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Transcript
13 The Central Nervous System PowerPoint® Lecture Presentations prepared by Leslie Hendon University of Alabama, Birmingham © 2014 Pearson Education, Inc. Brain and Spinal Cord © 2014 Pearson Education, Inc. I. The Brain A. Brain controls: 1. heart rate, respiratory rate, blood pressure 2. autonomic nervous system 3. endocrine system 4. innervation of head through the cranial nerves © 2014 Pearson Education, Inc. B. Performs the most complex neural functions ► Intelligence ► Consciousness ► Memory ► Sensory-motor integration ► Emotion ► Behavior ► Socialization © 2014 Pearson Education, Inc. II. Embryonic Development of the Brain Prosencephalon—the forebrain ► telencephalon ► diencephalon Mesencephalon—the midbrain Rhombencephalon—the hindbrain ► metencephalon ► myelencephalon © 2014 Pearson Education, Inc. Structures of the adult brain (superior) Telencephalon the cerebral hemispheres Diencephalon thalamus, hypothalamus, epithalamus Mesencephalon midbrain Metencephalon pons and cerebellum Myelencephalon medulla oblongata (inferior) © 2014 Pearson Education, Inc. Neural tube Anterior (rostral) Primary brain vesicles Week 4 Secondary brain vesicles Week 5 Adult brain structures Adult neural canal regions Cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei) Lateral ventricles Telencephalon Prosencephalon (forebrain) Diencephalon (thalamus, hypothalamus, epithalamus), retina Third ventricle Diencephalon Mesencephalon (midbrain) Mesencephalon Brain stem: midbrain Cerebral aqueduct Metencephalon Brain stem: pons Rhombencephalon (hindbrain) Cerebellum Myelencephalon Posterior (caudal) © 2014 Pearson Education, Inc. Fourth ventricle Brain stem: medulla oblongata Spinal cord Central canal Anterior (rostral) Metencephalon Mesencephalon Diencephalon Posterior (caudal) Midbrain Cervical Flexures Telencephalon Myelencephalon Spinal cord Week 5: Two major flexures form. Cerebral hemisphere Outline of diencephalon Midbrain Cerebellum Pons Medulla oblongata Spinal cord Week 13: Cerebral hemispheres grow posterolaterally, enclosing the diencephalon and the rostral brain stem. Cerebral hemisphere Cerebellum Pons Medulla oblongata Spinal cord Week 26: Surface of the cerebrum begins to fold. Cerebrum Diencephalon Cerebellum Brain stem Midbrain Pons Medulla oblongata Birth: Brain shows adult pattern of structures and convolutions. © 2014 Pearson Education, Inc. III. Basic Parts and Organization of the Brain A. Classified into four regions 1. brain stem = midbrain, pons, and medulla 2. cerebellum 3. diencephalon 4. cerebral hemispheres (cerebrum) cerbral cortex © 2014 Pearson Education, Inc. III. Ventricles of the Brain A. The Ventricles - 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 the spinal cord © 2014 Pearson Education, Inc. B. Lateral ventricles - located in cerebral hemispheres ► horseshoe-shaped from bending of the cerebral hemispheres B. Third ventricle - lies in diencephalon ► connected with lateral ventricles by interventricular foramen D. Cerebral aqueduct - connects 3rd and 4th ventricles E. Fourth ventricle - lies in hindbrain ► connects to the central canal of the spinal cord © 2014 Pearson Education, Inc. Lateral ventricle Interventricular foramen Third ventricle Median aperture Cerebral aqueduct Fourth ventricle Lateral aperture Central canal Anterior view © 2014 Pearson Education, Inc. Left lateral view IV. The Brain Stem A. General Features 1. Passageway for all fiber tracts running between the cerebrum and spinal cord 2. Heavily involved with the innervation of the face and head 10 of the 12 pairs of cranial nerves attach to it 3. Produces automatic behaviors necessary for survival 4. Integrates auditory and visual reflexes © 2014 Pearson Education, Inc. Midbrain Pons Medulla oblongata © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. B. The Medulla Oblongata 1. Areas a. pyramids of the medulla - lie on its ventral surface b. decussation of the pyramids - crossing over of motor tracts *** c. inferior cerebellar peduncles - tracts to medulla and cerebellum d. olive (olive of the medulla) - contains inferior olivary nucleus 2. Functions a. cardiac center b. vasomotor center c. medullary respiratory center d. centers for hiccupping, sneezing, swallowing, and coughing © 2014 Pearson Education, Inc. C. The Pons 1. the “bridge” between the midbrain and medulla 