Brain Development Flashcards
The cells of the nervous system connect with one another in trillions of remarkably specific patterns that form and ) ove rth ecourse of an organisms life
These connections develop among various types of neurons process that begins where
in the embryo
What is the first step
appropriate type sof neurons must arise in appropriate numbers and migrate to appropriate places
The axons and dendrites that form the connection then extend from _____ cells
nerve
What must happen to the growth of the axons
Must be guided over long distanes so that htey reach the appropriate targets. T
What happens to the connections that form initially then _ with the activity and experience of early posternal life
mature
The degree of complexity in the ______ and therefore the amount of interaction required to regulate its development
What is the brain to other organs in the body
much more complex
Are the initial steps in brain development similar accross the brain?>
They are similar, but later become different
What is an example of the brain development?
Diseases that are thought to be in the brain
Advances in teh study of bran development hve become increasingly relevent for what?
medical treatments
Three to four weeks after conception, one of the two cell layers of the empryo starts to do what?
Thicken up and build up along the middle,
As the cells continue to divide and this flat neural plate grows, parallel rides similar to the creases in a paper airplane rise across its
surface
When the top of the tube thickens …to makes haat?
three bulges that form the hind, mid and forebain
The emryo has three layers that undergo many interactions in order to grow in to what?
organ, bone, buscle, skin or neural tissue.
What do skin and neural tissue arise form
the ectoderm in response to signals provided ny the adjacent layer
A number of molecules interact to determine whether the ectoderm becomes what?
neural tissue or develops in another way to beomc skin
Studies of spinal cord development in forgs show that one major mechanism depends on specific proteins that inhibit
the activity of other proteins
IN an area where no inhibition occurs, what happens to the tissue?
It becomes skin
IN areas where proteins secreted form the esodern do lead inhibition, what happens to the tissue
It becomes neural
What does inhibit mean
to block a psycological process
Once the ectodermal tisssue has aquared its neural fate more signaling interactions determing what happen?>
What type of brain cell forms. The mature nervous system contains a vast array of cell types which can be divided into two main categories
What can the neurons in the nervous system be divided into?
They can be divided into two main categories: neurons responsible for signaling and for uspporting cells called glial cells
Researchers are finding that hte destiny of neural tissue depends on what
cell position withi the nervous system that define the environmental signals to which the cels are exposed.
What is a key factor in spinal cord development
a secreted protein called osnic hedgehog that is similar to a signaling protein found in flies W
When is the protein originally secreted?
From mesodermal tissue lying beneath the developing spinal cord, marks directly adjacent neural cells to become specialized class of lial cells
Cells that are further away athat are exposed become
motor neurons that control muscles.
A Combination of signals also determines the type of
chemical messages or neurotransmitters that a neuron will use to communicate with other cells.
Is the neurotransmitter fixed for nuerons?
Some it is fixed, but others it is a matter of choice
Neurons are initially produced along the central canal in the
neural tube
The neurons then migrate form their birthplace to a final destination wher?
in teh brain
How do the neurons form each of the various brain strucures and acquare specific ways of transmiting nerve messages?
They collect together to form various structures
What do the axons do?
They grow long distances to find and connect with apppropriate partner, forming elaborate and specific circuits.
How many neurons arethere
100 billion
As neurons are produced they move from where to where?
form the ventricular zone or inner surface to the near of the marginal zone or outter surface
After the neurons stop dividing, whatdo they form>
An intermediatezone where they gradually accumulate as the brain develps
The migration of neurons occurs in most of the structures of the brian but is prominent in the formation of
a large cerebral cotex in primates
How do the neurons form the cerebral cortex structure?
Neurons slither from the place of origin near the venricular surface, along non neuronal fibers that form a trail to their proper destination
What does proper neuron migration require?
Multiple mechanims, including the recognition of the proper path and the ability to move long distances
What does proper neuron migration require?
multiple mechanisms including the recognition of the proper path and the ability to move long distanes
One mechanism for long distance migration is the movement of nuerons
along elongated fibers that form transietn scaffoling in the fetal brain
What external forces can prevent proper neural nigration?
alcool, cocaine, or radiation can inhibit
Once the neurons reach thier final location, what must htey do?
make the proper connections for a particular function to occur-for example vision or hearing, They do this through axons
What is an axon’s growth directed by?
Cones
How do molecules help the cones?
Some lie down,and cue the cones that have to move
The bining of particular signals with receptors tell the growth cone whether to
move forward, stop recoil or change direction
What are some signaling molecuels?
netrin,semaphorin, and ephrin
What is the most remarkable findin about these proteins
They are common to many other animal
Once axons reach thier targets, what do they form?
synapses which permit electirc signals in the acon to jump to th enext cell where htey can either provoke or prevent the generation of a new signal
The regulation of these transmisison at synapses and the integration of inputs from the thousands of synapses each neuron recieves
are responsible for the astounding information -processing capcaity of th ebrain
For processin to occur properly, the connections must be
highly speciifc
Some specifity arises form the mechaniss that guide
guide each acons to its proper targe area
Additional molecules mediate target recognition which means
the axon chooses THE PROPER NEURON AND OFTEN THE RPOPER PART OF THE TARGET, ONCE IT ARRIVES AT ITS DESTINATION
What have researchers also had success in identifying?
The ways inwhich the synapse differntiates one conact have been made
The tiny porion of the axon that contacts the dendrite becomes s what
specialized for the release of the neurotransmitters and the tiny portion of the dendrite that recieves the contact becoms specialized to recieve nad respond to the signal
Special molecules pass between the sending and recieving cells to ensure that hte contact is formed properly and that the sending and recieve specializations are
precisely matched
These processes ensure that the synapse can transmit signlas quickly and effectvely. Finally, other moleculses coordinate the maturation of the synapse after it has formed so that it can occomodate the changes as our bodies mature
Many axons in the brain require a sheath of mylien to enhance what?
The speed of conduction
