Exam 2: Nervous Tissue Flashcards
Which embryonic layer is nervous tissue derived from?
ectoderm
Cells from ectoderm that give rise to diverse variety of cells (especially nervous tissue)
Neural Crest Cells
Where are gray/white matter located in spinal cord?
Gray matter- inside
White matter- outside
Nissl substance
dark purple, clumped material in neuron cell bodies
made up of ribosomes & RER
Axon Hillock
where axon leaves cell body
absence of Nissl substance
Node of Ranvier
between two neurolemmocytes (Schwann cells)
no myelin –> saltatory conduction of AP
Endoneurium
layer of collagenous CT around individual nerve fibers (or axons)
reticular fibers (collagen type III)
Neurokeratin
protein of myelin sheath left after histo processing
striations/lines around axon
Perineurium
DICCT lined by perineural epithelioid cells and surrounds nerve fascicles
Plexus
branching network of intersecting nerves
nerve fibers + cell bodies of ANS
Myenteric Plexus
between intestine muscle layers
pale stain
function for motility / secretion
Submucosal Plexus
in submucosa of tubular organs
function for motility / secretion
Free Nerve Endings
unsheathed terminal branches of myelinated axons
pain/temperature receptors
Merkel’s cells
nonencapsulated tactile corpuscles
mechanoreceptors
How do Merkel’s cells appear on microscopy?
colorless
Merkel’s cells location
stratum basale
Encapsulated Tactile Corpuscles
capsule with intertwining axon in neurolemmocyte cytoplasm
Location of Encapsulated Tactile Corpuscles
below epithelium within connective tissue
Lamellated Corpuscles (Pacinian Corpuscles)
receptors sense pressure/vibration
Tactile Corpuscle
nerve endings
mechanoreceptors
Neuromuscular Spindles
stretch-activated receptors
regulate muscle tone, posture, movement
Two fiber types in neuromuscular spindles
Intrafusal nuclear chain fibers
nuclear bag fibers
Nuclear Bag Fibers
fiber in neuromuscular spindles
dilated middle zone w/ nuclei
Nuclear Chain Fibers
fiber in neuromuscular spindles
small w/ center nuclei chain
Motor End Plate
neuron terminals from neuron to muscle fiber
Neuroglia
supportive cells in CNS
Origin of neuroglia
neuroectoderm
EXCEPT microglia (mesoderm)
Which glial cell is most abdunant?
astrocyte
Where are astrocytes found?
gray matter = protoplasmic astrocyte
white matter = fibrous astrocyte
Where are oligodendrocytes found?
white & gray matter of CNS
Microglia
type of neuroglia
small/elongated nuclei | dense chromatin
phagocytic (macrophages)
main immune defense in CNS
What type of stain is the only method to show cell processes in microscopy?
heavy metal stain (gold or silver)
Fibrous Astrocytes
astrocytes in white matter
insert between myelinated axons
What structure is nearby most astrocytes?
capillary / blood vessel
What type of astrocytes are found in the gray matter in brain?
protoplasmic astrocytes
What type of astrocytes are found in the white matter of the brain?
fibrous astrocytes
Astrocyte function
metabolic role in regulationing ions (K+)
“scarring cells”
fill areas after brain injury
foot processes form glial limiting membrane
Oligodendrocytes
neuroglial cells responsible for myelination of axons in white matter (in CNS)
Neurolemmocytes
aka “schwann cells”
neuroglial cells responsible for myelination of axons in PNS
Microglia
phagocytic / macrophages
immune defense
Ependymal cells
type of neuroglial cell
line central canal of spinal cord + brain ventricles
separate nervous tissue from CSF
What tissue type are ependymal cells made of?
Simple Columnar Epithelium
some w/ cilia / microvilli
Tanycytes
modified ependymal cells with long processes + apical CSF portion
What is the function of tanycytes?
facilitate passage of hypothalamic-regulating hormones from CSF –> hypophyseal portal circulation
Where are gray / white matter located in cerebrum/cerebellum?
white matter- inside
gray matter- outside
Layers of the Cerebellum
Molecular layer
Purkinje layer
Granular layer
Purkinje cells
make up purkinje layer in cerebellum
extend into molecular layer and receives excitatory impulses from cerebral cortex
Cerebellum function
modulate/organize motor impulses from cerebrum
regulate/coordinate movements of muscle groups
Meninges
connective tissue layers that surround brain & spinal cord
Meninges Layers
dura mater
arachnoid
pia mater
Dura Mater
outermost meninges layer
under bone of skull
DICCT lined w/ perineural epithelioid cells
Arachnoid
middle meninges layer
collagen fibers + CT trabeculae
Pia Mater
innermost meninges layer
tightly adhere to brain/spinal cord
Subarachnoid space
space where arachnoid trabeculae extend filled with CSF
Choroid Plexus
vascular structure projecting into brain ventricles
covered with modified ependymal cells
produces CSF
What makes up the CNS?
