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69 Cards in this Set

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nodes of ranvier
speeds up transmission, hopping from spot to spot
What is the basic structural and functional unit of the nervous system?
Neurons- electrically excitable cells that can be highly polarized and are able to communicate signals long distances with action potentials.
Describe the structure of a neuron.
A neuron has a main cell body with processes calls axons and dendrites.
What are synapses?
Cell junctions specialized for transmitting signals from other neurons.
What is the 2nd major component of nervous tissue?
Glial cells. These are cells that separate neurons from one another. Glial cells surround neurons and provide metabolic and physiological support for neuronal functions.
Is nervous tissue cellular or mostly acellular?
Very cellular with neurons and glia comprising most of tissue. Very little intercellular space or ECM
What is the relationshp b/w nervous tissue and the nervous system.
Nervous tissue is the "parenchyma" (supporting tissue) of the entire nervous system, which is a main organ system of the body.
In addition to glial cells and neurons, what else makes up the nervous system?
The nervous system also contains stroma components, like CT cells and matrix, epithelial and muscle cells. These non neuronal cells are mainly found in blood vessels, blood and lymph, meninges and CT sheaths.
Describe the 2 parts of the nervous system.
Central nervous system is the brain and spinal cord. The peripheral nervous system is comprised of axons that extend out from CNS, ganglia and other various neuronal processes.
What are ganglia?
Clusters of nerve cell bodies found in the PNS.
Name 3 types of neuronal cell bodies.
bipolar, pseudo-unipolar and multipolar.
Desrcibe a pseudounipolar cell body.
A globular neuronal body with a single bifurcated process, e.g., sensory neurons in the dorsal root ganglia.
Describe a bipolar cell body.
A cell body with spindle shaped processes at each end, e.g., neurons of acoustic ganglia, olfactory neurons and some retinal neurons.
Describe a multipolar cell body.
A cell body with multiple processes. Most common nerve cell type.
What is a nissl body and where is it found?
granular ER, found in cytoplasm of neuron.
What are lipofuscin granules?
Pigment granules that accumulate in neurons with age.
Where are microtubules and neurofilaments found in neurons?
In the axons and dendrites.
What is the role of the dendrite?
Dendrites are processes that get stimuli and then transmit signals toward the cell body. THey have a stem that branches in a brush like manner not far from cell body.
What is a dendritic spine?
Spines on some dendrites which are the sites of synaptic contact.
What is the role of an axon?
Axon is a single cell process that conducts impulses away from the cell body. It is longer and thinner than a dendrite. THese are smooth and don't usually branch near the cell body.
Where does one find the axon hillock?
This is the conical projection in the cell body from which the axon extends.
What are collateral branches?
Axon branching at their ends (also called terminal arborizations).
What is the role of myelin and where is it found?
Myelin wraps some axons forming a sheath and increases conductivity of signals. Myelin is made by glial cells.
WHere are synapses?
These communication sites are found between end of an axon and a cell body or dendrite if another neuron.
What is the terminal buoton?
The bulbous expansion at the axon terminal that contains synaptic vesicles.
Describe a synaptic region.
On one cell- a terminal buton with synaptic vesicles. On the other cell, a post-synaptic membrane. Cells are separated by a synaptic cleft into which neurotransmitter is released.
Describe neurotransmitter release.
Following depolarization of a membrane of the axon terminal, a synaptic vesicle containing neurotransmitter is released into the synaptic cleft for uptake by the postsynaptic membrane.
What is a neurotransmitter?
A chemical signal.
What is neuroglia and name 4 main types.
Nerve glue originating from ectoderm that serves as support cells of the nervous system. They have lots of branching and require special stain to visualize structure. Astrocytes, Oligodendroglia, Microglia and Schwann cells.
Describe Astrocytes.
Star shaped glia with branching parts. Protoplasmic astros are in gray matter of CNS, while fibrous astros are thinner and found in white matter. Astros transport material b/w neurons, blood vessesl, give rigidity to CNS, Regulate amounts of EC space around neurons, store energy as glycogen, secrete growth factors, act as phagocytes and prevent neurons for contacting ea other.
What are most brain tumors?
Astrocyte gliomas.
Describe oligodendrocytes?
Common glial cells. More abundant in white matter where they make myelin sheaths of axons. In gray matter, they surround cell bodies.
Describe microglia.
Small, dense, elongated cells with processes covered with thorny projections. THey are muigratory and phagocytic.
What are Schwann cells?
Glial cells of PNS. They develop in embryo from neural crest cells. SOme make myelin sheaths around axons in PN, some are phagocytic and some act as sattellite cells in PNS ganglia. Some function in nerve regeneration.
