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PNS Histology
PNS histology Exam 4
92
Anatomy
Graduate
08/29/2010
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Term
The myelinating cell of the PNS is the ___ ___, this cell is ___, espcially following nerve injury.
 Definition
Schwann cell
mitotic
Term
The myelinating cell in the CNS is the ____.
 Definition
oligodendrocyte
Term
The Schwann cell is ___ and myelinates ____ axon at a time. The oligodendrocyte is not____ but can myelinate ____ axons at one time.
 Definition
- mitotic
- one
- not mitotic
- many
Term
All nerves in the PNS are surrounded by ___ ____, even though not all nerves are myelinated. This is not the case in the CNS.
 Definition
- Schwann cells
Term
Nerve fibers are ____ surrounded by sheaths of cells of ___ _____ (_____).
 Definition
- axons
- ectodermal origin (Schwann cells)
Term
In the PNS, axons not ensheathed by the Schwann cell membrane are enveloped by ?
 Definition
- clefts of Schwann cells
Term
Areas on a myelinated nerve fiber between two myelinated areas are called ___ __ ___.
 Definition
nodes of ranvier
Term
unmyelinated axons do not have ___ __ ____.
 Definition
nodes of ranvier
Term
in the CNS, unmyelinated axons project between ___ and ___ cell processes.
 Definition
- neuronal
- glial
Term
In the PNS, you have a ___ ___ made of collagen, you do not have this in the CNS.
 Definition
- basal lamina
Term
In the PNS, a ____ axon is embedded in the ___ ___.
 Definition
- axon
- Schwann cell
Term
A Schwann cell is able to house numerous ____ in cytoplasm invaginations, but with this arrangement ___ does not occur b/c the Schwann cell cannot wrap around all the axons.
 Definition
- axons
- myelination
Term
The ___ is the ____ ____ ____ that surrounds the PERIPHERAL ___ and fills the space between nerve fiber bundles.
 Definition
- epineurium
- external fibrous coat
- nerve
Term
The epineurim in the PNS is made of ____, ____, and ___ _____.
 Definition
- collagen
- fibroblasts
- blood vessels
Term
The epineurium provides ___ ___ and ____ for the nerve.
 Definition
- structural support
- elasticity
Term
Nerve fibers are arranged in ___ to form nerves.
 Definition
- bundles
Term
what kind of cell is found in the PNS, but not the CNS?
 Definition
- fibroblast
Term
each individual nerve bundle/fasicle is surrounded by a ____.
 Definition
- perineurium
Term
The perineurium consists of :
 Definition
- flattened epithelial like cells
Term
The flattened epithelial like cells of the perineurium are connected by ___ ____ to protect the nerve fiber from ___ ____.
 Definition
- tight junctions
- toxic macromolecules
Term
Each nerve fiber in the PNS is surrounded by Schwann cells. The ____ surrounds the Schwann cells.
 Definition
- endoneurium
Term
The endoneurium consists of:
 Definition
- reticular cells
- collagen fibers
Term
each individual PNS nerve fiber is covered by a thin delicate cytoplasmic sheath of the Schwann cell, called the ____.
 Definition
- neurilemma
Term
The Neurilemma is the outermost ___ ____ of a ___ ____ that surrounds an axon.
 Definition
- cytoplasmic layer
- Schwann cell
Term
The neurilemma forms the outermost layer of the ___ ___ in the PNS, and lays over the ___.
 Definition
- nerve fiber
- endoneurium
Term
Nerve fibers are myelinated by Schwann cells at only ___ ____ on the fiber.
 Definition
- one point
Term
early on in myelination a Schwann cell encloses many axons, but as mitosis continutes it becomes segregated to a ___ ___. The lips of the Schwann cell envelpiong process extend around the axon is a spiral fashion forming the ___ ___.
 Definition
- single axon
- intraperiod line (IPL)
Term
each wrap is ___ to the previous wrap.
 Definition
internal
Term
As the cytoplasm is lost in the spiral myelinating process, a ____ ___ ___ forms.
 Definition
- major dense line
Term
Compaction:
 Definition
- sheath becomes more mature, number of turns around axon increases, lamallae of the sheath become more compact
Term
Some areas of myelin do not compact, these areas are called ____ ____ ____.
 Definition
Schmidt-Lanterman Clefts
Term
Schmidt-Lanterman clefts allow for passage of newly synthesized ___ ____ (protein, lipids) from the ___ ___ ___ to the ___ ___.
 Definition
- myelin components
- Schwann cell cytoplasm
- myelin proper
Term
Myelin, both in the CNS and PNS, is ___ % protein and ___% lipid.
