Fourth Exam Flashcards
What are the 4 extraembryonic membranes
amnion
chorion
yolk sac
allantoic sac
What are the functions of these extra embryonic membranes
protection
nutrition
respiration
excretion
In birds, what occurs to the ectoderm and the somatic plate mesoderm
laminate
What does this lamination produce
a single layer of membrane
What is the name of this membrane created by the lamination of the ectoderm and the somatic plate mesoderm
somatopleure
What occurs to the endoderm and the visceral plate mesoderm in birds
they laminate
What is the name of the layer that formed from the lamination of the endoderm and visceral plate mesoderm
splanchnopleure
What does the somatopleure do
lifts up to fuse on the dorsal side of the embryo
What does the lifting and fusing of the somatopleure produce
two coverings for the embryo
What are the two coverings produced called
chorion and amnion
What is the space between chorion and amnion membranes
extra embryonic ceolom
What is the name of the cavity between the amnion and the epidermis
amniotic cavity
What does the amniotic cavity serve as in birds
a shock absorber
heat capacity
avoids dehydration
What does the splanchnopleure do
moves downwards to surround the yolk
What does surrounding the yolk sac with the splanchnopleure produce
the yolk sac
How does the yolk sac retain connection to the embryo
via the gut
What occurs to the splanchnopleure other than surrounding the yolk sac
an evagination occurs of the hindgut
What does the evagination of the hindgut form
the allantoic sac
What occurs to the allantoic sac
grows, pushes into the extraembryonic coelom to surround the entire embryo
Do mammals have the same membranes as birds
yes
What is the difference of the membranes of mammals rather than birds
they have different origins
Where does the amnion come from in mammals
amniotic ectoderm
What is the final product of the amnion
it surrounds the entire embryo
What creates the somatopleure in mammals
amniotic ectoderm and extra embryonic mesoderm
Why is it important for the allantoic sac to surround the bird
allows for gas exchange to occur since it doesn’t have a placenta, allows for collection of metabolic wastes
What metabolic waste collects in the allantoic sac
uric acid
What are the three initial layers of cells in mammals
amniotic, epiblast, hypoblast
Where do extra embryonic mesoderm come from
nothing holds some mesoderm cells as the three primary germ layers are being created
Where do the extra embryonic mesoderm cells travel
around to the top of the amniotic ectoderm
What does the amniotic ectoderm and extra embryonic mesoderm create
somatopleure layer
What occurs to the amniotic cavity
it surrounds the embryo to bath it in fluid
Where does amniotic fluid come from initially
most diffuses from the endometrium
Where does amniotic fluid come from once the embryo’s circulatory system is set up
it oozes out through the non-karotinized skin cells
Where does amniotic fluid come from later in develop
baby’s mucous membranes
What mucous membranes contribute to amniotic fluid
respiratory, digestive, urinary
What is the importance of amniotic fluid
allows symmetrical external growth of the embryo
acts as a barrier to infection
permits fetal internal organ development
cushions the embryo
prevents adherence of amnion to the embryo
maintains constant temperature
allows fetal movement, promotes muscle development
assists in maintaining fluid and electrolytes
How does amniotic fluid permit fetal internal organ development
lungs inhale
digestive system swallow
urinary system filters it
organs practice on the amniotic fluid
What is the disease where one does not have enough amniotic fluid
olgohydramnios
What does olgohydramnios cause symptom wise in babies
alters facial development
How does the amnion maintain fluid and electrolytes
amnion is a filter between maternal and baby blood supply
How often is the amniotic fluid changed
every 3 hours
Is amniotic stationary
no, it is always moving
Near the end of pregnancy, how much amniotic fluid is present
700-1000ml
How does the artificial womb work
takes over the circulation system of an embryo, pumps fluid through amniotic cavity to keep moving the amniotic fluid, connects umbilical circulation with o2 and CO2 lines
Where does the chorion come from in human embryos
cytotrophoblast
Where does the cytotrophoblast come from
naturally surrounds the embryo, from the endometrium
The endometrium is made up of what two layers
cytotrophoblast and syncytiotrophoblast
What occurs to the cytotrophoblast layer to create the chorion
sends out fingers through the synctiotrophoblast
What are these fingers called
chorionic villi
What do the villi do for function
reach into pools of maternal blood in the endometrium
Where do umbilical vesicles develop from
extra embryonic mesoderm
Where do the umbilical vesicles form
inside of the connecting stalk
