Nervous Tissue Flashcards
most numerous of the neuroglial cells
Astrocytes
have a euchromatic nucleus that is considerably smaller than that of the neurons. Their principal role is to clear neurotransmitters from within the synaptic cleft, and to that end, their attenuated processes surround every synaptic junction in the CNS.
Astrocytes
Their processes contribute to the blood-brain barrier and surround all penetrating blood vessels and all the free surfaces of the brain and spinal cord.
Astrocytes
The extensive network of astrocytes and their processes is integrated by ___ _____, and they signal each other using _____.
gap junctions; calcium
enlarge and form the scar that follows damage to areas of nervous tissue.
Astrocytes
The three main types of glial cells; location?
Astrocytes, oligodendrocytes, microglia
CNS
small cells with a heterochromatic nucleus that form and maintain central myelin for axons in the central nervous system
Oligodendrocytes
small cells with a heterochromatic nucleus. They perform functions similar to those of the macrophage. They are mobile within the brain and can multiply when the brain is damaged
Microglia
What are the origins of all three neuroglia
Oligodendrocytes and astrocytes - ectodermal tissue
microglial - hematopoietic stem cells; mesodermal tissue
Which of the neuroglia has the smaller more heterochromatic nuclei?
Oligodendrocyte and microglia
Which of the neuroglia has the larger more euchromatic nuclei?
Astrocytes
Expand to form the glial limitans
astrocytes
List the supporting cells of the PNS
Schwann cells
What are the origins of Schwann cells?
They originate in the neural crest of the developing embryo and migrate throughout the body in parallel with the developing peripheral nervous system.
What is the relationship between neurons and Schwann cells?
Every surface of a neuron in the periphery is in contact with a Schwann cell.
The cell bodies of the ganglion cells are encapsulated by a layer of Schwann cells, known classically as ___________ in that location.
Satellite cells
envelop bundles of unmyelinated axons, providing physical support and protection
Schwann cells
Following damage to axons, __________ phagocytose the debris of degenerating fibers and establish guidance paths for axon regeneration
Schwann cells
the endoneurium consists of _____ and _______ of the nerve fiber
reticular fibers and the external lamina
Describe the perineurium
is a fiber-reinforced layer of fibroblast-like cells that surrounds fascicles of axons
Describe the epineurium; what is it made up of?
outer covering that binds the multiple nerve fascicles into a larger peripheral nerve.
The epineurium is a dense irregular connective tissue with many collagen fibers arranged in parallel to the fascicle.
The presence of a perineurium is one way to differentiate between _____________, ____________________, and peripheral nerve in a light microscope tissue section.
smooth muscle, dense regular connective tissue
In some neurons, the cytoplasm may contain _____ _____. These are also
called ‘age pigment’ because they increase in number and prominence with age;
lipofuscin granules
What are the three types of neurons and how do they differ?
Multipolar neurons are characterized by mutiple dendrites
emerging from the cell body and a single axon, bipolar neurons have two dendritic processes
(one serves as an input process, the other as an output process), and unipolar (also
known as pseudounipolar) neurons have one process.
