers • Shivering to warm, sweating to cool • Regulates hunger and satiety (food intake) – Monitors nutrient blood levels or hormones • Blood glucose levels • Regulates water balance, thirst center – Osmoreceptors monitor blood osmotic pressure • Dehydration causes release of antidiuretic hormone • Feel thirsty © 2013 Pearson Education, Inc.

Hypothalamic Function • Regulates sleep-wake cycles – Circadian rhythm (biological clock) • Controls endocrine system – Infundibulum connects pituitary gland – Produces hormones stored in posterior pituitary • Stimulates release – Controls secretions of anterior pituitary gland • Releasing or inhibiting hormones from hypothalamus © 2013 Pearson Education, Inc.

Epithalamus • Most dorsal portion of diencephalon • Forms roof of third ventricle • Pineal gland (body) – Melatonin—helps regulate sleep-wake cycle • Prevents precocious behavior © 2013 Pearson Education, Inc.

Brain Stem • Contains nuclei embedded in white matter • Automatic behaviors for survival

Brain Stem: 3 regions Corpora quadrigemina Cerebral aqueduct Fourth ventricle Pons Medulla oblongata ©

Midbrain • White matter – Cerebral peduncles ventrally • Pyramidal motor tracts (corticospinal) •

Midbrain Nuclei • Cranial nerve nuclei – III Occulomotor – IV Trochlear Motor for eye movement • • Corpora quadrigemina – Superior colliculi - visual reflex centers • Track & scan – Inferior colliculi - auditory relay centers • Startle reflex © 2013 Pearson Education, Inc.

Midbrain Nuclei • Substantia nigra – Functionally linked, regulates the Basal Nuclei – Dopamine modulates GABA • Melanin is precursor • Degeneration causes Parkinson’s disease • Red nucleus – Relay nuclei for some descending motor pathways – Rich blood supply, iron pigment © 2013 Pearson Education, Inc.

Basal Nuclei Regulation Receive input from entire cerebral cortex Provide output thru thalamus to motor cortex Frontal eye &Cerebral Premotorcortex Thalamus GABA Body movements Caudate nucleus Eye movement Putamen Globus pallidus Dopamine Substantia nigra Function: Modulate: Initiation, termination of movements Multi-tasking, rhythmic motions

Pons • Bridge, conduction fibers – Links higher brain centers and spinal cord – Relay impulses between motor cortex and cerebellum • Cranial nerves – V (trigeminal) – VI (abducens) – VII (facial) © 2013 Pearson Education, Inc.

Medulla Oblongata: White matter • Pyramids – Pyramidal tracts (corticospinal) • Decussation of the

Medulla Oblongata: Functions • Autonomic reflex center – Functions overlap with hypothalamus • Hypothalamus relays instructions via medulla • Cardiovascular center – Cardiac center • Adjusts force and rate of heart contraction – Vasomotor center • Adjusts blood vessel diameter • Blood pressure regulation © 2013 Pearson Education, Inc.

Medulla Oblongata • Respiratory centers – Generate respiratory rhythm – Control rate and depth

Medulla Oblongata: Nuclei • Cranial nerves – – – VIII (vestibulochoclear) IX (glossopharyngeal) X (vagus) XI (accessory to vagus) XII (hypoglossal) • Relay sensory input – Proprioceptors to cerebelllum – General senses © 2013 Pearson Education, Inc.

Medulla Oblongata • Additional protective reflex centers – Vomiting – Hiccuping – Swallowing –

Anatomy of Cerebellum • 2 Cerebellar hemispheres – Vermis connects • Each hemisphere has 3 lobes – Anterior, posterior coordinate body movements – Flocculonodular process equilibrium input • Folia—transversely oriented gyri – Purkinje cells • Arbor vitae - treelike projection fibers Folia © 2013 Pearson Education, Inc. Vermis

Cerebellar Peduncles: White matter • All fibers connect to same side (ipsilateral) – Superior cerebellar peduncles • Cerebellum to midbrain • Instructions to adjust motor output – Middle cerebellar peduncles • Pons to cerebellum • Motor output from primary motor cortex – Inferior cerebellar peduncles • Medulla to cerebellum • Incoming sensory input © 2013 Pearson Education, Inc.

Cerebellar Processing of Motor Activity • Cerebellum receives impulses – Motor cortex of intent to initiate muscle contraction – Proprioceptors regarding body position, speed – Visual and equilibrium • Integrates input, calculates – Force, direction, extent of muscle contraction – For smoothly coordinate muscle contraction © 2013 Pearson Education, Inc.