What does the connecting stalk do
connect the embryonic circulatory system with the chorionic villi
In the embryonic circulatory system, how are nutrients obtained, through which route
umbilical vein
In the embryonic circulator system how are wastes disposed of into maternal blood
umbilical arteries
What happens to the cavity between the chorion and amnion
it disappears as the embryo grows
As the embryo grows, what occurs
it bulges out of the endometrium into the uterine cavity
As the embryo bulges into the uterine cavity, it remains in contact with what
the chorionic villi and endometrium on one side
What does the contact with the chorionic villi and endometrium on one side form
placenta
What do many people think the yolk sac is
a junk sac
In mammals what is the yolk sac known as
umbilical vesicle
What are functions of the umbilical vesicle
transfers nutrients
blood initially develops here
contributes to buds and branches of gut
primordial germ cells originate
What eventually occurs to the umbilical vesicle in mammals
it shrivels up
Where do the nutrients come from that the umbilical vesicle transfers
endometrium into the embryo’s gut
How is blood initially developed by the umbilical vesicle
EE mesoderm on the outside of the umbilical vesicle
What part of the umbilical vesicle contributes to the buds and branches of gut
endoderm
After the primordial germ cells are made in the umbilical vesicle, what occurs
they move up to the mesonephros
Where does the allantoic sac come from in mammals
evagination of the hindgut
Does the allantoic sac in mammals expand as it does in mammals
no
Why does the allantoic sac in mammals not expand
respiratory and excretory functions are performed by the placenta
How is the umbilical cord created
ventral closure squeezes all EE membranes and umbilical vessels into the cord
In a cross section of the umbilical cord, what things can be seen
ectoderm on edge mesoderm on inner vein in middle two arteries allantoic stalk leftover yolk of umbilical vesicle
In regards to sex, how do all embryos start out
the same
Most vertebrate species will develop to what kind of sex
look, act quite differently, sexually dimorphic
In many invertebrate species what will develop in regards to sex
males and females are less obviously different, some are both male and female
What are organisms that are both male and female called
hemaphrodites
Why do organisms begin developing differently at some stage
the environment or its the
genes they inherent
How does the environment contribute to sex determination
temperature, nutrient level, bacterial infection, population density
In a dense population, what sex is not common
females
Why are there more males in a dense population
no need to reproduce
How does temperature develop sex
alligators make one sex in cold water and the other in warm water
How do genes influence sex determination
determining what genes you have determines sex
In mammals what genes determine sex
XY male
XX female
In birds, what determines sex
zz male
zw female
one has same gene the other has two different
For some animals what part of the gene determines sex
autosome, locus on a chromosome that if you are heterozygous you are male and homozygous is female
insects that are haploid are what sex
male
insects that are diploid are what sex
female
In mammals is it the X or the Y gene that leads to male
Y gene, two XX don’t make you a female automatically
What chromosomes do Klinefelter syndrome individuals have
XXY
What anatomical sex do individuals with Klinefelter syndrome have
sterile male
What chromosomes do Turners syndrome individuals have
XO
What anatomical sex do individuals with Turners syndrome have
sterile female
In the beginning you develop as what
both genders
At some point, what occurs
differentiation into final gender
What is the default pathway for gender differentiation
female unless you have a Y chromosome
At the indifferent sex stage, what is present in the embryo
mesonephric duct
mesonephros
mullerian ducts
What forms from the mesonephric duct
the vas deferens
What forms from the mesonephros
gonads are occurring, indifferent gonads
What do the mullerian ducts connect with
the cloaca
What do the mullerian ducts become
ovaducts
In males, what does the gonads become
testes
What occurs to the nephric duct in males
becomes vas deferens
What occurs to the mullerian ducts in males
they disassemble
If you inherit one Y chromosome, what do you become
male
If you lack a Y chromosome, what do you become
female
In females, what happens to the mullerian ducts part way
they fuse
What does the Y chromosome contain
a gene called TDF or SRY
What is TDF
testis determining factor
What is SRY
sex determining region of the Y chromosome
In females, what occurs to the nephric ducts
they disassemble
What do the gonads in females become
ovaries
If the mullerian ducts don’t completely fuse into one, what is caused
