By Leonard Henderson,2014-03-18 16:47
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Hole’s Human Anatomy and Physiology

    Shier, Butler & Lewis

    Twelfth Edition

Chapter 10 Outline

    10.1: Introduction

     A. Cell types in neural tissue:

     1. Neurons

     2. Neuroglial cells (also known as neuroglia, glia, and glial)

     Divisions of the Nervous System

     A. Central Nervous System (CNS)

     1. Brain

     2. Spinal cord

     B. Peripheral Nervous System (PNS)

     1. Cranial nerves

     2. Spinal nerves

     Divisions of Peripheral Nervous System

     A. Sensory Division

     1. Picks up sensory information and delivers it to the CNS

     B. Motor Division

     1. Carries information to muscles and glands

     C. Divisions of the Motor Division:

     1. Somatic carries information to skeletal muscle

     2. Autonomic carries information to smooth muscle, cardiac muscle, and


    10.1 Clinical Application: Migraine

    10.2: General Functions of the Nervous System

     A. The three general functions of the nervous system:

     1. Receiving stimuli = sensory function

     2. Deciding about stimuli = integrative function

     3. Reacting to stimuli = motor function

     Functions of Nervous System

     A. Sensory Function

     1. Sensory receptors gather information

     2. Information is carried to the CNS

     B. Motor Function

     1. Decisions are acted upon

     2. Impulses are carried to effectors

     C. Integrative Function

     1. Sensory information used to create:

     a. Sensations

     b. Memory

     c. Thoughts

     d. Decisions

    10.3: Description of Cells of the Nervous System

     A. Neurons vary in size and shape

     B. They may differ in length and size of their axons and dendrites

     C. Neurons share certain features:

     1. Dendrites

     2. A cell body

     3. An axon

     Myelination of Axons

     A. White Matter

     1. Contains myelinated axons

     2. Considered fiber tracts

     B. Gray Matter

     1. Contains unmyelinated structures

     2. Cell bodies, dendrites

    10.2 Clinical Application: Multiple Sclerosis

    10.4: Classification of Neurons and Neuroglia

     A. Neurons vary in function

     1. They can be sensory, motor, or integrative neurons

     B. Neurons vary in size and shape, and in the number of axons and dendrites that

     they may have

     C. Due to structural differences, neurons can be classified into three (3) major


     1. Bipolar neurons

     2. Unipolar neurons

     3. Multipolar neurons

     Classification of Neurons: Structural Differences

     A. Bipolar neurons

     1. Two processes

     2. Eyes, ears, nose

     B. Unipolar neurons

     1. One process

     2. Ganglia of PNS

     3. Sensory

     C. Multipolar neurons

     1. 99% of neurons

     2. Many processes

     3. Most neurons of CNS

     Classification of Neurons: Functional Differences

     A. Sensory Neurons

     1. Afferent

     2. Carry impulse to CNS

     3. Most are unipolar

     4. Some are bipolar

     B. Interneurons

     1. Link neurons

     2. Aka association neurons or internuncial neurons

     3. Multipolar

     4. Located in CNS

     C. Motor Neurons

     1. Multipolar

     2. Carry impulses away from CNS

     3. Carry impulses to effectors

     Types of Neuroglial Cells in the PNS

     A. Schwann Cells

     1. Produce myelin found on peripheral myelinated neurons

     2. Speed up neurotransmission

     B. Satellite Cells

     1. Support clusters of neuron cell bodies (ganglia)

     Types of Neuroglial Cells in the CNS

     A. Microglia

     1. CNS

     2. Phagocytic cell

     B. Astrocytes

     1. CNS

     2. Scar tissue

     3. Mop up excess ions, etc.

     4. Induce synapse formation

     5. Connect neurons to blood vessels

     C. Oligodendrocytes

     1. CNS

     2. Myelinating cell

     D. Ependyma or ependymal

     1. CNS

     2. Ciliated

     3. Line central canal of spinal cord

     4. Line ventricles of brain

     Regeneration of A Nerve Axon

    10.5: The Synapse

     A. Nerve impulses pass from neuron to neuron at synapses, moving from a pre-

     synaptic neuron to a post-synaptic neuron.

     Synaptic Transmission

     A. Neurotransmitters are released when impulse reaches synaptic knob 10.6: Cell Membrane Potential

     A. 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).

     B. This is as a result of unequal distribution of ions on the inside and the outside

     of the membrane.

