Week 2 Quiz Flashcards
Includes lecture 1 & 2 (22 cards)
what are the types of neurons and some examples of each?
multipolar: a single axon with many dendrites (ex. purkinje cells and granule cells in cerebellum, projection neurons, spinal cord motor neurons, and pyramidal neurons in the cortex)
bipolar: a single axon with dendrites on the end and a long dendrite/axon on the opposite side (ex. olfactory receptor neurons)
unipolar: a neuron with a single process that multiple axons can branch out from (ex. dorsal root ganglion cells)
white vs gray matter?
gray: outermost layer, contains interneurons, projection neurons, motor neurons, and endings of sensory fibers and fibers arriving from other parts of the CNS
white: inner layer, contains ascending and descending pathways
*in the spinal cord white matter lays on outside and gray matter is on the inside
what do Nissl stains label for?
nissl stain labels proteins, since the rough ER does protein synthesis then nissl bodies are labeled in the cell body and dendrites, nissl bodies are stacks of rough ER with clusters of free ribosomes
what organelles does the initial segment of the axon contain?
microtubules funnel into the axon from the hillock, the axon also contains mitochondria, clusters of ribosomes, and scattered bits of ER but no nissl bodies
how are microtubules organized?
axonal microtubules are arranged with plus ends directed away from the cell body and toward the axon’s terminal, while dendritic microtubules can be oriented in either direction, tubulin that forms the microtubules can only be added at plus ends
what are the mechanisms of fast and slow axonal transport?
fast: kinesin and dynein bind to membranous organelles (mitochondria and vesicles) which allows organelles to move down the microtubule towards its plus (kinesin) or minus end (dynein), since all the plus ends of axonal microtubules point in the same direction kinesin mediates anterograde (towards terminal) and dynein mediates retrograde (towards soma) transport
slow: slow transport is only anterograde (kinesin only)
what are the types of synaptic contact?
first part indicates the presynapse while second part indicates the postsynapse, these include axodendritic, axosomatic, dendrodendritic, and axoaxonic, the postsynaptic element can be another axon terminal or the initial segment of an axon
what are Schmidt-Lanterman incisures?
thin extensions of schwann cell cytoplasm that spiral around with the myelinating membranes
which glia are responsible for myelination?
schwann cells myelinate the PNS while oligodendrocytes myelinate the CNS, oligos can myelinate more than one axon at once
what are the glial cells of the CNS?
protoplasmic astroctes: their end-feet form a leaky membrane that covers the surface of the CNS, separating it from the PNS, other end-feet are in the gray matter against neurons or capillaries
fibrous astrocytes: interspersed among nerve fibers in the white matter
oligodendrocytes: myelinate neurons and even fibrous astrocytes
microglia: scavengers in response to injury
ependymal cells: line the ventricular cavities
what are the glial cells of the PNS?
schwann cells: myelinate peripheral nerve fibers
satellite cells: surround sensory neurons like dorsal root ganglia and autonomic ganglia
what is the structure of the neural plate?
the neural plate forms at about 18 days of development and contains the beginning of the neural groove, at 20 days the neural groove has deepened as the neural tube starts to close (diagram on L2S2)
how does primary neurulation take place?
once the neural tube has closed and the neural crest lies above it neural folds begin to fuse at the cervical level (middle), the fusion expands rapidly in both directions until the rostral end of the neural tube has closed and then the caudal end will also close, before the tube closes enlargements and bends that will eventually become the primary ventricles form (prosencephalon, mesencephalon, and rhombencephalon), the notochord helps form the vertebral column, on either side of the neural tube the mesoderm turns into somites that form most of the vertebral column and segmental structures like skeletal muscle and dermis corresponding to spinal cord segments (diagram on L2S3)
what are the migratory paths of neural crest cells?
neural crest cells break off of neural crest and form dorsal root ganglion, cells that travel towards the notochord become autonomic ganglia or adrenal medulla, cells that enter ectoderm form epidermal pigment cells (diagram on L2S5)
what signaling proteins appear where during development of the neural tube?
in the middle of the mesoderm, the notochord produces sonic hedgehog protein, ectoderm on lateral pieces of the neural plate that eventually become the neural crest produce bone morphogenetic proteins, at first SHH moves outward and BMP moves inward causing the neural tube to form, from there SHH moves upwards and BMP moves downwards causing the neural tube to close, this opposition continues even after the neural tube is closed (diagram on L2S6)
how are motor and sensory functions separated in the spinal cord?
the sulcus limitans separates the dorsal and ventral sides of the spinal cord, DRG that derive from the neural crest send their processes to terminate on alar plate cells that become the dorsal horn, basal plate cells become motor neurons in the ventral horn (diagram on L2S7)
what are the different sections of the neural tube during the 3 vesicle stage?
primary vesicles form during 4th week, the prosencephalon at the top, mesencephalon at the cephalic flexure below, the rhombencephalon at the bottom before the spinal cord starts below the cervical flexure (diagram on L2S8)
what are the different sections of the neural tube during the 5 vesicle stage?
secondary vesicles form during 6th week, telencephalon at the top, diencephalon below that, mesecephalon below that, then metencephalon (contains the pontine flexure), followed by myelencephalon at the bottom (diagram on L2S10)
how does the floor of the fourth ventricle form?
walls of neural tube are spread by the pontine flexure so that they and the sulcus limitans become the floor of the ventricle and the roof is a thin membrane, this means the sensory and motor areas become lateral-medial with motor neurons in the middle and sensory neurons on the sides (diagram on L2S11)
how does the cerebellum develop?
during the second month of development the lateral parts of the alar plate (sensory areas) in the metencephalon thicken to form rhombic lips, these lips continue to enlarge and form fissures, forming the cerebellum
what is myelomeningocele/spina bifida?
when the spinal cord does not fully fuse during neural tube development, this creates a pocket which contains the spinal rootlets
what are the effects of fetal alcohol syndrome, heterotopias, and lissencephaly?
FAS: in severe cases missing corpus callosum
heterotopias: one lateral ventral is enlarged and a thick layer of gray matter has formed in its wall or in the white matter as a result of neuron not properly migrating away during development
lissencephaly: cortical folding is absent, thought to be due to defective migration of neurons during the third and fourth month of development
