Development of the Brain

Question 1

CNS development

Answer 1

begins at 2 weeks old

Question 2

Proliferation

Answer 2

production of new cells

they then begin to migrate

nearly all neurons are formed within first 28 weeks of gestation

generally neurons do not form new in adults

Question 3

stem cells

Answer 3

these remain on the ventricles of the brain and continue to divide

Question 4

migration

Answer 4

primitive cells, not yet identifi- able as neurons or glia, begin to migrate

majority of cells migrate before birth but some continue

Question 5

immunoglobulins and chemokines

Answer 5

guide neuron mi- gration. A deficit in these chemicals leads to impaired migration, decreased brain size, and mental retardation

Question 6

differentiation

Answer 6

where cells start to form into what they will be;

this is when dendrites, axon, synapses form

Question 7

Synaptogenesis

Answer 7

formation of synapses

begins long before birth and continues throughout life

Question 8

mylenation

Answer 8

this happens later and more slowly

first in the spinal cord and then in the hindbrain, midbrain, and forebrain

Question 9

Paul Weiss

Answer 9

discovered Chemical Pathfinding by Axons by grafting an extra leg oto salamanders

Question 10

Chemical Pathfinding by Axons - Chemical Gradients

Answer 10

growing axon follows a path of cell surface molecules, at- tracted by certain chemicals and repelled by others, in a process that steers the axon in the correct direction

follow a gradient of chemicals

Question 11

Roger Sperry

Answer 11

showed how sensory axons find their way to their correct targets with optic nerves of newts

Question 12

Competition among Axons as a General Principle

Answer 12

thalamic neurons receive messages from neurons in many different places that are led towards it by checmical gradients

it rejects and accepts synapses from different locations

Question 13

neural Darwinism

Answer 13

we start with more neurons and synapses than we can keep, and then a selection process keeps some of the synapses and rejects others. The most successful combinations survive, and the others fail

Question 14

Rita Levi-Montalcini

Answer 14

one hypothesis was that the muscles sent chemical messages to tell the sympathetic ganglion how many neurons to form

eventually discovered that the muscles do not determine how many axons form; they determine how many survive.

Question 15

nerve growth factor (NGF)

Answer 15

the brain is born with more neurons than is neeeded

when one of its neurons forms a synapse onto a muscle, that muscle delivers a protein called nerve growth factor (NGF) that promotes the survival and growth of the axon

it is a neurotrophin

if an axon does not receive NGF, it degenerates

Question 16

apoptosis

Answer 16

programmed mechanism of cell death

If its axon does not make contact with an appropriate postsynaptic cell by a certain age, the neuron kills itself

Question 17

neurotrophin

Answer 17

a chemi- cal that promotes the survival and activity of neurons

Question 18

fetal alcohol syndrome

Answer 18

a condition marked by hyperactivity, impulsiveness, difficulty maintaining atten- tion, varying degrees of mental retardation, motor problems, heart defects, and facial abnormalities

caused by drinking during pregnancy

Alcohol inhibits receptors for glutamate, the brain’s main excitatory transmitter, and en- hances receptors for GABA, the main inhibitory transmitter. this causes neurons to stop receiving excitation

when washing away alcohol, Overstimulation at glutamate synapses can poison the mitochondria.

Question 19

ferret experiments

Answer 19

damaged ferrets brain on one side in SC and occipital lobe; instead, optic nerves attached to the auditory area of the thalamus, developing some features of visual ability

Question 20

enriched environment rat

Answer 20

developed a thicker cortex, more dendritic branching, and improved learning

wild-caught rats had more neurons in the visual areas of the brain and fewer in the auditory areas

often due to physical activity

Question 21

far transfer

Answer 21

to teach something challenging and hope students get smarter in other ways

Question 22

musical training

Answer 22

temporal cortex in the right hemisphere was about 30 percent larger in the musicians

brain changes help musicians attend to slight changes in sounds that other people might not distinguish

Question 23

focal hand dystonia

Answer 23

Moving one finger without mov- ing another becomes more difficult

Question 24

closed head injury

Answer 24

a sharp blow to the head that does not puncture the brain

Question 25

stroke, cerebrovascular accident

Answer 25

temporary interruption of normal blood flow to a brain area

Question 26

hemorrhage

Answer 26

ruptured artery

Question 27

ischemia

Answer 27

type of stroke that is the result of a blood clot or other obstruction in an ar- tery.

Question 28

edema

Answer 28

(the accumulation of fluid), which increases pressure on the brain and the probability of additional strokes

Question 29

tissue plasminogen activator (tPA)

Answer 29

breaks up blood clots

Question 30

Diaschisis

Answer 30

the decreased activity of surviv- ing neurons after damage to other neurons

Question 31

denervation supersensitivity or receptor supersen- sitivity

Answer 31

if a certain set of synapses becomes inactive—perhaps because of damage elsewhere in the brain—the remaining synapses become more responsive, more easily stimulated

helps compensate for de- creased input

can be beneficial or harmful

Question 32

collateral sprouts

Answer 32

After a cell loses input from an axon, it secretes neurotrophins that induce other axons to form new branches, or collateral sprouts, that take over the vacant synapses

new synapses form at a high rate, especially for the first two weeks

contributes to behav- ioral recovery in some cases

Question 33

phantom limb

Answer 33

a continuing sensa- tion of an amputated body part

develop when the relevant portion of the somatosensory cortex reorganizes and be- comes responsive to alternative inputs

Question 34

deafferented

Answer 34

it has lost its afferent (sensory) input

A monkey with a deafferented limb does not spontaneously use it for walking, picking up objects, or any other voluntary behaviors

but if both are deafferented then it will use them both normally

Question 35

Brain-derived neurotrophic factor (BDNF)

Answer 35

another neurotrophin that promotes survival and activity of neurons

plays a crucial role in reinforcing plastic changes during critical periods

On performing an activity, neurons fire together, BDNF is released to consolidate the connections between the neurons, and promote growth of myelin sheaths

BDNF turns on nucleus basalis, which promote attention focusing and remembering the experiences, hence “effortless learning”

Question 36

New neuronal cells

Answer 36

hippocampus and basal ganglia

Question 37

innervate

Answer 37

supply (an organ or other body part) with nerves