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