didephys uterus
What is didephys uterus
split uterus with a wall between
The gonads are made from at least how many kinds of cells
two different
What two kinds of cells make up the gonads
intermediate mesoderm
germ cells
What region of the intermediate mesoderm contributes to gonads
mesonephros
What does the intermediate mesoderm form for the gonad structure
body of the organ
The intermediate mesoderm is also the what of the organ
somatic cells or permanent framework
In opposition of the germ cells that become gametes and leave, what does the intermediate mesoderm do
never leave
Where do the primordial germ cells come from
migrates from the umbilical vesicle via the gut tube
What do the germ cells form as part of the gonad
arrange themselves in rows and cords
What are these rows or cords called
primitive sex cords
What other cells do the intermediate mesoderm create
supporting cells
steroidal cells
connective tissue cells
What are the two steroidal cells/ gender
male=interstitial
female=granulosa
What are the two supporting cells/gender
sertoli=male
follicle cells=female
What do the connective tissue cells make up
scaffold of the organ
At the arrangement of the sex cords, has sex differentiation occurred
no
What causes the differentiation of the gonads
if the supporting cells have Y chromosomes or not
If the supporting cells have Y chromosomes, what occurs
the supporting cells express the TDF gene
What does expressing TDF gene cause
neighboring cells to develop in certain ways that could have gone either way
What occurs to the primitive sex cords when TDF gene is expressed
the cords on the edges of the gonad disappear, leaving only those in the middle
What do the sex cords in the middle of the gonad develop into
seminiferous tubules
How do the cells on the edge of the gonad disappear
cell suicide
What do the primordial germ cells become when TDF is expressed
spermatogonia
What do the steroidal cells produce when TDF is expressed
testosterone
What does testosterone do
influence many other cells near and far
What do the supporting cells produce when TDF is expressed
anti-Mullerian duct hormone
What does the anti-Mullerian duct hormone do
kills mullerian duct cells
Where do the testis initially form
abdominal cavity
What occurs to the testes shortly before birth
descend to their eventual location
what occurs to the edges of the gonads when TDF is expressed
it gets a thick capsule
What is the thick capsule called
tunica albuginea
If there is a mutation for the anti-mullerian duct hormone or the receptor what occurs
genetic male, anatomic male with ova-ducts
If the supporting cells do not have a y chromosome what pathway is taken
the default pathway to become female
What occurs to the sex cords when no y chrom is present
the middle sex cords disappear, leaving only the ones on the edges
What is the edge of the gonad called
cortex
What is the middle of the gonad called
medulla
What do the sex cords on the edges of the gonads do
break up into primordial follicles
What occurs to the primordial germ cells right away
they enter into meiosis
What week of development do the germ cells enter meiosis
before the 12th week of development
What do the steroidal cells produce in females
estrogen
What occurs to the mullerian ducts
persist to become oviducts which merge at far end of the uterus
Where do the ovaries initially develop
abdominal cavity
What occurs in development to the ovaries in placement within the body
descend to the pelvic cavity
How could an XY female persist
if TDF gene or the promotor is mutated, TF is mutated
At the most fundamental level, what three things determine sex
genetics
embryology
choice
How does genetics determine sex
testosterone vs estrogen genes. Combo of genes not just one
How does embryology determine sex
the way things develop if primordial germ cells don’t make it
How does choice determine sex
freedom/nature, worldview, person gets to decide
What is the ratio for the number of individuals that the anatomy does not match the genes
1/4500
In males vs females, how could the sex chromosomes lead to differences in gene products
more products could be produced from X chromosome in females than in males
How many genes on X chromosomes
1606
What could the extra doses of gene products of the X chromosome lead to
disease and or death
If the X chromosome had a growth factor, how could double of X products be a problem
twice the urge to have cells proliferate, 2x chance of cancer
How is this double dosage problem in females solved
inactivation of one of the chromosomes
When is the one chromosome entirely inactivated
in each cell of the epiblast layer, shortly after cell mass is formed
How many cells are present when an X is inactivated
a few hundred cells at this stage
Is this a random or scheduled inactivation process. Are the paternal or maternal ones inactivated?
