Endocrine System
Hormones
& Homeostasis
AP Biology
2006-2007
Homeostasis

Homeostasis

maintaining internal balance in the body



organism must keep internal conditions
stable even if environment changes
also called “dynamic equilibrium”
example: body temperature

humans:
 too cold = shiver
 too warm = sweat

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lizard:
 too cold = bask in sun
 too warm = hide in shade
Regulation

How we maintain homeostasis

nervous system


nerve signals control body functions
endocrine system


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hormones
chemical signals control body functions
Nervous System Control
Feedback
Controlling Body Temperature
nerve signals
brain
sweat
high
body temperature
low
brain
constricts surface shiver
blood vessels
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nerve signals
dilates surface
blood vessels
Hormones

Why are hormones needed?
chemical messages from one body part
to cells in other parts of body
 communication needed
to coordinate whole body
 maintaining homeostasis

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growth hormones
Endocrine System

Endocrine system releases hormones

glands which secrete (release)
chemical signals into blood

chemicals cause changes
in other parts of body
 growth hormones
 sex hormones
 response hormones
 metabolism hormones
 and more….
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Responding to hormones

Lock and key system

hormone fits receptor on “target” cell
target
cell
secreting
cell
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can’t
read
signal
nontarget
cells
can’t
read
signal
Glands

Pineal


Pituitary


insulin, glucagon
Ovary


adrenaline
Pancreas


thyroxine
Adrenal


many hormones:
master gland
Thyroid


melatonin
estrogen
Testes

testosterone
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Feedback
Maintaining homeostasis
hormone 1
lowers
body condition
gland
high
specific body condition
low
raises
body condition
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gland
hormone 2
Negative Feedback

Response to changed body condition

if body is high or low from normal level


signal tells body to make changes that will
bring body back to normal level
once body is back
to normal level,
signal is
turned off
gland
hormone 1
lowers
body condition
high
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specific body condition
Endocrine System Control
Regulation of Blood Sugar
Feedback
insulin
liver stores
sugar
body
cells take
up sugar
from blood
pancreas
high
liver
blood sugar level
(90mg/100ml)
low
triggers
hunger
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liver
releases
sugar
liver
pancreas
glucagon
reduces
appetite
Everyone’s doing it, so
Ask Questions!!
AP Biology
2006-2007
Sex & Growth Hormones

Large scale body
changes

how do they work


turn genes on
start new processes
in the body by
turning genes on
that were lying
“dormant”
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Pituitary gland hormones

Sex & reproductive hormones

FSH



LH




luteinizing hormone
stimulates ovaries & testes
prepares uterus for fertilized egg
oxytocin



follicle stimulating hormone
stimulates egg & sperm production
stimulates childbirth contractions
releases milk in nursing mothers
prolactin

milk production in nursing mothers
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hormones
hormones
Reproductive hormones

Testosterone



from testes
sperm
production &
secondary sexual
characteristics
Estrogen


from ovaries
egg production,
preparing uterus
for fertilized egg
& secondary
sexual
characteristics
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Male
reproductive
system

Sperm production
over 100 million produced per day!
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Biology
~2.5 million released per drop!

seminiferous
tubule
sperm
spermatocytes
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Male reproductive system

Testes & epididymis


sperm production &
maturation
Glands
seminal vesicles,
prostate,
bulbourethal
 produce seminal
fluid


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nutrient-rich
Male reproductive system

Testicles


Scrotum


where sperm mature
Vas deferens


sac that holds testicles outside of body
Epididymis


produces sperm & hormones
tubes for sperm to travel from testes to penis
Prostate, seminal vesicles,
Cowper’s (bulbourethal) glands

nutrient rich fluid to feed & protect sperm
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Female reproductive system
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Female reproductive system

Ovaries


Uterus


tubes for eggs to travel from ovaries to uterus
Cervix


nurtures fetus; lining builds up each month
Fallopian tubes


produces eggs & hormones
opening to uterus, dilates 10 cm for birthing baby
Vagina

birth canal for birthing baby
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Female reproductive system
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Egg maturation in ovary
releases
progesterone
maintains
uterus
lining
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produces estrogen
LH
Menstrual cycle

Controlled by
interaction of
4 hormones egg development
FSH & LH
 estrogen
 progesterone
FSH
ovulation = egg release

corpus luteum
estrogen
progesterone
lining of uterus
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days 0
7
14
21
28
Feedback
Female reproductive cycle
egg
matures &
is released
(ovulation)
estrogen
builds up
uterus lining
corpus
luteum
ovary
progesterone
FSH & LH
maintains
uterus lining
fertilized egg
(zygote)
HCG
yes
pituitary
gland
pregnancy
GnRH
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hypothalamus
no
corpus luteum breaks down
progesterone drops
menstruation
corpus
luteum
progesterone
maintains
uterus lining
Female hormones

FSH & LH




Estrogen




released from pituitary
stimulates egg development & hormone release
peak release = release of egg (ovulation)
released from ovary cells around developing egg
stimulates growth of lining of uterus
decreasing levels causes menstruation
Progesterone
released from “corpus luteum” in ovaries
 cells that used to take care of developing egg
 stimulates blood supply to lining of uterus
 decreasing levels causes menstruation
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
Fertilization
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Any Questions??
AP Biology
2006-2007
What do they do?

Maintain homeostasis
blood sugar level
 temperature control


Start a new process
growth
 fetal development
 sexual development

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Body Temperature
Negative Feedback

Negative feedback

every time body is
high or low from
normal level a signal
tells the body to
make changes that
will bring body back


body temperature
control of blood sugar
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Regulation by chemical messengers


Neurotransmitters released by neurons
Hormones release by endocrine glands
endocrine gland
neurotransmitter
axon
hormone
carried by blood
receptor proteins
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receptor proteins
target cell
Body Regulation

Nervous system &
Endocrine system work
together

hypothalamus



“master nerve control center”
receives information from
nerves around body about
internal conditions
communicates with
pituitary gland


“master gland”
releases many hormones
hormones
 sexual development, growth,
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milk production, pain-relief
hormones