Insulin, glucagon, thyroxine, leptin, melatonin, and reproductive hormones help regulate homeostasis and reproduction. Insulin and glucagon regulate blood glucose levels. Thyroxine regulates metabolism. Leptin regulates appetite. Melatonin regulates circadian rhythms. Reproductive hormones like testosterone and estrogen influence sexual development and control the menstrual cycle through feedback mechanisms. New technologies like IVF involve manipulating hormone levels to induce superovulation and establish pregnancies.

1. 6.6 HORMONES,
HOMEOSTASIS, AND
REPRODUCTION
Part 1

2. Understandings
Insulin and glucagon are
secreted by beta and alpha
cells in the pancreas,
respectively, to control
blood glucose
concentration.
Thyroxin is secreted by the
thyroid gland to regulate
metabolic rate and help
control body temperature.
Leptin is secreted by cells in
adipose tissue and acts on
the hypothalamus of the
brain to inhibit appetite.
Applications/Skills
A: Causes and treatments of
Type I and Type II Diabetes.
A: Testing of leptin on
patients with clinical obesity
and reasons for the failure
to control the disease.
A: Causes of jetlag and use
of melatonin to alleviate it.

3. HOMEOSTASIS
Limits for physiological variables
Variable Limits or range
Blood pH 7.35-7.45
Blood glucose 0.8-1.0 g glucose/ L blood
Body temperature 37C/98.6F

4. GETTING BACK TO SET POINT
http://upload.wikimedia.org/wikipedia/commons/2/22/105_Negative_Feedback_Loops.jpg

5. HORMONES
Secreted by endocrine
glands into the blood
stream
Some have few target
tissues (glucagon-
hepatic cells and
muscle cells) and some
have many target
tissues (insulin- all
body cells)
https://ohgoshmygrades.files.wordpress.com/2014/11/09-endocrine-glands.jpg

6. THYROXIN
Secreted by the thyroid
gland
Two forms: T3 (three iodine
atoms) and T4 (four iodine
atoms)
Targets almost all cells
Responsible for metabolic
rate

7. HYPO- AND HYPERTHYROIDISM
Hypothyroidism
 Body doesn’t produce enough thyroxin
 Slow metabolic rate
 Gains weight easily
 Often cold
Hyperthyroidism
 Weight loss
 Rapid heartbeat
 Nervousness/anxiety
 Sensitivity to heat

8. LEPTIN
Secreted by adipose tissue
Targets hypothalamus of
the brainstem
Lowers appetite
http://www.bullyextreme.com/wp-content/uploads/2013/03/leptin-weight-loss.gif

9. LEPTIN AND OBESITY
Greater fat stores=more leptin secretion
Obese individuals seem to be resistant to desired effects of leptin
 Why?
http://sevendeadlysynapses.com/wp-content/uploads/2011/05/ob-mice-leptin.gif

10. MELATONIN
Secreted by pineal gland to
regulate circadian rhythm
Peak production occurs after
dark
Can be altered by changing
exposure to light
http://nabulsi.com/images/inside-arts/en/11665/01.jpg

11. JET LAG
Disruption of sleep cycles, generally due to travelling across time
zones.
Can be alleviated by taking melatonin supplement until natural
rhythms resume
http://www.precisionnutrition.com/wordpress/wp-content/uploads/2013/07/Precision-Nutrition-Blog-All-About-Jet-Lag-

12. INSULIN
Secreted by beta cells in the
pancreas
Causes protein channels in cells to
open
Allows for diffusion of glucose into
the cell for cellular respiration
Stimulates hepatocytes to convert
glucose into glycogen to be stored
in the liver or in muscles
https://ntp.niehs.nih.gov/nnl/hepatobiliary/liver/hglycoacc/images/figure-004-a71199_medium.jpg

13. GLUCAGON
Secreted by alpha cells of the pancreas
Stimulates hydrolysis of glycogen
Increase in blood glucose levels
http://www.nicerweb.com/bio1152/Locked/media/ch45/45_12GlucoseHomeostasis.jpg

14. TYPE I DIABETES
Immune system targets beta cells
Insufficient insulin is produced
Controlled by insulin injection
Often called “juvenile diabetes” but
can develop at any age
http://blog.joslin.org/wp-content/uploads/2012/10/insulin-injection.jpg

15. TYPE II DIABETES
Cell receptors stop responding to insulin
(insulin resistance)
Controlled by diet
Can be caused by genetics, poor diet,
obesity, and/or age

16. EFFECTS OF DIABETES
Blindness
Kidney failure
Nerve damage
Increased risk of cardiovascular disease
Poor wound healing leading to
amputation
http://www.activeonegroup.com/wp-content/uploads/2014/10/type-2-diabetes.jpg

17. 6.6 HORMONES,
HOMEOSTASIS, AND
REPRODUCTION
Part 2

18. Understandings
A gene on the Y chromosome causes
embryonic gonads to develop as testes
and secrete testosterone.
Testosterone causes prenatal
development of male genitalia and
both sperm production and
development of male secondary sexual
characteristics during puberty
Estrogen and progesterone cause
prenatal development of female
reproductive organs and female
secondary sexual characteristics
The menstrual cycle is controlled by
negative and positive feedback
mechanisms involving ovarian and
pituitary hormones.
Applications/Skills
A: The use in IVF of drugs to suspend
the normal secretion of hormones,
followed by the use of artificial doses of
hormones to induce superovulation and
establish a pregnancy
A: William Harvey’s investigation of
sexual reproduction in deer
S: Annotate diagrams of the male and
female reproductive system to show
names of structures and their functions.
Guidance
- The roles of FSH, LH, estrogen, and progesterone in the menstrual cycle are expected.
- William Harvey failed to solve the mystery of sexual reproduction because effective microscopes
were not available when he was working, so fusion of gametes and subsequent embryo
development remained undiscovered.

