Chapter 4: Brain Development, Damage & Neuroplasticity

Question 1

what factors does brain development depend on

Answer 1

1. Maturation
2. learning

Question 2

the human nervous system starts developing during

Answer 2

it forms when the embryo is approximately 2 weeks old
the dorsal surface thickness and different parts like the midbrain, forebrain, and hindbrain start forming

Question 3

Cerebrospinal fluid

Answer 3

It is a fluid that exists in the central canal of the spinal fluid and the ventricles of the brain provide nourishment and removes waste

Question 4

Brain weight

Answer 4

just born: 350g
1 year: 1000g
adult human brain weight: 1200 to 1400g

Question 5

process of the development of neurons

Answer 5

1. proliferation
2. migration
3. differentiation
4. myelination
5. synaptogenesis

Question 6

Proliferation: development of neurons

Answer 6

is the production of new cells\ neurons in the brain in the early stages of life
after the production, some cells become stem cells that continue to divide and others remain where they are or become neurons or glia that migrate to other locations.

Question 7

Migration: development of neurons

Answer 7

the movement of newly formed neurons and glia to their eventual location some don’t reach their location until adulthood chemicals like immunoglobulin and chemokines guide neuron migration

Question 8

Differentiation: development of neurons

Answer 8

is the forming of axons and dendrites that give the neuron its distinctive shape the axon forms during the migration or when it reaches its destination and it is followed by the development of dendrites

Question 9

Myelination: development of neurons

Answer 9

the process where glia produce the fatty sheet that covers the axons of some neurons

myeline protects the neuron and speeds up the transmission of impulses myelination first occurs in the spinal cord and then the hindbrain and then the midbrain and then the forebrain it occurs gradually

Question 10

Synaptogenesis: development of the neuron

Answer 10

The final stage of neural development –
the formation of the synapses between
neurons
– Occurs throughout life as neurons are
constantly forming new connections and
discarding old ones
– Slows significantly later in the lifetime

Question 11

what is life span of new neurons

Answer 11

it was believed in the past that no new neurons were formed after the early stages but later research showed otherwise

Question 12

Stem cells

Answer 12

Stem cells: undifferentiated cells found in the interior of the brain that generates “daughter cells” that can transform into glia or neurons

Question 13

how often do olfactory receptors replace dying ones

Answer 13

New olfactory receptors also continually replace dying ones

Question 14

where does the development of neurons occur in brain regions

Answer 14

Development of new neurons also occurs in other brain regions
Example: songbirds have a steady replacement of new neurons in the singing area of the brain
* Stem cells differentiate into new neurons in the adult hippocampus of mammals and facilitate learning

Question 15

Life Span of Neurons: skin cells

Answer 15

Different cells have a different average life
spans
* Skin cells are the newest; most are under
a year old

Question 16

Life Span of Neurons: Heart cells

Answer 16

• Heart cells, on the other hand, tend to be
  as old as the person

Question 17

Life Span of Neurons: mammalian cerebral cortex

Answer 17

• Mammalian cerebral cortexes form few or
  no new neurons after birth

Question 18

What is Pathfinding by Axons

Answer 18

Axons must travel great distances across
the brain to form the correct connections

it is the process by which neurons send out axons to reach their correct targets.

Question 19

How do axons get to their targeted area

Answer 19

to reach their correct targets. Axons often follow very precise paths in the nervous system following the chemical trail to reach their appropriate target.

Growing axons reach their target area by
following a gradient of chemicals in which
they are attracted by some chemicals and
repelled by others

Question 20

Competition among axons as a general principle

Answer 20

When axons initially reach their targets, they form synapses with several cells
* Postsynaptic cells strengthen the connection with some cells and eliminate connections with others

The formation or elimination of these connections depend on the pattern of input from incoming axons

Question 21

Neural Darwinism

Answer 21

Some theorists refer to the idea of the selection process of neural connections as neural Darwinism

Question 22

synaptic connections competition

Answer 22

In this competition among synaptic connections, we initially form more connections than we need

The most successful axon connections and combinations survive while the others fail to sustain active synapses

Question 23

Determinants of Neuronal Survival

Answer 23

chemicals called neurotrophins such as NGF are responsible for the survival of the neurons

Nerve growth factor (NGF) is a type of protein released by muscles that promote the survival and growth of axons

Question 24

Neurotrophins

Answer 24

Chemicals that promote the survival and
activity of neurons (i.e., NGF)

Axons that are not exposed to neurotrophins
after making connections undergo apoptosis –
a preprogrammed mechanism of cell death

– Therefore, the healthy adult nervous system
contains no neurons that failed to make
appropriate connection

Question 25

What happens if axons are not exposed to neuro tropins

Answer 25

Axons that are not exposed to neurotrophins after making connections undergo apoptosis –a preprogrammed mechanism of cell death Therefore, the healthy adult nervous system contains no neurons that failed to make the appropriate connection

Question 26

apoptosis

Answer 26

Apoptosis is a form of programmed cell death that occurs in multicellular organisms.

