Presentation on theme: "Identify structures of the nervous system."— Presentation transcript:
1 Identify structures of the nervous system. Objectives:Identify structures of the nervous system.Explain differences in the function of the peripheral nervous system and the central nervous system.
2 D. Nervous Tissue Nervous tissue is: found in the brain, spinal cord, and nerves.made up of:Neurons: nerve cells (bundles of axons)Neuroglial cells: helper cells“glia” = glueSupport and bind components of nervous tissue to each other and to blood vesselsFunction similarly to connective tissue in other organ systems
4 Nervous System Organs of this system are divided into 2 groups: Central Nervous System (CNS)BrainSpinal cordPeripheral Nervous System (PNS)Composed of the nerves (peripheral nerves) that connect the CNS to other body partsFunctions of the nervous system:SensoryIntegrativeMotor
5 1. Sensory FunctionSensory receptors at the ends of peripheral neurons:Gather info by detecting changes inside and outside the body.Inside: temperature and oxygen concentrationOutside: light and sound intensitiesConvert info into nerve impulses (electrochemical changes) which are transmitted along peripheral nerves to the CNS
6 2. Integrative FunctionNerve impulses are integrated (brought together) in the CNS.Allows us to make conscious or subconscious decisions.
7 3. Motor FunctionPeripheral nerves carry impulses from the CNS to effectors (responsive structures).Effectors are NOT part of the nervous system, but include muscles and glands.
8 Motor Function Motor functions can be divided into 2 groups: Somatic nervous systemConsciously controlled (voluntary)Controls skeletal muscleAutonomic nervous system:InvoluntaryIncludes heart, smooth muscle, and various glands
9 Nervous System Function Recap Detects changes inside and outside the body,Makes decisions based on the information received, andStimulates muscles or glands to respond.What is the purpose of this process?????
10 Neuroglial Cells Functions: Vary from CNS to PNS Fill spacesProvide structural frameworksProduce myelinCarry on phagocytosisVary from CNS to PNSTable: Type of Cell, Location, Function, Other specific info
11 CNS Neuroglial CellsGreatly outnumber neurons in the CNS (think worker ants vs. Queen ant)Microglial cellsScattered throughout CNSSupport neurons and phagocytize bacterial cells and cellular debrisOligodendrocytesOccur in rows along nerve fibersProvide layers of myelin around axons within brain and spinal cord
12 CNS Neuroglial Cells, continued…. AstrocytesFound between neurons and blood vesselsProvide structural support, help regulate nutrients and ions in tissuesForm scar tissue to fill spaces after CNS injuriesEpendymal cellsForm epithelial-like membrane in parts of the brain (choroid plexuses)Form inner linings that enclose ventricles in the brain and central canal in the spinal cord
14 PNS Neuroglial cellsSchwann cells: form myelin sheath around axons
15 Neurons Vary in size and structure, but have common features: Cell BodyDendritesAxonMature neurons do not divide, but neural stem cells can divide and form neurons or neuroglial cells.
16 1. Cell BodyContains normal cellular structures (golgi apparatus, mitochondria, cytoplasm, cell membrane, etc.)Neurofibrils – fine threads that extend into the axonNissl bodies (chromatophilic substances)Membranous sacs in the cytoplasmSimilar to rough ERRibosomes on Nissl bodies synthesize ______proteins
17 2. Dendrites Usually short and highly branched (dendr = ?) The main receptive surfaces for receiving communication from axons of other neurons
18 3. AxonsArise from a slight elevation of the cell body, called the axonal hillock.Conduct nerve impulses away from the cell bodyContains many mitochondria, microtubules, and neurofibrilsOriginates as a single structure, but may have branches, especially at the end to interact with receptive surfaces of other cells
19 PNS Axons Enclosed in myelin sheaths composed of many Schwann cells Myelin is a lipoprotein.Neurilemma sheath surrounds the myelin sheathNodes of Ranvier – narrow gaps in the myelin sheath between the Schwann cells
20 Classification of Neurons Classification based on Structural differences:Bipolar neuronsUnipolar neuronsMultipolar neuronsClassification based on Functional differences:Sensory neurons (afferent neurons)Interneurons (association or internuncial neurons)Motor neurons (efferent neurons)
21 Structural Differences Sketch the neurons below. Notes on the next 3 slides:
22 Structural Differences, cont….. Bipolar:2 processesAxonDendriteFound in specialized parts of the eyes, nose, and ears
23 Structural Differences, cont….. Unipolar:1 process divides into 2 branches, which function as a single axon1 branch (peripheral process) associated with dendritesOther branch (central process) enters brain or spinal cord
24 Structural Differences, cont….. Multipolar:Many processes arising from cell body:1 axonMany dendritesMost neurons whose cell bodies lie in the brain or spinal cord are multipolar.Direction of impulse is ALWAYS from dendrites to axon.
25 Functional Differences Sensory (afferent) neuronsFrom peripheral body parts to the brain or spinal cordHave specialized receptor ends at the tips of their dendrites ORDendrites closely associated with receptor cells in the skin or sensory organs.Most are unipolar, but some are bipolar.
