1. Hormones & Homeostasis
Endocrine System
Hormones & Homeostasis
Ch. 39

2. 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
lizard:
too cold = bask in sun
too warm = hide in shade

3. Regulation How we maintain homeostasis nervous system endocrine system
nerve signals control body functions
endocrine system
hormones
chemical signals control body functions

4. Controlling Body Temperature
Nervous System Control
Feedback
Controlling Body Temperature
nerve signals
brain
sweat
dilates surface blood vessels
high
body temperature
low
constricts surface blood vessels
shiver
brain
nerve signals

5. 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
growth hormones

6. 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….
Hormones coordinate slower but longer–acting responses to stimuli such as stress, dehydration, and low blood glucose levels. Hormones also regulate long–term developmental processes by informing different parts of the body how fast to grow or when to develop the characteristics that distinguish male from female or juvenile from adult. Hormone–secreting organs, called endocrine glands, are referred to as ductless glands because they secrete their chemical messengers directly into extracellular fluid. From there, the chemicals diffuse into the circulation.

7. Responding to hormones
Lock and key system
Nonsteriod Hormones
hormone fits receptor on “target” cell
Steroid Hormones – find receptor inside of “target” cell
target cell
secreting cell
non- target cells
can’t read signal
can’t read signal

8. Glands Pineal Pituitary Thyroid Adrenal Pancreas Ovary Testes
Melatonin – sleep cycle
Pituitary
many hormones: master gland
Thyroid
Thyroxine - metabolism
Adrenal
Adrenaline – “fight or flight” response
Pancreas
insulin, glucagon – blood sugar levels
Ovary
Estrogen – egg production and prepares uterus
Testes
Testosterone – sperm production

9. Maintaining homeostasis
Feedback
Maintaining homeostasis
hormone 1
gland
lowers body condition
high
specific body condition
low
raises body condition
gland
hormone 2

10. specific body condition
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
hormone 1
gland
lowers body condition
high
specific body condition

11. Regulation of Blood Sugar
Endocrine System Control
Feedback
Regulation of Blood Sugar
insulin
body cells take up sugar from blood
liver stores sugar
reduces appetite
pancreas
liver
high
blood sugar level
(90mg/100ml)
low
liver releases sugar
triggers hunger
pancreas
liver
glucagon

12. Everyone’s doing it, so Ask Questions!!

13. Hormones & Reproduction
Endocrine System
Hormones & Reproduction

14. 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”

15. Pituitary gland hormones
Sex & reproductive hormones
FSH
follicle stimulating hormone
stimulates egg & sperm production LH
luteinizing hormone
stimulates ovaries & testes
prepares uterus for fertilized egg
oxytocin
stimulates childbirth contractions
releases milk in nursing mothers
prolactin
milk production in nursing mothers
hormones
hormones

16. Reproductive hormones
Testosterone
from testes
sperm production & secondary sexual characteristics
Estrogen
from ovaries
egg production, preparing uterus for fertilized egg & secondary sexual characteristics

17. Male reproductive system
Sperm production
over 100 million produced per day!
~2.5 million released per drop!

18. seminiferous tubule
sperm
spermatocytes

19. Male reproductive system
Testes & epididymis
sperm production & maturation
Glands
seminal vesicles, prostate, bulbourethal
produce seminal fluid
nutrient-rich

20. Male reproductive system
Testicles
produces sperm & hormones
Scrotum
sac that holds testicles outside of body
Epididymis
where sperm mature
Vas deferens
tubes for sperm to travel from testes to penis
Prostate, seminal vesicles, Cowper’s (bulbourethal) glands
nutrient rich fluid to feed & protect sperm

21. Female reproductive system

22. Female reproductive system
Ovaries
produces eggs & hormones
Uterus
nurtures fetus; lining builds up each month
Fallopian tubes
tubes for eggs to travel from ovaries to uterus
Cervix
opening to uterus, dilates 10 cm for birthing baby
Vagina
birth canal for birthing baby

23. Female reproductive system

24. Egg maturation in ovary
releases progesterone
maintains uterus lining
produces estrogen

25. Menstrual cycle Controlled by interaction of 4 hormones FSH & LH
estrogen
progesterone
FSH
ovulation = egg release
egg development
corpus luteum
estrogen
progesterone
lining of uterus
days 7 14 21 28

26. Female reproductive cycle
Feedback
Female reproductive cycle
egg matures &
is released (ovulation)
builds up uterus lining
estrogen
ovary
corpus luteum
progesterone
FSH & LH
fertilized egg (zygote)
maintains uterus lining
HCG
yes
pituitary gland
corpus luteum
pregnancy
GnRH no
progesterone
corpus luteum breaks down
progesterone drops
menstruation
maintains uterus lining
hypothalamus

27. Female hormones FSH & LH Estrogen Progesterone released from pituitary
stimulates egg development & hormone release
peak release = release of egg (ovulation)
Estrogen
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

28. Fertilization

29. Placenta
Food & gases diffuse across blood vessels

30. Any Questions??