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nervous v. endocrine system
nervous = fast, direct, specific
endocrine = slow, spread out, diverse
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Neurons depend on glucose. How is glucose diffused from blood to inside of neuron cell?
facilitated diffusion
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Does neuron store glycogen and oxygen in order to convert it to glucose?
No
it relies on blood to supply the nutrients
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Signal pathway across neuron:
- dendrite = receives signal
- axon hillock = generates action potential
- axon = carries action potential to synapse
- s synapse = carries signal to another cell
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What defines the resting potential?
equilibrium of Na+/K+ pump across membrane
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How many Na+ and K+ pumped in/out of the cell in the sodium/potassium pump?
3 Na+ out
2 K+ in
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depolarization
inside of the cell is more positive
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hyperpolarization
inside of cell is more negative
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sodium voltage-gated channel:
channel opens when voltage has reached the threshold
flows Na+ ions into the cell = depolarization
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when cell is depolarized, what happens to potassium voltage-gated channels?
they open and K+ ions flow out of the cell
making inside less positive
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by the time K+ flows out, what is going on with Na+ channels?
they are already closed
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What method returns the membrane to its resting potential?
passive diffusion
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What must happen in order to propagate an action potential?
stimulus to membrane must be greater than threshold.
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Action Potential is an All or Nothing!
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Which is faster, an electrical or chemical synapse?
electrical
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Once action potential has reached the synapse, what happens next?
pre-synaptic cells holds vesicles with neurotransmitters
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How does pre-synaptic cell release neurotransmitter?
Ca2+ voltage gated channels open and Ca2+ flow in
Ca2+ releases neurotransmitter vesicles
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How are neurotransmitter vesicles released?
endocytosis
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How does post-synaptic cell receive the neurotransmitter?
it has the corresponding receptor
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What happens if neurotransmitters are fired too often?
it can't replenish neurotransmitter vesicles:
fatigue
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What happens to neurotransmitter after post-synaptic cell has received its signal?
degraded by enzymes
recycled
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Does a single synapse release more than one type of neurotransmitter?
no
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What kind of receptors?
ion channels
or
second messenger systems:
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second messenger systems (G-protein coupled)
G protein is attached to receptor protein
neurotransmitter stimulates protein and alpha subunit breaks off
alpha subunit can open channels, activate enzymes, transcribe etc.
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saltatory conduction
- AP down a myelinated axon jumps from one node of
- Ranvier to the next quickly
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three functions of neurons
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afferent and efferent
afferent = sensory
efferent = motor
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sensory neurons do what?
receive signals from receptor cell that interacts with its environments
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where is sensory neuron located?
dorsal of spinal chord
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interneurons do what?
transfer signals from neuron to neuron
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motor neurons do what?
carry signals to muscle or gland
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where are motor neurons located?
vertically of spinal chord
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CNS v. PNS
CNS = interneurons (brain and spinal chord)
PNS = sensory and motor neurons (everything else)
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PNS divisions
somatic nervous system
autonomic nervous system
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What kind of movement is somatic nervous system responsible for?
voluntary movement
innervates skeletal muscle
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What is automatic nervous system responsible for? How?
involuntary action
sensory ANS sends signals to motor ANS, which signals it to smooth muscle, cardiac muscle, or glands
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What controls the automatic nervous system?
hypothalamus
sympathetic and parasympathetic
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sympathetic v. parasympathetic
sympathetic = fight or flight
parasympathetic = rest and digest
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pre-ganglionic neurons in ANS (sympathetic and parasympathetic)
acetylcholine
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post-ganglionic neurons in ANS (sympathetic and parasympathetic)
sympathetic = epinephrine and noepinephrine
parasympathetic = acetylcholine
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How can the time between heart beats be increased?
increasing ACh
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Central Nervous System involves activity of
brain and spinal chord
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lower brain
medulla, hypothalamus, thalamus, cerebellum
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What is the lower brain responsible for?
subconscious activities
[respiratory, arterial pressure, salivation, emotions, reaction to pain/pleasure]
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What is the higher brain responsible for?
stores memory and processes thoughts
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exocrine . endocrine
exocrine = releases enzymes through ducts
endocrine = releases hormones into blood
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Where are peptide hormones made?
rough ER, cleaved in ER lumen, transported to Golgi
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How are peptide hormones secreted?
stimulation by another hormone
exocytosis
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Do peptide hormones have difficulty passing through membrane of target cell?
