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Chapter 10 Lecture PowerPoint To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please Note: Once you have used any of the animation functions (such as Play or Pause), you must first click in the white background before you can advance to the next slide. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Type Institution Name Here Type Course Number Here: Type Course Name Here Chapter 10 Type Professor Name Here Type Academic Rank Here Type Department Name Here 2 Hole’s Human Anatomy and Physiology Twelfth Edition Shier w Butler w Lewis Chapter 10 Nervous System I: Basic Structure and Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 10.1: Introduction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrites • Cell types in neural tissue: • Neurons • Neuroglial cells (also known as neuroglia, glia, and glial cells) Cell body Nuclei of neuroglia Axon 4 © Ed Reschke Divisions of the Nervous System • Central Nervous System (CNS) • Brain • Spinal cord • Peripheral Nervous System (PNS) • Cranial nerves • Spinal nerves 5 Divisions of Peripheral Nervous System • Sensory Division • Picks up sensory information and delivers it to the CNS • Motor Division • Carries information to muscles and glands • Divisions of the Motor Division: • Somatic – carries information to skeletal muscle • Autonomic – carries information to smooth muscle, cardiac muscle, and glands 6 Divisions Nervous System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central Nervous System (brain and spinal cord) Brain Peripheral Nervous System (cranial and spinal nerves) Cranial nerves Sensory division Spinal cord Sensory receptors Spinal nerves Motor division Somatic Nervous System Skeletal muscle Autonomic Nervous System Smooth muscle Cardiac muscle Glands 7 (a) (b) 10.1 Clinical Application Migraine 8 10.2: General Functions of the Nervous System • The three general functions of the nervous system: • Receiving stimuli = sensory function • Deciding about stimuli = integrative function • Reacting to stimuli = motor function 9 Functions of Nervous System • Sensory Function • Sensory receptors gather information • Information is carried to the CNS • Integrative Function • Sensory information used to create: • Sensations • Memory • Thoughts • Decisions • Motor Function • Decisions are acted upon • Impulses are carried to effectors 10 10.3: Description of Cells of the Nervous System • Neurons vary in size and shape • They may differ in length and size of their axons and dendrites • Neurons share certain features: • Dendrites • A cell body • An axon 11 Neuron Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chromatophilic substance (Nissl bodies) Dendrites Cell body Nucleus Nucleolus Axonal hillock Synaptic knob of axon terminal Impulse Neurofibrils Axon Nodes of Ranvier Myelin (cut) Axon Schwann cell Nucleus of Schwann cell Portion of a collateral 12 Myelination of Axons • White Matter • Contains myelinated axons • Considered fiber tracts • Gray Matter • Contains unmyelinated structures • Cell bodies, dendrites Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrite Unmyelinated region of axon Myelinated region of axon Node of Ranvier Axon (a) Neuron Neuron cell body nucleus Enveloping Schwann cell Schwann cell nucleus Longitudinal groove (c) Unmyelinated axon 13 10.2 Clinical Application Multiple Sclerosis 14 10.4: Classification of Neurons and Neuroglia • Neurons vary in function • They can be sensory, motor, or integrative neurons • Neurons vary in size and shape, and in the number of axons and dendrites that they may have • Due to structural differences, neurons can be classified into three (3) major groups: • Bipolar neurons • Unipolar neurons • Multipolar neurons 15 Classification of Neurons: Structural Differences • Bipolar neurons • Two processes • Eyes, ears, nose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrites • Unipolar neurons • One process • Ganglia of PNS • Sensory • Multipolar neurons • 99% of neurons • Many processes • Most neurons of CNS Peripheral process Axon Direction of impulse Central process Axon (a) Multipolar Axon (b) Bipolar (c) Unipolar 16 Classification of Neurons: Functional Differences • Sensory Neurons • Afferent • Carry impulse to CNS • Most are unipolar • Some are bipolar • Interneurons • Link neurons • Aka association