3 - Embryology and Development of Nervous System; Aging Flashcards
3 developmental stages in utero?
- pre-embryonic
- embryonic
- fetal
Pre-embyronic stage timeline?
0-14 days
What stage in utero?
- inner cell mass of sphere of cells becomes embryonic disk with 2 cell layers
pre-embryonic
what 2 cell layers found in pre-embryonic stage?
- ectoderm
- endoderm
mesoderm follows later
embryonic stage timeline?
15 days to 8 weeks
Ectoderm develops into what?
- sensory organs
- epidermis
- nervous system
endoderm develops into what?
- gut
- liver
- pancreas
- respiratory system
Mesoderm develops into what?
- dermis
- muscles
- skeleton
- excretory system
- circulatory system
fetal stage timeline?
end of 8 weeks to birth
when does myelination start?
at fetal stage
neural tube development timeline?
days 18-26
Neural tube development:
1. neural plate forms ___ from ectoderm
longitudinally
Neural tube development:
1. neural plate forms longitudinally from ectoderm
2. edges of plate fold to make ___ ___
neural groove
Neural tube development:
1. neural plate forms longitudinally from ectoderm
2. edges of plate fold to make neural groove
3. folds grow together day ___ forming neural tube
21
Neural tube development:
1. neural tube forms longitudinally from ectoderm
2. edges of plate fold to make neural groove
3. folds grow together day 21 forming neural tube
4. tube closes first in ___ region
cervical
Neural tube development:
1. neural tube forms longitudinally from ectoderm
2. edges of plate fold to make neural groove
3. folds grow together day 21 forming neural tube
4. tube closes first in cervical region
5. quickly fuses together rostrally/caudally with open ends called _____
neuropores
Neural tube development:
1. neural plate forms longitudinally form ectoderm
2. edges of plate fold to make neural groove
3. folds grow together day 21 forming neural tube
4. tube closes first in cervical region
5. quickly fuses together rostrally/caudally with open ends called neuropores
6. neural ___ formed from cells close to tube and ectoderm
7. neural crest moves ___ embryo
8. overlying ectoderm covers the tube/crest
crest, inside
Neural tube development:
1. neural plate forms longitudinally from ectoderm
2. edges of plate fold to make neural groove
3. folds grow together day 21 forming neural tube
4. tube closes first in cervical region
5. quickly fuses together rostrally/caudally with open ends called neuropores
6. neural crest formed from cells close to tube and ectoderm
7. neural crest moves inside embryo
8. overlying ectoderm covers tube/crest
9. superior neuropore closes day ___ and inferior neuropore closes day ___
27, 30
Neural tube development:
- inner and outer cell layers formed by neural tube by day ___
26
inner layer of neural tube cell bodies to become ___ matter
gray
Neural tube separates into dorsal and ventral sections.
Ventral = ___ function
Dorsal = ____ function
ventral = motor
dorsal = sensory
ventral neural tube > motor plate > ventral horn:
- axons of cell bodies of motor plate extend to innervate ___ > motorneurons
myotome
dorsal neural tube > association/alar plate > _____ or ____ neurons > dorsal horm
interneurons or projection neurons
Outer layer of neural tube:
- processes of cells with ___ in inner layer
- becomes ___ matter with axons and glial cells
bodies, white
neural crest cells are on both sides of neural tube, separating to correspond with respective parts of ____
somites
neural crest cells form what 3 things?
- peripheral sensory neurons
- autonomic neurons
- endocrine organs (ex. adrenal gland, pancreas)
Peripheral sensory neurons form from neural crest cells:
- cells extend 2 processes, 1 to spinal cord and 1 to dermal part of somite forming ___
- cell bodies of peripheral sensory neurons are outside of spinal cord and located in __ __ __
dermatomes
dorsal root ganglion
somites first appear in region that will become ___ area, then appear caudally
occipital
what comes from the anteriomedial part of somite?
sclerotome > vertebrae and skull
what comes from the posteromedial part of somite?
muscles of myotome
what comes from lateral part of somite?
dermatome becomes dermis
what is the end of the spinal cord called?
conus medullaris
what is the connection of pia, arachnoid and dura mater form end of spinal ford to coccyx?
filum terminale
when does the spinal cord stop growing?
4-5 years
When does the vertebral column stop growing?
16-18 years
when does brain development begin in utero?
day 28
brain region starts to develop after closure of what?
superior neuropore
when brain begins development what 3 fluid filled englargements form?
- hindbrain
- midbrain
- forebrain
brain development: what does the hindbrain consist of?
medulla, pons, cerebellum, with central canal forming 4th ventricle
what happens in hindbrain during brain development?
inner layer cell bodies migrate through white matter to outside
brain development: ____: central canal forms cerebral aqueduct connecting 3rd and 4th ventricles
midbrain
5th lobe of brain?
insula (deep to lateral sulcus)
brain development: forebrain
- ___ region remains near midline forming diencephalon to include thalamus and hypothalamus
- ____ region forms telencephalon to become cerebral hemispheres (includes deep nuclei of basal ganglia, white matter of axons and myelin, cortex(layers of cell bodies on surface of hemispheres))
- central canal forms bilateral ___ ventricles
posterior, anterior, lateral
___ hemispheric areas do not grow as much as others
lateral
2 possible ways neurons travel to final destinations during brain development?
- sending an extension to brain surface and then pulling self along the extension
- climbing along glial cells that reach from center of brain to its surface
Do neurons differentiate into special functions before or after reaching final destination? predetermined or function based on location
AFTER - function depends on where cell lands
Cellular level development:
- neurons sprout ___ ___ from processes that samples potential environment, recoiling from some areas and attracted to others
- when growth cones contact their target cells, synaptic vesicles form, microtubules extend beyond growth cone to ___ ___
- as neurotransmitters are released, neighboring post-synaptic membrane creates ____ ___
growth cones, presynaptic membrane, receptor sites
How many neurons may go to a single muscle cell during development? during adulthood?
several, only 1
Neuron connections also shape development of muscles: experimentally, muscle fiber type is dependent on type of ___
innervation
Myelination of long axons begins in ___ fetal month with most finished at ___ years, depending on the system
4th, 3
- motor roots of SC are myelinated at 1 month old, but nerves from cortex to motor neurons are not fully myelinated until 2 years (children may “grow into deficits”)
- critical periods seem to exist where synapses are competing to establish optimal neural outcomes
possible neural tube defects?
- anencephaly: brain has not developed
- arnold chiari malformation - part of brain (cerebellum) pushed down into foramen magnum
- spina bifida - cord does not close
when abnormal events occur prior to ___ weeks gestation, major deformities of nervous system will be present
20
Some cognitive abilities decline with age, which 3?
- working and long term memories
- visiospatial memories
- verbal fluency
Some cognitive abilities seem to be preserved with aging, which 2?
- vocabulary
- comprehension
Neural death within aging:
- ___% of motorneurons die in healthy older adults
- ___ loss of brain neurons in healthy brains of older adults
25%, minimal
Causes of changes with aging:
- myelin fragmented compromising white matter (particularly present in ___ and ___ lobes)
- ___ density loss
- decline in ____
- declines in ___ number and structure in brain and periphery
frontal and temporal
dendrite
neurotransmitters
synapse
- healthy 80 year old brain doesn’t look like 20 year old brain (shrinkage in volume and weight)
Normal age related cognitive changes dont markedly hinder __ ___ __
quality of life
Mild cognitive involvement (MCI) includes memory loss with/without other cognitive involvement
- may be able to do most ADL but others starting to notice issues
- about ___% develop alzheimers disease within 5 years
90%
