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47 Cards in this Set
- Front
- Back
What are the 3 main categories of neurons?
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1) sensory (afferent) neurons
2) motor (efferent) neurons 3) interneurons (connect sensory and motor within CNS) |
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What are the 3 regions of a cell?
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1) cell body (soma)
2) dendrites 3) axons |
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What are the peripheral neuroglia?
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- Schwann cells
- Satellite cells |
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What do Schwann cells do?
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- surround axons, secretes myelin to insulate nerve
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What do Satellite cells do?
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- surround some of ganglia, no myelin, maintain environment
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What is the structural unit of the nervous system?
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The Neuron
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What are 2 properties of all neurons?
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1) irritability (receive stimulus)
2) conductivity (convey information as an impulse) |
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What are the 3 types of neurons according to their number of axons/dendrites?
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1) Unipolar
2) Bipolar 3) Multipolar |
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Unipolar Neurons
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- sensory
- part of process is the 'axon' part is the 'dendrite' - soma is near the CNS |
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Bipolar Neurons
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- 1 axon/1 dendrite
- Found in the retina II, olfactory mucosa I, and ganglion of the vestibulcochlear |
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Multipolar axons
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- motor neurons and interneurons
- 1 axon and many dendrites |
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What are microglia?
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- in the CNS
- macrophages - mononuclear phagocytic system and role in inflammation (lysosomes, inclusions, vessicles) - derived from mesenchyme |
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What are oligodendrocytes?
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- myelinate many axons in the CNS
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What is myelin from?
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- cytoplasm of Schwann cells or Oligodendrocytes
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What are myelinated areas of the axon called?
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- internodal segments
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What are unmyelinated areas of the axon called? (between myelinated areas)
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- nodes of Ranvier
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What are ganglia?
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- collection of nerve cell bodies in the PNS
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What are some properties of axons?
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- 1 per neuron
- branch at right angles - maintain consistent caliber - no RER/ribosomes - vessicles/mitochondria at synhapse - contain more neurofilaments than microtubules - can travel far - convey impulse away from soma |
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What are some properties of dendrites?
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- many per neuron
- branch at acute angles - caliber varies, large near soma - not myelinated - many organelles, but no Golgi - more microtubules than neurofilaments - close to soma - conveys impulse towards soma |
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What is the functional unit of the nervous system?
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- circuit of neurons
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What are the 3 connective tissues that surround peripheral nerves and ganglia?
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- endoneurium
- perineurium - epineurium |
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Endoneurium wraps around?
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- individual axons
- delicate collagen, few fibroblasts |
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Perineurium wraps around?
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- clusters of axons with endoneurium
- thick collagen, semipermeable layer |
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Epineurium wraps around?
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- clusters of perineurium
- dense connective tissue with vessels |
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Parts of a chemical synapse?
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- synaptic bulb (terminal button)
- synaptic cleft - post-synaptic membrane |
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What comprises the blood-brain barrier?
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- tight junctions (zona occludans) which prevent leaking into ECM
- end feet of protoplasmic and fibrous astrocytes also create barrier |
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What happens in PNS injury and regeneration?
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- macrophages remove all axons anterograde the injury
- schwann cells proliferate and create a column - axon produces sprouts - sprouts try to find schwann column - reaches effector organ **return of motor function more likely if NOT an interneuron |
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What occurs in chromatolysis?
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- nissle dissolution
- increase volume of the perikaryon (cytoplasm around nucleus) - nucleus moves to the periphery |
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Why does chromatolysis occur?
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- wounded nerve in the PNS, retrograde changes
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What are the central neuroglia?
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- microglia
- astrocytes - oligodendrocytes - ependyma cells |
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What are the 2 components of all nervous tissue?
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1) Neurons
2) support cells (neuroglia) |
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What are astrocytes?
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- CNS
- high number of projectiosn, cover vessel/neuronal process, contains bundles of intermediate filament, GFAP |
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What are the 2 types of astrocytes and where are they located?
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1) protoplasmic (grey matter)
2) fibrous (white matter) |
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Describe an electrical synapse
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-passage of ions between neurons for electron coupling
- no neurotransmitter release - not polarized, flows both ways - Smooth and cardiac muscles - gap junction (connexon and connexins) form channels |
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What is the ependyma?
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- CNS
- single layer of columnar cells that line ventricle and spinal canal - apical surface has microvilli and cilia - cells can be modified to produce CSF |
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What are peripheral nerves?
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- bundles of nerve fibers held together by connective tissue
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What are the 2 types of axonal transport systems?
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- Anterograde (cell body to terminal synapse)
- Retrograde (terminal synapse to cell body) |
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Describe anterograde axonal transport systems
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- kinesin, uses ATP
- 2 speeds 1) Fast: membrane organelles 2) Slow: growth |
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Describe retrograde axonal transport systems
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- dynein, uses ATP
- only fast |
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What are the 4 regions where schwann cell cytoplasm is extruded out of the schwann cell?
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1) outer collar cytoplasm
2) inner collar cytoplasm 3) Schmidt-Lanterman cleft (between schwann cell layers) 4) Perinodal cytoplasm (between schwann cell and node of ranvier) |
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Describe chemical synapses
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- conduction of impulses depends on the release of a chemical substance across the cleft
- other substances can interrupt/ block the neurotransmitter - polarized direction of impulse |
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Where are electrical synapses found?
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- smooth and cardiac muscle
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What intermediate filament does microglia contain?
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- vimentin
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What is the relationship between oligodendrocytes and multiple sclerosis?
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- oligodendrocytes mylinate many axons, when they are injured many axons are affected which is what occurs in multiple sclerosis
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What are 2 areas in the PNS where neurons regularly regrow?
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1) olfactory mucosea: bipolar neurons replaced monthly
2) autonomic ganglia: replaced 'as needed' |
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Why can PNS regenerate but not CNS?
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- injured axons have a difficult time regenerating sprouts that would be able to go through glial scarring
- lack paths/guid channels to get to the right spot - CNS myelin inhibits axon regeneration - if reconnections are incorrect, all of CNS is thrown off |
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What are factors that favor return of function
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- cut/crush injury
- limited loss of internodeal tissue - high neural sprouting - purely motor/sensory nerve - low scarring/blood loss - no infection - low axon damage |