19. HISTORICAL PERSPECTIVE OF SEXUAL
REPRODUCTION
One of the earliest theories as to how animals reproduce sexually was
the 'soil and seed' theory proposed by Aristotle
According to this theory, the male produces a ‘seed' which forms
an ‘egg' when mixed with menstrual blood (the ‘soil’)
The ‘egg’ then develops into a fetus inside the mother according to
the information contained within the male 'seed’ alone
http://ib.bioninja.com.au/standard-level/topic-6-human-physiology/66-hormones-homeostasis-
and/sexual-reproduction.html

20. DEBUNKING THE ’SOIL AND SEED’
THEORY
William Harvey studied the sexual organs of female deer after mating
in an effort to identify the developing embryo
He was unable to detect a growing embryo until approximately 6 – 7
weeks after mating had occurred
He concluded that Aristotle’s theory was incorrect and that menstrual
blood did not contribute to the development of a fetus
Harvey was unable to identify the correct mechanism of sexual
reproduction and incorrectly asserted that the fetus did not develop
from a mixture of male and female ‘seeds’
http://ib.bioninja.com.au/standard-level/topic-6-human-physiology/66-hormones-homeostasis-and/sexual-
reproduction.html

21. HUMAN REPRODUCTION
Fertilization of a female egg by a male
sperm
Hormones play key role in further
development and gender determination
https://www.papermasters.com/images/human-reproduction.jpeg

22. MALE OR FEMALE?
XX- female
 High estrogen and progesterone production
 Development of female reproductive structures
XY- male
 High testosterone production
 Early testes development
https://tse2.mm.bing.net/th?id=OIP.M1c56c49552cb050d624637001cc313dbH0&pid=15.1&P=0&w=275&
Eight week embryo

23. THE ROLE OF TESTOSTERONE
Formation of male genitalia during embryonic development
Secondary sex characteristics during puberty
 Body hair
 Enlargement of larynx
 Deepening of the voice
 Increased muscle mass
 Enlargement of the penis
Production of sperm
Sex drive
Adapted from http://www.raw-milk-facts.com/images/Testostero

24. Sperm produced here in seminiferous tubules
Sperm are stored here to mature
Sperm travels from epididymis to ureth
Produces seminal fluid with nutrients
Sacs that hold testes
outside of the body
cavity
Male sex organ; becomes
erect as a result of blood
engorgement to facilitate
ejaculation

25. THE ROLE OF ESTROGEN
Formation of female genitalia during embryonic development
Secondary sex characteristics in puberty
 Enlargement of breasts
 Growth of pubic and underarm hair
 Widening of hips
Onset and regulation of the menstrual cycle
http://blogs.psychcentral.com/depression/files/2011/03/estrogen.jpg

26. Produce/secrete estrogen; produce/release ovum
Carries ovum/early embryo to uterus
Embryo implants/develops if pregnancy occurs
Inner lining of uterus
Lower
portion of
uterus that
opens into
Female sex organ; canal that leads
from external genitalia to cervix
Vulva External female genitalia

27. MORE ON ESTROGEN
Released by ovaries
Enters bloodstream
Endometrium Pituitary gland
Increases density of blood
vessels in preparation of
implantationhttp://images.clipartpanda.com/uterus-clipart-uterus-1024x697.jpg
Releases more FSH/LH

28. MENSTRUAL CYCLE
Regulated by hypothalamus; 28ish days
1. Follicular Phase : low estrogen, FSH = egg develops in ovary
2. Ovulation (Day 14): LH = egg released into Fallopian tube
3. Luteal Phase :
• progesterone, estrogen = lining of uterus
(endometrium) thickens to prepare for pregnancy
• Egg travels down Fallopian tube, waits for fertilization
4. Menstruation (no fertilization) :
• P/E = lining of uterus breaks down
• Blood and unfertilized egg discharged

29. EFFECTS OF FSH AND LH
Target tissue: Ovaries
Increase production/secretion of estrogen
Production of Graafian follicles
Elevated levels leads to ovulation
http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/Image721.gif

30. OVULATION
http://schoolbag.info/biology/humans/humans.files/image321.jpg

31. PROGESTERONE
Produced by corpus luteum for
10-12 days following ovulation
Maintains thickened endometrium
High levels of progesterone
combined with high levels of
estrogen prevent production of
another Graafian follicle

32. HUMAN EMBRYONIC
DEVELOPMENT
Conception: in oviduct
Implantation: in uterus
Hormones:
 Human Chorionic Gonadotropin (hCG):
maintain estrogens in early pregnancy;
pregnancy test
About 40 weeks
Egg lodged in oviduct = ectopic
(tubal) pregnancy

33. Implantation of blastocyst
Blastocyst
Endo-
metrium
Cavity
Inner cell mass
Trophoblast
EARLY POSTFERTILIZATION
EVENTS

34. THE PILL
“Contains estrogen and progesterone
Main effect: Prevent ovulation
Other effects:
 Thickens cervical mucus – slows down sperm
 Thins uterus lining – prevent implantation of fertilized egg
Usage: active pill for 21 days, inactive pills for 7 days (“period”)
Other medical uses:
 Medication for mild/moderate acne
 Decrease painful menstruation
 Treat polycystic ovary syndrome (PCOS)
 Correct irregular menstrual cycle
 Reduce risk of ovarian and endometrial cancers

35. IVF
Woman receives hormone
therapy
 1st two weeks: hormone injections
to halt normal ovulation
 2nd two weeks: hormone injections
to induce superovulation
Eggs are harvested
Sperm collected from man
Eggs and sperm combined in culture dish
Usually multiple fertilized eggs are
implanted into the woman’s uterus
Unused embryos frozen