Neuro Lecture B1 Flashcards
CNS
- Brain
2. Spinal Cord
PNS
- Peripheral Nerves, all cranial nerves, except CN II
2. Neurons in ganglia outside of brain and spinal cord
Neurite
An axon or dendrite
Perikaryon
Cell body or soma
Afferent Neuron
Neuron with an axon carrying impulses inward to the CNS
Efferent Neuron
Neuron with an axon carrying impulses outwards from the CNS
Synapse
specialized junction where neuron has functional contact with another cell
Presynaptic Neuron
A neuron that releases transmitter at a synapse with another neuron
Postsynaptic Neuron
A neuron that receives transmitter at a synapse
Membrane Potential
The difference in electrical potential recorded across the cell membrane.
What the two major cell types in the CNS and PNS?
Neurons and Glia
At a very basic level, what are the two major structural components of a neuron?
Membrane and cell body
Is the membrane of a neuron permeable?
semi permeable that is embedded with protein complexes
what does the cell body of a neuron house?
the nucleus and many other organelles
what extends from the cell body of a neuron?
Neurites (axons and denrites)
explain the basic role of a dendrite and axon that extend off the neuron
denrites —> listen for signals from other cells
signals from dendrites pass on to the cell body of the neuron then influences the
axon —–> which send their signals to other neurons
Nucleus (organelle) of a Neuron
porous double layered membrane encapsulates the chromatin-rich machinery for synthesis of RNA
Nissl Substance (organelle) of Neuron
consists of RNA granules which is responsible for creation of proteins so the neuron will work properly
Mitochondria (organelle) of Neuron
Involved in generation of ENERGY (ATP)
Golgi Apparatus (organelle) of Neuron
Aggregated vesicles that package and allow controlled modification and transport of products of the Nissl substance.
Lysosomes (organelle) of Neuron
Scavenger Vesicles loaded with decretory enzymes (basically they are the trash disposals of the neuron)
What is the importance of cytoskeletal filaments for a neuron?
- Maintain the shape of a mature cell
2. Important in transporting materials within the cells
Microtubules function in a neuron
- Transport tracks for two axonal transport system that move materials in opposite directions between the somata and the axonal endings.
(side note they are stabilized by Tau Proteins)
Kinesin is a fast ATP dependent process, describe its mechanism of action
Anterograde transport from the soma toward the + end of the microtubules.
Binding sites allow attachment of large structures (vesicles or mitochondria)
When Kinesin becomes inactivated in the nerve ending what happens?
returns to the soma by retrograde axonal transport
Dynein is also an ATP dependent process, describe its mechanism of action
Retrograde transport from nerve ending toward the negative end of the microtubule.
How does dynein become reactivated?
becomes inactivated in the soma an d returns to the nerve ending for reactivation
what trophic molecule, released by cells, is taken up by endocytosis in the axonal terminals and transported to the soma to promote growth in developing or regenerating axons?
Nerve Growth Factor
what are the most common filaments in neurons and astroglia ( but absent from oligodendrocytes)
Neurofilaments/ intermediate filaments
How are neurofilaments different from microtubules and microfilaments?
They undergo very little turnover
what role do neurofilaments play in neurons?
Axonal diameter
what role do microfilaments play in neurons?
form a network just beneath the cell membrane, through the use of actin (helps hold the shape of the cell)
participate in advancement of the growth cone during neuronal growth or repair after injury.
Describe the specific orientation of microtubules in axons?
positive ends situated distally
Describe the specific orientation of microtubles in dendrites
Mixed Orientation. Half having positive ends near soma and the other half oppositely directed. (therefore this allows some materials to move toward dendrites instead of down axons)
Multipolar neurons
- Multiple Dendrites attached to soma
2. Central or Peripheral special sensory function
Golgi Type I and Golgi Type II
- Multipolar Neurons with long axons= type I
2. Multipolar Neurons with short axons= type II
Bipolar Neurons
- Elongated Cell Body and 2 processes
- 1 process=forms axonal structures
- 2 process= conveys information from the dendrites to the soma
- Linked to CN VIII (found in the retina)
Pseudo-Unipolar Neurons
2 processes:
*1. carries information to the soma from the periphery
* 2. Other away from the soma toward and into the CNS
Remember example in class he gave about the hot stove! THERMAL ENERGY —> INFO ABOUT ENERGY –> INFO TO CNS then further communication
There are three different Neuron types, efferent/afferent and interneuron, most neurons work in which type?
