Essentials of Anatomy and Physiology Fifth edition Seeley, Stephens and Tate Slide 2.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 8: Nervous System

Functions of the Nervous System Slide 7.1a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sensory input – gathering information  Changes occurring inside and outside the body  Changes = stimuli  Integration  Process and interpret sensory input  Determine action needed

Functions of the Nervous System Slide 7.1b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Motor output  A response to integrated stimuli  Activates muscles or glands (effectors)  May be voluntary  May be involuntary

Structural Classification of the Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Central nervous system (CNS)  Brain  Spinal cord  Peripheral nervous system (PNS)  Nerves attached to brain and spinal cord

Functional Classification of the PNS Slide 7.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sensory (afferent) division  Nerve fibers that carry information to the central nervous system Figure 7.1

Functional Classification of the PNS Slide 7.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Motor (efferent) division  Nerve fibers that carry impulses away from the central nervous system Figure 7.1

Functional Classification of the PNS Slide 7.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Motor (efferent) division  Two subdivisions  Somatic nervous system = voluntary  Autonomic nervous system = involuntary Figure 7.1

Organization of the Nervous System Slide 7.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.2

Nervous Tissue: Support Cells (Neuroglia = “Nerve Glue”) Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Astrocytes  Star-shaped cells  Support neurons  Form blood-brain barrier  Control the chemical environment Figure 7.3a

Nervous Tissue: Support Cells Slide 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Microglia  “little glue” cells  Spider-like phagocytes  Dispose of debris Figure 7.3b, c

Nervous Tissue: Support Cells Slide 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Ependymal cells  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid (CSF) Figure 7.3b, c

Nervous Tissue: Support Cells Slide 7.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Oligodendrocytes  “few branch” cells  Produce myelin sheath in the CNS Figure 7.3d

Nervous Tissue: Support Cells Slide 7.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Schwann cells  Form myelin sheath in the PNS Figure 7.3e

Nerve Fiber Coverings: Schwann Cells, con’t… Slide 7.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Wrap around axons  Nodes of Ranvier:  gaps in myelin sheath Figure 7.5

Nervous Tissue: Neurons Slide 7.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurons = nerve cells  Functional cells of the nervous system  Specialized to transmit messages  Anatomy  Cell body – nucleus and organelles  Processes – fibers that extend from the cell body

Neuron Anatomy Slide 7.9a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cell body  Nissl substance:  specialized RER  Neurofibrils:  cytoskeleton  maintains cell shape Figure 7.4a

Neuron Anatomy Slide 7.9b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cell body, con’t.  Nucleus  Large nucleolus Figure 7.4a

Neuron Anatomy Slide 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Processes  Dendrites: conduct impulses toward the cell body  Axons: conduct impulses away from the cell body Figure 7.4a

Axons and Nerve Impulses Slide 7.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Axons end in axon terminals  Axonal terminals  house vesicles with neurotransmitters  Synaptic cleft – gap between adjacent neurons  Synapse – junction between nerves

Neuron Cell Bodies: Location Slide 7.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Most are in the CNS  Gray matter = cell bodies and unmyelinated fibers  Nuclei = clusters of cell bodies within the white matter of the central nervous system  Ganglia = collections of cell bodies outside the CNS

Functional Classification of Neurons Slide 7.14a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sensory (afferent) neurons  Carry impulses from sensory receptors  Cutaneous sense organs  Proprioceptors: detect stretch or tension

Functional Classification of Neurons Slide 7.14a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Motor (efferent) neurons  Carry impulses from the central nervous system  To an effector (muscle or gland)

Functional Classification of Neurons Slide 7.14b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Interneurons (association neurons)  Found in neural pathways in the CNS  Connect sensory and motor neurons

Functional Classification of Neurons Slide 7.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.6

Structural Classification of Neurons Slide 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Multipolar neurons – many extensions from the cell body  Most common: these are motor neurons Figure 7.8a

Structural Classification of Neurons Slide 7.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bipolar neurons – one axon and one dendrite  Rare: these are sensory neurons (eye, ear) Figure 7.8b

Structural Classification of Neurons Slide 7.16c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Unipolar neurons – short single process leaving the cell body  These are Sensory neurons in the PNS Figure 7.8c

Nerve Impulse Transmission Slide 7.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Two mechanisms involved  Transmission along a neuron  An electrical process  Transmission between neurons  A chemical process

Functional Properties of Neurons Slide 7.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Irritability – ability to respond to stimuli  Conductivity – ability to transmit an impulse  The plasma membrane at rest is polarized (like a resting muscle fiber)

Transmission of a Nerve Impulse along a Neuron Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Depolarization – stimulus causes a change in membrane permeability  Allows sodium (Na + ) to enter the neuron Figure 7.9a–c

Transmission of a Nerve Impulse along a Neuron Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The exchange of ions creates an action potential in the neuron  “potential to do work”  Sound familiar?? Figure 7.9a–c

The Action Potential Slide 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Once the action potential (nerve impulse) begins, it spreads along the entire neuron  “all-or-none” law: sound familiar??  Potassium ions (K + ) leave the neuron after Na + enters

The Action Potential Slide 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Exchange of Na + and K + repolarizes the membrane  The sodium-potassium pump restores ions to their original location  Protein pump in the membrane  This action requires ATP

Nerve Impulse Propagation Slide 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The impulse continues to move along the neuron  Impulses travel faster along myelinated fibers Figure 7.9c–e

Nerve Impulse Propagation Slide 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myelinated fibers: ~200 feet/second  Unmyelinated fibers: ~10 feet/second Figure 7.9c–e

Transmission of the Nerve Impulse between Neurons Slide 7.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Impulses can cross the synapse to another nerve  Depolarization activates vesicles in axon terminal  Requires Ca ++  Neurotransmitter is released

Transmission of the Nerve Impulse between Neurons Slide 7.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The dendrite of the “next” neuron has receptor sites  Neurotransmitter attaches to receptors  If enough molecules of NT attach:  A new action potential is generated  Sound familiar??

How Neurons Communicate at Synapses Slide 7.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.10