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Nervous Tissue: Neurons and Support Cells (glial cells)

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Presentation on theme: "Nervous Tissue: Neurons and Support Cells (glial cells)"— Presentation transcript:

1 Nervous Tissue: Neurons and Support Cells (glial cells)

2 Support Cells: Neuroglia
Astrocytes Brace/anchor neurons, provide chemical barrier Most abundant glial cells Microglia Destroy threatening particles/cells; phagocytes Ependymal cells Line ventricles and central canal; cilia circulate CSF Oligodendrocytes Produce myelin sheath around axons (in the CNS) © 2015 Pearson Education, Inc.

3 Figure 7.3a Supporting (glial) cells of nervous tissue.
ASTROCYTES Capillary Neuron Astrocyte (a) Astrocytes are the most abundant and versatile neuroglia.

4 Figure 7.3b Supporting (glial) cells of nervous tissue.
MICROGLIA Neuron Microglial cell (b) Microglial cells are phagocytes that defend CNS cells.

5 Figure 7.3c Supporting (glial) cells of nervous tissue.
EPENDYMAL CELLS Fluid-filled cavity Ependymal cells Brain or spinal cord tissue (c) Ependymal cells line cerebrospinal fluid-filled cavities.

6 Figure 7.3d Supporting (glial) cells of nervous tissue.
OLIGODENDROCYTES Myelin sheath Process of oligodendrocyte Nerve fibers (d) Oligodendrocytes have processes that form myelin sheaths around CNS nerve fibers.

7 Support Cells: PNS glial cells
Satellite cells Protect neuron cell bodies Schwann cells Form myelin sheath around axons (in the PNS) © 2015 Pearson Education, Inc.

8 Figure 7.3e Supporting (glial) cells of nervous tissue.
Satellite cells Cell body of neuron Schwann cells (forming myelin sheath) Nerve fiber (e) Satellite cells and Schwann cells (which form myelin) surround neurons in the PNS.

9 Neurons (nerve cells) specialized to transmit messages
Major regions of neurons Cell body— contains the nucleus metabolic center of the cell Processes—fibers that extend from the cell body Dendrites : pick up sensory stimuli Axons : receive impulse from cell body Impulses are UNIDIRECTIONAL along the axon © 2015 Pearson Education, Inc.

10 Figure 7.4a Structure of a typical motor neuron.
Dendrite Mitochondrion Cell body Axon Nucleus One Schwann cell Node of Ranvier Axon terminal Schwann cells, forming the myelin sheath on axon (a)

11 Figure 7.4b Structure of a typical motor neuron.
Neuron cell body Dendrite (b)

12 Axons and the Synaptic Cleft
End in axon terminals Terminals contain vesicles filled with neurotransmitters Neurons are separated from other cells by a gap called the synaptic cleft: Synapse—junction between nerves Neurons NEVER touch each other © 2015 Pearson Education, Inc.

13 © 2015 Pearson Education, Inc.
The Myelin Sheath whitish, fatty material covering axons Nodes of Ranvier gaps in myelin sheath along the axon impulse jumps from one node to the next The current cannot flow across the axon where there is myelin so it jumps between the myelin bundles The presence of the myelin sheath speeds the nerve impulse transmission © 2015 Pearson Education, Inc.

14 Multiple Sclerosis Myelin sheath becomes destroyed
Replaced with hardened scleroses Sclerosis: hardening of body tissue Incomplete/staggered transmission of impulse Autoimmune disease- potientially caused by: Genes Smoking Viral infections Vitamin D deficiency

15 Classification of Neurons
Sensory (afferent) neurons Carry impulses from sensory receptors to the CNS Cutaneous (skin) sense organs Pain receptors Temperature receptors Touch/pressure receptors Proprioceptors—detect stretch or tension Muscle spindle in muscles Golgi tendon organ in tendonw © 2015 Pearson Education, Inc.

16 Functional Classification of Neurons
Motor (efferent) neurons Carry impulses from the central nervous system to viscera, muscles, or glands Interneurons (association neurons) Located in the spinal cord (CNS) Connect sensory and motor neurons Play role in reflex arc – allow quicker response without involving the brain © 2015 Pearson Education, Inc.

17 Figure 7.6 Neurons classified by function.
Central process (axon) Sensory neuron Spinal cord (central nervous system) Cell body Ganglion Dendrites Peripheral process (axon) Afferent transmission Interneuron (association neuron) Peripheral nervous system Receptors Efferent transmission Motor neuron To effectors (muscles and glands)

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