2. motor tracts – coming from the cerebral cortex 3. connects the cortex with the cerebellum a. through the middle cerebellar peduncles © 2014 Pearson Education, Inc. D. The Midbrain 1. lies between the diencephalon and the pons 2. location of the cerebral aqueduct 3. cerebral peduncles a. with the corticospinal tracts 4. superior cerebellar peduncles a. connect midbrain to cerebellum 5. periaqueductal grey matter a. fight-or-flight actions b. mediates response to visceral (non-skin) pain © 2014 Pearson Education, Inc. D. The Midbrain 6. Superior colliculi – nuclei that respond to visual reflexes 7. Inferior colliculi – nuclei that respond to auditory reflexes 8. Substantia nigra – involved in motor function (Parkinson’s disease) © 2014 Pearson Education, Inc. Cerebellar peduncles Superior Middle Inferior Medulla oblongata Illustration of parasagittal section © 2014 Pearson Education, Inc. V. The Cerebellum A. General Features 1. located dorsal to the pons and medulla 2. smoothing and coordinating body movements 3. helps maintain equilibrium 4. contains “folds” called folia 5. consists of two cerebellar hemispheres a. anterior, posterior and flocculonodular lobes in each 6. three regions – cortex (grey), arbor vitae (white) and cerebellar nuclei © 2014 Pearson Education, Inc. Anterior lobe Cerebellar cortex Arbor vitae Pons Posterior lobe Medulla oblongata Flocculonodular lobe Illustration of parasagittal section © 2014 Pearson Education, Inc. Illustration of parasagittal section © 2014 Pearson Education, Inc. Anterior lobe Arbor vitae (Arbor = Tree) Cerebellar cortex Folia Pons Fourth ventricle Medulla oblongata Midsagittal section © 2014 Pearson Education, Inc. Posterior lobe B. Functions 1. To coordinate body movements a. information on equilibrium b. information on current body movements c. information coming from cerebral cortex (voluntary) 2. Superior, Middle and Inferior Cerebellar Peduncles a. fibers (axons) to/from brainstem that are ipsilateral © 2014 Pearson Education, Inc. VI. The Diencephalon A. General Features 1. forms the central core of the forebrain 2. surrounded by the cerebral hemispheres 3. composed of three paired structures a. thalamus b. hypothalamus c. epithalamus 4. primarily composed of gray matter © 2014 Pearson Education, Inc. Cerebral hemisphere Thalamus (encloses third ventricle) Posterior commissure Pineal gland Hypothalamus Pituitary gland Pons Medulla oblongata © 2014 Pearson Education, Inc. Cerebellum Epithalamus Thalamus (encloses third ventricle) Posterior commissure Pineal gland Hypothalamus Cerebellum Pons Medulla oblongata © 2014 Pearson Education, Inc. Epithalamus B. Thalamus 1. “football” shaped structure the size of the thumb phalanx 2. makes up 80% of the diencephalon 3. contains many important nuclei 4. relay station for all information up/down to the cortex!! 5. nuclei dampen or amplify relay messages © 2014 Pearson Education, Inc. Medial dorsal nucleus Lateral dorsal nucleus Internal medullary lamina Lateral posterior nucleus Pulvinar Anterior nuclei Medial geniculate body Reticular nucleus Lateral geniculate body Ventral anterior Ventral lateral Ventral posterolateral The main thalamic nuclei. (The reticular nuclei that “cap” the thalamus laterally are depicted as curving translucent structures.) © 2014 Pearson Education, Inc. B. Hypothalamus 1. main visceral control center of the body 2. pituitary gland projects inferiorly 3. functions include the following: ► Control of the ANS ► Control of emotional responses ► Regulation of body temperature ► Regulation of hunger and thirst sensations ► Control of behavior ► Regulation of sleep-wake cycles ► Control of the endocrine system ► Formation of memory © 2014 Pearson Education, Inc. Anterior commissure Paraventricular nucleus Fornix Preoptic nucleus Posterior hypothalamic nucleus Anterior hypothalamic nucleus Lateral hypothalamic area Supraoptic nucleus Suprachiasmatic nucleus Optic chiasma Infundibulum (stalk of the pituitary gland) The main hypothalamic nuclei © 2014 Pearson Education, Inc. Dorsomedial nucleus Ventromedial nucleus Arcuate nucleus Pituitary gland Mammillary body C. Pineal Gland 1. Secretes the hormone melatonin 2. Under influence of the hypothalamus 3. Aids in control of circadian rhythm © 2014 Pearson Education, Inc. VII. The Cerebral Hemispheres A. General Features 1. account for 83% of brain mass 2. composed of gray