Histology Of The Nervous System Flashcards
Multipolar neurons
Single axons w/ two or more dendrites
Most common type of neurons on the body
- all motor neurons of CNS/PNS
- all CNS interneurons
Pseudounipolar
Single axon that bifurcates
- peripheral process goes to targets
- central process goes to CNS
No dendrites
Makes up most of the primary sensory neurons in the spinal ganglion
Unipolar neurons
Single axon that doesnt bifurcate
No dendrites
Specific cells only (cerebellum and dorsal cochlear nucli/nerves)
Bipolar nerouns
Single axon
Single dendrite
Special primary sensory neurons
- retina
- olfactory
- vestibular
Anaxonic
No axon
Multiple dendrites
Don’t produce action potential and instead helps regulate electrical activity in other neurons
- common most in retina
Parts of the cerebellum from superficial to deep
1) molecular layer
- contains stellate and basket neurons
- contains parallel fibers and Purkinje dendrites
2) Purkinje cell layer
- Purkinje cell bodies locations
3) granular layer
- golgi and granule neurons
- mossy fibers synapse
- contains primarily granular cells
4) sub cortical white matter
- deep cerebellar nuclei
- purkinjie cell axons
- mossy and climbing fibers
- note: 1-3 are found in the Cortex of the cerebellum*
Pyramidal neurons
Present in all layers of the cerebral cortex except layer 1
- most common in 2/3/5
Histologically contains
- pyramid-shaped cell body
- single apical dendrite that goes upward
- multiple basal dendrites that go laterally
- single axon that descends and exits the cortex (efferent fiber)
Different axon fibers found in the cerebral cortex
Association fibers
- travel to and terminate in the cortex of the ipsilateral cerebral hemisphere
Callosal fibers
- decussate in the corpus callosum and terminate in the contralateral cerebral hemisphere
Projection fibers
- descend to sub cortical targets in the forebrain/brainstem/cerebellum and spinal cord.
are virtually the only output of the cerebral cortex
Cell types in the PNS and its histologically shapes
Schwann cells
- possess larger nuclei
- Are large oval shaped cells and nuceli
- make up the myelin sheath
- are surrounded by myelin
Fibroblasts
- possess smaller nuceli
- generate CT of the endoneurium
- are surrounded by myelin
- are small spindle shaped cells and nuclei
Differences between epineurium perineurium and endoneurium
Epineurium
- outer most layer of a a nerve and its Connective tissue
Perineurium
- underlies the epineurium and houses the nerve fascicle
Endoneurium
- innermost layer that surrounds each individual nerve fiber
- is always myelinated
Why is the external capsule of a nerve ganglion more vascularized than a nerve?
Requires more metabolic demand due to having to synthesize most of the cellular components (nerves dont need to do this)
What is the soma or perikaryon?
Individual Neuronal cell body
What are satellite cells?
Small cells that surround cellular bodies
Function to:
- support cells
- provide protection and insulation
- transfer metabolites
- modify ECM
Derived from neural crest cells
How is lipofuscin distinguished in histologically slides?
It is brown-ish in color
It is a build up of enzymatically digested materials that are unable to be removed from the cells
What kind of general neurons are found in the anterior horn of the gray matter in the spinal cord?
Somatic efferent neurons That are multipolar
What kind of general neurons are found in the lateral horn (IML) of the gray matter in the spinal cord?
Visceral efferent neurons and presynaptic sympathetic neurons
Multipolar neurons are most common
What kind of general neurons are found in the posterior (dorsal) horn of the gray matter in the spinal cord?
Somatic and visceral afferent neurons and secondary sensory neurons
Neurons are multipolar
What type of cells line the lumen of the central canal of the spinal cord?
Ependymal cells
note these aren’t epithelium cells since they got no basement membrane to anchor cells to
What is the most common type of glial cell isn’t he gray matter of the CNS?
Astrocytes
Parkinson’s disease
A slowly progressing disorder that caused by a gradual loss of dopamine-producing neurons within the substantia Nigra
Treated with L-dopa injections which are precursors to dopamine
Local anesthetics
Low molecular weight molecules that bind to voltage-gated sodium channels of the axolemma
They interfere with sodium influxes and inhibit action potentials responsible for nerve impulses
Selective serotonin reuptake inhibitors (SSRIs)
A class of drugs that help treat depression and anxiety disorders.
They inhibit reuptake of serotonin at the presynaptic membrane which increases levels of serotonin postsynaptically
Astrocytoma
Tumors Derived from fibrous astrocytes
Distinguished pathologically by overexpression of GFAP
Alzheimer’s disease
Abnormal build up of neuorfibrillary tangles (accumulations of tau proteins) and neurotic plaques (dense aggregates of B-amyloid proteins)
These build ups affect the synapses and neuronal perikarya in the cerebrum overtime
Multiple sclerosis
Autoimmune disorder where the immune system attacked the myelin sheaths around affected neurons and produces various neurological problems
- specifically T lymphocytes and microglia
This slows conduction down of these neurons and causes multiple neurologic defects.