neurons or internuncial neurons • Multipolar • Located in CNS Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central nervous system Peripheral nervous system Cell body Dendrites Sensory receptor Cell body Axon (central process) Axon (peripheral process) Sensory (afferent) neuron Interneurons • Motor Neurons • Multipolar • Carry impulses away from CNS • Carry impulses to effectors Motor (efferent) neuron Axon Effector (muscle or gland) Axon Axon terminal 17 Types of Neuroglial Cells in the PNS 1) Schwann Cells • Produce myelin found on peripheral myelinated neurons • Speed up neurotransmission 2) Satellite Cells • Support clusters of neuron cell bodies (ganglia) 18 Types of Neuroglial Cells in the CNS 1) Microglia • CNS • Phagocytic cell 3) Oligodendrocytes • CNS • Myelinating cell 2) Astrocytes 4) Ependyma or ependymal • CNS • CNS • Scar tissue • Ciliated • Mop up excess ions, etc. • Line central canal of spinal • Induce synapse formation cord • Connect neurons to blood vessels • Line ventricles of brain • Part of Blood Brain Barrier 19 Types of Neuroglial Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fluid-filled cavity of the brain or spinal cord Neuron Ependymal cell Oligodendrocyte Astrocyte Microglial cell Axon Capillary Myelin sheath (cut) Node of Ranvier 20 Regeneration of A Nerve Axon Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal muscle fiber Motor neuron cell body Changes over time Site of injury Schwann cells Axon (a) Distal portion of axon degenerates (b) Proximal end of injured axon regenerates into tube of sheath cells (c) Schwann cells degenerate (d) Schwann cells proliferate (e) Former connection reestablished 21 10.5: The Synapse Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Nerve impulses pass from neuron to neuron at synapses, moving from a pre-synaptic neuron to a post-synaptic neuron. Synaptic cleft Impulse Dendrites Axon of presynaptic neuron Axon hillock of Postsynaptic neuron Axon of presynaptic neuron Impulse Cell body of Impulse postsynaptic neuron 22 Synaptic Transmission Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Direction of nerve impulse • Neurotransmitters are released when impulse reaches synaptic knob Axon Ca+2 Synaptic knob Synaptic vesicles Presynaptic neuron Ca+2 Cell body or dendrite of postsynaptic neuron Mitochondrion Ca+2 Synaptic vesicle Vesicle releasing neurotransmitter Axon membrane Neurotransmitter Synaptic cleft Polarized membrane Depolarized membrane (a) 23 Animation: Chemical Synapse Please note that due to differing Please note that duesome to differing operating systems, animations operating systems, some animations is will not appear until the presentation will not in appear until theMode presentation viewed Presentation (Slide is viewed in Presentation Mode (Slide Show view). You may see blank slides Show view). You may see blank in the “Normal” or “Slide Sorter”slides views. in the “Normal” or “Slide Sorter” views. All animations will appear after viewing All animations will appear after viewing in Presentation Mode and playing each in Presentation Mode and playing each animation. Most animations will require animation. Most animations will require the latest version of the Flash Player, the latest version of which is available at the Flash Player, which is available at http://get.adobe.com/flashplayer. http://get.adobe.com/flashplayer. 24 10.6: Cell Membrane Potential • A cell membrane is usually electrically charged, or polarized, so that the inside of the membrane is negatively charged with respect to the outside of the membrane (which is then positively charged). • This is as a result of unequal distribution of ions on the inside and the outside of the membrane. 