Transcript Nervous Tissue

Biology 322
Human Anatomy I
Histology of Nervous Tissue
Recall:
Nervous system
begins in trilaminar
embryo as a “neural
plate” of the ectoderm.
This develops into a
“neural groove” that
closes over to form a
“neural tube”
One end (caudal) of this neural tube thickens but stays
tube-shaped to form the spinal cord.
The other (cephalic) end of this
neural tube enlarges and folds
to form the brain and its various
divisions, which we will discuss
later.
The cranial nerves and spinal
nerves will form as outgrowths
of this embryonic brain and
spinal cord.
Recall: All organs are composed of, at most, four tissues
Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
Nervous tissue:
Connective tissue:
Epithelium
Muscle (smooth)
Cells of Nervous Tissue:
1) Excitable cells = Neurons
1) Neurons Classified by: Location
2) Neurons Classified by: Shape
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
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).
Non-excitable cells of Peripheral Nervous System
2)
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