matter 3. folds in cortex - triples its size 4. fissures - grooves that separate major regions of the brain a. transverse fissure - separates cerebrum and cerebellum b. longitudinal fissure - separates cerebral hemispheres 5. sulci - valleys on the surface of the cerebral hemispheres 6. gyri - ridges (“hills”) © 2014 Pearson Education, Inc. 7. lobes – frontal, parietal, occipital, temporal 8. central sulcus separates frontal and parietal lobes a. precentral gyrus – primary motor cortex b. postcentral gyrus – primary somatosensory cortex 9. parieto-occipital sulcus - separates occipital from parietal lobe 10. lateral sulcus - separates temporal from parietal and frontal lobes 11. Brodmann areas - 47 structurally & functionally distinct areas!!!!! © 2014 Pearson Education, Inc. Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Parietooccipital sulcus Lateral sulcus Occipital lobe Fissure (a deep sulcus) Temporal lobe Gyrus Cortex (gray matter) Sulcus White matter Lobes and sulci of the cerebrum © 2014 Pearson Education, Inc. Fissure (a deep sulcus) Gyrus Cortex (gray matter) Sulcus White matter Lobes and sulci of the cerebrum © 2014 Pearson Education, Inc. B. Primary Functions 1. home of our conscious mind 2. be aware of ourselves and our sensations 3. initiate and control voluntary movements 4. communicate, remember, and understand © 2014 Pearson Education, Inc. VIII. Functional Regions of the Cortex !!!! A. Three general kinds of functional areas 1. Sensory areas – area for each of the major senses 2. Association areas – process sensory and motor information 3. Motor areas – plans and initiates motor functions © 2014 Pearson Education, Inc. WOW!! Motor areas Central sulcus Primary motor cortex Sensory areas and related association areas Premotor cortex Primary somatosensory cortex Frontal eye field Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Somatic sensation Taste Anterior association area (Prefrontal cortex) Wernicke’s area (within the posterior association area outlined by dashes) Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Primary visual cortex Solving complex, multitask problems Visual association area Vision Auditory association area Hearing Primary auditory cortex Lateral view, left cerebral hemisphere Primary motor cortex © 2014 Pearson Education, Inc. Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex WOW!! Primary motor cortex Premotor cortex Central sulcus Corpus callosum Primary somatosensory cortex Frontal eye field Parietal lobe Somatosensory association cortex Prefrontal cortex Parieto-occipital sulcus Limbic association area Cingulate gyrus Occipital lobe Processes emotions related to personal and social interactions Visual association area Orbitofrontal cortex Olfactory bulb Olfactory tract Calcarine sulcus Primary visual cortex Fornix Temporal lobe Parasagittal view, right hemisphere Primary motor cortex © 2014 Pearson Education, Inc. Motor association cortex Primary olfactory cortex Primary sensory cortex Uncus Parahippocampal gyrus Sensory association cortex Multimodal association cortex B. Dr. Wilder Penfield – experiments on patients who are awake! 1. Precentral gyrus – primary motor cortex 2. Postcentral gyrus – primary somatosensory cortex 3. Homonculus – making of body functions onto these gyri!! © 2014 Pearson Education, Inc. Posterior Motor Sensory Anterior Motor map in precentral gyrus Sensory map in postcentral gyrus Foot Knee Toes Genitals Lips Jaw Tongue Swallowing © 2014 Pearson Education, Inc. Primary motor cortex (precentral gyrus) Primary somatosensory cortex (postcentral gyrus) C. Sensory areas of the cortex 1. primary visual cortex – occipital lobe a. largest of all sensory areas b. receives visual information that originates on the retina c. first of a series of areas processing visual input 2. visual association area a. continues the processing of visual information b. analyzes color, form, and movement 3. primary auditory cortex a. conscious awareness of sound b. information comes from the cochlea of the inner ear © 2014 Pearson Education, Inc. 4. Wernicke’s area - recognizing and understanding speech 5. vestibular cortex – conscious awareness of sense of balance 6. gustatory cortex - conscious awareness of taste stimuli 7. olfactory cortex - awareness of smells (oldest sense!) a. connects the brain to the limbic system (emotions) b. explains why smells trigger emotions © 2014 Pearson Education, Inc. Sensory areas of cortex Central sulcus Sensory areas and related association areas Primary somatosensory cortex Somatosensory association cortex Gustatory cortex (in insula) Somatic sensation Taste Wernicke’s area Primary visual cortex Visual association area Vision Auditory association area Hearing Primary auditory cortex Lateral view, left cerebral hemisphere Primary motor cortex © 2014 Pearson Education, Inc. Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex D. Motor areas of the cortex 1. Premotor cortex - Located anterior to the precentral gyrus a. Controls more complex movements b. Controls voluntary actions dependent on sensory feedback c. Involved in planning movements 2. Frontal eye field - Lies anterior to the premotor cortex a. Controls voluntary movement of the eyes 3. Broca’s area - Manages speech production © 2014 Pearson Education, Inc. Motor areas of cortex Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca’s area Anterior association area (Prefrontal cortex) Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems Lateral view, left cerebral hemisphere Primary motor cortex © 2014 Pearson Education, Inc. Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex E. Multimodal association areas 1. make associations between kinds of sensory information 2. posterior ass. area - integrates sensory input into perception 3. anterior ass. area - integrates information with past experience 4. limbic ass. area - involved with memory and emotions a. integrates sensory and motor behaviors b. aids in the formation of memory c. processes emotions © 2014 Pearson Education, Inc. F. Lateralization of cortical function 1. The two hemispheres control opposite sides of the body 2. Contralateral opposite side 3. Hemispheres are specialized for different cognitive functions 4. Left cerebral hemisphere—control over: a. language abilities, math, and logic 5. Right cerebral hemisphere—involved with: a. visual-spatial skills b. reading facial expressions c. Intuition, emotion, artistic and musical skills © 2014 Pearson Education, Inc. IX. Cerebral White Matter A. Different areas of the cerebral cortex: 1. Communicate with each other 2. Communicate with the brain stem and spinal cord 3. Consists of tracts carrying information from point A to point B B. Commisures - communication between cerebral hemispheres 1. corpus callosum – connects left and right hemispheres a. “split brain” patients are special C. Association fibers - connect parts of the same hemisphere D. Projection fibers – cortex to/from lower brain regions © 2014 Pearson Education, Inc. Corpus callosum Parasagittal view, right hemisphere Primary motor cortex © 2014 Pearson Education, Inc. Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex White fiber tracts of the cerebral hemispheres Superior Association fibers (within hemisphere) Commissural fibers (between hemispheres) Corpus callosum Projection fibers (cerebral cortex to or from lower area) Frontal section © 2014 Pearson Education, Inc. Decussation (cross-over) of motor tracts) White fiber tracts of the cerebral hemispheres Association fibers Commissural fibers Corpus callosum Projection fibers © 2014 Pearson Education, Inc. X. Deep Gray Matter of the Cerebrum A. Basal nuclei (basal ganglia) - involved in motor control 1. group of nuclei deep within the cerebral white matter a. caudate nucleus—arches over thalamus b. putamen c. globus pallidus 2. cooperate with the cerebral cortex in controlling movement 3. start, stop, and regulate intensity of voluntary movements B. Basal forebrain nuclei - associated with memory C. Amygdaloid body - considered part of the of the limbic system © 2014 Pearson Education, Inc. Basal nuclei (ganglia) Caudate nucleus Thalamus Putamen Substantia nigra of midbrain © 2014 Pearson Education, Inc. X. Other Brain Systems A. Limbic system 1. the “emotional” and “memory” part of the brain 2. located in the temporal lobe a. cingulate gyrus - allows us to shift between thoughts b. hippocampus – formation of memories c. amygdala – retrieval of memories d. Alzheimer’s disease – location of “tangles” and “plaques” © 2014 Pearson Education, Inc. Limbic system Corpus callosum Fornix Cerebral structures of the limbic system Cingulate gyrus Amygdala Hippocampus Olfactory bulb © 2014 Pearson Education, Inc. B. Reticular formation 1. arousal of the brain as a whole 2. maintains consciousness