Lecture 36 Flashcards
How many neurons does the brain have and how many connections with other neurons does each of these neurons have?
10 to the 11
1000 connections
State and describe the phases of neural development
Phase 1: Different cell types develop independently at widely separate locations in an embryo according to their local programming (they are unconnected at this point)
Phase 2: axons and dendrites grow out along specific routes setting up a “provisional” but orderly network of connections (synapse formations) between various parts of the nervous system
Phase 3: connections are adjusted and refined through interactions with distant regions via electric signals (Continues to occur into adult life)
state the range of length that axons can occur in
1 mm to 1 m in length
neurons are produced in association with ____ cells. define this term.
glial
provide supporting framework and nutrition to neurons
Neurons develop from which layer of the gastrula? what about glial cells?
both develop from the ectoderm
Compare where the CNS and PNS are derived from.
The CNS is derived from the neural tube
The PNS is derived from the neural crest
Describe the formation of the neural tube, beginning with the single layered epithelium. (include the term that describes the inner portion of the neural tube)
a neural groove appears on the dorsal side of the embryo, and it’s deepening forms the neural folds
neural folds elevate and then “coalesce” in the middle line to form the neural tube
the neural canal is found within the neural tube
what signaling induction method controls differentiation into neurons?
delta notch
where does the cells of the neural crest originate? how to they reach their final position?
the dorsal end of the neural tube
they migrate during or shortly after the closure of the neural tube (neurulation)
The fate of the neural crest cells depends on what? state the 3 types of cells that are generated from neural crest cells.
where they migrate
neurons and glial cells of the PNS
epinephrine-producing cells of the adrenal gland
many of the skeletal and CT components of the head
Describe the distribution of the neurons in terms of the time they were “born” and their final distance migrated along the radial glial cell processes.
first born neurons settle closest to their site of formation (means they have a shorter migration distance compared to later born neurons)
what structure do neurons migrate along?
radial glial cell processes
What is a growth cone? what is it’s function? (include axon formation)
growth cone: spikey enlargement at the tip of an axon/dendrite
it crawls through surrounding tissue, allowing the axon/dendrite to trail behind it
a single growth cone starts migrating faster than all of the others and develops “axon-specific proteins” to form the axon
What are Rho and Rac? what is their function?
Rho and Rac are monomeric GTPases
they control the assembly/disassembly of actin filaments, which control the movement of growth cones
what structures do growth cones use to move?
they throw out filopodia and lamelopodia in order to move
how is the behavior of growth cones dictated?
by it’s cytoskeletal machinery