Exercise 15: Histology of Nervous Tissue Flashcards
“nerve glue”; supporting cells; serve the needs of the neuron by bracing and protecting them; these cells are not capable of generating and transmitting nerve impulses; different types depending on the central (CNS) and peripheral (PNS) nervous systems
neuroglia
the basic functional units of nervous tissue; cells of the nervous system; specialized to transmit messages (nerve impulses) from one part of the body to another
neurons
the 2 principle cell populations in nervous tissue
neurons and neuroglia
Neuroglia of the CNS
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
In CNS, control the chemical environment around neurons; most abundant
astrocytes
In CNS, myelinate cytoplasmic extensions of the neuron to speed up signal conduction
Oligodendrocytes
phagocytic; destroys pathogens or cellular debris
Microglia
line cerebrospinal fluid-filled cavities to secrete cerebrospinal fluid (a clear liquid that bathes the CNS)
Ependymal cells
Neuroglia of the PNS
- Schwann cells
2. Satellite cells
In PNS, myelinate cytoplasmic extensions of the neuron to speed up signal conduction; assist in regeneration of damaged fibers
Schwann cells
surround the neurosomas in ganglia of the PNS; provide electrical insulation around the soma; regulate the chemical environment of the neurons
Satellite cells
region of the neuron that houses the nucleus and cytoplasm
Cell body (aka neurosoma)
The cytoplasm of the neuron is riddled with _____ and ______.
Neurofibrils and Nissil bodies
clusters of cell bodies in the CNS; neuron fibers running through the CNS form tracts of white matter
Nuclei
clusters of cell bodies outside the CNS; neuron fibers running form the peripheral nerves
Ganglia
cytoskeletal elements of the neuron that helps maintain support and intracellular transport functioning
Neurofibrils
a type of rough endoplasmic reticulum that is involved with the metabolic activities of the cell
Nissil bodies
receptive regions for neurotransmitters released by other neurons; neurons can have many of these
Dendrites
nerve fibers that generate and conduct nerve impulses; neurons have only one of these
Axon
where the cell body transitions into the axon
Axon hillock
form synapses or junctions with neurons or effector cells
Axon terminals (aka synaptic knobs)
Each axon terminal is separated from the cell body or dendrites of the next neuron by a ______.
Synaptic cleft
gaps or indentations in the myelin sheath
Nodes of Ranvier
a fatty material that covers the nerve fibers
Myelin
In PNS: axons are myelinated by ____
____ which wrap tightly around the axon in jellyroll fashion; this wrapping is called a ____ ____
- Schwann cells
2. Myelin sheath
the peripheral part of the Schwann cell and its exposed plasma membrane
Neurilemma (aka sheath of Schwann)
In CNS: myelination is accomplished by ____; these CNS sheaths do not exhibit ____; myelin insulates the fibers and greatly increases the speed of neurotransmission by ____ ____.
- Oligodendrocytes
- Neurilemma
- Neuron fibers
What is neuron classification based upon?
- Structure (number of processes attached to the cell body)
2. Function
one very short process that extends from the cell body; divides into peripheral and central processes; only the most distal portions of the peripheral process act as receptive endings; the rest acts as an axon along with the central process
Unipolar neurons
two processes attached to the cell body; rare – found only as part of the receptor apparatus of the eye, ear, and olfactory mucosa
Bipolar neurons
many processes that come from the cell body that are all called dendrites; has a single axon
Multipolar neurons
neurons carrying impulses from sensory receptors in the internal organs, the skin, skeletal muscles, joints, or special sensory organs; receptive endings are often equipped with specialized receptors that are stimulated by specific changes in their immediate environment; cell bodies found in a ganglion outside the CNS; typically unipolar
Sensory (afferent) neurons
neurons carrying impulses from the CNS to the viscera and/or body muscles and glands; often multipolar; cell bodies located in the CNS
Motor (efferent) neurons
neurons that help connect sensory and motor neurons; cell bodies located within CNS; multipolar structure
Interneurons (aka association neurons)
bundle of neuron fibers (axons) wrapped in connective tissue coverings that extends to and/or from the CNS and visceral organs or structures of the body periphery
Nerve
Nerves that transmit impulses toward CNS
Sensory (afferent) nerves
Nerves that transmit impulses away from CNS
Motor (efferent) nerves
nerves that carry both sensory and motor fibers
Mixed nerves
a connective tissue sheath that surrounds each nerve fiber (axon); provides insulation from the other neuron processes adjacent to it; this CT layer is often mistaken for the myelin sheath
Endoneurium
connective tissue that surrounds groups of fibers; this forms bundles of fibers called fascicles
Perineurium
bundles of fibers formed by the perineurium
Fascicles
fibrous connective tissue that surrounds all the fascicles to group them together to make the nerve
Epineurium
