Nervous Tissue Flashcards
neuron
basic structural and functional unit of nervous system
w/ cell body, dendrites, axon
cell bodies
aka soma aka perikaryon
trophic/nutritional and metabolic center of the cell
where protein synthesis occurs
membrane specialized for nerve impulse generation
cell body appearance
clear, euchromatic nucleus
dense nucleolus
has organelles and cytoplasm
nucleus is always active/synthesizing proteins
multipolar neuron
organelles
most common type
-Nissl bodies (RER) for neurotransmitter syn
-Golgi apparatus to package NTs into vesicles
-Mitochondria
-lysosomes
multipolar structural components
microfilaments/actin
neurofilaments-changes in formation characteristic of alzheimers
microtubules: form neuronal cytoskeleton for framework to support axons/axonal transport
multipolar appearance
Nissl bodies = basophilic clumps of RER
axons = pale since no RER or golgi
inclusions
neuromelanin: in substantia nigra, @ midbrain
lipofuscin: in ganglion cells sympathetic
multipolar dendrites
radiate from soma to inc receptive area of neuron like antennas that branch and taper
transmit impulses to cell body or other dendrites
never myelinated, have organelles
bipolar neurons
special senses aka smell/vision/hearing/balance
pseudounipolar/unipolar
cell bodies enclosed in cranila nerve sensory ganglia OR dorsal root ganglia
impulse bypasses cell body (peripheral dendrites > axon terminals to CNS
somatic sensory neurons
innervate skin, muscle, tendons, ligaments, joints
transmit touch, pressure, pain, temp, position
visceral sensory neurons
mucous membranes, glands, blood vessels, organs
pain or pressure sensations
skeletal motor neurons
skeletal muscle
visceral motor neurons
smooth muscle, cardiac muscle or glands
neuroglial cells
physical and physiological support to neurons
types:
astrocytes
microglia
oligodendrocytes
astrocytes
largest glial cell
cover capillaries w/ vascular feet
assist in blood brain barrier w/ sealant deep to pia mater, scar tissue, monitor ECS
oligodendrocytes
myelinate axons in CNS in segments of 3
microglia
phagocytic, clean up debris in CNS
ependymal cells
line CNS cavities aka ventricles and central canal of spinal cord,
cover choroid plexus
simple cuboidal-columnar shape
unmyelinated axons
in CNS: not covered by glia
in PNS: occupy groove of Schwann cell
Schwann cells
myelinate axons in PNS
via membrane circles around axon until sheath is formed
nodes of ranvier
bare segments of axon b/t internodes
larger in CNS than PNS
PNS axon layers
indiv axon= myelin sheath > basal lamina> endoneurium
bundle of axons = perineurium
gross nerve = epineurium
gray matter
arrangement
cerebral cortex & cerebellar cortex: sheet of cell bodies + neuroglia
nuclei: collections/clusters of cell bodies + neuroglia in CNS
white matter
myelinated axons and neuroglia in CNS
contain tracts, fasiculi, commissure, funiculi
PNS
consists of
nerves (bundles of axons + neuroglia)
plexuses: (network of nerves)
ganglia: (collections of cell bodies + ganglia in PNS)
voluntary/somatic system
control skeletal muscle and movement
involuntary/autonomic system
divisions:
sympathetic
parasympathetic
enteric
sympathetic
thoracolumbar
flight/fight/fright
ganglia: sympathetic trunk/chain, visceral
parasympathetic
craniosacral
smooth and cardiac muscle, glands of head/thoracic/abdominal/pelvic viscera
maintain homestasis
ganglia: ciliary, pterygopalatine, submandibular, otic
enteric
peristalsis, gland secretions, blood flow thru GI tract
cells embedded w/i wall of GI
chemical synapses
have
presynaptic membrane, synaptic vesicles
presynaptic density (active site)>
synaptic cleft >
postsynaptic membrane w/ neurotransmitter receptors, postsynaptic density, ligand gated sodium channel
associated with neurotransmitters
choroid plexus
consists of
in folds of pia mater and brain vetricles
fenestrated capillaries aka leaky
covered by ependymal cells w/ ZO’s
choroid plexus
forms
makes CSF
transported from subarachnoid space to SSS via arachnoid villi>granulations
superior sagittal sinus
axoplasmic transport
anterograde: away from cell body via kinesin
OR
retrograde: toward cell body via dynein
anterograde systems
- slow transport: uses tubulin, actin, neurofilament proteins, enzymes
- fast transport: uses ATP, organelles, vesicles, neurotransmitters, calcium
retrograde transport system
fast only- uses ATP, SER, vesicles, mitochondria, amino acid sugards, nucleotides, neurotransmitters, Ca2+
viruses and toxins too
astrocytoma
fibrous
make up 80% primary brain tumors in adults
ependymoma
tumor growing into fourth ventricle
that compreses surrounding structures
5% of primary brain tumors
myelin
has lipoprotein
formed by concentric layers of cell membranes w/ high lipid content
inc impulse conduction and insulate neuron
synapse
definition
junction b/t
presynaptic AKA neuron
postsynaptic AKA another neuron, muscle cell, gland cell
types of synapses
axodendritic: most common, axon >dendrite
axosomatic: axon>soma
axoaxonic: axon>axon
electrical synapses
not common in mammals
impulse transmission is rapid
@cerebral cortex, brainstem, retina
fusion methods
vesicle and presynaptic membrane
kiss and run
collapse: empty entire contents
nerve regeneration
PNS-anterograde changes
-distal to injury
-axonal degradation and elimination of debris by phagocytic cells
-schwann cells proliferate w/ external lamina =empty guiding tubes/tunnels
nerve regeneration
PNS, retrograde changes
-proximal to injury
-chromatolysis: cell body hypertrophies/swells, nissl bodies disperse, nucleus moves periphery
-axon grows sprouts that are guided by schwann cells thru tube
-sprouts become endoneurium except first one to reach target cell = synapse