25 Distribution of Ions • Potassium (K+) ions are the major intracellular positive ions (cations). • Sodium (Na+) ions are the major extracellular positive ions (cations). • This distribution is largely created by the Sodium/Potassium Pump (Na+/K+ pump). • This pump actively transports 3 sodium ions out of the cell and 2 potassium ions into the cell. 26 Resting Potential • Resting Membrane Potential (RMP): • 70 mV difference from inside to outside of cell • It is a polarized membrane • Inside of cell is negative relative to the outside of the cell • RMP = -70 mV • Due to distribution of ions inside vs. outside • Na+/K+ pump restores Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. High Na+ Low K+ Low Na+ Impermeant anions High K+ Cell body Axon Axon terminal + – (a) + – + – +– – – + + – – + + + – – + + – + – – – + + –70 mV + – – + (b) + + – + – + + – Na – Low + Na+ Pump – – K+ + – Low K++ – High K+– + + High Na+ + – – – + + –70 mV + – – + + – – + (c) 27 + – – + Local Potential Changes • Caused by various stimuli: • Temperature changes Gate-like mechanism • Light • Pressure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protein Cell membrane (a) Channel closed Fatty acid tail Phosphate head (b) Channel open • Environmental changes affect the membrane potential by opening a gated ion channel • Channels are 1) chemically gated, 2) voltage gated, or 3) mechanically gated 28 Local Potential Changes • If membrane potential becomes more negative, it has hyperpolarized • If membrane potential becomes less negative, it has depolarized • Graded (or proportional) to intensity of stimulation reaching threshold potential • Reaching threshold potential results in a nerve impulse, starting an action potential 29 Local Potential Changes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Na+ Na+ –62 mV Neurotransmitter (a) Chemically-gated Na+ channel Presynaptic neuron Voltage-gated Na+ channel Trigger zone (axon hillock) Na+ Na+ Na+ Na+ Na+ –55 mV 30 (b) Action Potentials • At rest, the membrane is polarized (RMP = -70) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Na+ • Threshold stimulus reached (-55) Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ Na+ Na+ Na+ Na+ –0 –70 Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ (a) • Sodium channels open and membrane depolarizes (toward 0) K+ Na+ Na+ K+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ –0 K+ Threshold stimulus K+ K+ Na+ Na+ channels open K+ channels closed K+ Na+ Na+ –70 • Potassium leaves cytoplasm and membrane repolarizes (+30) • Brief period of hyperpolarization (-90) Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Region of depolarization (b) K+ K+ Na+ K+ Na+ K+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ Na+ Na+ Region of repolarization (c) Na+ Na+ Na+ Na+ Na+ –0 K+ channels open Na+ channels closed –70 Na+ 31 Action Potentials Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. +40 Membrane potential (millivolts) Action potential +20 0 –20 Resting potential reestablished –40 Resting potential –60 –80 Hyperpolarization 0 1 2 3 4 5 Milliseconds 6 7 8 32 Action Potentials Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Region of action potential + + + + + + + + + + + – – – – – – – – – + + – – – – – – – – – + + + + + + + + + + + + + + + – – – – – – – – – – – – + + + (a) + – + + – – + + Direction of nerve impulse – – – + + + + + + + + + + + + + + + + + (b) – – – – – – – + + – – – – – – – – – + + – – + (c) + + + + + + + + 33 Animation: Action Potential Propagation in Myelinated Neurons Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 34 Animation: Action Potential Propagation in Unmyelinated Neurons Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 35 All-or-None Response • If a neuron axon responds at all, it responds completely – with an action potential (nerve impulse) • A nerve impulse is conducted whenever a stimulus of threshold intensity or above is applied to an axon • All impulses carried on an axon are the same strength 36 Refractory Period • Absolute Refractory Period • Time when threshold stimulus does not start another action potential • Relative Refractory Period • Time when stronger threshold stimulus can start another action potential 37 Impulse Conduction 38 Animation: The Nerve Impulse Please note that due to differing Please note that duesome to differing operating systems, animations operating systems, some animations is will not appear until the presentation will not in appear until theMode presentation viewed Presentation (Slide is viewed in Presentation Mode (Slide Show view). You may see blank slides Show view). You may see blank in the “Normal” or “Slide Sorter”slides views. in the “Normal” or “Slide Sorter” views. All animations will appear after viewing All animations will appear after viewing in Presentation Mode and playing each in Presentation Mode and playing each animation. Most animations will require animation. Most animations will require the latest version of the Flash Player, the latest version of which is available at the Flash Player, which is available at http://get.adobe.com/flashplayer. http://get.adobe.com/flashplayer. 