 Definition
30% protein
70% lipid
Term
major protein in PNS myelin is:
 Definition
- Proglycoprotein
Term
Poglycoprotein is a ___ ___ found in the ___ and the ___.
 Definition
- transmembrane protein
- IPL
- MDL
Term
Schmidt clefts are only in the ___.
 Definition
PNS
Term
Myelin basic proteins make up 20% of myelin and are found within the ___.
 Definition
- major dense line
Term
if you lose a myelin basic protein, what component of myelin would you lack?
 Definition
- major dense line
Term
In the PNS, myelin basic protein is not essential for formation of the ____ since PNS also has __ _____. In the CNS you have to MBP for MDL formation.
 Definition
- major dense line
- Po glycoprotein
Term
A collection of nerve cell bodies outside the CNS is called a ___ ____.
 Definition
- nerve ganglion
Term
In the CNS, nerve cell bodies are called:
 Definition
- nuclei
Term
Each neuron cell body in the PNS is surrounded by ___ ___, which function as glial or supportive cells.
 Definition
- satellite cells
Term
The satellite cells that around a nerve cell body are surrounded by ___ ___ .
 Definition
basal lamina
Term
There are two types of nerve ganglia in the PNS categorized based on morphology and function and direction of impulse. What are they?
 Definition
- sensory ganglion
- autonomic ganglion
Term
What are the two types of sensory ganglia?
 Definition
- cranial sensory ganglia- associated with cranial nerve
- spinal sensory ganglia- associated with dorsal root ganglia of spinal nerves)
Term
Sensory ganglia are ___ ganglia since they send impules to the brain.
 Definition
- afferent
Term
Dorsal root sensory ganglia have ____neurons that send one thin process to the CNS. The other thicker processes go to the ____. These neurons have ___ as large as ____ in diameter.
 Definition
- pseudounipolar
- periphery
- perikaryia
- 100 micrometers
Term
Since dorsal root ganglia are ___ and the perikarya do not receive impulses, there are no ____ within the ganglia itself.
 Definition
- pseudounipolar
- synapses
Term
With sensory ganglia, nerve fibers are found in ____, nerve cell bodies are found at the ____, and there is a centrally located ___ with a darker nucleolus.
 Definition
- bundles
- peripheray
- nucleus
Term
Autonomic ganglia are distributed within the ___ and ___ divisions of the auonomic nervous system.
 Definition
- sympathetic
- parasympathetic
Term
Autonomic ganglia appear as ___ ____ in autonomic nerves.
 Definition
- bulbous dilations
Term
Autonomic ganglia found in the walls of the digestive tract are called ____ ____. These ganglia are not surrounded by connective tissue, but rather by the ___ of the organ and only have a few ___ cells.
 Definition
- intramural ganglia
- stroma
- satellite
Term
Autonomic ganglia include ___ _____ ___ ___ and ___ ___ __ ____.
 Definition
- submucosal plexus of Meissner
- myenteric plexus of Auerbach
Term
the submucosal plexus of meissner is in ____. the myenteric plexus of auerbach is in ___ ___.
 Definition
- glands- secretion
- smooth muscle- peristalsis
Term
Autonomic ganglia are ____ neurons that are ___ shaped, and have a small diameter of 15-45 micrometeres. The nucleus is round and ___ placed, and the cytoplasm contains ____ bodies.
 Definition
- multipolar
- star
- eccentrically
- Nissl bodies
Term
Nissl bodies are part of the ___.
 Definition
RER
Term
Neuron cell bodies of autonomic ganglia are surrounded by a layer of satellite cells, although in intramural ganglia, only a few satellite cells are found
 Definition
Term
autonomic ganglia do ____, but dorsal root ganglia do not do this.
 Definition
- synapse
Term
cell bodies in autonomic ganglia are not grouped but are ___ b/w nerve fibers.
 Definition
scattered
Term
rarely are neurons able to divide so degeneration is a permanent loss. But Schwann cells, glial cells, and ganglionic cells can ___.
 Definition
divide
Term
The olfactory nerve CNI is not a nerve.
 Definition
Term
Neurons can divide in the ___ ___. This is an exception. usually this can't happen.
 Definition
nasal epithelium
Term
when a peripheral nerve axon is severed, degenerative changes occur, called ___ ____.
 Definition
Wallerian degeneration
Term
If the proximal axon stays in tact with the perikaryion, it can ____, but degrades 1-2 internodes.
 Definition
-regenerate
Term
the distal segement degernates and is removed by what?
 Definition
Schwann cells
macrophages
Term
Axonal injury causes the following events in the perikaryon.