yes:
so they attach to a receptor, which can activate ion channel, activate other membrane protiens, activate intracellular second messenger
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example of peptide hormones
anterior pituitary = FSH, LH, ACTh, TSH, Prolactin
posterior pituitary = ADH and oxytocin- parathyroid = PTH
- pancreatic hormone = glucagon and insulin
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Where do steroid hormones come from?
derived from cholesterol
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How do steroid hormones travel through the blood
lipoproteins
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Do steroid hormones have difficulty passing membrane of target cell?
no
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Steroid effects on target cell
diffuse easily through membrane and into cytosol
acts at transcription level
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Where do steroid hormones bind?
receptor protein in the cytosol
then transported to nucleus
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tyrosine derivatives
thyroid hormones and calecholamines (epinephrine and norepinephrine)
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thyroid hormones: lipid or protein like?
lipid soluble, must be carried in the blood by plasma protein carriers
transcription effects
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Why do thyroid hormone effects last long?
they have high affinity to their binding proteins in the plasma
create a latent period in nucleus
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epinephrine and norepinephrine: lipid or protien-like?
water soluble and dissolve in blood
bind to receptors on target tissue
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Effects on target cell of epinephrine and norepinephrine
act mainly through second messenger cAMP
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If the conduct of an effector is given, is the hormone found going to be the one that is responding to the condition or the one creating it?
(ex: aldosterone increases blood pressure. Would you expect aldosterone levels be high or low in a person with low blood pressure?)
gland lags behind effect
high aldosterone because the body tries to bring blood pressure back to normal
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Where are the hormones coming from (distinguish types of hormones)?
- cortex = steroids
- medulla = catecholamines
- thyroid = tyrosine derivatives (thyroid and calcitonin)
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hormones released by anterior pituitary
- hGH
- ACTH
- TSH
- FSH
- LGH
- Prolactin
all peptide hormones
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hGH
human growth hormone
increases amino acid transport across the cell membrane
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so what does hGH do, essentially?
increases transcription and translation
decreases breakdown of proteins
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ACTH
stimulates adrenal cortex to release glucocorticoids
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What are glutocorticoids? When adrenal cortex releases glutocorticoids, what does it do to target cell?
stress hormone
adrenal cortex acts by a second messenger (cAMP)
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TSH
what and how?
stimulates thyroid to release T3 and T4
through a second messenger: cAMP
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Prolactin
promotes lactation (milk production) by the breasts
*not milk ejection
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What inhibits prolactin before birth?
progesterone and estrogen
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hormones released by posterior pituitary
oxytocin and ADH
mostly support tissue for nerve endings
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What kind of hormones are oxytocin and ADH? Where are they synthesized?
peptide hormones
- syntesized in neural cell bodies of hypothalamus
- transported down axons to posterior pituitary
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oxytocin
ejection of milk from breasts
increases uterine concentration during pregnancy
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ADH
makes collecting ducts in kidney permeable to water
reduces the amount of urine and concentrating the urine
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What other effects does ADH have?
increase in blood pressure (b/c it absorbs fluids)
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What are the adrenal glands?
located on top of kidneys -
cortex and medulla
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What does the adrenal cortex secrete?
only steroid hormones
[aldosterone and glucocorticoids]
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aldosterone
increase in Na+ and Cl- reabsorption
increase in K+ and H+ secretion
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how does aldosterone affect ion channels?
increase protein production (a transcription factor)
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glucocorticoids
increase blood glucose concentrations
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cortisol
stimulates gluconeogenesis in liver to increase blood glucose concentration
also degrades tissue to fatty acids for cell energy
[stress hormone]
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What does the adrenal medulla secrete?
catecholamines (epinephrine and norepinephrine)
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catecholamine effects
similar to effects of sympathetic nervous system
vasoconstrictors and vasodilators
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What does vasoconstrictors and vasodilators mean?
constrict blood vessels to internal organs
but,
increase blood flow to skeletal muscles
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What hormones are secreted by the thyroid?
T3 and T4 and calcitonin
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T3 and T4
what kind of hormone? what does it do? how is it regulated?
lipid soluble
increases basal metabolic rate
regulated by TSH
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calcitonin:
what kind of hormone? what does it do?
peptide hormone
- slightly decreases blood calcium
- builds bone mass
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Parathyroid secretes what hormone?
