Name some short-range (contact dependent) attractants for the growth cone.
In the hindbrain (rhombencephalon), ____ plays a role in defining the identity of each segment.
What is multiple/polyneuronal innervation?
each muscle fiber is initially innervated by several motor neurons
When do the caudal portions of the corticospinal tract become myelinated?
Synapse formation involves _____ to a _____.
conversion of the growth cone to a presynaptic terminal
What physical changes are seen in apoptosis?
- nuclear and cytoplasmic condensation
- DNA fragmentation
Name 2 ways the growth cone is guided.
- long range chemotaxis
- local subtle cues (contact dependent)
What are semaphorins?
long range (diffusible) repulsive molecules
Normally, during the first postnatal year, the density of cortical dendritic spines ____ as dendritic spines ____.
What is the difference btw an axon and a dendrite?
- axons= long, send signals to target neurons
- dendrites = shorter, stubbier, receive signals from input neurons
At birth, the density of neural connections is ____.
_____ serve as important regulators of neuronal survival, development, and function.
How does microcephaly occur?
not enough neurogenesis --> small brain
What are netrins?
long range (diffusible) attractant OR repulsive molecules
Growth cone guidance cues over long distances are _____.
What can disruption of axon outgrowth in development lead to?
What is selective synapse elimination?
reducing the excess of contacted cells from multiple motor neurons innervating one muscle fiber to a 1:1 relationship
The neural crest dorsal stream gives rise to the _____.
____ and _____ are components of the ECM that are involved in neural crest cell migration.
Laminin and fibronectin
What induces differentiation and formation of processes?
What do cadherins, CAMs, collagin, laminin, fibronectin, and proteoglycans all have in common?
they are short-range (contact dependent) attractants for the growth cone
In MS, there is ______ of the CNS axons.
Neutrophins interact with membrane receptors that are members of the tropomyosin-related kinase (Trk) family, including ____, ____, and _____.
TrkA, TrkB, and TrkC
Name some short-range (contact dependent) repellants for the growth cone.
Name 7 neurotrophic factors.
How are GABA receptors different en utero?
- receptors have many different subuints and isoforms
- eq potential for Cl- is lower
- Cl- levels are higher
- activation of GABA receptors is excitatory
What do neurotrophic factors do?
promote cell survival
What is the neurotrophic hypothesis?
there is a limited amount of nutrients and trophic factors provided by the synapse targets to establish proper neuronal connections
What do semaphoris, ephrins, and tenascin all have in common?
they are short-range (contact dependent) repellants for the growth cone
CNS neurons appear to need _____ for survival.
multiple neurotrophic factors
Even if axons can be induced to grow across a lesion, what will probably go wrong?
it's unlikely that they will make the same connections as before the injury
What is the growing tip of the axon called?
the growth cone
The neural crest ventral stream gives rise to the _____.
sensory, autonomic, and enteric ganglia
Synapse elimination is due to _____.
competition for the target (NOT death)
_____ are involved in outgrowth, adhesion, and fasciculation.
When does myelination begin?
during embryonic development in the periphery
These are long range (diffusible) attractant molecules.
Local growth cone guidance cues are ______ and require _____.
bound to cell membranes or ECM and require direct cell contact
______ are examples of short-range contact dependent signals.
_____ abnormalities are associated with Down's Syndrome.
Where is the first CNS location that is myelinated? When?
the spinal cord @ the end of the 1st trimester
____ is associated with abnormal social/emotional behaviors.
During the first prenatal year, the brains of ASD show ______, especially in white matter areas, and _____.
abnormally high increases in size; neuronal cell bodies are smaller and dendrites branch less
_____ inhibit apoptotic cell death programs.
These are long range (diffusible) repulsive molecules.