Functional Brain Systems • Networks of neurons from different areas • Override each component

Limbic System Thalamus Cingulate gyrus Fornix Parahippocampal gyrus Hippocampus Amygdala Olfactory bulb Mammillary bodies Hypothalamus

Limbic System • Amygdala – Recognizes angry, fearful expressions – Assess danger, elicit fear response • Cingulate gyrus – Express emotions through gestures – Resolves mental conflict • Output relayed through hypothalamus – Autonomic responses – Psychosomatic illnesses © 2013 Pearson Education, Inc.

Limbic System: Emotion and Cognition • Interaction with Prefrontal cortex – React emotionally to things – May over-ride logic • Hippocampus and amygdala – Play a role in memory • Fornix – connecting circuit • Olfactory bulb, mammillary bodies – Ties odors to emotions © 2013 Pearson Education, Inc.

Reticular Formation • Loose clusters of neurons in brain stem – Arranged as 3 columns • Has far-flung axonal connections – Arousal of entire brain • Hypothalamus, thalamus • Spinal cord, cerebellum • Cerebral cortex © 2013 Pearson Education, Inc.

Reticular Formation: RAS • Reticular activating system (RAS) • Maintains alert state – Streams impulses to cerebral cortex • Neurotransmitter orexin – Filters out repetitive, familiar, or weak stimuli ~99% of all stimuli – Inhibited by sleep centers, alcohol, drugs • All input to higher brain centers synapse with RAS • Severe injury results in coma © 2013 Pearson Education, Inc.

Brain Wave Patterns and the EEG • EEG = electroencephalogram • Measures electrical potential differences – Between areas of cerebral cortex • Brain waves – Electrical patterns – Generated by synaptic activity of cortex • Graded potentials © 2013 Pearson Education, Inc.

EEG and brain 1 -second waves. interval Alpha waves—awake but relaxed Beta waves—awake, alert

Consciousness • Conscious perception of sensation • Voluntary initiation, control of movement • Higher mental processing – Simultaneous activity of large cortical areas – Superimposed on other neural activities – Holistic and totally interconnected © 2013 Pearson Education, Inc.

Consciousness • Clinically defined on continuum that grades behavior in response to stimuli – Alertness – Drowsiness (lethargy) – Stupor – Coma • Syncope – brief loss of conscious • Sleep – partial unconsciousness © 2013 Pearson Education, Inc.

Sleep and Sleep-Wake Cycles • Two major types of sleep – Defined by EEG patterns – Non-rapid eye movement (NREM) sleep • Restorative sleep – Rapid eye movement (REM) sleep • Important for emotional stability © 2013 Pearson Education, Inc.

NREM Sleep Stage 1 Stage 2 Stage 3 Stage 4 © 2013 Pearson Education, Inc. Relaxation begins; EEG shows alpha waves; arousal is easy. Irregular EEG Sleep spindles arousal is more difficult. Sleep deepens; Theta, delta waves appear Vital signs decline. Delta waves dominate; Arousal is difficult; Bed-wetting, night terrors, Sleepwalking may occur.

REM Sleep Awake, alert REM sleep 90 min after stage 4, REM begins All

Sleep Disorders • Narcolepsy “sleep attack” – Abrupt lapse into sleep from awake state – Often have cataplexy – Loss of Orexins • "wake-up" chemicals from hypothalamus • Destroyed by immune system © 2013 Pearson Education, Inc.

Sleep Disorders • Insomnia – Chronic inability to obtain amount or quality of sleep needed – Aging, anxiety • Sleep apnea – Temporary cessation of breathing during sleep – Hypoxia activates brain stem activity – Obstructive apnea from loss of muscle tone © 2013 Pearson Education, Inc.

Memory • Storage and retrieval of information • Two stages of storage – Short-term memory “working memory” • Temporary holding of information • Limited to seven or eight pieces of information – Long-term memory has limitless capacity © 2013 Pearson Education, Inc.

Transfer from STM to LTM • Factors affecting transfer from STM to LTM – Emotional state • Best if alert, motivated, surprised, and aroused – Rehearsal • Repetition and practice – Association • Tying new information with old memories – Automatic memory • Subconscious information stored in LTM © 2013 Pearson Education, Inc.

Categories of Memory 1. Declarative (fact) memory – Explicit information – Related to conscious thoughts and language ability – Stored in LTM with context in which learned © 2013 Pearson Education, Inc.

Categories of Memory 2. Non-declarative memory – Less conscious, accidental learning – Experience and repetition, habitual – Best remembered by doing; hard to unlearn • • • © 2013 Pearson Education, Inc. Procedural (skills) memory Motor memory Emotional memory

Brain Structures Involved in Memory • Hippocampus, surrounding temporal lobes – Function: consolidation, access to memory • Basal forebrain supplies Ach – Required for memory formation and retrieval • Loss disrupts formation of new, loss of old memories • Association areas © 2013 Pearson Education, Inc.