some are paternal, some are maternal, random
What causes the inactivation of an X chromosome
accumulation of the produce XIST
Where is the XIST gene located
on a locus on the chromosomes
What occurs to produce XIST
gets transcribed into RNA, never gets translated, RNA attaches to rest of chromosome
What occurs as the RNA coats the chromosome
it gets inactivated
How does the RNA coating the chromosome lead to inactivation
RNA attracts methylation enzymes that cause methyl groups to be put everywhere and inactivate it
What happens to the inactivated chromosome
it forms into a Barr body
When does the Barr body unfold
only for replication prior to mitosis
What does the random inactivation lead to
chimerism
What is an example of X linked chimerism
calico cats
What is the most obvious example of pattern formation in development
limb development
How is a pattern seen in limb development
humans have the similar structures in the same pattern
This pattern develops from what
the same embryonic structure
What causes the patterns to develop
cells dividing at different speed cell aggregation cell growth programmed cell death embryonic induction expression of certain genes
How does cells dividing at different speeds contribute to patterns
cells with faster speed make greater amount of cells
How does cell aggregation contribute to patterns
cells aggregate in certain areas and don’t in other areas
How does cell growth contribute to patterns
elongation, esp, muscle cells
How does programmed cell death lead to patterns
occurs at certain points to get rid of cells
How does embryonic induction lead to patterns
chemical morphogens lead to ends and gradients of chemicals, concentration is proportional to distance, cells respond differently to different concentrations
How do genes contribute to patterns
specify regional differences in the anteroposterior body pattern during embryonic development
What are pattern forming genes
homeotic genes
homeotic genes are expressed in what motion across the embryo
anterior to posterior
When homeotic genes get mutated what occurs to the patterns
they get disrupted
If the wingless gene in flies gets mutated, what happens
flies don’t have wings and instead have more legs
Homeotic genes are how long
1000bp
of the 1000bp a certain region codes for what
consensous sequence
How long is the region that codes for the consensous sequence
180bp
What does the consensous region code for
homeobox
What is the homeobox
HOX genes
How are the HOX genes arranged on a chromosome
in order and clustered together to be expressed in bunches
the 180bp region codes for what
homeodomain
How big is the homeodomain
60 AA
What is the function of the homeodomain
bind to DNA, making the products of homeotic genes, transcription factors
some of the HOX genes are what kind of genes
master control genes
What are the three axis of limb development
proximal-distal
dorsal-ventral
anterior-posterior
All limbs begin as what
a limb field
What is a limb field
limb fate map
What occurs within the limb fate map on a cellular level
limb forming cells + limb inducing cells
What type of interaction occurs between limb forming and limb inducing cells
reciprocal interaction
What type of development is limb development
regulative, very flexible, not fixed
The limb forming and inducing cells form in what
concentric circles
Where are the limb forming cells in the concentric circles
anterior edge of circle
Where are the limb inducing cells in the concentric circle
in the middle
What does the concentric circle produce
one limb on each side
If a concentric circle splits on one side what occurs
two limbs form on one side
What week of development do limb buds start forming
5th week of human development
The limb bud has what covering
ectoderm
What occurs following the production of the initial bud
mesenchyme cells condense in the forming bud
Where do the mesenchyme cells come from
the hypaxial myotome of the somite
What do the mesenchyme cells form in the limb bud
muscles on the outside of the bones
Once the hypaxial myotome cells aggregate, what occurs
they secrete FGF10
Does the FGF10 make them aggregate
no they aggregate in response to something else
What is the thing that makes them aggregate
unknown
What dictates what limb is formed
concentration gradient and expression of HOX genes
What dictates formation of an arm
noggin and OTX2 expression
What dictates formation of a leg
BFGF production on the posterior end
What does equal concentrations of noggin OTX2 and BFGF produce
flank
What is a flank
no limb formation, flat layer of skin
What HOX genes code for a flank
b9 =c9 production
What HOX genes code for a leg bone production
d9=c9>b9
What HOX genes code for an arm
d9>b9>c9
What forms the bone in limbs
somatic plate mesoderm starts cartilage
In the proximodistal axis, the mesenchyme cells induce the formation of what
apical ectodermal ridge
What is the apical ectodermal ridge
ridge of elongated cells along the anterio-posterior axis
What does the apical ectodermal ridge correspond with
finger tips
what does the ridge induce
mesencyme cels to proliferate
As the mesenchyme cells proliferate, what occurs
they push AER outward
The cells that are proliferating are in what area of the limb bud
the progress zone
The AER and the progress zone are always on what end of the limb
the distal end
The first mesenchyme cells are on what axis
proximal axis
What parts of the bone are formed first
proximal bones
What is the last portion of bone finished
distal end bones and muscles
How are joints formed
unknown mechanism
All of cell proliferation requires what
blood supply
What is needed to provide the blood supply
angiogenesis
How does angiogenesis occur
branches of dorsal aorta
If no blood vessels what occurs
no limbs are formed
What drug was used in teh 1960s for morning sickness
thalidimide
What was a side effect of the thalidimide drug
blocks angiogenesis=blocked limb formation
What did children of mothers that took thalidimide have instead of limbs
flippers, hand attached to the shoulder, no limb
When is limb formation initiated along the dorsoventral axis
before the limb bud is formed
What occurs to the ectoderm for limb formation
it becomes dorsalized
What is dorsalized ectoderm