26 Functional Differences, cont….. Interneurons (association or internuncial neurons)Lie entirely in the brain or spinal cordMultipolar and link other neuronsTransmit impulses from one part of the brain or spinal cord to anotherMotor (efferent) neuronsMultipolarCarry nerve impulses from brain or spinal cord to effectorsStimulate muscles or glands
27 Copy Diagram on Whiteboard Identify the direction of nerve impulse.How can you tell the direction?Label all dendrites, cell bodies, and axons.Label each nerve as either sensory neuron, interneuron, or motor neuron.Color code the CNS and PNS portions of the pathway.
28 Reflex ArcsNerve impulse pathways that are responsible for involuntary actionsLook like the pathway you drew and labeled:Receptor toSensory neuron to(optional step) Interneurons in the CNS (a reflex center) toMotor neurons toEffector
29 ReflexesAutomatic subconscious responses to changes within or outside the body:Maintain homoestasis: blood pressure, heart rate, respirations, digestion, temperatureAutomatic actions: swallowing, coughing, sneezing, vomiting
30 2 Examples of Types of Reflexes (?) Knee-jerk reflex (patellar tendon reflex)Employs only 2 neurons: sensory neuron communicating directly with a motor neuronWithdrawal reflex:A response to painful stimuliSensory neuron takes impulse to interneurons in the spinal cord reflex center, where it is transmitted to motor neurons.Other interneurons carry impulses to the brain for processing of the experience and pain.
36 Dura Mater Outermost layer Contains many blood vessels and nerves Attaches to the inside of the cranial cavity and forms the internal periosteum (???) of the surrounding skull bonesForms partitions between lobes of the brainContinues into vertebral canalTerminates as a blind sac below the end of the spinal cord
37 Arachnoid MaterThin, weblike membrane located between dura and pia matersLacks blood vesselsSpreads over brain and spinal cord, but does not dip into grooves and depressions on their surfaces
38 Pia MaterCerebrospinal fluid (CSF) – clear, watery fluid that fills space between arachnoid and pia matersPia mater – very thin and contains many nerves and blood vessels that nourish cells of the brain and spinal cordHugs surfaces and follows all irregular contours of brain and spinal cordSubdural hematoma (?)
40 ReviewList and describe the 3 layers of the meninges.
41 Spinal CordSlender nerve column that passes downward from the brain into the vertebral canalStarts at the foramen magnum and ends between first and second lumbar vertebrae
42 Structure of Spinal Cord 31 segments that each give rise to a pair of spinal nerves
43 Functions of the Spinal Cord What do you think would be the functions of the spinal cord?Conducting nerve impulsesServing as a center for spinal reflexesNerve tracts (major nerve pathways) of the spinal cord are made up of axons that provide 2-way communication between brain and body parts:Ascending tracts - sensory information to brainDescending tracts – motor impulses from brain
44 Brain About 100 billion multipolar neurons 3 major portions: Cerebrum Largest partContains nerve centers associated with sensory and motor functionsProvides higher mental functions, including memory and reasoningCerebellum - includes centers that coordinate voluntary movementsBrain stem –Connects parts of the nervous system (???)Regulates some visceral (???) activities
45 Cerebrum Cerebral hemispheres: 2 large, mirror-image halves Corpus callosum: deep bridge of nerve fibers that connect the cerebral hemispheresSurface of the cerebrum has:Ridges: convolutionsGrooves:Shallow grooves: sulci (sulcus, singular) – separates lobesDeep Grooves: fissuresLongitudinal fissure – separates cerebral hemispheresTransverse fissure - separates cerebrum and cerebellum
46 Locations and Boundaries of the Lobes of the Cerebral Hemisphere Use textbook, pp to complete the table below.LobeLocationBoundaries
47 Functional Regions of the Cerebrum Complete graphic organizer.Color-code and label diagram of association areas of the brain to correspond to your graphic organizer.
48 Hemisphere Dominance Right-Left Brain Test The dominant hemisphere controls the ability to use and understand language.Which hemisphere do you think is dominant in most of the population?Broca’s area (???) in the dominant hemisphere controls the muscles used in speaking.
49 Non-dominant Hemisphere Hemisphere FunctionsDominant HemisphereNon-dominant HemisphereLanguage-related activities: reading, writing, speakingNonverbal functions:1. Motor tasks requiring orientation of body in spaceComplex intellectual functions requiring verbal, analytical, and computational skills2. Recognition and understanding of musical patterns3. Nonverbal visual experiences
50 Corpus Callosum (???) and Hemisphere Dominance What is it? Nerve fibers connecting the 2 cerebral hemispheresFunctions:Allows the dominant hemisphere to control the motor cortex of the non-dominant hemisphere.Transfers info received by the non-dominant hemisphere to the dominant hemisphere for use in decision-making.
