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Organization of the Nervous System and the Neuron

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  • Organization of the Nervous System and the Neuron

  • Organization of the Nervous SystemThe Nervous System maintains body homeostasis with electrical signals; providesfor sensation, higher mental functioning, and emotional response; and activates muscles and glands.

  • 3 Overlapping Functions of Nervous SystemSENSORY INPUT-

    INTEGRATION-

    MOTOR INPUT-

  • Works with the Endocrine System to maintain homeostasis.

    Nervous System-

    Endocrine System-

  • Organization of the nervous system can bebased on:

    Structural Classification-

    2.Functional Classification-

  • STRUCTURAL CLASSIFICATION

  • FUNCTIONAL CLASSIFICATION

  • Nervous TissueNervous tissue is made up of two types of cells-Supporting and Neurons

    Supporting cells of the CNS are called Neuroglia or nerve glue.

    Neuroglia includes many types of cells that generally support, insulate, and protect neurons.

  • Types of Neuroglial cells-

    Astrocytes-

    Microglia-

    Ependymal cells-

    Oligodendrocytes-

  • What about gliomas???

  • Supporting Cells of the Peripheral Nervous SystemSatellite cells-

    Schwann cells-

  • THE NEURON

  • Nerve fibers may be microscopic up to a length of 3-4 feetNeurons never touch each otherAxonal terminals release neurotransmitters into the synapseMost long nerve fibers are myelinated or covered with a white fatty sheath called myelin which protects and insulates fibers and increases transmission rate of nerve impulses

  • Neurilemma is found covering the neuronsof the Peripheral Nervous System and helps regenerate damaged nerve fibers

    Which brings us to bundles of nerve fibers-

    Tracts-Nerves-

    And gray matter vs. white matter-

  • Neurons classified according to structure and functionFunctional-

    Sensory or Afferent-Motor or Efferent-Associative or Interneurons-

    2. Structural- based on # of processes extending from cell body

  • Physiology of NeuronsNeurons have two major functions

    Irritability-

    2. Conductivity-

  • Irritabililty- the short version

    Resting or inactive neuron is polarizedA stimulus excites the neuron to become active and generate an impulseThe stimulus changes the permeability of the neurons membrane Sodium gates open and Na diffuses into the cellNeuron is now depolarized Depolarization activates the neuron to transmit an action potential or nerve impulse

  • Depolarization is followed almost immediatelyby repolarization

    Until the neuron repolarizes it cannot conductanother impulse= absolute refractory period

    There also exists a relative refractory periodwhen a stronger than usual stimulus is required

  • Alcohol, sedatives, anesthetics-

    Cold and continuous pressure-

    Warm or remove pressure-

  • YouTube - Neurotransmitter Synapse 3D Animation

  • No contact between neurons except at electrical synapses (escape reflexes, retina, heart)

    Axonal terminals release neurotransmitters which cause depolarization of next neuron

    Neurotransmitter is removed from synapse by re-uptake at axonal terminal or enzymatic breakdown Conductivity

  • Peripheral Nervous SystemThose nerves found outside the central nervous systemEach nerve is made of bundles of neuron fibers Neuron fibers are surrounded by a delicate tissue sheathGroups of fibers are bound by coarser connective tissue wrapping to form bundles called fascicles

  • CRANIAL NERVES SPINAL NERVES

  • Spinal Nerves

  • DISORDERS AFFECTING NEURONSPOLIOMYELITIS

  • MULTIPLE SCLEROSIS-

    BELLS PALSY-

    SHINGLES-

  • And then theres CARPAL TUNNEL SYNDROME-