biology 211 anatomy & physiology i dr. thompson histology of nervous tissue
TRANSCRIPT
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
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
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) Astrocytes
2) Oligodendrocytes:
3) Microglia:
4) Ependyma:
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.
Non-excitable cells of Peripheral Nervous System 1) Satellite cells surround and protect neuron cell bodies in P.N.S.
Satellite Cells
Non-excitable cells of Peripheral Nervous System 2) Schwann cells produce myelin sheaths which surround axons (and some dendrites) in P.N.S.
Schwann Cells
Nodes of Ranvier
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