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Ch13 notes - Chapter13 TheCentralNervous System...

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Unformatted text preview: Chapter 13 The Central Nervous System Important Directional Terms for the CNS Rostral vs. Caudal Embryonic Development of the Brain This information will not be on your exam, but it is helpful in explaining the gross structures of the brain regions as well as the fluid‐filled ventricles inside the brain. Major Divisions of the Brain Cerebrum ‐ largest part of the brain…left and right hemispheres Diencephalon ‐ gives rise to thalamus, hypothalamus and epithalamus Cerebellum ‐ second largest part of the brain Brain stem ‐ rostral continuation of the spinal cord; consists of the medulla oblongata, pons and midbrain The Brain Ventricles • Cerebrospinal fluid‐filled spaces in the brain • Continuous with each other and the central canal • Lined with ciliated ependymal cells • Provide CSF to nearby brain regions Anatomy of The Ventricles The Cerebrum • Makes up over 80% of the brain’s mass • Right and left hemispheres • External “wrinkles” increase surface area Gross Anatomy of the Cerebrum Fissure Sulcus Cerebral cortex Cerebral white matter Deep grey matter Gyrus Cerebral Cortex ‐ Lobes of the Brain Cerebral Cortex – Insular Lobe Longitudinal Fissure Fissures, Sulci, and Gyri A Few Functional Regions of the Cerebral Cortex Precentral gyrus Primary Motor Cortex Primary Auditory Cortex Postcentral gyrus Primary Somatosensory Cortex Primary Visual Cortex Associational areas are adjacent to their respective functional region. Somatotopy The Basics of Cerebral Integration Primary Sensory Cortex (sensory info is received) Sensory Association Area Multimodal Associational Areas (meaning) (understanding and motor plan) Primary Motor Cortex (motor plan enacted) Cerebral White Matter Commissural Fibers • Right Hem ↔ Left Hem • Largest = Corpus Callosum Associational Fibers • Intrahemispheric • Long or short Projection Fibers • Cortex ↔ lower CNS areas • Vertical fibers Cerebral Deep Grey Matter • Basal Nuclei (Ganglia) – Initiates and terminates body movements – Suppresses unwanted movements • Basal Forebrain Nuclei • Claustrum • Amygdala The Diencephalon The Thalamus is a Relay Station The Hypothalamus Controls Homeostasis Forms the lateral walls of the 3rd ventricle Pituitary gland -Inferior/ventral view of brain -optic chiasm: some of the axons from each nerve will cross over to the other side...creating a chiasm - Optic Chiasm Infundibulum Mammillary bodies of Hypothalamus corpus collosum Interthalamic adhesion has connection to vision falling asleep in darkness Pineal gland (epithalamus) produces melatonin -as you age, pineal gland shrivels up (problems falling asleep and staying asleep Posterior commissure (epithalamus) Hypothalamus commissure- goes from right to left Optic chiasm Pituitary gland Mammillary body The Midbrain • Cerebral peduncles – composed mostly of motor axons from the cortex to the cerebellum and spinal cord – Look like columns/pillars supporting the cerebrum – Located ventrally • Cerebral aqueduct – passes through the center of the midbrain – 3rd ventricle 4th ventricle • Corpora quadrigemina – nuclei that form 4 bumps on the dorsal midbrain – Superior colliculi – visual reflexes – Inferior colliculi – auditory reflexes -peduncles=little feet (pedicle) -right at the base of the cerebrum appearing to hold it up -tracts (collection of axons traveling together in CNS) Cerebral peduncles optic tracts wrap around peduncles cerebrum removed pons review structures with parts of the brain removed pons fibers typically point directly back to the cerebellum corpora quadrigemina Lateral Ventral Corpora quadrigemina Corpora quadrigemina superior and inferior colliculi associated with reflexes -superior=visual reflexes (protective mechanism) -inferior=auditory reflexes (turning and orienting to where a sound is coming from cerebral aqueduct -channel that communicates between third and fourth ventricle -CSF produced in all major ventricles Cerebral aqueduct The Pons is a Bridge Pons=bridge -communicates between brainstem and cerebellum -motor coordination -transverse fibers send motor information to cerebellum and spine -only a ventral structure, transversely striped • Viewed ventrally as superficial, transverse fibers • Functions as a bridge between the brain stem and the cerebellum Superior pontine border Pons Inferior pontine border The Medulla Oblongata is also key to Homeostasis • Continuous with superior aspect of the spinal cord • From the foramen magnum to inferior pontine border • Pyramids – motor tracts that form bulges on the anterior surface of the medulla • Olives – nuclei that form bulges just lateral to the pyramids…sensory relay station medulla oblongata is central to survival -continuous with spinal cord -as soon as the medulla exits foramen magnum it is now the spinal cord - if you see pons you are looking from the front (ventral view) Pyramids Olives Motor decussation -pyramids contain axons from pyramital neurons coming from motor cortex -pyramids are motor tracts -cross hatchings is called motor decussation -where axons of the primary motor cortex cross to the opposite side of the CNS -right motor cortex controls left side; left motor cortex controls right side -olive because olivary nucleus sits there -identify olives and pyramids csf is going to pons, medulla, and ventricle Pons Medulla oblongata 4th Ventricle The Cerebellum • Similar arrangement as the cerebrum: – – – – Two hemispheres Cortex ‐ grey matter with many folds called folia White matter – tracts called arbor vitae Deep grey matter -2nd largest structure of the brain -external grey matter, internal white matter, deep grey matter -white matter called arbor vitae (means tree of life) -grey matter called folia (like foliage on tree) surrounds branches of white matter -vermis is the midline structure (body of butterfly) -hemisphere (butterfly wings) lateral view Lobes and Functions of the Cerebellum -anterior and posterior lobes associated with smoothing out motor functions -flocculonodular lobe plays a large role in equilibrium - Motor coordination of trunk and limbs Equilibrium via head/eye motor coordination cerebral peduncles -Middle cerebellar peduncle (MCP) -distinguish between middle cerebellar peduncle and the cerebral peduncle -cerebellar peduncle are motor axons going from the pons into the cerebellum -DO NOT NEED TO KNOW SUPERIOR AND INFERIOR CEREBELLAR PEDUNCLES - Protective Coverings of the CNS: The Meninges • The Skull – protects the brain • Vertebrae – protects the spinal cord • Meninges – connective tissue sheaths that surround the brain and spinal cord – Dura mater – most superficial meninx – Arachnoid mater – middle meninx – Pia mater – deepest meninx pia mater is closest to the tissue -arachnoid mater has lots of fibers stringing in between pia mater and dura mater -dura mater (tough mother) fuses with the periosteum of the bone. leathery dense layer -coroid plexus: makes CSF UNDERSTAND DURAL VENUS SINUS The Meninges: Spaces and Septa below dura mater (subdural space) below arachnoid mater (subarachnoid space) CSF sits in subarachnoid space • CSF is found inside and outside the brain • CSF gets deposited into dural venous sinuses around the brain dural septum=function to keep things separate within the cranial space (similar to separater in chocolate box) arachnoid granulation (villus)- arachnoid mater pokes through the dura mater to allow CSF into the dural venus sinus -all of the dural sinuses come together at the base of skull to form internal jugular veins dura mater has two layers -periosteal layer=periosteum of cranial bones (dense irregular tissue) -meningeal layer=extremely dense connective tissue -two layers stay completely fused together WHERE THERE IS BONE -separation between periosteal and meningeal layer=dural venus sinuses (serve as veins for brain) Falx Cerebri – separates the cerebral hemispheres Tentorum Cerebelli – separates the cerebellum from the cerebrum just double layer of meningel layer (dura mater) sitting in a deep fissure of the brain. -Helps keep everything in place inside the cranium (chocolate box separator) The Spinal Cord • Sensory and motor innervation of the whole body (inferior to the head) • Two‐way conduction pathway between the brain and the body (inferior to the head) • Major integration center for reflexes (inferior to the head) Gross Anatomy of the Spinal Cord -conus medullaris is the most caudal part of teh spinal cord -below the spinal cord, is the cauda equina (collection of spinal nerves) -cauda equina is part of the PNS -no nerves in brain or spinal cord -filum terminale: the pia mater that has condensed down to attach the spinal cord to the coccyx bone -keeps spinal cord taught to keep it in place -cervical enlargement and lumbar enlargement Because the spinal cord does not extend to the end of the spinal column, spinal cord segments are typically located superior to their respective vertebrae. -shows where the spinal nerves exit (points of issue) from the spinal column -spinal cord segments corrrespond to the spinal nerves -cervical has 8 segments of the spinal cord so 8 nerves -spinal nerve on top of c1, last cervical spinal nerve is below c7, forces all other nerves below to have points of issue below the vertebra - FOLLOW SPINAL NERVES IDENTIFY POINTS OF ISSUE Gross Anatomy of the Spinal Cord and Nerve Roots -central canal is filled with CSF (continuous with 4th ventricle) -lateral horn is only present in T1-L2 vertebra -columns sometimes labeled funiculi (hold white matter (myelinated axons)) -called columns because axons are arranged up and down -roots are coming off the -ventral rootlets are motor axons, as condensed down called ROOT -dorsal root looks thicker (dorsal root ganglion) purely sensory information (axons traveling into the spinal cord) -posteriorly is sensory, ventrally is motor Spinal Cord Segments ASKED TO DIFFERENTIATE BETWEEN SPINAL CORD SEGMENTS -cervical is largest around. lots of white matter, giant ventral horns -thoracic tiny ventral horns, -lumbar and sacral, spinal cord becomes more round, very large ventral horns, relativley little white matter lateral horn Dorsal and Ventral Roots picture of reflex (polysynaptic) -lumbosacral -dorsal root and ventral root -unipolar neurons (somatosensory) -central axon is one going into CNS -peripheral axon is going away from CNS -synapse with multipolar axon -motor neuron sends axon out ventral root -interneuron = associational neuron -associated sensory and motor thing to get response - DO NOT NEED TO KNOW NAMES OF WHITE MATTER TRACTS -both ascending and descending tracts -ascending=axons carrying information up the spinal cord -descending=from the brain down the spinal cord -names tell where the tract begins and where it ends -cortico=cortex • Groups of the white matter columns are named according to where a tract begins (soma) and where it ends (axon terminals) • Spinal cord white matter is both sensory and motor -spinothalamic pathway (sensory) -sensory pain information being carried -interneurons live in the dorsal horn -at the dorsal horn, the sensory neuron synapses -went from right side of PNS to left side of CNS all the way up to thalamus -sensory neuron information crosses over right when it comes to spinal cord -motor information crosses over in the medulla - Projection fibers ONLY LOOK AT PINK PATHWAY -lateral corticospinal pathway -frontal lobe of brain sends axon through projection fibers traveling down same side of teh brain to medulla, crosses over at decussation and goes all the way down to the lumbar region, synapses on motor or interneuron and axon produces ventral righ to get to gastrocnemius The images used in this presentation are from the following sources: • • • • • • • en.wikipedia.org journalofcosmology.com what-when-how.com • • • • kentsimmons.uwinnipeg.ca • Your textbook: Marieb, Mallatt, and Wilhelm’s Human Anatomy, 7th Edition ...
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