and alertness 3. functions in sleep and arousal from sleep 4. malfunctions in people with narcolepsy © 2014 Pearson Education, Inc. Radiations to cerebral cortex Reticular formation nuclei in brain stem © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. XI. The Meninges A. Dura mater (“tough mother”) 1. Outer layer - cover and protect the brain and spinal cord 2. Enclose and protect the vessels that supply the CNS B. Arachnoid layer (“spider-like”) 1. Middle layer – location beneath which is cerebral spinal fluid (CSF) C. Pia mater (‘light mother”) 1. Clings tightly to the surface of the brain and spinal cord © 2014 Pearson Education, Inc. The Meninges Skin of scalp Periosteum Bone of skull Dura mater Arachnoid mater Pia mater © 2014 Pearson Education, Inc. The Meninges © 2014 Pearson Education, Inc. XII. Cerebral Spinal Fluid A. Formed in choroid plexuses of all four brain ventricles 1. composed of ependymal cells and capillaries 2. derived from the liquid portion of the blood 3. 500 ml produced per day 4. only 100–160 ml present at any one time © 2014 Pearson Education, Inc. B. The Blood-Brain Barrier 1. prevents most blood borne toxins from entering the brain 2. nutrients such as oxygen pass through 3. allows passage of alcohol, nicotine, and anesthetics 4. does not allow some drugs to enter brain and spinal cord © 2014 Pearson Education, Inc. Superior sagittal sinus Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Interventricular foramen Third ventricle 3 Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord CSF circulation © 2014 Pearson Education, Inc. 2 XIII. The Spinal Cord A. Functions 1. spinal nerves attach to it 2. provides two-way conduction pathway up and down 3. major center for reflexes B. Location 1. runs through the vertebral canal 2. from the foramen magnum to vertebra L1 or L2 © 2014 Pearson Education, Inc. C. Gross Anatomy 1. conus medullaris - the inferior end of the spinal cord 2. filum terminale - filament of connective tissue to the coccyx 3. cervical and lumbar enlargements – upper and lower limbs 4. cauda equina (“horse tail”) - collection of spinal nerve roots 5. central canal – hole in center for passage of CSF D. Spinal Cord “Segments” 1. indicate region of spinal cord from which spinal nerves emerge 2. designated by the spinal nerve that issues from it 3. NOTE: 7 cervical vertebrae but 8 cervical spinal nerves © 2014 Pearson Education, Inc. Cervical enlargement Spinal Cord Dura and arachnoid mater Cervical spinal nerves Thoracic spinal nerves Lumbar enlargement Conus medullaris Cauda equina Lumbar spinal nerves Filum terminale Sacral spinal nerves © 2014 Pearson Education, Inc. 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. Dorsal (posterior) Spinal cord segment C1 Spinal cord segment T1 Spinous process T1 Ventral (anterior) Spinal nerve C1 Spinal nerve C8 Spinal nerve T1 Spinal cord segment T5 Spinal nerve T5 Spinal Segments Spinal cord segment L1 Spinal nerve L1 Spinal nerve S1 © 2014 Pearson Education, Inc. Epidural space (contains fat) Pia mater Arachnoid mater Dura mater Spinal meninges Subdural space Subarachnoid space (contains CSF) Body of vertebra Cross section of spinal cord and vertebra, cervical region © 2014 Pearson Education, Inc. Dorsal root ganglion XIV. The Spinal Cord Areas A. Grey matter – nerve cell bodies of motor and internuerons 1. two deep grooves run the length of the cord a. posterior median sulcus b. anterior median fissure 2. grey commisure – cross bar “H” in the middle 3. anterior (ventral) horns 4. posterior (dorsal) horns 5. lateral (intermediate) horns (T, L, S only) See drawing on the board. © 2014 Pearson Education, Inc. B. Gray matter is divided according to somatic and visceral regions ► SS - somatic sensory ► VS - visceral sensory ► VM - visceral motor ► SM - somatic motor Also note: dorsal area = sensory ventral area = motor © 2014 Pearson Education, Inc. Dorsal root (sensory) Dorsal horn (interneurons) Dorsal root ganglion Somatic sensory neuron Visceral sensory neuron Visceral motor neuron Somatic motor neuron 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 © 2014 Pearson Education, Inc. C. White matter – myelinated axons of motor/sensory fibers 1. funiculus – anterior, posterior and lateral (only in T, L, S) 2. have tracts - carry information up and down the spinal cord a. ascending tracts = sensory info UP to the brain b. descending