Nervous Tissue Flashcards
(34 cards)
how many neurons in the body? how many glia?
100 billion. 10x as many glial
what do neural crest cells develop into?
schwann cells, sensory nerves, postganglionic nerves
what does the neural tube develop into?
brain, spinal cord, cranial and spinal nerves, preganglionic nerves
what are some of the prominent characteristics of neuron cell bodies?
- prominent nucleolus 2. large amounts of rER and polyribosomes 3. prominent golgi 4. many mitochondria
what is Nissl substance?
rER and polyribosomes- stains extremely basophilic (blue) d/t nucleic acids
what determines the polarity of a neuron
dendrites
what is axon collateralization
axon branching
what is terminal arborization
ends with many synpases
do axons produce proteins?
no
what are the intermediate filaments of neurons
neurofilaments
describe axonal transport
axons have many microtubules. kinesin moves things towards the synapse with anterograde transport. dynein moves things towards the cell body via retrograde transport
saltatory conduction
travels via nodes of Ranvier, skipping myelinated portions of the axon
describe what happens in the presynaptic terminal following an AP?
depolarization leads to the release of Ca. Ca releases presynaptic vesicles w/ neurotransmitters. Neurotransmitters get released into the synaptic cleft
what are the 3 types of synapses?
axosomatic- body; axodendritic- dendrite; axoaxonic
what are the 2 types of postsynaptic receptors and what do they do?
ionotropic- ion channels that directly influence the postsynaptic membrane potential. metabotropic- activate second messenger system.
how are temporal effects of metabotropic and ionotropic receptors different?
metabotropic are slower but longer lasting and broader effects
name 3 mechanisms for synaptic cleft clearance
- enzymatic breakdown 2. diffusion 3. reuptake
where do you find 1. bipolar neurons 2. pseudounipolar 3. multipolar
- rare in adults, special senses 2. afferent PNS 3. motor neurons and interneurons
what are the differences between oligodendrocytes and schwann cells
oligodendrocytes myelinate the CNS but do so remotely and associate with many axons but do not myelinate the entire axon. schwann cells themselves form the myelin in the PNS and thus their nuclei are visible.
how do schwann cells decide whether to myelinate a neuron or not?
there are proteins on the outside of the axon and on the outside of the schwann cell that mediate their connectoin
why do the interior membranes of a schwann cell appear dark?
d/t increased protein concentration of the membranes
can cells in the PNS regenerate?
yes, 1 to 2 mm per day
what determines the speed of conduction in axons?
size and myelin thickness
describe the anatomy of a nerve
epineurium surrounds the whole thing, perineurium separates fasicles, fasicles are bundles of axons, axons separated by endoneurium
