Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology SIXTH EDITION Frederic H. Martini PowerPoint ® Lecture Slide Presentation prepared by Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii Chapter 12, Neural tissue
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Learning Objectives Describe the two major divisions of the nervous system and their characteristics. Identify the structures/functions of a typical neuron. Describe the location and function of neuroglia. Explain how resting potential is created and maintained. Describe the events in the generation and propagation of an action potential.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Learning Objectives Define the structure/function of a synapse. List the major types of neurotransmitters and neuromodulators. Explain the processing of information in neural tissue.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 12-1 An Overview of the Nervous System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings nervous system overview Nervous system Provides swift, brief responses to stimuli Endocrine system Adjusts metabolic operations and directs long- term changes Nervous system includes All the neural tissue of the body Basic unit = neuron
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Divisions of the Nervous system CNS (Central Nervous system) Brain and spinal cord PNS (Peripheral Nervous system) Neural tissue outside CNS Afferent division brings sensory information from receptors Efferent division carries motor commands to effectors Efferent division includes somatic nervous system and autonomic nervous system
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.1 Figure 12.1 Functional Overview of the Nervous System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 12-2 Neurons
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Perikaryon Neurofilaments, neurotubules, neurofibrils Axon hillock Soma Axon Collaterals with telodendria Neuron structure
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.2b Figure 12.2 The Anatomy of a Multipolar Neuron
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Site of intercellular communication Neurotransmitters released from synaptic knob of presynaptic neuron Synapse
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.3 The Structure of a Typical Synpase Figure 12.3
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Anatomical Anaxonic Unipolar Bipolar Multipolar Neuron classification
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.4 Figure 12.4 A Structural Classification of Neurons
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Sensory neurons deliver information from exteroceptors, interoceptors, or proprioceptors Motor neurons Form the efferent division of the PNS Interneurons (association neurons) Located entirely within the CNS Distribute sensory input and coordinate motor output Functional
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.5 Figure 12.5 A Functional Classification of Neurons
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 12-3 Neuroglia
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Four types of neuroglia in the CNS Ependymal cells Related to cerebrospinal fluid Astrocytes Largest and most numerous Oligodendrocytes Myelination of CNS axons Microglia Phagocytic cells Neuroglia of the Central Nervous System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.6 An Introduction to Neuroglia Figure 12.6
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.7 Neuroglia in the CNS Figure 12.7a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.7 Neuroglia in the CNS Figure 12.7b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Two types of neuroglia in the PNS Satellite cells Surround neuron cell bodies within ganglia Schwann cells Ensheath axons in the PNS Neuroglia of the Peripheral Nervous System Animation: Nervous system anatomy review PLAY
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Electrochemical gradient Sum of all chemical and electrical forces acting across the cell membrane Sodium-potassium exchange pump stabilizes resting potential at ~70 mV The transmembrane potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure An Introduction to the Resting Potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Electrochemical Gradients Figure 12.12
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Membrane contains Passive (leak) channels that are always open Active (gated) channels that open and close in response to stimuli Changes in the transmembrane potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Gated Channels Figure 12.13
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemically regulated channels Voltage-regulated channels Mechanically regulated channels Three types of active channels
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings A change in potential that decreases with distance Localized depolarization or hyperpolarization Graded potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Graded Potentials Figure
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Graded Potentials Figure
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure Depolarization and Hyperpolarization
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Appears when region of excitable membrane depolarizes to threshold Steps involved Membrane depolarization and sodium channel activation Sodium channel inactivation Potassium channel activation Return to normal permeability Action Potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure The Generation of an Action Potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure The Generation of an Action Potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Generation of action potential follows all- or-none principle Refractory period lasts from time action potential begins until normal resting potential returns Continuous propagation spread of action potential across entire membrane in series of small steps salutatory propagation action potential spreads from node to node, skipping internodal membrane Characteristics of action potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure Propagation of an Action Potential along an Unmyelinated Axon
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure Saltatory Propagation along a Myelinated Axon
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure Saltatory Propagation along a Myelinated Axon
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Type A fibers Type B fibers Type C fibers Based on diameter, myelination and propagation speed Axon classification
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Muscle tissue has higher resting potential Muscle tissue action potentials are longer lasting Muscle tissue has slower propagation of action potentials Animation: The action potential PLAY Muscle action potential versus neural action potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Action potential travels along an axon Information passes from presynaptic neuron to postsynaptic cell Nerve impulse
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Rare Pre- and postsynaptic cells are bound by interlocking membrane proteins General properties of synapses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical synapses More common Excitatory neurotransmitters cause depolarization and promote action potential generation Inhibitory neurotransmitters cause hyperpolarization and suppress action potentials General properties of synapses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Release acetylcholine (ACh) Information flows across synaptic cleft Synaptic delay occurs as calcium influx and neurotransmitter release take appreciable amounts of time ACh broken down Choline reabsorbed by presynaptic neurons and recycled Synaptic fatigue occurs when stores of ACh are exhausted Cholinergic synapses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Animation: Overview of a cholinergic synapse PLAY Figure The Function of a Cholinergic Synapse Figure
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure The Function of a Cholinergic Synapse Figure
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Adrenergic synapses release norepinephrine (NE) Other important neurotransmitters include Dopamine Serotonin GABA (gamma aminobutyric acid) Other neurotransmitters
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Influence post-synaptic cells response to neurotransmitter Neurotransmitters can have direct or indirect effect on membrane potential Can exert influence via lipid-soluble gases Neuromodulators Animation: Synaptic potentials, cellular integration, and synaptic transmission PLAY
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Neurotransmitter Functions Figure 12.21a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Neurotransmitter Functions Figure 12.21b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Neurotransmitter Functions Figure 12.21c
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 12-6 Information Processing
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Simplest level of information processing occurs at the cellular level Excitatory and inhibitory potentials are integrated through interactions between postsynaptic potentials Information processing
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings EPSP (excitatory postsynaptic potential) = depolarization EPSP can combine through summation Temporal summation Spatial summation IPSP (inhibitory postsynaptic potential) = hyperpolarization Most important determinants of neural activity are EPSP / IPSP interactions Postsynaptic potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Temporal and Spatial Summation Figure 12.22a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Temporal and Spatial Summation Figure 12.22b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure EPSP – IPSP Interactions Figure 12.23
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings GABA release at axoaxonal synapse inhibits opening calcium channels in synaptic knob Reduces amount of neurotransmitter released when action potential arrives Presynaptic inhibition
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Presynaptic Inhibition and Facilitation Figure 12.24
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Activity at axoaxonal synapse increases amount of neurotransmitter released when action potential arrives Enhances and prolongs the effect of the neurotransmitter Presynaptic facilitation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Presynaptic Inhibition and Facilitation Figure 12.24
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Neurotransmitters are either excitatory or inhibitory Effect on initial membrane segment reflects an integration of all activity at that time Neuromodulators alter the rate of release of neurotransmitters Rate of generation of action potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Can be facilitated or inhibited by other extracellular chemicals Effect of presynaptic neuron may be altered by other neurons Degree of depolarization determines frequency of action potential generation Rate of generation of action potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings You should now be familiar with: The two major divisions of the nervous system and their characteristics. The structures/ functions of a typical neuron. The location and function of neuroglia. How resting potential is created and maintained.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings You should now be familiar with: The events in the generation and propagation of an action potential. The structure / function of a synapse. The major types of neurotransmitters and neuromodulators. The processing of information in neural tissue.