Question 27

Neuronal Death and its benefits

Answer 27

The elimination of massive cell death is part of normal development and maturation After maturity, the apoptotic mechanisms become dormant

Question 28

describe how is brain vulnerable during the early stages of development

Answer 28

The early stages of brain development are critical for normal development later in life A mutation in one gene can lead to many defects Chemical distortions in the brain during early development can cause significant impairment and developmental problems

Question 29

what is Fetal Alcohol Syndrome

Answer 29

A condition that children are born with if the mother drinks heavily during pregnancy and it causes to the child do the following

Question 30

what are the effects of fetal Alcohol Syndrome on children

Answer 30

it causes to the child do the following Hyperactivity and impulsiveness – Difficulty maintaining attention – Varying degrees of mental retardation – Motor problems and heart defects – Facial abnormalities

Question 31

How are the neurons of children who are born with fetal alcohol syndrome different?

Answer 31

The dendrites of children born with fetal alcohol syndrome are short with few branches * Exposure to alcohol in the fetus brain suppresses glutamate and enhances the release of GABA * Many neurons consequently receive less excitation and exposure to neurotrophins than usual and undergo apoptosis

Question 32

How are the neurons of children who are born with fetal alcohol syndrome different?

Answer 32

The dendrites of children born with fetal alcohol syndrome are short with few branches * Exposure to alcohol in the fetus brain suppresses glutamate and enhances the release of GABA * Many neurons consequently receive less excitation and exposure to neurotrophins than usual and undergo apoptosis

Question 33

explain how fetal alcohol syndrome affects neurons: the process

Answer 33

Exposure to alcohol in the fetus's brain suppresses glutamate and enhances the release of GABA Many neurons consequently receive less excitation and exposure to neurotrophins than usual and undergo apoptosis

Question 34

explain how neurons differ according to their location

Answer 34

Neurons in different parts of the brain differ from one another in their shape and chemical components – Immature neurons transplanted to a developing part of the cortex develop the properties of the new location – Neurons transplanted at a later stage of development develop some new properties but retain some old properties * Example: ferret experimen

Question 35

what happens if the immature neuron is transplanter in a new location: early stages

Answer 35

Immature neurons transplanted to a developing part of the cortex develop the properties of the new location

Question 36

what happens if the neuron is transplanter in a new location: later stages

Answer 36

Neurons transplanted at a later stage of development develop some new properties but retain some old properties Example: ferret experiment

Question 37

Brain Adaptations> deaf people

Answer 37

People who are deaf from an early age become more responsive to touch and vision. Touch and vision come to activate what would be the auditory cortex in deaf people

Question 38

Effects of Special Experiences> blind people how their brains adapt

Answer 38

Blind people improve their attention to touch and sound, based on practice Touch information activated this occipital cortex area, which is ordinarily devoted to vision alone * The occipital lobe is normally dedicated to processing visual information and adapts to also, process tactile and verbal information

Question 39

differences between the brains of musicians and non-musician

Answer 39

MRI studies reveal the following: The temporal lobe of professional musicians in the right hemisphere is 30% larger than non-musicians Thicker gray matter in the part of the brain responsible for hand control and vision of professional keyboard players Results suggest that practicing a skill reorganizes the brain to maximize the performance of that skill

Question 40

adulthood experiences affect on the brain

Answer 40

Adult experiences can also modify the brain anatomy however research is needed to determine if the changes can be observed by fMRI

Question 41

what happens when Brain Reorganization Goes Too Far?

Answer 41

The fingers of musicians who practice extensively become clumsy, fatigue easily, and make involuntary movements This condition is a result of the extensive reorganization of the sensory thalamus and cortex so that touch responses to one finger overlap those of another

Question 42

Brain Development and Behavioral Development> adolescents

Answer 42

Adolescents tend to be more impulsive than adults Adolescents are not equally impulsive in all situations The prefrontal cortex of adolescents is relatively inactive in certain situations, but this may or may not be the cause of impulsivity

Question 43

When do people claim that adolescents make risky decisions because of a lack of inhibition, which brain area do they point to as being responsible for inhibition?

Answer 43

The prefrontal cortex of adolescents is relatively inactive in certain situations, but this may or may not be the cause of impulsivity

Question 44

how being older compensates for neural loss?

Answer 44

Some neurons lose their synapses, and the remaining synapses change more slowly than before in response to experiences Brain structures begin to lose volume Older people have a greater base of knowledge and experience, and many find ways to compensate for losses

Question 45

Plasticity

Answer 45

The brain's special capacity for change

Question 46

Plasticity after Brain Damage

Answer 46

Almost all survivors of brain damage show behavioral recovery to some degree Some recovery relies on the growth of new branches of axons and dendrites. Functional plasticity refers to the brain's ability to heal itself after injury. To achieve this, healthy regions of the brain adapt to take over certain functions that the damaged parts of the brain used to perform.