What is gray matter?
In CNS, Gray matter is mostly nerve cell bodies, glial cells and unmyelinated processes. Gray matter makes cortex of brain and central horns of spinal cord.
What is white matter?
White matter is rich in myelinated nerve fibers and is located mostly in central area of brainand around periphery of spinal cord.
If a slide is stained for myelin, what happens to the appearance of the gray and white matter?
Gray matter looks light and white matter looks dark, e.g., colorations are reversed.
What are nuclei in nervous tissue?
Aggregates of neuronal cell bodies forming islands of gray matter embedded in white matter.
What are laminae?
Distinct layers or sheets of nerve bodies found in the cortex or cerebellum.
What are sattelite cells?
Abundant small glial cells that surround the cell body of each ganglion nerve cell. They originate from the neural crest.
What are ganglia?
Neuronal cell body groups outside of CNS.
What is the capsule?
Connective tissue that surrounds the ganglia outside the CNS.
DEscribe the dorsal root ganglia.
THese contain the cell bodies of pseudounipolar sensory neurons that carry impules away from the PNS to the CNS.
Describe the autonomic ganglia.
Found as enlargements of sympathetic trunks or collecton of nerve cell bodies in visceral organs. Have neurons with unmyelinated postganglionic axons.
What are ependymal cells?
Cells derived from neural tube that develop into an epithelium lining of brain ventricles (cavities) and central canal of spinal cord.
Where is cerebrospinal fluid found?
Cerebrospinal fluid is found in the brain ventricles (cavities).
What are meninges?
Fibrous connective tissue-like coverings of CNS.
What are 3 layers of meninges?
Dura mater (tough mother), arachnoid layer (spider-web like) and pia mater (tender mother).
What is a choroid plexus?
Folds of ependyma (choroidal villi) extending into ventricles of brain. Plexus has blood vessels and is coverd by cuboidal epithelium that secretes CSF.
What is a blood-CSF barrier?
IN the choroid plexus, the zonula occludens b/w epis creates a barrier.
Describe the blood brain barrier.
Capillaries in the brain have limited permeability that limits exchange of large molecules from the blood to CNS. Barrier is due to zonula occludens b/w cap. endothelial cells and also due to glial cells. This barrier prevents metabolites in blood from entering brain freely.
What is function of brain capillary endothelial cells?
Along with choroid plexus, their function is to allow transport of essential metabolites in blood across BBB.
Describe Peripheral nerves.
These nerves are composed of fibers which mostly pass through dorsal or ventral roots of the spinal cord. Fibers are surrounded by folds of Schwann cells.
When is a PNS neuron said to be myelinated?
When the Shwann cell folds are tightly wrapped and include myelin. If Schwann cell only hugs fiber, the axon is not myelinated.
WHat is a nerve fiber?
An axon or dendrite with its surrounding Schwann cell, regardless of whether or not myelin is present.
What are nodes of ranvier?
Interjucntions of adjacent Schwann cells that creates an interruption of the myelin sheath. These allow for nerve signals to move more quickly.
What is the internode?
The length of 1 Schwann cell between 2 nodes of ranvier.
What is the significance of the Schmidt-Lanterman cleft.
These occasional gaps in myeline membrane wrapping have no known purpose.
What are fascicles?
Archaec word for bundles of peripheral nerve fibers
What is endoneurium?
Enclosure surrounding individual Schwann cells and their enclosed axons.
What is perineurium?
Surrounds fasicles of nerve fibers in a nerve.
What is epineurium?
Ensheaths groups of fiber bundles.
Describe Meissner's corpuscle.
Mulitlaminar stacks of Schwann cells surrounding the terminus of an axon that are found in the papillary layer of the dermis.
Describe Pacinian corpuscle.
Unmyelinated nerve endings surrounded by concentric layers of fibroblasts found in the deeper layers of the dermis. Looks like a sliced onion in tranverse section.
What are muscle spindles?
A complex of skeletal muscle fibers and nerve endings encapsulated in CT that monitor muscle activity.
Describe olfactory cells.
Bipolar neurons with processes intruding through olfactory epithelium to get chemical stimuli via cila on their apical surfaces.
What is the role of chemoreceptor?
To function in taste and smell reception.
Describe taste buds.
Specialized non-neuronal sensory cells which transduce stimuli into electrical impulses that are passed onto neurons.
Describe myenteric plexus of Auerbach.
Provides intrinsic parasympathetic motor innervation to intestine. Clumps of parasympathetic nerves between layers of smooth muscle. A type of autonomic ganglia.