39 10.3 Clinical Application Factors Affecting Impulse Conduction 40 10.7: Synaptic Transmission • This is where released neurotransmitters cross the synaptic cleft and react with specific molecules called receptors in the postsynaptic neuron membrane. • Effects of neurotransmitters vary. • Some neurotransmitters may open ion channels and others may close ion channels. 41 Synaptic Potentials • EPSP • Excitatory postsynaptic potential • Graded • Depolarizes membrane of postsynaptic neuron • Action potential of postsynaptic neuron becomes more likely • IPSP • Inhibitory postsynaptic potential • Graded • Hyperpolarizes membrane of postsynaptic neuron • Action potential of postsynaptic neuron becomes less likely 42 Summation of EPSPs and IPSPs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • EPSPs and IPSPs are added together in a process called summation • More EPSPs lead to greater probability of an action potential Neuron cell body Nucleus Presynaptic knob Presynaptic axon 43 Neurotransmitters 44 Neurotransmitters 45 Neuropeptides • Neurons in the brain or spinal cord synthesize neuropeptides. • These neuropeptides act as neurotransmitters. • Examples include: • Enkephalins • Beta endorphin • Substance P 46 10.4 Clinical Application Opiates in the Human Body 47 10.8: Impulse Processing • Way the nervous system processes nerve impulses and acts upon them • Neuronal Pools • Interneurons • Work together to perform a common function • May excite or inhibit • Convergence • Various sensory receptors • Can allow for summation of impulses • Divergence • Branching axon • Stimulation of many neurons ultimately 48 Neuronal Pools • Groups of interneurons that make synaptic connections with each other • Interneurons work together to perform a common function • Each pool receives input from other neurons • Each pool generates output to other neurons 49 Convergence Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Neuron receives input from several neurons • Incoming impulses represent information from different types of sensory receptors 1 2 • Allows nervous system to collect, process, and respond to information • Makes it possible for a neuron to sum impulses from different sources 3 (a) 50 Divergence • One neuron sends impulses to several neurons Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Can amplify an impulse 4 • Impulse from a single neuron in CNS may be amplified to activate enough motor units needed for muscle contraction 6 5 51 (b) Important Points in Chapter 10: Outcomes to be Assessed 10.1: Introduction Describe the general functions of the nervous system. Identify the two types of cells that comprise nervous tissue. Identify the two major groups of nervous system organs. 10.2: General Functions of the Nervous System List the functions of sensory receptors. Describe how the nervous system responds to stimuli. 10.3: Description of Cells of the Nervous System Describe the three major parts of a neuron. Define neurofibrils and chromatophilic substance. 52 Important Points in Chapter 10: Outcomes to be Assessed Describe the relationship among myelin, the neurilemma, and the nodes of Ranvier. Distinguish between the sources of white matter and gray matter. 10.4: Classification of Neurons and Neuroglia Identify structural and functional differences among neurons. Identify the types of neuroglia in the central nervous system and their functions. Describe the Schwann cells of the peripheral nervous system. 10.5: The Synapse Define presynaptic and postsynaptic. Explain how information passes from a presynaptic to a postsynaptic 53 neuron. Important Points in Chapter 10: Outcomes to be Assessed 10.6: Cell Membrane Potential Explain how a cell membrane becomes polarized. Define resting potential, local potential, and action potential. Describe the events leading to the conduction of a nerve impulse. Compare nerve impulse conduction in myelinated and unmyelinated neurons. 10.7: Synaptic Transmission Identify the changes in membrane potential associated with excitatory and inhibitory neurotransmitters. 10.8: Impulse Processing Describe the basic ways in which the nervous system processes information. 54 Quiz 10 Complete Quiz 10 now! Read Chapter 11. 55