Neurons Flashcards
Ultrastructural characteristics of a neuron
abundant mitochondria, large centrally located euchromatic nucleus with prominent nucleolus, abundant RER (Nissl bodies)
What are the pigment granules of a neuron?
lipofusicin and melanin. lipofuscin may reflect wear and tear.
What are the dendritic sites of synaptic contacts?
dendritic spines
Where on the axon are APs generated?
initial segment
What kinds of axons have larger conduction velocities?
larger axons; myelinated axons
What ultrastructural characteristics are absent in axons?
no RER or ribosomes
What are two kinds of axon terminals?
at the end of the target: end boutons
if targets are adjacent to axons, the axon displays varicosities (aka boutons en passage)
What is anterograde transport? What mediates anterograde transport?
movement of things from the cell body out. can be fast or slow. slow is like diffusion; fast mediated by kinesins. ATP dependent.
What is retrograde transport? What mediates retrograde transport?
Dyneins mediate retrograde transport (related to cilia). moves things from the axon toward the cell body.
3 kinds of neurons
pseudounipolar, multipuola, bipolar
What is a pseudounipolar neuron? Where seen?
single process that bifurcates. example: sensory neurons as in DRG
What is a multipolar neuron? Where seen?
single axon and multiple dendrites. both sensory and motor; seen in brian, spinal cord, and peripheral autonomic nervous system
What is a bipolar neuron? Where seen?
2 processes that extend from opposite poles of the cell body. sensory. have been modified for olfaction, visual, vestibular, and auditory receptors
Describe interneurons
multipolar microneurons (golgi type II)
From where are macroglia derived?
neuroectoderm. can divide throughout life
From where are microglia derived?
mesoderm
From where are the support cells of the PNS derived?
neural crest
What are the major roles of astrocytes?
9 roles
guardians of the CNS extracellular space
potassium sink to absorb K ions released during AP firing
also participate in neurotransmitter metab, esp. of glutamate.
transport btw blood and brain
provide lactate to neurons for energery
isolate receptive surfaces to prevent haphazard flow of impulses
repair and scar formation in response to injury
framework for migration during devo
produce growth factors that help with neuro devo and survival
How do astrocytes participate in glutamate metabolism?
they take up glutamate, metabolize it to glutamine, which is shuttled back to neurons for converstion to glutamate
What are radial glia?
astrocytes that help provide a framework for migration during development
What are reactive astrocytes?
swollen/hypertrophied astrocytes that form in response to injury and help fill the space of injuty via proliferation. makes a glial scar.
What is the function of oligodendrocytes? Promiscuous or monogomous?
oligos are responsible for formation and maintenance of the myelin sheath. these are promiscuous
What are microglia?
from the mononuclear phagocyte system (neural crest). migrate to the CNS during devo. phagocytize cell depris. may secrete substances that are toxic to neurons.
What is the role of perivascular cells?
communication btw brain and body; help with fever production
What are ependymal cells?
line the ventricles of the brain and help move CSF in the ventricles. some help with CSF production; others help move substances btw the ventricles and the blood.
What is Wallerian degenderation?
changes to the stumps of damaged neurons and complete degeneration along the length of the detached neuron.
What is chromatolysis?
follows damage to the axon. cell body swells and becomes distended. nissl bodies undergo dissolution and the nucleus is displaced to the periphery of the cell. 12-14 days post injury
Why doesn’t regenration in the CNS work like in the PNS?
slower, inhibited by glial scarring, CNS white matter may repel axons, and there aren’t sheaths to guid regenerating axons.