 Definition
Dissolution of the Nissl substance - chromatolysis.
Decrease in cytoplasmic basophilia.
Increase in the volume of the perikarya.
Migration of nuclei to a peripheral position in the perikarya.
Term
during nerve regeneration, ____ cells proliferate giving rise to tube like structures which are surrounded by collagen of an _____.
 Definition
- Schwann cells
- endoneurium
Term
Each ___ of the surviving neuron cell body splits into nerve fibers, aka ____, and reaches the ___ ___ tube of the degerating stump. This tube guides the axons during regrowth. Some axons/neurites reach peripheral tubes, while others reach central tubes and become completely surrounded by Schwann cell cytoplasm.
 Definition
- axon
- neurites
- Schwann cell
Term
In nerve regeneration, only one fiber persists and becomes ____, this is usually the____ fiber.
 Definition
- myelinated
- largest
Term
Enlargement of one fiber and elimination of the others, only occurs if the regenerating axons make sensory or motor contact with the appropriate receptor or effector endings in the periphary.
 Definition
Term
What are the two types of receptors?
 Definition
- encapsulated receptors
- nonencapsulated receptors
Term
nonencapsulated receptors respond to ___ and ___ sensations. These are not ____ and are ___ ___ ___. They are found in the ____.
 Definition
- pain and touch
- not myelinated
- free nerve endings
- epidermis
Term
Are Merkel discs/cells encapsulated or unencapsulated?
 Definition
- unecapsulated
Term
Merkel cells are specialized epithelial cell masses located in the ___ ___ of the ___.
 Definition
basal layer
epidermis
Term
The merkel cell is enmeshed in a terminal branch of an underlying axon terminal and is senstive to ___. Thus it is called a ___.
 Definition
- touch
- mechanoreceptor
Term
The outer connective tissue sheath of the hair follicle is surrouned by ____ ____ to form a ___ ___ that is sensitive to touch when the hair is perturbed or bent.
 Definition
- unmyelinated nerve fibers
- nerve ending
Term
The Meissner corpuscle is _____ and ____ shaped, located just below the ____ in a ___ ____. It is made of a stack of flattened cells, and is sensitive to ____.
 Definition
- encapsulated
- bee-hive shaped
- epidermis
- dermal papilla
- touch
Term
more specifically the meissner corpuscle is in the ___ ____.
 Definition
stratum spinosum
Term
Pacinian corpuslces are also ____ and are located in the ___ of skin and respond to ___, ___, and ___. This receptor has a cylindrical core surrounded by ___ ____ of ___ and ___ ___ fibers.
 Definition
- encapsulated
- dermis
- pressure, tension, vibrations
- concentric lamellae
- fibroblasts
- thin collagen fibers
Term
A Pacinian Corpuscle has an axon through its center that terminates at its expanded end.
 Definition
Term
Role of muscle spindles:
 Definition
- relay sensory information to the CNS for : controlling muscle activity, posture, and regulating activities of opposing muscle groups (muscle tone) involved in walking and other motor activities
Term
These spindles consist of a fluid-filled space with modified muscle fibers encased in groups within a connective tissue shell
 Definition
Term
Fibers outside the muscle spindle are called ___ fibers. Fibers inside the muscle spindle are called ___ fibers.
 Definition
- extrafusal
- intrafusal
Term
2 types of intrafusal fibers:
 Definition
- nuclear chain intrafusal fibers- small diameter, short
- nuclear bag intrafusal fibers- larger fibers
Term
Intrafusal fibers are richly ____ by ____ fibers that monitor the degree of stretch placed on these fibers.
 Definition
- innervated
- sensory
Term
A __ ___ organ is found at the site where the skeletal muscle fibers insert on its ____.
 Definition
- Golgi Tendon Organ
- tendon
Term
What function does the golgi-tendon organ have?
 Definition
- proprioceptive sensory function
Term
The golgi tendon organ is surrounded by a fibrous ____and the body consists of ____ that connects the skeletal muscle fibers with its tendon.
 Definition
- capsule
- collagen
Term
The golgi tendon organ is innervated by ___ ___ ___ that terminates as endings around the ___ fibers.
 Definition
type 1b sensory fibers
collagen
Term
muscle tension ___ the fiber, which signals the force being developed within the muscle.
 Definition
stretches
Term
motor unit:
 Definition
single axon and its association with a single muscle fiber/cell
Term
An axon sends short terminals, called ___, to the surface of the muscle fiber to form a ____ junction. An action potential triggers release of ___ via ____at this junction.
 Definition
- boutons
- myoneural junction
- acetylcholine
- exocytosis
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