Nervous System Fundamentals

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    Neural Tissue and NeruophysiologyNeural Tissue and Neruophysiology

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    Summary of Nervous System Function

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    Major Structual

    and Functional

    components ofthe Nervous

    SystemCentral Nervous System

    Peripheral Nervous System

    Sensory

    Somatic Visceral

    Motor

    Somatic

    Visceral (Autonomic NS)

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    Astrocyte Microglial cell

    Ependymal cells

    Oligodendrocyte

    Schwann cells and Satellite cells

    Neuroglia (Glial Cells)

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    The structure of a neuron

    Soma

    Dendrites

    Axon

    Synapse

    Myelin sheath(Schwann cells)

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    Schwann Cells

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    Multipolar Neuron:

    Motor neurons and

    interneurons

    Types of Neurons

    Unipolar Neuron:

    Sensory neurons

    Bipolar Neuron:

    Special sensory (vision,

    hearing, smelling

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    Types of Synapses

    Neuron-to-neuron

    Neuromuscular

    Neuroglandular

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    Principles of Electricity

    Voltage: A potential energy that exists due to aseparation of charges

    Current: Flow of electrical charge from one point to

    anotherCurrent Voltage

    Current 1/ Resistance

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    Chemically (Ligand) Gated Channels

    Changes in the Transmembrane Potential

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    Na+

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    Voltage Gated Channels

    Changes in the Transmembrane Potential

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    Na+

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    Changes in the Transmembrane Potential

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    Na+

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    Mechanically Gated Channels

    Movement

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    The Resting Transmembrane PotentialThe Transmembrane potential = Sum of

    chargesSum of

    charges -

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    The Transmembrane Potential:

    Dynamic equilibrium

    Na+

    K+

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    Na+

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    Na+ Na+

    Na+

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    K+K+

    K+K+

    K+

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    K+ K+

    K+

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    Membrane potential is resting, but not static:

    Leak channels permit ions (esp. K+) to escape Na+/K+ Exchange pump

    - Removes 3 Na+ and pulls in 3 K+ using ATP

    K+K+

    Na+ Na+

    K+

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    Signals: depolarization and hyperpolarization

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    K+K+

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    Graded Potentials

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    1 resting state

    2 depolarization phase

    3 repolarization phase

    4 hyperpolarization

    Action

    Potentials

    1

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    4

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    Action Potentials:

    Na+ and K+ voltage gated channels

    70

    55

    0

    +30

    M

    emb

    ranep

    ote

    ntial

    (m

    V)

    Relat ive

    membrane

    permeabili t

    y

    Action potential

    PNa

    PKThreshold

    2

    3

    411

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    Voltage gated Na+ channels open in response to

    graded potentials at the trigger zone

    Voltage gated Na+ channels open in response to

    action potentials at the conduction zone

    Conduction zone

    Receptive zone

    Action Potentials: Propagation

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    Action Potentials: Propagation

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    Action Potentials: Propagation

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    Refractory Periods

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    Coding for Stimulus Intensity

    All action potentials are alike and areindependent of stimulus intensity

    The CNS determines stimulus intensity by thefrequency of impulse transmission

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    Conduction VelocityFactors:

    Axon diameter

    Degree of myelination

    Saltatory Conduction

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    Types of Synapses:

    Electrical vs. Chemical Synapses

    Chemical synapse

    Electrical synapse

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    The Cholinergic Synapse:From Action Potential to Graded Potential

    Ion channel (open)

    Ion channel closed

    Ion channel open

    Neurotransmitter

    Receptor

    Postsynaptic

    membrane

    Degraded

    neurotransmitter

    Na+

    Na+

    Ca2+

    Actio

    nPoten

    tial

    1

    2

    34

    5

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    Termination of Neurotransmitter Effects

    Degradation (AChE)

    Reuptake

    Diffusion from synapse

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    Post-synaptic potentials