51 Ventricles and CSF Ventricles: interconnected cavities within the cerebral hemispheres and brain stemcontain CSFChoroid plexuses: tiny, reddish, cauliflower-like masses of specialized capillaries from the pia mater that secrete CSF into the ventriclesInfections, tumors, blood clots can block the flow of CSF and increase intracranial pressure.
53 DiencephalonLocated between the cerebral hemispheres and above the midbrainContains:ThalamusHypothalamusOptic tracts and optic chiasma – formed by crossing of optic nervesInfundibulum – attaches to pituitary glandPosterior pituitary gland – hangs from floor of hypothalamusPineal gland – attached to upper diencephalon
54 DiencephalonThalamus – receives all sensory input, EXCEPT smell, and sends them to proper region of cerebral cortexHypothalamus – maintains homeostasis by regulating:Heart rateBlood pressureBody temperatureWater and electrolyte balanceHunger control and body weightMovements and secretions of stomach and intestinesNeurosecretory substances that stimulate the pituitary glandSleep and wakefulness
55 Brain Stem Connects _______ to _______. Three sections: Midbrain Pons Medulla oblongataBetween diencephalon and ponsContains some visual and auditory reflex centersCerebrum; spinal cord
56 Brain Stem2. PonsRounded bulge on the underside of the brain stem, between midbrain and medulla oblongataRelays impulses from medulla oblongata to cerebrumTransmits impulses from cerebrum to cerebellumRelays sensory impulses from peripheral nerves to higher brain centersHelps regulate breathingCerebrum; spinal cord
57 Brain Stem 3. Medulla oblongata Extends from pons to foramen magnum All ascending and descending nerve fibers must pass thoughControl of visceral activities:Cardiac center – heart rateVasomotor center – constriction and dilation of blood vessels to control blood pressureRespiratory center – regulates rate, rhythm, and depth of breathingCerebrum; spinal cord
58 CerebellumLocated below the occipital lobes of the cerebrum and posterior to the pons and medulla oblongataLike cerebrum, has two hemispheres, connected by a structure called the vermis.Cerebrum; spinal cord
59 CerebellumCommunicates with other parts of the CNS by 3 nerve tracts (cerebellar peduncles):Inferior peduncles: receives sensory info about position of body partsMiddle peduncles: signals from cerebrum to cerebellum about desired position of limbsSuperior peduncles: takes correcting info from cerebellum to midbrainCerebrum; spinal cord
60 Functions of Cerebellum Based on the previous slide, what do you think are the main functions of the cerebellum?Answer:Reflex center for integrating sensory info concerning body positioning and coordinationHelps maintain postureWhat do you think damage to the cerebellum would cause?Cerebrum; spinal cord
61 Peripheral Nervous System Includes:Cranial nervesSpinal nervesCan also be divided into:Somatic nervous system – controls conscious activitiesAutonomic nervous system – controls unconscious activities
62 Cranial Nerves Where would these originate? 12 pairs 1st pair originates in the cerebrumThe rest originate from the brain stem
63 Cranial Nerves, continued….. Olfactory nerves (I)Optic nerves (II)Oculomotor nerves (III)Trochlear nerves (IV) – smallest; takes impulses to a muscle that moves the eyeTrigeminal nerves (V) – largest cranial nervesOphthalmic division – sensory info from eyesMaxillary division – sensory info from upper mouthMandibular division – sensory info from scalp behind ears and lower mouth
64 Cranial Nerves, continued….. Abducens nerves (VI) – small; motor impulses to move eyeFacial nerves (VII) –Sensory associated with taste receptorsMotor impulses to facial muscles and tear glands and salivary glandsVestibulocochlear nerves (VIII) – inner earVestibular branch – maintaining balanceCochlear branch - hearing
65 Cranial Nerves, continued….. Glossopharyngeal nerves (IX) – tongue and pharynx; swallowingVagus nerves (X) –Larynx muscles associated with speech and swallowingSupplies muscles of the heart and smooth muscles and glands in thorax and abdomenVasovagal response
66 Cranial Nerves, continued….. Accessory nerves (XI) – originate in the medulla oblongata AND spinal cord, so has cranial AND spinal branchesCranial branches – join a vagus nerve and carry impulses to muscles of soft palate, pharynx, and larynxSpinal branches – motor impulses to trapezius and sternocleidomastoid musclesHypoglossal nerves (XII) – motor impulses to tongue
67 Spinal NervesThirty-one pairs providing 2-way communication between spinal cord and parts of upper and lower limbs, neck, and trunkDivided into:Cervical nervesThoracic nervesLumbar nervesSacral nervesCoccygeal nervesNaming and how many of each????
68 Autonomic Nervous System Two divisions:Sympathetic division – prepares body for stressful situationsParasympathetic divisionMost active under ordinary conditionsCounterbalances sympathetic division
69 Cranial Nerves Mnemonic Devices Naming:O! O! O! There’s The Abercrombie and Fitch. Very Gorgeous and Very Adorable! Hot!Type of Nerve:Some Say Money Matters, But My Brother Says Big Boobs Matter More.