Nervous Tissue Flashcards
3 different types of cell bodies
angular, ovoid, and spherical
Cell body
contains nucleus and nucleolus, and most of cellular organelles. Is trophic metabolic center of cell
Multipolar Neuron
most common type of neuron. Has a euchromatic nucleus. Cells are always active, forming proteins
Nissl
stacks of rER indicating high amount of protein synthesis
Neurofilaments
are contractile.
Microtubules
contribute to structural integrity. Act like bones of the cell
Axon hillock
proximal end of axon. Looks like a funnel. Contains neurofilaments and microtubules. Doesn’t have rER, so it stains pale
What does a multipolar neuron look like
almost clear nucleus
dark, prominent nucleolus
scattered nissl bodies in cytoplasm
blue paint splatter appearance
Substantia nigra
contains neuomelanin
Anterograde transport
Uses kinesin. Flow away from cell body
Retrograde transport
Uses dynein. Flow towards cell body. Viruses and toxins can use this pathway
Bipolar neuron
simplest. Associated with special sense of vision, hearing, balance, and olfaction
Pseudo-unipolar neurons
Neurons located in sensory ganglia (like trigeminal ganglion) Axon synapses in brainstem or spinal cord
Multipolar neuron
Most prominent type of nerves
Motor nervous
can be skeletal, or visceral or interneurons.
Dorsal horn
sensory
Lateral horn
autonomic/sympathetic
ventral horn
motor
Neuroglia
provide physical and physiological support. Packing material between neuron cell bodies
Astrocytes
have astrocytic feet that cover the surface of capillaries in the brain and spinal cord that have basal lamina on them
microglia
derived from monocytes. Acts as vacuum cleaner of CNS
Oligodendrocyte
forms myelin
Astrocytoma
make up about 80% of adult brain tumors
Ependymal cells
type of glial cell that line ventricles and central canal of spinal cord and choroid plexus
Ependymoma
tumor growing into the fourth ventricle. Compresses surrounding structures as it expands. Only 5% of primary brain tumors
Can nerves divide/form tumors
no! but glial cells can
Myelination in CNS is done by
oligodendrocytes
Myelination in PNS is done by
Schwann Cells
Myelin
- lipprotein
- has high lipid content
- increases impulse conduction
- insultaes neurons
Myelination by Schwann cells
-Axons occupy groove on Schwann cell
-Cell starts to form jelly roll layers of membrane around axon.
Think of squeezing toothpaste out of the tube and wrapping the tube around a pencil
Clefts of Schmidt-Lanterman
pockets of cytoplasm trapped between two cell membranes within the myelin sheath
Endoneurium
delicate layer of loose connective tissue with collagen that surrounds axons
Perineurium
surrounds bundle of axons
Epinerium
dense collagenous connective tissue sleeve that surrounds nerve. Contains blood and lymph vessels
Multiple Sclerosis
an autoimmune disease that is caused by oligoendrogliopathy
CNS
brain and spinal cord
PNS
nerves, plexuses, ganglion
Gray matter
made up off cerebral cortex and nuclei
White matter
lighter areas. Made of mylinated axons
Where are cell bodies in PNS located
in the ganglia
Where are cell bodies in the CNS located
nerves
Voluntary nervous system
control voluntary movement
Involuntary nervous system
autonomic nervous system (sympathetic and parasympathetic)
Enteric division of autonomic nervous system
Controls peristalisis, gland secretions, blood flow through the GI
Sympathetic
thoracolumbar outflow
Parasympathetic
craniosacral outflow
Synapse
connection for communication between neuron and something else
Axosomatic synapse
junction between axon terminal and membrane of cell body of nerve cell
Axodendritic synapse
(most common). Junction between axon terminal and dendrite of another nerve cell
Axoaxonic
junction between axon terminal and another axon
Eletrical synpases
not common in mamals
in cerebral cortex, brainstem, and retina
have gap junctions that allow electrical current to flow from one cell to another
very rapid impulse transmission
Chemical synapses
most common type. Associated with neurotransmitter
Where are neurotransmitters synthesized
mostly in neuron cell body, but some are in axon terminal
Steps of impulse propagation
1) go down axon and sweep over membrane, changing membrane permeability
2) Ca++ ions pass into presynaptic terminal through voltage-gated channels
3) Ca++ causes synaptic vesicles to attach to inner surface of membrane and release neurotransmitters into synaptic cleft
4) Neurotransmitters diffuse across cleft and bind to receptors on postsynaptic membrane
5) Postsynaptic membrane is depolarized and nerve impulse is propagated down that neuron
Kiss and run fusion
Vesicles briefly attach to membrane of presynaptic neuron, release part of contents into synaptic cleft, then move backwards into neuron and attach to nearby docking station
Collapse fusion
vesicles attach to membrane, completely empty contents into synaptic cleft, vesicle membrane becomes part of presynaptic membrane, then vesicle membrane is pinched off neuron membrane back into cell
Circulation of cerebrospinal fluid
- Made in choroid plexus
- Flows from 2 lateral ventricles
- 3rd ventricle
- Cerebral aqueduct of Sylvius
- 4th ventral
- Central canal of spinal cord
Anterograde changes to neuron
- Distal segment of axon degenerates
- Elimination of debris by phagocytic cells
- Schwann Cells proliferate, form Schwann cell tubes along with their external lamina
Retrograde reaction and regeneration
- Cell body swells, Chromatolysis occurs
- Protein synthesis occurs
- Axon grows sprouts, Schwann cells guide axon growth toward target cell, growing axon grows into endoneurium
