Neuro: Neurons, Glia, Histology Flashcards
Soma is the:
Cell body of the neuron
Soma is involved in:
-gene expression
-biosynthesis
-cell. Survival mechanisms
-responses to injury
-receives synaptic input
Dendrites:
-“fingers”
-receive synaptic input
-can be structurally altered by activity
Axons:
Send out action potential that initiates at the axon hillock
Terminals:
Where axons send their information to, and terminals release neurotransmitter into synapses
Terminal boutons
Site of release of synaptic vesicles and neurotransmitters into synaptic cleft
In the terminal bouton, neurotransmitter molecules are stored inside ______________
Synaptic vesicles
When an action potential reaches the terminal…
The vesicles fuse with the cell membrane, releasing the stored neurotransmitter into the synaptic cleft where it binds to receptor in cell mem. of postsynaptic neuron
Post-synaptic density:
Appearance of the synapse region by electron microscopy
In the resting state of pre-synaptic activation:
-few vesicles are already docked at active zone, not yet fused
-most vesicles tethered by actin and not docked
In the activated state of presynaptic activation:
-Ca2+ influx allows neurotransmitter release by pre-docked vesicles
-Ca2+ influx causes actin filaments to dis-associate from vesicles
Axon terminals can form synapses on what part of the neuron?
Any part!
Synapses can mediate either excitatory or inhibitory effects on the post-synaptic neuron. This depends on:
-nature of neurotransmitter
-nature of the receptor for that neurotransmitter
Synapses on dendritic spines are…
ALWAYS excitatory
At axoaxonic synapses, neurotransmission can excite or inhibit the…
Postsynaptic axon terminal s
Sensory/pseudo-unipolar neurons :
-Touch/pain receptors in skin/viscera and taste receptor cells
-Typically located in a ganglion
Motor neurons are located in:
Located in the anterior horn of the spinal cord and in cranial nerve motor nuclei in brainstem
Local interneuron
Usually very short, unmyelinated axons in PNS and CNS
Neuroendocrine neuron
-Mostly in hypothalamus
-release peptide hormone into blood (systemic or portal circulation
Antrograde axonal transport:
-from cell body to terminals
-synaptic vesicles
-neurotransmitters, synthetic enzymes
Retrograde axonal transport:
-from terminals to cell body
Kinesin is ____________ because it goes toward _____ end
Anterograde, plus end
Dynein is ______________ because it goes towards ______ end
Retrograde, minus
Clinical significance of axonal transport:
-pathophysiological role in neurodegenerative disorders
-role in viral infections of PNS
-potential tool for viral delivery of gene therapy
In PNS, _____________ form the myelin sheath
Schwann cells (glia)
Myelin sheath:
Electrical insulation that boosts speed of current down the axon
Along the length of the axon, the myelin sheath is normally…
Interrupted by small gaps exposing bare axon
Gaps in myelin sheath are called:
Nodes of ranvier
Adaptive purpose of nodes of ranvier
-allows electrical signal to renew intensity at each node of ranvier
White matter
Region dominated by myelinated axons that give a shiny white color
Grey matter
Region dominated by cell bodies and dendrites, few/no axons
Disorders that cause demyelination of axons:
-peripheral neuropathy
-multiple sclerosis
-vitamin B12 deficiency
-poor attempts of rehydrating someone too rapidly
Microglia
-small glia
-phagocytic cells that attack pathogens
-can alter blood-brain barrier to white blood cells to enter CNS and drive inflammatory response
Astrocytes function:
-star shaped cells
-form barrier inside pia material
-part of blood-brain barrier surrounding capillaries
-envelopes parts of neurons to control extracellular environment for normal neurons
Ependymal cells
Cells that form a single layer along the deepest part of the brain and spinal cord forming a border between CNS tissue and the ventricular spaces containing CSF
Pericyte
Envelopes endothelial cells and control substances moving across endothelial cell membranes
What can diffuse across blood brain barrier?
-lipids
-hydrophobic substances in blood
What has to be actively transported across blood brain barrier?
Water soluble substances (glucose, nucleotides, some AA)
Gliosis stages:
-growth of each astrocyte
-proliferation (mitosis)
-clustering of astrocytes at pathology site
-formation of barrier around damage
-isolates the pathological area
Role of Schwann cells in injury
Provide scaffolding and protection for regeneration of axon
Is there better regeneration to an axonal injury in CNS or PNS?
PNS
Steps after axonal injury in PNS:
-macrophage enters nerve and cleans up debris
-Schwann cells survive and help with axon regrowth
Steps after axonal injury in CNS:
-monocytes enter CNS and morph into Microglia to clean up debris
-Oligos often die creating scar tissue that inhibits axonal regrowth
