Module 4 Flashcards
historical perspective of neurobiology
2000 years ago;
Seneca and Younger proposed preformation
mid 1800s
recognition that embryos didn’t resemble adults and similarities between different species
Embryonic vertebrate nervous system
forebrain
midbrain
and hindbrain are visible in the human embryo at 28 days
what happens between fertilization to embryo stage
day 1 = zygote formation
day 2 = zygote divides
day 15 = embryo disc begins to form
what are the prenatal stages
zygote = 2 weeks
embryo = 2-8 weeks
fetus = 9 weeks until birth
what is the neural plate
thickened region of ectodermal layer that gives rise to the neural tube (3 weeks after conception)
what is the neural tube
structure in early stage of brain development which the brain and spinal cord form from
what are the major events during the development of the human nervous system
day 49 = embryo begins to resemble a miniature person
day 60 = sexual differentiation occurs (genitals + brain regions)
day 100 = brain looks distinctly human
7 months = gyri and sulci begin to form
9 months = brain looks like an adult brain
T/F The human brain requires approximately 10 billion (1010) cells to form the cortex that blankets a single hemisphere.
True
when does cell migration occur
- Begins shortly after the first neurons are generated.
- Continues for 6 weeks in the cortex and throughout life in the
Hippocampus.
- May have serious consequences when damaged.
Radial glial cell
- These are a path-making cell that a migrating neuron goes to appropriate place
what’s cell differentiation
- neuroblasts become specific types of neurons
- begins after cells migrate
- essentially complete at birth (excluding neuron maturation which goes on for years and may continue until adulthood in some parts of the brain)
What is neural maturation
1.) dendritic growth
arborization (branching - growth of dendrite spines)
2.) axonal growth
growth cone; growing tip of axon
- responsive to cues from 2 molecules (1) cell adhesion molecules (cam) and (2) tropic molecules (produced by targets being sought by the axons – tells the cones to “get over here’)
filopod; process at end of a developing axon that guides the growth cone by reaching out to search for a target or to sample the intercellular environment
takes place after neurons migrate to destination and differentiate into specific types
Synaptogenesis
5th gestational month:
simple synaptic contacts.
7th gestational month:
synaptic development of deep cortical neurons.
After birth:
synaptic development increases rapidly during the first year of life.
Cell Death and Synaptic Pruning
- brain chisels away pieces through cell death and synaptic pruning.
(Chisels: genetic signals, experience, reproductive hormones, even stress) - Cortex becomes measurably thinner in a caudal–rostral (back-to-front) gradient,
probably due to synaptic pruning - Synaptic connections that are not part of a
functional network are pruned away
T/F We are born with an overabundance of neurons and synaptic connections
true
Hypothesis that cell death and synaptic pruning are, like natural selection in species, the outcome of competition among neurons for connections and metabolic resources in a
neural environment
neural darwinism
what is apoptosis
genetically programmed death
glial development
formation of astrocytes and oligodendrocytes begins after most neurogenesis is complete (continues throughout life)
progress of myelination
myelination of the cortex begins after birth and continues until at least age 20
T/F your frontal lobe is done developing by 20
False, dendrite spines continue to be eliminated well beyond 20, stabilizing at an adult age of ~30
T/F the frontal lobe is especially sensitive to epigenetic influences
true, studies have shown that adverse childhood experiences are predictive of middle age physical and mental health
2 important features of frontal lobe development
1.) reduction in cortical thickness
2.) increase in connectivity between the medial regions of the frontal love, poster regions of the cingulate cortex and the lateral regions of the parietal love
called “default network”
sex differences in brains
women;
reach max volume and max gray matter volume
sooner than men
development of motor behaviours
axons from motor cortex neurons myelinate about the time that reaching and grasping develop.
2 months = hand orients towards an object and gropes to hold it
4 months = grasps appropriately shaped object with entire hand
10 months = uses pincer grasp
Eric Lenneberg theorized that
- children reach certain important speech milestones in a fixed sequence and at constant chronological ages.
- The speed of language development is influenced by a wealth of environmental variables, including those associated with socioeconomic status.
- although language skills and motor skills generally develop in parallel, the capacity for language depends on more than the ability to make controlled movements of the mouth, lips, and tongue.