Long-term Potentiation • Molecular basis • Neuronal RNA increases – New m. RNA moves to axons, dendrite • Dendritic spines increase • Extracellular proteins deposited at synapses • Number of presynaptic terminals increase – Presynaptic neurons release more neurotransmitter © 2013 Pearson Education, Inc.

Protection of the Brain • • Bone (skull) Meninges – CT membranes Cerebrospinal fluid

Meninges • Cover and protect CNS – Protect blood vessels – Enclose venous sinuses

Meninges: 3 layers • Dura mater • Arachnoid mater • Pia mater • Meningitis

Dura Mater • Strongest meninx • Surrounds the brain • Two layers of fibrous

Dura Mater: limit excessive movement • Falx cerebri – Longitudinal fissure – Attach to crista galli • Falx cerebelli – Between 2 hemispheres of cerebellum • Tentorium cerebelli – Transverse fissure © 2013 Pearson Education, Inc.

Arachnoid Mater • Middle layer with weblike extensions – Subdural space is superficial – Subarachnoid space is deep • CSF and largest blood vessels of brain • Arachnoid villi – Protrude into superior sagittal sinus – Return CSF to circulation © 2013 Pearson Education, Inc.

Pia Mater • Delicate vascularized connective tissue that clings tightly to brain © 2013

Dural septa and dural venous sinuses. Superior sagittal sinus Falx cerebri Pia mater Tentorium

Cerebrospinal Fluid (CSF) Watery solution formed from blood plasma • Less protein • Different

Cerebrospinal Fluid (CSF): Functions • Gives buoyancy – Reduces weight by 97% • Protect

CSF synthesis: Choroid Plexus 3 rd ventricle Lateral ventricles Arachnoid villi Sagittal sinus Subarachnoid

Choroid plexus: BBB missing Ependymal cells form impermeable barrier Ependymal cells Capillary Pia mater Wastes absorbed © 2013 Pearson Education, Inc. Section of choroid plexus CSF forms as a filtrate Glucose O 2 Vitamins Ions

Blood Brain Barrier: Functions • Allows nutrients by facilitated diffusion – Fat-soluble by simple diffusion • Alcohol, nicotine, anesthestics • Prevents passage – Metabolic wastes, proteins, toxins, drugs, K+ • Maintains stable environment for brain • Absent in hypothalamus, medulla – Blood sampling required for homeostasis © 2013 Pearson Education, Inc.

Blood Brain Barrier: Structure • Continuous capillaries – Tight junctions are complete in endothelium • Thick basal lamina • Feet of Astrocytes – Signal the endothelium about tight junctions © 2013 Pearson Education, Inc.

Homeostatic Imbalances of the Brain • Traumatic brain injuries – Concussion—temporary alteration in function

Cerebrovascular Accidents (CVAs) • Anything causing ischemia – Initial event not disasterous – Damaged neurons release buckets of glutamate • Excitotoxin, excites healthy neurons to death • Spreads from initial site – Transient ischemic attacks (TIAs) • Temporary episodes of reversible cerebral ischemia © 2013 Pearson Education, Inc.

Alzheimer’s disease • Progressive degeneration → dementia – Memory loss, disorientation, language loss – Moody, confused, hallucinations – Neurological changes • Plaques of beta-amyloid peptide form in brain – Prion proteins • Neurofibrillary tangles inhibit axon transport – Tau no longer keeps microtubules in place – Neuron dies • Brain shrinks – hippocampus, basal forebrain © 2013 Pearson Education, Inc.

Homeostatic Imbalances of the Brain • Parkinson's disease – Degeneration of substantia nigra neurons • Loss of dopamine – Basal nuclei become overactive – Tremors at rest • Rhythmic bursts of glutamate/GABA • No dopamine to modulate GABA © 2013 Pearson Education, Inc.

Huntington’s Disease • Fatal hereditary disorder • Accumulation of mutated protein huntingtin – “C-A-G” repeats multiply – Degeneration of basal nuclei → cerebral cortex • Initial symptoms wild, jerky "flapping" movements • Later marked mental deterioration © 2013 Pearson Education, Inc.

Huntington’s Chorea

Spinal Cord: Gross Anatomy and Protection • Vertebral column • Epidural space filled with

Spinal Cord: Gross Anatomy and Protection • Cord terminates at conus medullaris – Cauda equina – collection of spinal nerves – Filum terminale – fibrous extension • Extends to coccyx • Anchors spinal cord – Denticulate ligaments • Lateral extensions of pia mater that secure cord to dura mater © 2013 Pearson Education, Inc.

