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Nervous System Notes

Nervous System Notes
Course

Human Anatomy And Physiology I (PSIO 201)

179 Documents
Students shared 179 documents in this course
Academic year: 2021/2022
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23

Chapter 12 Nervous Tissue

  • Organization of the Nervous System

    • Central nervous system (CNS)
      1. brain and spinal cord a. integrating and command center
    • Peripheral nervous system (PNS)
      1. cranial nerves a. carry electrical signals to and from brain
      2. spinal nerves a. carry electrical signals to and from the spinal cord
      3. two main functional divisions a. sensory (afferent) division
        1. carries signals toward CNS, from skin, muscles and joints (somatic), and from visceral organs (visceral) b. motor (efferent) division
        2. carries signals away from CNS to effector organs
        3. somatic division (to skeletal muscle, voluntary control)
        4. autonomic division (to smooth and cardiac muscle, glands; involuntary control; further divided into sympathetic division ("fight or flight") and parasympathetic division ("resting and digesting")

  • Histology

    • Nervous tissue made up of...
      1. neurons a. cells that receive and transmit electrical signals
      2. neuroglia (glial cells) a. supporting cells of CNS and PNS

  • Neuroglia

    1. in CNS a. astrocytes
      1. hold neurons together
      2. repair of injury and scar formation
      3. induce changes in blood vessels to form the blood-brain barrier hold neurons together
      4. take up and break down some neurotransmitters (chemical signal molecules)
      5. maintain ion concentrations b. microglia
      6. defense cells c. ependymal cells
      7. line cavities in brain and spinal cord
      8. help form and circulate cerebrospinal fluid d. oligodendrocytes send out extensions that wrap neurons, forming myelin sheaths
    2. in PNS a. Schwann cells make myelin sheaths b. satellite cells support clusters of neuron cell bodies (in ganglia)

  • Neurons (nerve cells)

    1. highly specialized to conduct electrical signals
    2. can vary in structure but all have some common features
    3. common features a. cell body (soma)
      1. nucleus and other organelles
      2. well developed rough ER
      3. plasma membrane has receptors for neurotransmitters (receives chemical signals)
      4. clusters in CNS called nuclei, in PNS called ganglia

24

b. dendrites 1) relatively short, highly branched projections from cell body 2) plasma membrane has receptors for neurotransmitters (receives chemical signals) 3) conducts electrical signals toward cell body

c. axon (nerve fiber) 1) one long projection from cell body, begins at axon hillock 2) may be up to a few feet long 3) may have branches called collaterals 4) ends in many branches called axon terminals 5) carries electrical signals away from the cell body (signal called depolarization or action potential or nerve impulse) 6) when AP reaches terminals, neurotransmitters are released

d. myelin sheath 1) many neurons have their axons covered in myelin sheaths (helps conduct electrical signals faster)

  1. connect to other neurons at synapses

  • Bundles of Axons

    • Called a nerve in PNS
      1. wrapped in CT coverings (as in skeletal muscle) a. endoneurium wraps each fiber b. perineurium wraps groups of axons called fascicles c. epineurium wraps entire nerve

  • Called a tract in CNS

  • Structural classification of neurons

    • Multipolar neurons
      1. many dendrites, one axon
      2. most neurons of the brain and spinal cord

  • Bipolar neurons

    1. one dendrite, one axon
    2. in retina of eye, inner ear, olfactory (smell) neurons

  • Unipolar neurons

    1. one short process from cell body branches into two processes a. sensory neurons b. peripheral process has sensory receptor
    2. central process enters CNS

  • Functional Classification of Neurons

    • Sensory (afferent) neurons
      1. conduct signals toward CNS from skin, sensory organs, muscles, joints, viscera
      2. unipolar
      3. cell bodies in ganglia

  • Motor (efferent) neurons

    1. conduct signals away from CNS to muscles and glands
    2. multipolar
    3. cell bodies usually in CNS
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Nervous System Notes

Course: Human Anatomy And Physiology I (PSIO 201)

179 Documents
Students shared 179 documents in this course

University: The University of Arizona

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23
Chapter 12 Nervous Tissue
• Organization of the Nervous System
- Central nervous system (CNS)
1. brain and spinal cord
a. integrating and command center
- Peripheral nervous system (PNS)
1. cranial nerves
a. carry electrical signals to and from brain
2. spinal nerves
a. carry electrical signals to and from the spinal cord
3. two main functional divisions
a. sensory (afferent) division
1) carries signals toward CNS, from skin, muscles and joints (somatic), and from visceral
organs (visceral)
b. motor (efferent) division
1) carries signals away from CNS to effector organs
2) somatic division (to skeletal muscle, voluntary control)
3) autonomic division (to smooth and cardiac muscle, glands; involuntary control; further
divided into sympathetic division ("fight or flight") and parasympathetic division
("resting and digesting")
• Histology
- Nervous tissue made up of...
1. neurons
a. cells that receive and transmit electrical signals
2. neuroglia (glial cells)
a. supporting cells of CNS and PNS
- Neuroglia
1. in CNS
a. astrocytes
1) hold neurons together
2) repair of injury and scar formation
3) induce changes in blood vessels to form the blood-brain barrier hold neurons together
4) take up and break down some neurotransmitters (chemical signal molecules)
5) maintain ion concentrations
b. microglia
1) defense cells
c. ependymal cells
1) line cavities in brain and spinal cord
2) help form and circulate cerebrospinal fluid
d. oligodendrocytes send out extensions that wrap neurons, forming myelin sheaths
2. in PNS
a. Schwann cells make myelin sheaths
b. satellite cells support clusters of neuron cell bodies (in ganglia)
- Neurons (nerve cells)
1. highly specialized to conduct electrical signals
2. can vary in structure but all have some common features
3. common features
a. cell body (soma)
1) nucleus and other organelles
2) well developed rough ER
3) plasma membrane has receptors for neurotransmitters (receives chemical signals)
4) clusters in CNS called nuclei, in PNS called ganglia

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