cells are induced to end up on the dorsal side
Dorsalized ectoderm expresses what
Wnt-7a
What causes the dorsal ectoderm to move on the dorsal side
as limb bud grows it pulls it to the dorsal side
What occurs to other cells on the ectoderm
they are induced to be ventral side cells
What is the space between the dorsal and ventral cells of the ectoderm
future AER
Due to the concentration gradient of Wnt-7a, what does the dorsal side develop
knuckles, nails,
What causes knuckles and nails to form
expression of radical fringe TF
On the ventral side how much WNT7a is there
very little to none
What do the cells that do not get WNT7a express
transcription factors engrailed 1
What does engrailed 1 produce
palms and pads
without WNT-7a, what would occur to the dorsal and ventral sides
they would both be ventral and express pads
The anterior posterior axis of the limb distinguishes what
thumb vs pinky
In the posterior edge of the limb bud, what occurs
zone of polarizing activity
What does the zone of polarizing activity do
polarize the pole
What is causing this polarization
SHH is being secreted by the cells in the region
What does SHH being secreted on one end create
a concentration gradient
This causes the limb to be divided into what
5 concentration sections
In each section what occurs
HOX genes are expressed in varying degrees
In the highest concentration on the posterior end what HOX genes are expressed
HOX d9/10/11/12/13
What does the highest concentration end produce
pinky and everything on edge of arm
What does the second highest concentration have for HOX genes expressed
HOX d9/10/11/12
What does the second highest concentration produce
the ring finger
What does the mid concentraiton have for HOX gene expression
HOX d9/10/11
What does the mid concentration produce
middle finger
What does second lowest concentration have for HOX genes
HOX d9/10
What does the second lowest concentration produce
index finger
What does lowest concentration produce
thumb
What HOX genes make thumb
HOX d9
The concentration and finger formation initially forms what
a solid hand
What defines each finger
apoptosis of cells between
What are conjoined fingers or toes called
webbed, syndactyly
Initially, how do all limbs begin
outward, no bending ventrally or dorsally
What occurs to the upper limbs after formation
rotate 90 degrees to have elbows point backwards
What occurs to the lower limbs after formation
rotate 90 in the opposite direction to point bend ventrally
What two things produce neurons
neural tube, neural crest cells
How do neurons generally reach specific target cells
elongate
What are the two typical target cells
muscle or another neuron
Why is it best for the neurons to connect to their target cells in an embryo stage
neurons are close to their targets as the embryo is small
What is constructed between the neuron and its target
synapse
Throughout life, what occurs to synapses
the number and strength are adjusted
What is the rate at which neurons are produced
250,000 per minute
In total, how many neurons are produced during the embryo stage
2 billion
In comparison to the adult, 2 billion neurons is what
2x as many as the neurons the adults have
Why does the embryo produce 2x the number of needed neurons
body errs on the side of having too many, rather than too few as some cell will not make it, they will be defected, or commit suicide and be pruned
What is the mechanism towards which neurons extend
unknown
What is the length per day that neurons extend to
1mm a day
Does nerve regeneration occur in adults
yes, but it takes a lot of time
Where does outgrowth of neurites toward target cells occur
axon or dendrite growth is at the tip
What is the area on the axon or dendrite that extends called
growth cone
What is the growth cone/ what shape
a slightly enlarged area shaped like a hand
What does the hand shaped growth cone also have
cytoplasmic extensions
What are the cytoplasmic extensions on the growth cone called
microspikes or filopodia
What is the function of microspikes
transient feelers that probe the growth cone’s environemnet
What are the microspikes probing for
adhesive molecules on cell or substrate surfaces
What are the adhesive molecules that the microspikes are probing for
CAMs and SAMs
What occurs when the microspike encounters a non-adhesive or repellant molecule
the microspike rapidly withdraws
When an adhesive molecule is contacted, what does the microspike do
attaches and a new growth cone is set up at the location
In vivo, what serves as barriers for neuron extensions
ECM with collagen, ect. that it must break through
What path does the growth cone follow
path of greatest adhesion
How does the neuron get through collagen and ECM
secretes proteases
What are axons packed with that also aid in the breaking through of collagen and movement
microtubules
How do microtubules aid in moving through ECm
generate a ton of force to allow axons to “punch” through
What forms the path of adhesive molecules which a growth cone follows
a continuous pathway of ECM molecules
guidepost cells
contact guidance
chemotaxis
Neurons that follow a continuous pathway of ECM molecules will require what
SAMs
What is another name for the continuous pathway of ECM molecules
pathway guidance
1 neuron will attach to what
1 target cell
What is the basis for neural pathology
if a neuron does not reach its target cell and the affect this has on a disease
The pathway guidance is around for how long
transient pathway, available only for a short time
Is only one molecule used for the pathway guidance for one neuron
no, the ECM molecules may be used repeatedly at different locations and times to lead a series of neurons to targts
What gene regulates migration and GABA production
HOX genes
What is the pathway that involves guidepost cells
spots of adhesive ECM are secreted by guidepost cells
Are the guidepost cells secreting a continuous pathway
no, it is spots
How does the growth cone find the guidepost cells
extremely long microspikes are sent out in all directions
In the guidepost cell method what occurs when one microspike binds to a substrate
the other microspikes collapse and the one that binds is maintained
Once the neuron is filled in to a guidepost, what occurs
a new growth cone is set up to search for the next guidepost cell
