Week 9 Lecture Notes-Principles of Human Anatomy
Week 9 Lecture Notes-Principles of Human Anatomy Bio 103, Principles of human Anatomy
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Bio 103, Principles of human Anatomy
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This 8 page Class Notes was uploaded by Victoria Dorsey on Wednesday November 4, 2015. The Class Notes belongs to Bio 103, Principles of human Anatomy at University of Indianapolis taught by Justin Maiers in Fall 2015. Since its upload, it has received 21 views. For similar materials see Principles of human anatomy in Biology at University of Indianapolis.
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Date Created: 11/04/15
Principles of HumanAnatomy BIOL103-05 28 October2015 Introduction to the NervousSystem Things you should be able to do by the end of thissection: Understand the difference between CNS andPNS Understand how a signal moves across aneuron Learn the terms of brainanatomy Learn the terms of spineanatomy *Side note* This section is a lot more theoretical; you should think of concepts instead of littlepieces Functions of the NervousSystem Receive input—collects information about the internal and external environment;stimulus Process information—interprets the incoming stimuli and determines aresponse Initiate response—sends signals to muscles and glands in response to the internal and external environment; cellular response Functional Divisions of the NervousSystem Neurons—nerve cells; make up pretty much everything in the brain, spinal cord,PNS o Sensory neurons (afferent)—carry signals towards brain Saying that something ishot o Motor neurons (efferent)—carry signals away from brain Response and move hand away from hot surface o Interneurons—lie between motor and sensory neurons Communication between the othertwo Somatic NervousSystem o To and from skin and muscles of thebody To appendages o Subdivision: Somatic Sensory Somatic Motor Autonomic (visceral) NervousSystem o To and from visceralorgans To organs; not in control/involuntarymovement o Subdivisions: VisceralSensory Visceral Motor Parasympathetic (Rest anddigest) Sympathetic (fight or flight); shuts down parasympatheticcomponent Be sure to know that CNS is in the middle ofeverything PNS is the only way to get back to the CNS and thebrain Components of the NervousSystem Neurons—nerve cells o “Excitable” cells Take electrical charges to change how they react Also does chemical charges o Conduct electricalsignals o Longevity Dendra- is the root meaning“tree” Axon—long, slender projection of a nerve cell (neuron) thatconducts electrical impulses away from the neuron’s cellbody Innervate or Innervation—supply an organ or other body part with nerves for movement orsensation o Something that has a nerve going toit Soma (cell body)—mini brain between the dendrites andaxon There are three different shapes, you don’t have to memorize the different shapes, just know that there are there different ones and they do look different o Multipolar—majority of neurons; motor and interneurons o Bipolar—sensoryorgans o Unipolar—sensory neurons Don’t really worry about the details of the next couple of points because it is mostly BIOL 104; this is a FYI thing so that things make a little moresense o Synapse—chemical orelectrical There is a presynaptic and a postsynapticneuron o Once the presynaptic neuron is fully charged, it releases a chemical signal that communicates between the pre- and postsynaptic neurons o Myelin Sheath (mostly think about the fact that is speeds up the wholeprocess) Composed of myelin—whitish, fattysubstance Segmented (not complete!) sheath around most long or large-diameter axons (notdendrites) Function ofmyelin Protects and electrically insulates axon Increases speed of nerve impulse transmission (on myelinatedfibers) Nonmyelinated fibers conduct impulses moreslowly In CNS and PNS, thinnest, shortest nerve fibersunmyelinated o Myelination in the PNS Formed by Schwann cells Wrapped around axon in jelly rollfashion One cell forms one segment of myelinsheath Myelin sheath—concentric layers of Schwann cell plasma membrane aroundaxon Myelin sheath gaps (nodes ofRanvier) Gaps between adjacent Schwanncells Allows electrical impulses to “jump” from segment to segment, so signal moves more quickly Myelin Sheaths in theCNS Formed by multiple, flat processes of oligodendrocytes, not wholecells Can wrap up to 60 axons atonce Myelin sheath gap ispresent White Matter—regions of brain and spinal cord with dense collections of myelinated fibers; usually fibertracts Gray Matter—mostly neuron cell bodies (nuclei) and nonmyelinatedfibers Components of the NervousSystem White Matter of the CNS o Clusters ofaxons o Sends the signals o Myelinated cell axons o White because the myelin is mostlyfat Gray Matter of the CNS o Clusters of cellbodies What is the difference between a nerve and a tract? Nitpicky detail o Both: bundle of axons o Nerve: only in PNS/comes off of thebrain o Tract: only in CNS/inside thebrain White matter Only in the brain andspine What is the difference between a nucleus and aganglion? More nitpickiness o Both: bundle of cell bodies o Ganglion: only in PNS o Nucleus: only in CNS Gray matter PNS and CNS WorkTogether The nerve does not always have to go back to the brain to be processed and react to astimulus o Can go through the spinalcord The Central Nervous System Parts of theBrain Cerebrum—largest part of thebrain Diencephalon = midbrain Cerebellum means “minibrain” Brain Stem houses the automatic responses such as breathing Inner region of gray matter surrounded by white matter Gray matter also found on the brainsurface o CerebralCortex o