Lecture 3: Development Flashcards
after ejaculation
sperm cells make their way through the acidic environment of the vagina to the more hospitable environment of the uterus
ampulla
about 200 sperm cells reach the ampulla of the uterine tube. the ampulla is where fertilization occurs over a 24-hour period
acrosome
located at the tip of the sperm cell. contains enzymes that break down the outer layers of the egg cell
route of the sperm
the sperm and egg cell must fuse. the sperm must first pass through the layer surrounding the egg cell (corona radiata and zona pellucida). once past the barriers, the sperm cell leaves its plasma membrane and enter the cytoplasm of the egg cell
ootid
the egg cell that now contains the nuclei of the female and the male and has a haploid number of chromosomes from the sperm and the egg cell
capacitation
the process by which the sperm cell is prepared to enter the egg
zygote
when the fusion of the nuclei produces a diploid number of chromosomes it is then referred to as a zygote
diploid
the presence of two complete sets of chromosomes in an organism’s cells, with each parent contributing a chromosome to each pair
haploid
the presence of a single set of chromosomes in an organism’s cells
blastocyst
after 4-6 days, before implantation in the uterus, the mass of cells is called a blastocyst
stem cells
stem cells are undifferentiated cells that can turn into virtually any specialized cell. has two main types:
- embryonic stem cells
- adult stem cells
fission
the zygote single cells, or blastomere begins a series of mitotic divisions creating new cells
second week
by the end of the second week, the blastocyst implants itself into the uterus, the blastocyst nestles into the uterine wall, new cells must pass through the existing cells and layers. the cells build up from the inside out
around 9 to 10 weeks
the embryo develops teeth and nails
from 17 weeks
a baby can dream (REM sleep)
end of pregnancy
the baby can close and open its eyes, however a lot can go wrong, such as ectopic pregnancy in the fallopian tube: the embryo must then be removed
totipotent stem cells
they can differentiate into all possible cell types
pluripotent stem cells
they can differentiate into most cell types
multipotent stem cells
they can differentiate into related cell types
oligopotent stem cells
they can differentiate into limited types of cells
unipotent stem cells
they can only differentiate into their own type of cells
invagination
when the embryo begins to assume its multicellular form during the gastrulation phase of the embryonic development. in this process, the folding of the embryonic cells produces three cell layers
ectoderm (outer layer)
the layer of cell or tissue of an embryo in early development. the central nervous system forms from this
mesoderm (middle layer)
the layer of cells or tissues of an embryo. muscles, bones and connective tissues form from the mesoderm. the thicker cells in the mesoderm are called somites. this will later form the skeletal muscles
progenitor cells
are similar to stem cells, but cannot divide as easily and they differentiate themselves into a specific type of cell. they lie next to the somites and will later form the spinal cord
endoderm (inner layer)
the layer of cells or tissue of an embryo in early development. digestive and respiratory systems develop from the endoderm
notochord
cylinder-like structure in the mesoderm that forms as a result of gastrulation, which arises from the primitive streak
neural plate
the area of the embryonic ectoderm which all parts of the nervous system develop from. the neural plate further forms into the neural tube and the neural crest
neurulation
the process by which the neural tube is formed
spina bifida
the most common neural tube defect, where the lower neural tube fails to close. indiviuals with spina bifida may suffer from motor and sensory deficiets in the legs; incontinence, spinal curvature and increased cerbrospinal fluid pressure in the brain
folic acid
can help with spina bifida along with surgery
sonic hedgehog gene
a critical protein gene involved in signaling the development of the neural tube
primary vesicles of the brain
- prosencephalon (forebrain)
- mesencephalon (midbrain)
- rhombencephalon (hindbrain)
migration
the process in which the cells of the brain arrive at their specific locations. the migrating neurons are immature and lack dendrites. the genetic code assigns each cell to its place
radial glial cells
facilitates the journey of cells to a particular destination. radial glial cells provide a network of guiding cables and supporting structures that the migrating neurons uses to travel to its destination
myelin
increases speed of neurotransmission, provided around some axons of neurons by glial cells
myelination
begins in the spinal cord and progresses through regions of the brain. it is not limited embryonic development and continues into adulthood
aborisation
when the neuron differentiates and forms into its final cell, the dendrites grow and create connection
synaptogenesis
is final stage of development where formations of synapses happen. continues throughout life, but slows down in older age.
synapses
while almost all neurons are formed prenatally, there are few synaptic connections. synapses depends on experiences and interaction with an environment - it is at the synapse where the learning occurs
synaptic pruning
addresses the overproduction of synapses. synapses that are not being used are pruned. during childhood, pruning reduces the volume of grey matter in the cortex
apoptosis
preprogrammed cell death. happens after migration
nerve growth factor (NGF)
assists synaptogenesis. a protein that promotes the survival of only certain neurons
Barker hypothesis
states that the development of disorders starts in the womb
critical periods
life stages of an organism during which it is very sensitive to external influence
axonal elaboration
learning increases dendritic innervation and arborization takes place
synaptic elimiantion
pruning of many of the original embryonic axons, it is modulated by neuronal activity
synaptic consolidation
a mechanism that strengthens the synapses with cell adhesion molecules (CAMs) that insert into synapses that have become strong
thalidomide
most notable teratogen that has received widespread media attention. it is a drug used to treat morning sickness which is common in early pregnancy. the effects were that limb development was severely affected
fetal alcohol syndrome
consumption of alcohol during pregnancy is very unwise as it can lead to malformation of the child’s brain
three main features of FAS
- facial abnormalities
- growth disorder
- mental impairment
MRI studies of FAS
show that basal ganglia are less active in children with FAS. the corpus callosum appears to have abnormalities ranging from reduced size to complete absence and the volume of the cerebellum is reduced. also found asymmetry in the hippocampus, left temporal lobe was smaller than the right
teratogens after birth
can still have a major impact on the individual. one example is air pollution: this is associated with changes in the brain that closely resemble abnormalities caused by Alzheimer’s disease
cortisol
high maternal levels can cause high fetal cortisol levels
neurotransmitters
high maternal cortisol may affect cell migration, neural development and synaptogenesis
epigenetic changes
potentially transmissible changes without genetic modification: gene expression or gene inactivation
genetic transmissibility
the mother’s genes can transmit susceptibility to the baby
mature brain
during adolescence, the amount of grey matter in the brain continues to decrease while white matter increases (until about 40-50, then it decreases)
cognitive reserve
states that when the brain is trained until late in life, symptoms of the reduction in white matter and brain volume are less present