Interneuron (Example: lots of enteric nervous system in the GI tract)
what two factors does the speed of axons depend on?
diameter (The bigger the better) and electrical insulation (myelinated fibers are faster)
Neurons can be grouped according to axonal diameters, which correlate with conduction velocity, which neuron fibers considered class IV fibers
Class IV fibers, in addition to being the smallest, are unmyelinated also considered class C
Transmitter released by excitatory neurons tend to depolarize or polarize membranes?
depolarize membranes of other neurons
CNS, type of Glia: Astrocytes
- Most numerous cell type within the CNS
- Maintains ionic homeostasis
- Maintains synaptic homeostasis
- Regulates cerebral blood flow
- Protects neurons from oxidative damage
- Supplies lactate to glucose-deprived neurons
- Direct differentiation of neuronal precursors
- Release cholesterol (increase # of synapses)
- Release Gliotransmitters (glutamate, ATP)
- Blood brain barrier protection
- Formation of gliotic scars (after injury)
Explain the Astrocyte Ca++ current system
creates a calcium wave or current and this is important between neuronal activity and blood supply
Explain spatial buffering or potassium siphoning
Neuronal activity elevates K+ however large extracellular amounts of K+ can disturb intercellular signaling by depolarizing neurons.
Astrocytic K+ ion channels take up the excessive ions for shunting to neighboring astrocytes via gap junctions.
Radial glia become what in the cerebellum? And what in the retina?
Cerebellum: Bergman Glia
Retina: Muller Cells
CNS; type of glia: Microglia
- Immunocompetent and phagocytic
- Protect neurons from micro-organisms and toxic effects of cellular debris
- Secrete neurotrophic or neuron survival factors upon activation
- Contributes to initiation of pathological neuron degeneration
- Releases Cytotoxic molecules
CNS; type of glia: Oligodendrocytes
- Myelinate central axons
2. Many demyelinating neuro disorders are due to oligodendrite degeneration
CNS; type of glia; Ependymal Cells
- Form the walls of ventricles
- Produce neurons and glial cells after stroke
- Contribute some to glial scars (with astrocytes)
- Shield the brain from CSF (with astrocytes)
CNS; type of glia; Choroid Plexus Epithelial Cells
secrete CSF
CNS; type of glia; Tanycytes
derived from radial glia
interface between blood and CSF
PNS; type of glia; Schwann Cells
Myelinate peripheral axons
immature schwan cells arise from what?
precursors of neural crest cells
PNS; type of glia; Enteric Glial Cells
plentiful neurons of the enteric nervous system
PNS; type of glia; Satellite Glial Cells
Surround neurons in sensory, sympathetic and parasympathetic ganglia, regulating the chemical environment
describe the processor regeneration of axons in the PNS by schwann cells
- Proliferate, forming a guide tube
- Release nerve growth factors, encouraging axonal regeneration
- Re-myelinate the regenerating axon (rate of 2mm/day)
- Target cells may die unless reinnervated within denervated cells may die after 3 weeks
Chromatolysis
reflects post traumatic neuronal swelling and dilution of organelles
Anterograde degeneration
reflects the transynaptic death of the denervated (postsynaptic) cell
Retrograde degeneration
reflects the death of the presynaptic cell
why is there no regeneration of CNS axons?
central glial cells do not secrete significant amounts of nerve growth factor.
oligodendrites do not form guide tubes
gliotic scars block axonal growth
Virtually all PNS tumors are???
Schwannomas
50% of brain tumors are of what origin?
Glial origin
Guillain-Barre Syndrome or Multiple Sclerosis
loss of myelin