The first neuron to use a guidepost cell method is called what
pioneer cell
Different combinations of guidepost cells can do what
direct axons toward different targets
How do neurons use contact guidance to get to a target cell
axons going to the same region as a pioneer cell show high affinity towards them
What mediates contact guidance pathway
CAMs or cadherins
Cams or cadherins allow for what
cell to cell adhesion
How long does the contact guidance pathway work for
until the axon of the pioneer cell is myelinated
What about myelin prevents contact guidance pathway
NOGO protein
What does the NOGO protein do
blocks regeneration of neurons and their ability to follow pioneer cells
What is the name of the neurons that follow pioneer cells
secondary cells
At some point during the contact guidance pathway what occurs to secondary cells
the secondary cells veer off
What causes the secondary cells to veer off
BMP lures it away
What is an example of contact guidance pathway
autonomic nervous system
Organs are innervated by both what
parasympathetic and sympathetic neurons
What is the pioneer cell between parasympathetic and sympathetic neurons
sympathetic
What direction do sympathetic neurons send signals
from the spinal cord to the organ
What direction does the parasympathetic neuron travel
from organ to spinal cord
How does the parasympathetic neuron innervate the spinal cord
follows the sympathetic neuron using contact guidance
What is a nerve
a bundle of axons
What method creates a nerve
pioneer cells followed by secondary cells
Failed connections between neurons would lead to what of the neuron
apoptosis, as it is not being used and the cell trims any pathway not being used
What is the fourth mechanism that takes over as a growth cone approaches its target
chemotaxis
How do cells move in chemotaxis
movement is towards the direction of highest concentration of some soluble signaling molecule
What secretes the soluble signaling molecule
a target cell
What is the general name for a soluble signaling molecule
chemotactic factor
Since the chemotactic factor is referencing for neurons, what is the name of the soluble signaling molecule
neurotrophic factor
What is an example of neurotrophic factors forming specific neurons
interneuron formation in the spinal cord
what does the word neurotrophic factors mean
feeding neurons
What is the meaning of determined
fate is set
What is the meaning of differentiated
cell is acting out its fate
What attracts growth cone from interneuron to move towards the motor neuron
the neurotrophic factor netrin
What produces netrin
floor plate cells
netrin is not only a neurotrophic factor but also what
growth factor
What are the functions of netrin
support the neuron, keeps it alive
In mice, what neurotrophic factor contributes to Alzhiemers disease
reelin
If neurons are not kept alive, what occurs
they die and are removed
What other cell do neurotrophic factors stimulate
oligodendrocytes
Whern oligodendrocytes are signaled, what occurs
they myelinate the axons
If there is not enough neurotrophic factor to stimulate oligodendrocytes, what occurs
not enough myelin
What causes the establishmet of a synapse between the axon and its target cell
reciprocal interaction, exchange of signals between pre and post synaptic membranes
When the target cells secrete NTF, what occurs to the neuron
it attaches to the surface of the neuron to put in calcium channels
What is the function of the calcium channels in the membrane
when an AP comes down the neuron it opens the calcium channels to open and allow neurotransmitter vesicle release
How does the target cell respond to the release of neurotransmitters
clusters NT receptors on the side of the cell exposed to the highest concentration of NT
How were the receptors for the neurotransmitters prior in the membrane
distributed more or less ecenly over the whole cell
Why were the NTRs spread evenly over the whole cell
target cell did not know which direction its axon would come from
Once the growth cone and the target come into contact, what occurs to the growth cone
it become the nerve terminal
What is joined between the target cell and nerve terminal
junctional complex
What is the junctional complex
an ECM pad
What function does the ECM pad
both cells adhere to maintain a connection without the two synaptic membranes having to come into contact
What are the components of the ECM pad
Dok-7 and agrin procteins
What does the neuron membrane have to connect to the ECM pad
neurexin
What do target cells have to connect to the ECM pad
neuroligin
What does mutant neuroligin cause in mice
autism like cells
In strengthening the synapse with more receptors, where are NTRs sent
directly to the synapse rather than to the other membranes of the cell and moving later
What is pruning of synapses do
activity-dependent synapse elimination
Why is pruning of synapses activity dependent
inactive synapses are disconnected, while more used ones are maintained
Synapses used frequently undergo what
strengthening
Strengthening and Pruning of synapses forms the basis for what
memory formation and memory loss
How are synapses strengthened
more agrin in ECM
increase in neurotransmitter concentration
nerve terminal can expand and split into boutons
formation of ECm net arround synapse
How does more agrin in ECM strengthen synapse
stronger pad between
How does an increase in neurotransmitter concentration strengthen synapse
strong response by a target cells, more channels opened
How does nerve terminal expanding and splitting into more boutons strengthen the synapse
more surface area for more areas of contact
How does the formation of ECM net arround synapse strengthen the synapse
holds synapse together so the synapse is retained
What is the level of genetic variation among neurons
enormous diversity
When looking at the neurons within a brain what is observed
the brain is a mosaic of neurons, huge areas in the brain are different from other areas
Most of the variation is in what part of the chromosome
heterochromatin
What is heterochromatin
non-coding regulatory regions of the chromosome
While the gene looks normal, if the heterochromatin is off what occurs
expression regulation is off and does not work properly.
