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Fundamentals of the Nervous System and Nervous Tissue (part 1)

Fundamentals of the Nervous System and Nervous Tissue (part 1). Chapter 11. Functions and Divisions of the Nervous System. 3 overlapping functions: Sensory Input Integration Motor Output. Functions and Divisions of the Nervous System.

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Fundamentals of the Nervous System and Nervous Tissue (part 1)

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  1. Fundamentals of the Nervous System and Nervous Tissue (part 1) • Chapter 11

  2. Functions and Divisions of the Nervous System • 3 overlapping functions: • Sensory Input • Integration • Motor Output

  3. Functions and Divisions of the Nervous System • The Nervous System is highly integrated and divided into two principal divisions: • The Central Nervous System • The Peripheral Nervous System

  4. Divisions of the Peripheral Nervous System • Two Functional Divisions • Sensory (Afferent) Division • Somatic sensory fibers • Visceral sensory fibers • Motor (Efferent) Division • The somatic nervous system • The autonomic nervous system

  5. Check Your Understanding • What is meant by “integration” and does it primarily occur in the CNS or PNS • Which subdivision of the PNS is involved in (a) relaying the feeling of a full stomach after a meal (b) contracting the muscles to lift your arm (c) increasing your heart rate

  6. Histology of Nervous Tissue • 80% Cellular • Two principal cell types • Neurons • Neuroglia (or glial cells)

  7. Neuroglia • There are 6 types of glial cells • 4 in the CNS • 2 in the PNS

  8. Neuroglia in the CNS • Astrocytes • Microglial Cells • Ependymal Cells • Oligodendrocytes

  9. Neuroglia in the PNS • Satellite Cells • Schwann Cells

  10. Check Your Understanding • Which type of Neuroglia controls the extracellular environment around neuron cell bodies in the CNS? in the PNS? • Which two types of neuroglia form insulating coverings called myelin sheaths?

  11. Neurons • Structural units of the nervous system • 4 special characteristics • ability to conduct nerve impulses • extreme longevity • neurons are amitotic • exceptionally high metabolic rate

  12. Neuron Structure • Neuron Cell Body

  13. Neuron Structure • Neuron Processes • Dendrites • Axons • hillock • axon collaterals • terminal branches • axon terminals

  14. The Axon: Functional Characteristics • The conducting region • Axon Hillock (trigger zone) • Axon Terminals (secretory zone) • Cell membrane= axolemma • Lacks GA and ER

  15. Transport Along the Axon

  16. Myelination • The Myelin Sheath • Myelination in the CNS • Myelination in the PNS

  17. Myelination in the PNS Video

  18. Check your understanding • Which part of the neuron is its fiber? How do nerve fibers differ from the fibers of connective tissue, and the fibers in muscle tissue? • How does a nucleus within the brain differ from a nucleus within a neuron? • How is a myelin sheath formed in the CNS, and what is its function?

  19. Classifications of Neurons • Structural Classifications • Multipolar, Bipolar, Unipolar • Functional Classifications • Sensory (afferent) neurons • Motor (efferent) neurons • Interneurons

  20. Check your understanding • Which structural and functional type of neuron is activated first when you burn your finger? • Which type is activated last to move your finger away from the source of heat?

  21. Membrane Potentials • Role of membrane Ion channels • Leakage Channels • Gated Channels • Chemically gated channels • Voltage-gated channels • Mechanically gated channels

  22. The Resting Membrane Potential • The Charge difference across the membrane in a resting neuron • Differences in Ionic Composition • Differences in Plasma Membrane permeability

  23. Check Your Understanding • In an open channel, which factors determine which direction ions will move through that channel? • For which cation is there the greatest amount of leakage across the plasma membrane?

  24. Membrane Potentials That Act as Signals • Objectives • Compare and contrast graded potentials and action potentials • Explain how action potentials are generated and propagated along neurons • Define absolute and relative refractory periods • Define saltatory conduction and contrast it with continuos conduction

  25. Membrane Potentials That Act As Signals • Two types of membrane potentials that act as signals • Graded Potentials • Action Potentials

  26. Membrane Potentials That Act As Signals • Depolarization • Hyperpolarization

  27. Membrane Potentials • Graded Potentials • short lived • localized • decreased magnitude with distance

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