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16 Cards in this Set
- Front
- Back
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Compare the anatomical differences between the PNS and CNS |
--> CNS- brain and spinal cord *formed from neural tube (CNS glial cells- oligodendrocyte, astrocyte, microglia, ependymal cells) --> PNS- cranial, spinal, and peripheral nerves * formed from neural crest cells(these cells form lots of things, not just PNS) (PNS glial cells- Schwann cells, satelitte cells) |
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Differentiate between the different types of neurons |
1. Multipolar- multiple dendrites extending from soma (most common type) ex. motor neurons in anterior horn 2. Bipolar-single dendrites extending from soma (least common) ex. special senses; retina and ear 3. Pseudounipolar- dendrite and axon become fused into one big thing (still considered axon and dendrites) ex. sensory neurons in dorsal root ganglia ( aka posterior root ganglion) *** single axon common to all types |
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Describe the formation and function of myelin |
Schwann cells-(neurolemmocyte) -->Form myelin sheath that insulate axons in PNS --> Myelin= lipid rich membrane of Schwann cells *sheath wraps around axon --> Schwann cells only myelinates a single axon *single axon may have hundreds of schwann cells
*** Gaps between adjacent Schwann cells= nodes of ranvier (neurofibril node) |
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Differentiate between sensory and autonomic ganglia |
*Dorsal root ganglion-
Location of nucleus centrally located Type of neuron pseudounipolar Distribution of soma clustered together *Autonomic (Sympathetic and Parasympathetic)
Location of nucleus off center Type of neuron multipolar Distribution of soma dispersed |
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Compare the different connective tissue layers of PNS? |
Epineurium- outer capsule and tissue around all fascicles FXN: fibrous outer layer Perineureum- surrounding nerve fascicles FXN: layers of flattened cells with tight junctions blood-nerve barrrier; blood vessels run in this layer Endonerurium- surrounding nerve fibers FXN: in contact with abaxonal domain (outside part) of myelinated axon
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Describe the process involved with axonal regeneration in PNS |
1. During development develop of nervous system is plastic 2. In adult body this is not so a. Peripheral nerve can regenerate in adults THE CLOSER THE SITE OF INJURY TO THE CELL BODY THE LESS LIKELY REGENERTION WILL OCCUR AND THE MORE LIKELY THE CELL WILL GO THROUGH APOPTOSIS STEPS 1. Blood nerve barrier broken, allowing macrophages to proliferate and remove myelin a. Strutcures distal to site of injury removed( Wallerian degeneration) 2. Schwann cells dedifferentiate and form the endoneurial tube, which guides axonal growth a) mactophage and Schwann cells release factors that promote axon growth 3. Axon extends along the channel formed by schwann cells and hopefully reconnnects to deinnervated structure 4. Schwann cells redifferentiate and begin upregulating processes involved with myelin production
BANDS of Balgar???
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Basic cell of PNS and CNS is? |
neuron |
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Somatic refers to Autonomic refers to |
--> voluntary--innervates skeletal muscle and recieves sensory input --> involuntary-- innervates smooth muscle, cardiac muscle, and glands |
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ANS further subdivides into |
sympathetic and parasympathetic |
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Glial cells |
-supporting neurons - insulate cell bodies and processes -maintain internal envirnoment - repair injury |
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Myelination |
1. Axon sits on groove of surface of schwann cell 2. Cell surrounds axon and forms 3 distinct domains (mesaxon (comes in contact with two polarized ends) ,adaxon (inside), abaxonal (outside)) 3. Double layer mesaxon wraps around the axon forming multiple layers 4. Successive wrapping causes cytoplasm to be extruded and layers compact to myelin |
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Myelinated and unmyelinated axons |
* not all nerve fibers are myelinated - they can still be considered a schwann cell - thickness of myelin depends on axon size, not schwann cell - growth factors associated with myelin is regulated by the cell membrane of axon |
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Node of ranvier |
-neurofibril node *action potential jumps from node to node (saltutory conduction) --> voltage gated channels at nodes, whereas they exist down the entire length of an unmyelinated axonq
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Ganglion- |
cluster of cell bodies |
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Satellite cells |
-surround cell bodies in PNS ganglia -Function-general support cell that maintains internal envirnment of cell bodies |
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Compare and contrast the functional differences between CNS and PNS |
*Both CNS and PNS have somatic and autonomic components
*Regeneration possible in PNS because of breakdown of blood nerve barrrier
*CNS- glial scars form blocking regeneration Myelin contains inhibitors of axon regeneration, so removal of myelin by macrophage is vital to axonal repair -blood brain barrier maintained |