CerebellarCortex Ventricles of theBrain Expansions of the brain’s central cavity (central canal) Space filled with cerebrospinal fluid(CSF) Continuous with eachother Continuous with the central canal of the spinal cord Feed the brain by movingnutrients 4 ventricles Anatomical Divisions of theBrain o Forebrain Cerebral hemispheres (left and right brain) 83% of brainmass Five lobes—frontal, parietal, occipital, temporal(2) Corresponds with the bones o Corpus callosum—connects the right and lefthemispheres o Diencephalon (thalamus, hypothalamus) Pineal gland—hormone secretion; looks like an itty bitty seahorse Thalamus—nuclei bundles; gateway to cerebral cortex Hypothalamus—nuclei bundles; regulates visceral organs Pituitary gland—endocrine; secretes different bodies Mammillary bodies Midbrain o Proximal brainstem o Corpora quadrigemina (“the four twins”) Large nuclei Reflex centers, visual and auditory input Four small elevations on the dorsal region ofmidbrain 2 superior and 2 inferiorcolliculi o Cerebralpeduncles Ventral surface ofmidbrain Tracts that connect midbrain tocerebrum Connection between diencephalon to the rest of the midbrain Peduncles are the green foot like structures that goup Hindbrain o Remaining brain stem (pons,medulla) o Cerebellum o Medulla oblongata—most inferior part of the brain stem Continuous with the spinalcord Little oblongshape Pyramids—ventral side ofmedulla Tracts that carry motoroutput Five cranial nerves come out ofhere o Pons—bridge between midbrain andmedulla Regulates breathing Three cranial nerves come outhere Bulbous part in themiddle o Cerebellum 11% of brainmass Coordinates body movement andcognition Arbor vitae—internal whitematter Arbor vitae means “tree of life” Cortex—outer graymatter The Cerebral Hemispheres Fissures—deep grooves; separate major regions of thebrain o Transverse fissure—separates cerebrum andcerebellum o Longitudinal fissure—separates cerebralhemisphere Sulci (sulcus)—grooves on the surface of the cerebralhemispheres o Central Sulcus (redline) Separates frontal and parietallobes Bordered by two gyri Precentral gyrus o Green line Postcentral gyrus o Blue line Gyri (gyrus)—twisted ridges betweensulci o Prominent gyri and sulci are similar in allpeople Functional parts of thebrain o Cerebral cortex (grey matter = nucleus cellbodies) o Cerebral white matter (axons =tracts) o Deep grey matter (nucleus cellbodies) Cerebrospinal Fluid Clear fluid Fills the Subarachnoid space and central hollowcavities Cushions thebrain Reduces the weight of the brain (not primaryfunction) Providesnourishment Removes waste Buildup leads to Hydrocephaly and results in damage to the brain in order to make room for theCSF Protection of the CNS The CNS is protected from injuryby: o Cerebrospinalfluid o The skull andvertebrae o Meniges—spaces that house the spinalfluid 3 layers of connective tissue that: Cover and protect the CNS Enclose and protect the vessels that supply theCNS Contains the cerebrospinalfluid Like a fabric that holds everything inplace Same three layers no matter whether it is on the brain or spine 3 layers: dura matter, arachnoid matter, pia matter Dura- means“durable” The Dura Mater Strongest of theMeninges Composed of two layers o Periosteal layer (layer on thebone) Directly on the bone o Meningeal layer Two layers are fused except to enclose the duralsinuses Extensions that subdivide the cranialcavity Located in deepgrooves o Longitudinal fissure—separates brain into left and rightsides o Transverse fissure—separates cerebrum and thecerebellum Extensions that subdivide the cranialcavity o Falx Ceribi—median plane; longitudinalfissure Falx—sickle shape that wasa sword invented by the romans to get around shields Through thecerebrum o Falx Cerebelli—vertical extension of FalxCerebri Through thecerebellum o Tentorium Cerebelli—lies between the cerebrum and the cerebellum; transversefissure Dural Sinuses Blood is routed in between 2 layers of dura mater; between periosteal and meningeal layers Blood is drained from head via duralsinuses The head uses more blood than basically the rest of thebody Sinuses—drain blood from thebrain o Superior Sagittal (in longitudinalfissure) o Transverse-- drain into L andR o Drains into Sigmoid o Becomes the internal jugular vein o Takes out deoxygenated blood to berecycled The Arachnoid Mater Located beneath the duramater Subdural space—potential space between dura and arachnoid mater Subarachnoid space—filled with CSF; contains the blood vessels that supply thebrain Arachnoid villi—allow CFS to bass into the dural blood sinuses The Pia Mater Delicate connective tissue Clings tightly to the surface of thebrain o Follows all convolutions of the cortex The Spinal Cord Runs through the vertebralcanal o Vertebral foramen Extends from the foramen magnum to the level of1L o2L Protected by bone, meninges, andCSF o The spinal dural sheath is only onelayer Conus medullaris—inferior end of the spinalcord Filum terminalelong filament of connectivetissue o Attaches to the coccyx inferiorly Cervical and lumbar enlargements—where nerves for upper and lower limbs arise Cauda equina—collection of nerveroots Two deep grooves run the length of thecord o Posterior (dorsal) mediansulcus o Anterior (ventral) medianfissure Wider CentralCanal o Narrow central opening in spinal cord o Filled with CSF Gray Matter of the Spinal Cord and SpinalRoots o Anterior (ventral) horns—contain cell bodies of motor neurons o Posterior (dorsal) horns—consist of interneuron cellbodies o Dorsal root Ganglion—consists of cell bodies for sensory neurons 31 pairs of spinalnerves o Connected by dorsal and ventralroots o PNSstructures o Intervertebral foramen o Sacral foramen