Chapter 9 - Development of the Nervous System Flashcards
five phases of Neurodevelopment
(1) induction of the neural plate, (2) neural proliferation, (3) migration and aggregation, (4) axon growth and synapse formation, and (5) neuron death and synapse rearrangement
totipotent
the cell has the ability to develop into any class of cell in the body
pluripotent
cells have the ability to develop into many, but not all, classes of body cells
multipotent
Eventually, new cells can develop into different cells of only one class
unipotent
hey can develop into only one type of cell (e.g., bipolar neurons)
neural plate
small patch of ectodermal tissue on the dorsal surface of the vertebrate embryo, from which the neural groove, the neural tube, and ultimately, the mature nervous system develop
neural tube
the tube that is formed in the vertebrate embryo when the edges of the neural groove fuse and that develops into the central nervous system
ventricular zone
the region adjacent to the ventricle (the fluid-filled center of the tube)
migration
the movement of cells from their site of creation in the ventricular zone of the neural tube to their appropriate target location
> During this period of migration, the cells are still in an immature
form, lacking the processes (i.e., axons and dendrites) that characterize mature neurons
Radial migration
proceeds from the ventricular zone in a straight line outward toward the outer wall of the tube
tangential migration
occurs at a right angle to radial migration—that is, paral- lel to the tube’s walls
somal translocation
an extension grows from the developing cell in the direction of the migration; the extension seems to explore the immediate environment for attractive and repulsive cues as it grows. Then, the cell body itself moves into and along the extending process, and trailing processes are retracted
glia-mediated migration
one of two major modes of neural migration during development, by which immature neurons move away from the central canal along radial glia cells
radial glia cells
glia cells that exists in the neural tube during the period of neural migration and that from a network along which radial migration occurs; some radial cells are stem cells
neural crest
structure situated just dorsal to the neural tube, It is formed from cells that break off from the neural tube as it is being formed;
> Neural crest cells develop into the neurons and glial cells of the peripheral nervous system as well as many other cell types in the body and thus many of them must migrate over considerable distances
aggregation
Once developing neurons have migrated, they must align themselves with other developing neurons that have migrated to the same area to form the structures of the nervous system
cell-adhesion molecules (CAMs)
molecules on the surface of cells that have the ability to recognize specific molecules on the surface of the other cells and adhere to them
growth cone
amoebalike structure at the tip of each growing axon or dendrite that guides growth to the appropriate target
retinal ganglion cells
retinal neurons whose axons leave the eyeball and form the optic nerve
optic tectum
the main destination of retinal ganglion cells in non-mammalian vertebrates
chemoaffinity hypothesis
the hypothesis that growing axons are attracted to the correct targets by different chemicals released by the target sites
fasciculation
the tendency of developing axons to grow along the paths established by preceding axons
topographic gradient hypothesis
the hypothesis that axonal growth is guided by the relative position of the cell bodies in intersecting gradients, rather than by point-to-point coding of neural connections
synaptogenesis
the formation of new synapses
neurotrophins
chemicals that are supplied to developing neurons by their targets and that promote their survival
Nerve growth factor (NGF)
first neurotrophin to be isolated
Perseveration
the tendency to continue making a formerly correct response when it is currently incorrect
Permissive experiences
experiences that permit the information in genetic programs of brain development to be expressed and maintained
Instructive experiences
particular experiences that contribute to the information in genetic programs and influence the course of development
critical period
If it is absolutely essential (i.e., critical) for an experience to occur within a particular interval to influence development, the interval is called a critical period
sensitive period
If an experience has a great effect on develop- ment when it occurs during a particular interval but can still have weak effects outside the interval, the interval is called a sensitive period
Neurogenesis
the growth of new neurons
Pattern separation
refers to our ability to separate distinct percepts into individual memories for storage
Autism spectrum disorder (ASD)
a complex neurodevelopment disorder characterized by a reduced capacity for social interaction and communication and restricted and repetitive patterns of behavior, interests or activities
Savants
persons with developmental disabilities who nevertheless display amazing and specific cognitive or artistic abilities
Williams syndrome
a neurodevelopment disorder characterized by intellectual disability, accompanied by preserved language and social skills
orbitofrontal cortex
the inferior area of frontal cortex near the orbits, or eye sockets
superior temporal gyrus
the large gyrus of the temporal lobe adjacent to the lateral fissure; the location of the auditory cortex
