Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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.

2 Type Course Number Here: Type Course Name Here Chapter 10 Type Professor Name Here Type Academic Rank Here Type Department Name Here Type Institution Name Here

3 Hole’s Human Anatomy and Physiology Twelfth Edition Shier  Butler  Lewis Chapter 10 Nervous System I: Basic Structure and Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

4 10.1: Introduction Cell types in neural tissue: Neurons Neuroglial cells (also known as neuroglia, glia, and glial cells) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrites Cell body Axon Nuclei of neuroglia © Ed Reschke

5 Divisions of the Nervous System Central Nervous System (CNS) Brain Spinal cord Peripheral Nervous System (PNS) Cranial nerves Spinal nerves

6 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

7 Divisions Nervous System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sensory divisionSensory receptors Motor division Skeletal muscle Brain (a)(b) Spinal cord Spinal nerves Cranial nerves Central Nervous System (brain and spinal cord) Peripheral Nervous System (cranial and spinal nerves) Smooth muscle Cardiac muscle Glands Autonomic Nervous System Somatic Nervous System

Clinical Application Migraine

9 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

10 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

: 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

12 Neuron Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell body Neurofibrils Nucleus Nucleolus Dendrites Impulse Nodes of Ranvier Myelin (cut) Axon Chromatophilic substance (Nissl bodies) Axonal hillock Portion of a collateral Schwann cell Nucleus of Schwann cell Synaptic knob of axon terminal

soma dendrites axon Neuron Structure 13

axon hillocknucleussoma nucleolusNissl bodies Neuron Structure 14

15 Myelination of Axons White Matter Contains myelinated axons Considered fiber tracts Gray Matter Contains unmyelinated structures Cell bodies, dendrites Dendrite Node of Ranvier Myelinated region of axon Axon (a) Unmyelinated region of axon Neuron cell body Neuron nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (c) Enveloping Schwann cell Schwann cell nucleus Unmyelinated axon Longitudinal groove

Clinical Application Multiple Sclerosis

: 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

18 Classification of Neurons: Structural Differences Bipolar neurons Two processes Eyes, ears, nose Unipolar neurons One process Ganglia of PNS Sensory Multipolar neurons 99% of neurons Many processes Most neurons of CNS Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrites Axon Direction of impulse (a) Multipolar Central process Peripheral process (c) Unipolar(b) Bipolar

19 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 Motor Neurons Multipolar Carry impulses away from CNS Carry impulses to effectors Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central nervous systemPeripheral nervous system Cell body Interneurons Dendrites Axon Sensory (afferent) neuron Motor (efferent) neuron Cell body Axon (central process) Axon (peripheral process) Sensory receptor Effector (muscle or gland) Axon terminal

20 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)

21 Types of Neuroglial Cells in the CNS 2) Astrocytes CNS Scar tissue Mop up excess ions, etc. Induce synapse formation Connect neurons to blood vessels Part of Blood Brain Barrier 3) Oligodendrocytes CNS Myelinating cell 4) Ependyma or ependymal CNS Ciliated Line central canal of spinal cord Line ventricles of brain 1) Microglia CNS Phagocytic cell

22 Types of Neuroglial Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microglial cell Axon Oligodendrocyte Astrocyte Capillary Neuron Myelin sheath (cut) Node of Ranvier Ependymal cell Fluid-filled cavity of the brain or spinal cord

23 Regeneration of A Nerve Axon Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon Site of injury Schwann cells (a) (b) (c) (d) (e) Changes over time Motor neuron cell body Former connection reestablished Schwann cells proliferate Schwann cells degenerate Proximal end of injured axon regenerates into tube of sheath cells Distal portion of axon degenerates Skeletal muscle fiber

: The Synapse Nerve impulses pass from neuron to neuron at synapses, moving from a pre-synaptic neuron to a post-synaptic neuron. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrites Impulse Synaptic cleft Axon of presynaptic neuron Cell body of postsynaptic neuron Axon hillock of Postsynaptic neuron Axon of presynaptic neuron

axonaxon terminalmuscle fiber 10.5: The Synapse 25

26 Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mitochondrion Synaptic knob (a) Synaptic cleft Neurotransmitter Axon Ca +2 Presynaptic neuron Direction of nerve impulse Synaptic vesicles Cell body or dendrite of postsynaptic neuron Synaptic vesicle Vesicle releasing neurotransmitter Axon membrane Polarized membrane Depolarized membrane Ca +2

27 Animation: Chemical Synapse 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

: 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.

29 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.

30 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. Axon Cell body Low Na + Axon terminal Low K + High K + High Na + (a) + + – – + + – – + + – + – – + – + – + – + – + – + – + – + – + – + – + – –70 mV (b) + + – – + + – – + + – + – – + – + – + – + – + – + – + – + – + – –70 mV Low Na + Low K + High K + High Na + Na + K+K+ (c) Pump Impermeant anions

31 Local Potential Changes Caused by various stimuli: Temperature changes Light Pressure Environmental changes affect the membrane potential by opening a gated ion channel Channels are 1) chemically gated, 2) voltage gated, or 3) mechanically gated Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gate-like mechanismProtein (b) Channel open(a) Channel closed Cell membrane Fatty acid tail Phosphate head

32 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

33 Local Potential Changes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. –62 mV Na + Neurotransmitter (a) –55 mV Na + Trigger zone (axon hillock) (b) Chemically-gated Na + channel Presynaptic neuron Voltage-gated Na + channel

34 Action Potentials At rest, the membrane is polarized (RMP = -70) Sodium channels open and membrane depolarizes (toward 0) Potassium leaves cytoplasm and membrane repolarizes (+30) Threshold stimulus reached (-55) Brief period of hyperpolarization (-90) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Region of depolarization (b) Region of repolarization (c) –70 –0 –70 –0 –70 –0 K+K+ Na + K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ Threshold stimulus Na + K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ Na + channels open K + channels closed K + channels open Na + channels closed

35 Action Potentials Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Milliseconds Membrane potential (millivolts) Action potential Hyperpolarization –40 –20 –60 –80 Resting potential Resting potential reestablished

36 Action Potentials Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Direction of nerve impulse ––––––––– ––––––––– ––––––––– ––––––––– ––––––––– ––––––––– (b) (c) Region of action potential

37 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

38 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

39 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

40 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

41 Impulse Conduction

42 Animation: The Nerve Impulse 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

Clinical Application Factors Affecting Impulse Conduction

: 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.

45 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

46 Summation of EPSPs and IPSPs EPSPs and IPSPs are added together in a process called summation More EPSPs lead to greater probability of an action potential Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus Neuron cell body Presynaptic knob Presynaptic axon

Neurotransmitters 47

48 Neurotransmitters

49 Neuropeptides Neurons in the brain or spinal cord synthesize neuropeptides. These neuropeptides act as neurotransmitters. Examples include: Enkephalins Beta endorphin Substance P

Clinical Application Opiates in the Human Body

: 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

52 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

53 Convergence Neuron receives input from several neurons Incoming impulses represent information from different types of sensory receptors Allows nervous system to collect, process, and respond to information Makes it possible for a neuron to sum impulses from different sources (a) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

54 Divergence One neuron sends impulses to several neurons Can amplify an impulse Impulse from a single neuron in CNS may be amplified to activate enough motor units needed for muscle contraction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (b) 4 5 6

55 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.

56 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 neuron.

57 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.

58 Quiz 10 Complete Quiz 10 now! Read Chapter 11.