Spinal cord, dorsal view. Pia mater Denticulate ligament Arachnoid mater Spinal dura mater Denticulate

Anatomy of the spinal cord: Gray matter Gray commissure Dorsal horn Lateral horn Central

Gray Matter • Multipolar neurons – Dorsal horns • Somatic and visceral interneurons • Receive, integrate sensory input via dorsal roots – Ventral horns • Somatic (lower) motor neurons • Axons exit cord via ventral roots – Lateral horns (thoracic, upper lumbar) • ANS Sympathetic motor neurons • Axons exit via ventral roots © 2013 Pearson Education, Inc.

Dorsal Root Ganglion • Unipolar neuron cell bodies – Visceral sensory neurons • Central process enters via dorsal root – Somatic sensory neurons • Central process enters via dorsal root © 2013 Pearson Education, Inc.

Spinal Nerve formation: Mixed nerve Dorsal ramus Dorsal root of Central processes 100% sensory fibers Spinal nerve Motor & sensory Ventral ramus © 2013 Pearson Education, Inc. Ventral root Motor axons 100% Dorsal root ganglion Unipolar cell bodies

Spinal cord nuclei Visceral & somatic unipolar Dorsal root Ventral root Visceral sensory interneurons Somatic sensory interneurons Visceral motor Somatic motor

White Matter • Signal conduction between – Parts of the spinal cord and brain • Run in three directions – Ascending – up to higher centers • Sensory inputs – Descending – from brain to cord • Motor outputs – Transverse (commissural fibers) • Cross-over for bi-lateral control © 2013 Pearson Education, Inc.

Anatomy of the spinal cord: White Matter White columns Dorsal funiculus Ventral funiculus Lateral

3 Main Ascending Pathways: Sensory input • 3 neuron chain – 1 st order neuron: unipolar sensory – 2 nd order neuron: interneuron of dorsal horn – 3 rd order neuron: thalamic nuclei • Dorsal column-medial lemniscal pathways • Spinothalamic pathways • Spinocerebellar tracts © 2013 Pearson Education, Inc.

Dorsal Column–Medial Lemniscal Pathways • Transmit discriminative touch, vibrations – Dorsal white columns – spinal cord – Medial lemniscus – medulla to thalamus – Corona radiata to parietal lobe © 2013 Pearson Education, Inc.

Spinothalamic Pathways • Transmit pain, temperature, coarse touch, and pressure – Lateral & ventral white columns – Multiple synapses in brainstem – Thalamus to primary somatosensory cortex © 2013 Pearson Education, Inc.

Spinocerebellar Tracts • Convey information about muscle or tendon stretch – Used to coordinate

Descending Pathways and Tracts • Deliver efferent impulses from brain to spinal cord •

Direct (Pyramidal) Pathway: 2 neuron chain • Upper motor neurons – Pyramidal cells in primary motor cortex • Lower motor neurons – Ventral horn motor neurons – Innervate skeletal muscles • Regulates fast, skilled movements © 2013 Pearson Education, Inc.

Indirect (Multineuronal) System • Complex and multisynaptic • Includes brain stem motor nuclei, and all motor pathways except pyramidal pathways – Balance, posture – Crude limb movements – Head, neck, eye to follow movements © 2013 Pearson Education, Inc.

Spinal Cord Trauma: Flaccid paralysis • Damage to ventral root or ventral horn cells

Spinal Cord Trauma: Spastic paralysis • Damage to pyramidal motor neurons – Spinal neurons remain intact – Muscles are stimulated by reflex activity – No voluntary control of muscles © 2013 Pearson Education, Inc.

Amyotrophic Lateral Sclerosis (ALS • Aggressive destruction – Ventral horn motor neurons – Fibers of pyramidal tract – Symptoms—loss of ability to speak, swallow, and breathe • Genetic predisposition – Superoxide dismutase → no free radical protection – Glutamate toxicity • Drug riluzole – Interferes with glutamate signaling © 2013 Pearson Education, Inc.

Poliomyelitis • Polio virus – Destruction of ventral horn motor neurons • Paralysis, muscles atrophy – Death may occur • Respiratory muscles or cardiac arrest • Survivors often develop postpolio syndrome many years later from neuron loss © 2013 Pearson Education, Inc.

Post-polio Syndrome • Lethargy, burning pain, weakness, atrophy • Normal aging = loss of neurons • No reserve pool http: //www. nabeepchen. com/archives/2004/09/19