biology 211 anatomy & physiology i nerve histology
TRANSCRIPT
Biology 211Anatomy & Physiology I
Nerve Histology
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Recall: All organs are composed of, at most, four tissues Epithelial tissue Connective tissue Muscle tissue Nervous tissue
Nervous tissue: Excitable cells (neurons) Nonexcitable (supporting) cells
Connective tissue: Meninges - in central nervous system Endoneurium Perineurium in peripheral nervous system Epineurium
Epithelium found only in blood vesselsMuscle (smooth)
Cells of Nervous Tissue:
1) Excitable cells = Neurons Carry electrical signals from one place to another Pass these signals to other cells
2) Nonexcitable cells = Glia in CNS Satellite cells Schwann cells
in PNS
1) Excitable cells = Neurons Carry electrical signals from one place to another Pass these signals to other cells
Found in either central nervous system, peripheral nervous system, or may have parts in both
Do not divide
Long-lived
High metabolic rates
1) Neurons Classified by:
2) Neurons Classified by:
Stimulatory synapses
Inhibitory synapses
Cells of Nervous Tissue:
1) Excitable cells = Neurons Carry electrical signals from one place to another Pass these signals to other cells
2) Nonexcitable cells =
Non-excitable cells
By definition: Do not carry electrical information
Support, nourish, protect neurons
May divide
In CNS: Glia
In PNS: Satellite cells surround neuron cell bodies Schwann cells surround cell processes
Glia: 4 types in central nervous system
1)
2)
3)
4)
Glia: 1) Astrocytes: Regulate environment around neurons by controlling the passage of molecules into and out of capillaries, and by absorbing or secreting ions from/into extracellular matrix
Glia: 2) Oligodendrocytes: Produce myelin sheaths around axons (and some dendrites) of neurons in C.N.S.
Glia: 3) Microglia: Phagocytic. Remove degenerating cells and foreign debris from C.N.S.
Glia: 4) Ependyma: Line fluid-filled ventricles within C.N.S.
Non-excitable cells of Peripheral Nervous System 1) Satellite cells surround and protect neuron cell bodies in P.N.S.
Non-excitable cells of Peripheral Nervous System 2) Schwann cells produce myelin sheaths which surround axons (and some dendrites) in P.N.S.
Pathology of the Nonexcitable Cells
Loss of oligodendrocytes causes multiple sclerosis and a group of diseases called leukodystrophies
Injury to astrocytes, usually from toxic substances, leads to cerebral edema and swelling of the brain
Injury to Schwann cells causes degeneration of the neuron processes and prevents their healing and regrowth. It is also responsible for Guillain-Barre syndrome
Pathology of the Nonexcitable Cells
Tumors can arise from all four types of glia, and these tend to grow rapidly and destroy nearby regions of the brain or spinal cord
Tumors can also arise from satellite cells or Schwann cells, compressing and destroying the neurons they surround