     Distribution of Ions

     A. Potassium (K+) ions are the major intracellular positive ions (cations).

     B. Sodium (Na+) ions are the major extracellular positive ions (cations).

     C. This distribution is largely created by the Sodium/Potassium Pump (Na+/K+


     D. This pump actively transports sodium ions out of the cell and potassium ions

     into the cell.

     Resting Potential

     A. Resting Membrane Potential (RMP):

     1. 70 mV difference from inside to outside of cell

     2. It is a polarized membrane

     3. Inside of cell is negative relative to the outside of the cell

     4. RMP = -70 mV

     5. Due to distribution of ions inside vs. outside

     6. Na+/K+ pump restores

     Local Potential Changes

     A. Caused by various stimuli:

     1. Temperature changes

     2. Light

     3. Pressure

     B. Environmental changes affect the membrane potential by opening a gated ion


     C. Channels are 1) chemically gated, 2) voltage gated, or 3) mechanically gated

     D. If membrane potential becomes more negative, it has hyperpolarized

     E. If membrane potential becomes less negative, it has depolarized

     F. Graded (or proportional) to intensity of stimulation reaching threshold potential

     G. Reaching threshold potential results in a nerve impulse, starting an action


     Action Potentials

     A. At rest, the membrane is polarized (RMP = -70)

     B. Threshold stimulus reached (-55)

     C. Sodium channels open and membrane depolarizes (toward 0)

     D. Potassium leaves cytoplasm and membrane repolarizes (+30)

     E. Brief period of hyperpolarization (-90)

     All-or-None Response

     A. If a neuron responds at all, it responds completely

     B. A nerve impulse is conducted whenever a stimulus of threshold intensity or

     above is applied to an axon

     C. All impulses carried on an axon are the same strength

     Refractory Period

     A. Absolute Refractory Period

     1. Time when threshold stimulus does not start another action potential

     B. Relative Refractory Period

     1. Time when stronger threshold stimulus can start another action potential 10.3 Clinical Application: Factors Affecting Impulse Conduction

    10.7: Synaptic Transmission

     A. This is where released neurotransmitters cross the synaptic cleft and react with

     specific molecules called receptors in the postsynaptic neuron membrane.

     B. Effects of neurotransmitters vary.

     C. Some neurotransmitters may open ion channels and others may close ion


     Synaptic Potentials

     A. EPSP

     1. Excitatory postsynaptic potential

     2. Graded

     3. Depolarizes membrane of postsynaptic neuron

     4. Action potential of postsynaptic neuron becomes more likely

     B. IPSP

     1. Inhibitory postsynaptic potential

     2. Graded

     3. Hyperpolarizes membrane of postsynaptic neuron

     4. Action potential of postsynaptic neuron becomes less likely

     Summation of EPSPs and IPSPs

     A. EPSPs and IPSPs are added together in a process called summation

     B. More EPSPs lead to greater probability of an action potential



     A. Neurons in the brain or spinal cord synthesize neuropeptides.

     B. These neuropeptides act as neurotransmitters.

     C. Examples include:

     1. Enkephalins

     2. Beta endorphin

     3. Substance P

    10.4 Clinical Application: Opiates in the Human Body

    10.8: Impulse Processing

     A. Way the nervous system processes nerve impulses and acts upon them

     1. Neuronal Pools

     a. Interneurons

     b. Work together to perform a common function

     c. May excite or inhibit

     2. Convergence

     a. Various sensory receptors

     b. Can allow for summation of impulses

     3. Divergence

     a. Branching axon

     b. Stimulation of many neurons ultimately

     Neuronal Pools

     A. Groups of interneurons that make synaptic connections with each other

     B. Interneurons work together to perform a common function

     C. Each pool receives input from other neurons

     D. Each pool generates output to other neurons


     A. Neuron receives input from several neurons

     B. Incoming impulses represent information from different types of sensory


     C. Allows nervous system to collect, process, and respond to information

     D. Makes it possible for a neuron to sum impulses from different sources


     A. One neuron sends impulses to several neurons

     B. Can amplify an impulse

     C. Impulse from a single neuron in CNS may be amplified to activate enough

     motor units needed for muscle contraction

    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.

    ; Describe the relationship among myelin, the neurilemma, and the nodes of


    ; 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.

     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.

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