What is the last stage of development
senescence
What is senescence
deterioration of the body leading to natural death
What causes senescence
cell malfunction, deterioration, or death
What does senescence cause
changes visible on the outside of the body mirrors the changes happening on the inside
What are symptoms of senescence
gray hair skin cracked and leathery cataracts form muscles atrophy osteoarthritis menopause atherosclerosis osteoporosis hearing loss slowed would healing and immune response diabetes nervous system problems increased risk of cancer
What cell gives pigment to the hair
melanocytes
What replaces melancytes when they die out
melanocyte stem cells
Once melanocyte stem cells are gone and melanocytes are gone what occurs
no pigment
What leads to cracked and leathery skin
elastin fibers are being replaced with collagen
What causes collagen to form on the skin
UV radiation and sunburn damage the skin and lead to “scar tissue formation”
What causes cataracts
cells on the interior of the lens die
What causes muscle atrophy
myoblast and sattelite cells are being removed
What causes osteoarthritis
articular cartilage has worm out
What typically replaces articular cartilage
chondrocytes stem cells
Once chodrocytes are gone what occurs
cartilage cannot be replaced
What causes menopause
oogonia stem cells are gone
What does the removal of oogonia cause
no more follicles, no more estrogen
What causes atherosclerosis
collagen replaces elastin in the arteries
phospholipids are replaced with cholesterol
What occurs to cholesterol to cause damage in the arteries
leads to damage, inflammation, swelling, blocking and scar tissue buildup
What effects does inflammation and scar tissue have on arteries
decreased vesicle radis
How does decreased vesicla radius affect MAP
increases arterial pressure
What is the #2 cause of death if you include abortion
coronary artery disease
What is the #1 cause of death if you do not include abortion
coronary artery disease
What is the #3 cause of death
stroke
What causes osteoporosis
the balance between osteoblast and osteoclast is heavily weighted towards osteoclast activity
In middle age what is the relationship between osteoblast and osteoclast activity
equal
In development what is the relationship between osteoblast and osteoclast activity
heavy on the osteoblast activity
What causes hearing loss
ear drum hardens
graying of hair in cochlea
How does the ear drum harden
less elastic, doesn’t stretch or vibrate as much
How does graying of hair in cochlea lead to hearing loss
once out of hair stem cells, no new hair you can’t hear
What is the hair in the ears
cilia
What is the #8 leading cause of death
pneumonia and influenza
What is the #6 cause of death
type 2 diabetes
What causes type 2 diabetes in elderly individuals
impaired glucose regulation, no longer store glucose
Why can someone no longer store glucose
ran out of adipose cells
Type II diabetes is what kind of diabetes
non-insulin dependent
What is the #2 leading cause of death
cancer
What is the #7 leading cause of death
alzheimers and parkinsons
Most of the top deaths are what age related
old age
Why do christians believe senescence happens
the curse, the wages of sin is death, eat from the tree and you will die
What are suggested secondary causes to senescence (hypothesis)
mutation accumulation hypothesis
antagonistic pleiotrophy hypothesis
disposable soma hypothesis
What is the mutation accumulation hypothesis
random mutation accumulate throughout life and are passed on to daughter cells
Where do the random mutations come from
environmental factors and errors in DNA replication and repair
What does the accumulation of these mutations cause
stem cells die off or cause cancer development
What is the antagonistic pleiotrophy hypothesis
genes that promote reproduction early in life have the side effect of contributing to senescence later in life
What is the side effect of reproduction
senescence
What is pleiotrophy
a single gene leads to multiple conflicting effects
How is testosterone pleiotrophy
promotes sperm reproduction to build strong muscles, but also contributes to prostate cancer
How is estrogen pleiotrophy
promotes reproduction, enhances immune system to protect offspring but also leads to autoimmune diseases
What is the disposable soma hypothesis
bodies exist to produce germ cells, once the job is done the body serves no purpose
What does evolution not save
useless things
What does evolution save
only those things which confer a reproductive advantage
Why is an old body useless
maintaining and repairing an old body would take too much energy
Prior to the flood, how long did people live
1000 years
After the flood, humans live how long
120 years
Who was the last oldest person
Joseph
How old did joseph live to be
124 years
What genes are responsible for mutations to accumulate
DNA, RNA, and protein repair genes