tracts = motor info DOWN from the brain © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Ascending tracts Dorsal white column Fasciculus gracilis Fasciculus cuneatus Spinocerebellar tracts Dorsal Ventral Ventral white commissure Descending tracts Reticulospinal tracts Medial Lateral Corticospinal tracts (pyramidal tracts) Lateral Ventral Spinothalamic tracts Lateral Ventral Rubrospinal tract Vestibulospinal tract Tectospinal tract © 2014 Pearson Education, Inc. D. Ascending Tracts TRACT 1. anterior (ventral) spinothalamic FUNCTION - touch and pressure to thalamus 2. lateral spinothalamic tract - pain & temperature to thalamus 3. fasciculus gracilis & cuneatus - touch, 2-pt. discrimination conscious proprioception, stereognosis, weight discrimination, vibration 4. posterior spinocerebellar - subconscious proprioception 5. anterior spinocerebellar - subconscious proprioception © 2014 Pearson Education, Inc. Ascending tracts Ascending tracts Dorsal white column Fasciculus gracilis Fasciculus cuneatus Spinocerebellar tracts Dorsal Ventral Spinothalamic tracts Lateral Ventral © 2014 Pearson Education, Inc. Descending tracts Primary somatosensory cortex Axons of third-order neurons Thalamus Cerebrum Ascending tracts Midbrain Cerebellum Pons Dorsal spinocerebellar tract (axons of second-order neurons) Lateral Spinothalamic tract (axons of second-order neurons) Medial lemniscus tract (axons of second-order neurons) Nucleus gracilis Nucleus cuneatus Medulla oblongata Fasciculus cuneatus (axon of first-order sensory neuron) Pain receptors Joint stretch receptor (proprioceptor) Axon of first-order neuron Muscle spindle (proprioceptor) Cervical spinal cord Axons of first-order neurons Fasciculus gracilis (axon of first-order sensory neuron) Temperature receptors Lumber spinal cord Touch receptor Spinocerebellar pathway © 2014 Pearson Education, Inc. Dorsal column-medial lemniscal pathway Spinothalamic pathway E. Descending Tracts TRACTS FUNCTIONS 1. lateral & anterior corticospinal motor output from cortex motor to cells of ant. horn 2. rubrospinal motor from midbrain to anterior horn for precise movement 3. tectospinal motor from midbrain to anterior horn; movements in response to audiovisual/cutaneous stimuli 4. vestibulospinal motor from medulla to anterior horn; coordination/balance 5. lateral reticulospinal motor from medulla to anterior horn; inhibit extensor reflexes 6. medial reticulospinal motor from pons to anterior horn; facilitate extensor reflexes © 2014 Pearson Education, Inc. Descending tracts Ascending tracts Descending tracts Reticulospinal tracts Medial Lateral Corticospinal tracts (pyramidal tracts) Lateral Ventral Rubrospinal tract Vestibulospinal tract Tectospinal tract © 2014 Pearson Education, Inc. Pyramidal cells (upper motor neurons) Primary motor cortex Internal capsule Cerebrum Descending tracts Red nucleus Midbrain Cerebral peduncle Cerebellum Pons Rubrospinal tract Ventral corticospinal tract Medulla oblongata Pyramids Decussation of pyramids Lateral corticospinal tract Cervical spinal cord Skeletal muscle Lumbar spinal cord Somatic motor neurons (lower motor neurons) Pyramidal (lateral and ventral corticospinal) pathways © 2014 Pearson Education, Inc. Rubrospinal tract T12 Spinal Tap (Lumbar Puncture) L5 Ligamentum flavum Lumbar puncture needle entering subarachnoid space L4 Supraspinous ligament L5 Filum terminale S1 Intervertebral disc © 2014 Pearson Education, Inc. Arachnoid mater Dura mater Cauda equina in subarachnoid space XV. Disorders of the Central Nervous System A. Spinal cord damage 1. paralysis - loss of motor function 2. parasthesia - loss of sensation 3. paraplegia - injury to the spinal cord is between T1 and L2 a. paralysis of the lower limbs 4. quadriplegia - injury to the spinal cord in the cervical region a. paralysis of all four limbs © 2014 Pearson Education, Inc. B. Brain dysfunction 1. cerebrovascular accident (stroke) a. Blockage or interruption of blood flow to a brain region 2. Alzheimer’s disease a. Progressive degenerative disease leading to dementias C. Congenital malformations 1. hydrocephalus – “water on the brain” – CSF buildup 2. neural tube defects a. anencephaly - cerebrum and cerebellum are absent b. spina bifida - absence of vertebral lamina 3. cerebral palsy - voluntary muscles are poorly controlled a. results from damage to the motor cortex © 2014 Pearson Education, Inc.