Question 47

how does recovery take place after brain damage

Answer 47

Some of the mechanisms of recovery include those similar to the mechanisms of brain development such as the new branching of axons and dendrites

Question 48

Possible causes of brain damage

Answer 48

Tumors – Infections – Exposure to toxic substances or radiation – Degenerative diseases – Closed head injuries

Question 49

what is a closed head injury

Answer 49

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

Question 50

what is a stroke or cerebrovascular accident

Answer 50

is a temporary loss of blood flow to the brain A common cause of brain damage in elderly

Question 51

what is a common cause of brain dame in elderly and young adults?

Answer 51

A common cause of brain damage in the elderly is a stroke closed head injury is the main cause of brain damage in young adults

Question 52

Types of Strokes

Answer 52

Ischemia Hemorrhage

Question 53

apoptosis

Answer 53

a preprogrammed mechanism of cell death

Question 54

what happens if the brain of a fetus was exposed to an alcohol

Answer 54

Exposure to alcohol in the fetus's brain suppresses glutamate and enhances the release of GABA Many neurons consequently receive less excitation and exposure to neurotrophins than usual and undergo apoptosis

Question 55

Effects of Ischemia and hemorrhage strokes

Answer 55

they cause Edema: the accumulation of fluid in the brain resulting in increased pressure on the brain and increasing the probability of further strokes Disruption of the sodium-potassium pump leading to the accumulation of sodium ions inside neurons

Question 56

Effects of Ischemia and hemorrhage strokes 2

Answer 56

* The overstimulation of neurons leads to sodium and other ions entering the neuron in excessive amounts * Excess positive ions in the neuron block metabolism in the mitochondria and kill the neuro

Question 57

Treatments of stroke

Answer 57

A drug called tissue plasminogen activator (tPA) breaks up blood clots and can reduce the effects of ischemic strokes Research has begun to attempt to save neurons from death by blocking: – Glutamate synapses – Calcium entry Also cooling the brain helps with after-ischemia it prevents the brain from overstimulation apoptosis and inflammation and the Cannabinoids have been shown to minimize cell loss after brain stroke.

Question 58

Later Mechanisms of Recovery from Brain Damage

Answer 58

after a brain damage is survived areas reorganize or increase their activity as well as stimulate drugs are used to stimulate activity in healthy regions of the brain after a stroke

Question 59

Diaschisis

Answer 59

decreased activity of surviving neurons after damage to other neurons Because activity in one area stimulates other areas, damage to the brain disrupts patterns of normal stimulation

Question 60

regeneration of cell bodies after they die: how does that happen

Answer 60

Destroyed cell bodies cannot be replaced, but damaged axons do grow back under certain circumstances If an axon in the peripheral nervous system is crushed, it follows its myelin sheath back to the target and grows back toward the periphery at a rate of about 1 mm per day

Question 61

Regrowth of Axons: what is the process

Answer 61

Damaged axons do not readily regenerate in a mature mammalian brain or spinal cord – Scar tissue makes a mechanical barrier to axon growth – Neurons on the two sides of the cut pull apart – Glia cells that react to CNS damage release chemicals that inhibit axon growth

Question 62

Axon Sprouting

Answer 62

Collateral sprouts are new branches formed by other non-damaged axons that attach to vacant receptors * Cells that have lost their source of innervation releases neurotrophins that induce axons to form collateral sprouts * Over several months, the sprouts fill in most vacated synapses and can be useful, neutral, or harmful

Question 63

What is a phantom limb

Answer 63

the continuation of the sensation of an amputated body part a phantom limb can lead to the feeling of sensations in the amputated part of the body when other parts of the body are stimulated

Question 64

what helps with phantom limb

Answer 64

Use of an artificial limb can reduce the likelihood of experiencing phantom limb

Question 65

Deafferentated limb

Answer 65

limbs that have lost their afferent sensory input Can still be used but are often not because use of other mechanisms to carry out the behavior is easier – Has led to the development of therapy techniques to improve the functioning of the brain damaged people

Question 66

What happens when neurons in the brain die

Answer 66

you can't regenerate neurons but you can regenerate the growth of axons and dendrites

Question 67

What is Denervation supersensitivity

Answer 67

is the heightened sensitivity to a transmitter after the destruction of an incoming axon it can result to a chronic pain

Question 68

What chemicals help the migration process

Answer 68

Immunoglobulins and chemokines

Question 69

What is the function of myleine sheet?

Answer 69

myleine speeds up the transmission of neural impulses

Question 70

what is the life span of neurons

Question 71

what is life span of new neurons

Answer 71

it was believed in the past that no new neurons were formed after the early stages but later research showed otherwise