brain + spinal cord
What makes up PNS?
nerves, ganglia, receptors
Function of CNS
interconnection & processing
Function of PNS
sensory input (afferent) from receptors in skin, muscle, viscera
motor output (efferent) to viscera + muscle
Somatic NS
voluntary motor
conscious sensory
Visceral NS
involuntary motor
unconscious sensory
Autonomic Nervous System
parts of CNS + PNS that are motor (efferent) to visceral activities
Two divisions & locations of ANS
sympathetic: thoracolumbar
parasympathetic: craniosacral
CNS dervied from…
neural tube
PNS derived from…
neural crest cells
Multipolar neurons
most of CNS, autonomic ganglia of PNS
off-center nuclei, multiple dendrites
Bipolar neurons
spiral ganglion of cochlea, retina, sensory info –> CNS
Pseudounipolar neurons
cranial and spinal sensory ganglia (dorsal root)
sensory into –> CNS
central nuclei/large soma
Unipolar neurons
similar to pseudounipolar
Interneurons
between other neurons
Soma or Perikaryon
neuron cell body
support cell processes over loss distances
Neurofilaments
neuron-specific intermediate filaments
in neuron cell body
support rapid transport & structural support
Anterograde transport
molecules/organelles from cell body –> axon terminal
use motor protein kinesin
Retrograde transport
back to cell body (of neuron)
for degrading lysosomes
use motor protein dynein
Synapse Classifications by where contact occurs
axodendritic
axosomatic
axoaxonic
Axodendritic synapse
contact on dendrites
Axosomatic synapse
contact on cell body of postsynaptic neuron
Axoaxonic synapse
contact on terminals of another axon
Ganglia
group of cell bodies within nerve outside CNS
Sensory/Dorsal Root Ganglia
pseudounipolar neurons
cell body at periphery (organized)
central nuclei
heavily myelinated axons
cell bodies encapsulated by satellite cells & CT
Autonomic Ganglia
multi-unipolar neurons
disorganized appearance
thinly myelinated or unmyelinated axons
incomplete capsule around cell body made of satellite cells
“weblike” nerve fibers/axons
What tissue type is a ganglion capsule made of?
Dense Irregular Collagenous CT
Intramural Ganglia
in wall/connective tissue of organs
part of PSNS of ANS
Glial Limiting Membrane
separates CT of pia mater from nerve cells
formed by foot processes of astrocytes
Glial fibrillary acidic proteins
intermediate filaments in glial cells
List of Glial Cells in CNS
astrocytes
oligodendrocytes
ependymal cells
microglia
List of Glial Cells in PNS
satellite cells
neurolemmocytes (schwann cells)
Satellite cells
form capsule around pseudounipolar neuron cell bodies in dorsal root ganglia
more less complete capsule around multipolar neuron of autonomic ganglia
Myelin Sheath
multilayered myelinating cell membrane around axon (lots of lipids)
Mesaxon
where edges of schwann cell come together around axon
Unmyelinated nerve fibers (PNS)
aka axons in PNS
in autonomic ganglia
axons protected by schwann cells but plasmalemma specialized layers of myelin not formed
Unmyelinated nerve fibers (CNS)
not sheathed at all, “free fibers”
Lamellar Corpuscle location
skin, tendons, joints, periosteum of bone, pancreas, mesentery
Encapsulated Tactile Corpuscle location
dermis of hairless skin, lips, nose
Epineurium
CT around nerve and fascicles (bundles)
Layers of Choroid Plexus
outer: loose CT continuous w/ pia mater
inner: simple cuboidal epithelium continuous w/ ependymal cells
What’s in the white matter of spinal cord?
myelinated nerve fibers
neuroglial cells
Somatic
voluntary motor
conscious sensory
Visceral
involuntary motor
unconscious sensory
ANS
parts of CNS & PNS that are motor (efferent) to visceral activities (smooth muscle, gland secretion, cardiac muscle)
Sympathetic NS location
thoracolumbar
Parasympathetic NS location
craniosacral