What does mutations in the DNA, RNA, and protein repair genes lead to
proteins not being repaired
What occurs when proteins are not repaired
they accumulate inside cells and lead to cell death
What diseases feature proteins aggregating
Alzheimers and Parkinsons
What is one gene known to be involved in aging
WRN gene
What is the WRN gene named for
Werner’s syndrome
What is werner’s syndrome
people visibly age at an accelerated rate
People with werner’s syndrome typically die at what age
47
What does the WRN gene code for
helicase enzyme
If the helicase gene is mutated what occurs
DNA doesn’t unwind, no proteins no repair, less replication of stem cells
What role does helicase function as
unwinds DNA, reproduction
What is another accelerated aging disease
progerias
Who is affected by progerias
children
When do children with progerias die
within their teens
Children with progeria have a mutation in what
insulin signaling gene
This gene produces a mutated what
lamin
What is lamin
a protein that lines the inside of the nuclei
If lamin is mutated, what occurs
disorganized chromosomes
What is the most impressive and easily reproducible way of extendin the life spand of mice, rats, and hamsters
calorie restriction
What is calorie restriction
reduction in calories of an otherwise complete and balanced diet
What did calorie restriction lead to health problems wise
less frequenct atherosclerosis, auto-immunity and cancer
Calorie restriction idea has caused people to form what
calorie restriction society
because calorie restriction how is energy diverted
distributed towards survival rather than reproducing
In humans what does calorie restriction lead to
delayed menstruation
What shows correlations with calorie restriction
insulin levels and concentration are dependent upon calories
What genes prodect us from starvation
starvation avoidance genes
How do starvation avoidance genes contribute to senescence
when these genes are damaged or underexpressed
What is hormesis
minor stressors that get you cell’s guard up against other stressors
How is calorie restriction hormesis
under eating is a slight stress that promotes longevity
What are the mechanisms of senescence
accumulation of mutations
over-eating
oxidative stress
replicative arrest
How does ATP generation lead to senescence
oxidative phosphorylation generates some nasty by-products
What are the byproducts of oxidative phosphorylation
reactive oxidation species
What are the reactive oxidation species
superoxide ions O2-
hydrogen peroxide H2O2
hydroxyl radicals OH
What are strong reactive oxidation species affects
strong oxidizing agents that attack DNA, lipids, and proteins
When strong reactive oxidation species attack DNA, lipids, and proteins, what occurs
break bonds and alter their functions
What does breaking bonds and altering a cell’s function lead to
cell death
Hydroxyl radicals can lead to the formation of what chemical group
carbonyls
What is the affect of forming carbonyls rather than hydroxyl groups
cannot make hydrogen bonds to form protein structures
What proteins exist to neutralize the ROS
superoxide dismutase
catalast
peroxidase
What percent of all proteins are damaged by ROS forming carbonyls
40%
In fruit flies, extra superoxide dismutase causes what
increased longevity by 35%
What component do dietary supplements have
anti-oxidant actity
What dietary supplements are antioxidant activity
vitamin C, vitamin E, beta carotene
Do dietary supplements reduce risk of disease
no, they actually increase the risk of disease
What is necessary to replace worn-out, damaged and lost cells
replication and cell division
What are the 3 sources to replace damage
some cells are permanent
stable cells
adult stem cells
What cells are permanent
neurons and muscles
What are stable cells
liver, pancreas, kidney that can dedifferentiate
What does dedifferentiation lead to
regress and divide to serve as a replacement
How many times can stale cells divide
50X
What does the amount of division stable cells can undergo make them
a stable source, but limited
How many times can adult stem cells divide
unlimited
Why are stable cells limited to 50X division
every time a cell divides, part of the telomere gene is cleaved off
After 50X division, what occurs to the telomere gene
the telomere gene is gone and cannot acquire
fetal cells in culture will replicate how many times
50X
cells from and 80yo will replicate how many times
28 X
cells from someone with werners syndrome will replicate how many times
20X
how are adult stem cells able to replicate unlimitedly
they experess telomerase
What is the function of telomerase
replaces the tips of chromosomes to protect telomere gene
What other cells express telomerase
cancer cells
Even if cancer cells do not express telomerase, what can occur
still get a big cancer
In mice that had a knockout of telomerase, what occurred
they died prematurely, showed spleen atrophy and slow wound healing