PTH
peptide hormone
- increases blood calcium
- increases osteocyte absorption of calcium and phosphate
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Pancreas secretes what hormones? what kind of hormones are they?
insulin and glucagon
both peptide hormones
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insulin:
released by? released when? what does it do?
released by beta-cells of pancreas
released when blood levels of carb. or proteins are high
it lowers blood glucose levels
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glucagon:
released by? what does it do? how?
released by alpha-cells of pancreas
stimulates glycogenolysis (breakdown of glycogen) in liver
acts via 2nd messenger - raises blood glucose levels
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seminiferous tubules
site of sperm production
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spermatogonia
arise from epithelial tissue to become sperm
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What does LH do?
stimulates leydig cells to release testosterone
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What is testosterone?
the primary androgen (male sex hormone) -
stimulates germ cells to become sperm
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spermatid becomes spermatozoon: what is the structure of spermatozoon?
head, midpiece, and tail
only head (nuclear protion + acrosome) enter the egg
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What provides the energy for movement of the tail?
midpiece is filled with mitochondria
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Where does the spermatozoon mature?
epididymus
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Upon ejaculation, where does the spermatozoa propel through?
vas deferens - into urethra - out of penis
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What is semen?
mixture of spermatozoa and fluid that leaves the penis upon ejaculation
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Where does this fluid come from?
- seminal vesicles
- prostate
- bulbourethral glands
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Menstrual cycle
begins after puberty: what are the steps -
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at puberty what does FSH do?
stimulates growth of cells around primary oocyte
[stuck in prophase I]
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zona pellucida
growth of cells around primary oocyte stimulate zona pellucid around the egg
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What is the structure of the primary oocyte with growth and zone pellucida around it?
primary follicle
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once the primary follicle is set what happens next?
follicle grows further - consists of theca cells, growth of cells, and zona pellucid and the oocyte
this is the secondary follicle
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What does LH do?
stimulates theca cells to secrete androgen -
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What does FSH do?
converts androgen into estradiol ( a kind of estrogen)
estradiol is secreted to the blood
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What does the estradiol do?
it prepares uterine wall for pregnancy
that's why it's produced during menstrual cycle and secreted into the blood
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Just before ovulation, estradiol levels rise rapidly. What does this do?
dramatic increase in LH secretion
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What is this increase in LH secretion called?
luteal surge
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What does the luteal surge do? (rise in LH levels)
causes the follicle to burst, releasing the egg
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The egg that is released due to the luteal surge is what kind?
secondary oocyte
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What happens to the egg?
it is swept to the Fallopian tube or oviduct
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What happens to the rest of the folicle
it is left behind to become the corpus luteum
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What does the corpus luteum do?
secretes estradiol and progesterone throughout pregnancy
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If not pregnant, corpus luteum....
degrades into corpus ablicans
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Where does the egg go?
it is taken up by the frimbriae in fallopian tube
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Is the egg the only thing that enters the fallopian tube?
no, zona pellucida and some granulosa cells also enter
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After ovulation, what happens to secondary oocyte?
begins the second meiotic division
pauses at metaphase II until fertilization
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after the fallopian tube, where is the egg designated? and how?
uterus by cilia
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How does sperm move?
requires ATP
sperm acrosome makes path
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Where does the sperm end up?
cytoplasm of the oocyte
prevents other sperm from fertilizing the same egg
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Now that the sperm and egg have met, what can occur?
oocyte goes through second meitotic division
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What is the product of this second meiotic division?
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What is fertilization?
when ovum and sperm fuse to form the zygote
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What is cleavage:
zygote (still in fallopian tube) undergoes further mitotic division
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zygote comprised of 8 or more cells is called
morula
any of these 8 cells can produce a complete individual
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morula continues to divide forming....
hollow ball with fluid - blastocyst
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what is it called when blastocyst enters uterus?
implantation -
said to be pregnant
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Upon implantation, egg secretes...
HCG - human chorionic gonadotropin
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What does HCG do?
prevents degeneration of the corpus luteum
maintains secretion of estrogen and progesterone
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What happens next?
placenta is formed
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By when does placenta reach full development?
end of the first trimester
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What happens to HCG after placenta has developed?
placenta can produce its own progesterone and estrogen
so it lowers secretion of HCG
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gastrulation
cells begin to move around slowly
form 3 germ layers
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what are the germ layers? and their funcitons
ectoderm: outer covering, nervous sys., sensory organs
mesoderm: bone and muscle
endoderm: lining of digestive tract and liver & pancreas
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neurulation
notochord (mesoderm) induces the overlying ectoderm to thicken
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cell differentiation during development is extremely sensitive to:
timing of mRNA turnover
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