Topic 6: Human Physiology (2 hours)
6.6 Hormones, homeostasis and reproduction: Hormones are used when signals need to be widely distributed.
Nature of science: Developments in scientific research follow improvements in apparatus—William Harvey was
hampered in his observational research into reproduction by lack of equipment. The microscope was invented 17 years
after his death.
Understandings:
 Insulin and glucagon are secreted by β and α cells of the pancreas
respectively to control blood glucose concentration.
 Thyroxin is secreted by the thyroid gland to regulate the 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.
 Melatonin is secreted by the pineal gland to control circadian rhythms.
 A gene on the Y chromosome causes embryonic gonads to develop as
testes and secrete testosterone.
 Testosterone causes pre-natal development of male genitalia and both
sperm production and development of male secondary sexual
characteristics during puberty.
 Estrogen and progesterone cause pre-natal development of female
reproductive organs and female secondary sexual characteristics during
puberty.
 The menstrual cycle is controlled by negative and positive feedback
mechanisms involving ovarian and pituitary hormones. The roles of
FSH, LH, estrogen and progesterone in the menstrual cycle are expected.
Applications and skills:
Application: Causes and treatment of
Type I and Type II diabetes.
Application: Testing of leptin on patients
with clinical obesity and reasons for the
failure to control the disease.
Application: Causes of jet lag and use of
melatonin to alleviate it.
Application: 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.
Application: William Harvey’s
investigation of sexual reproduction in
deer.
Skill: Annotate diagrams of the male and
female reproductive system to show
names of structures and their functions.
Utilization: Hormones are used in a variety of therapies such as replacement therapies.
Aims: Scientists are aware that the drugs women take in fertility treatment pose potential risks to health. Should
scientific knowledge override compassionate considerations in treating infertile couples?
6.6 Homework Quiz
Don’t forget to title this “6.6 Homework Quiz” so Mr. Lawton can find it.
1. What are the sex chromosomes that a
human female has? What about a human
male?
2. List any 2 secondary sex characteristics of
males.
3. What is the function of insulin?
4. Where is the hormone thyroxin made?
5. What do you think would happen to you if
you had an underproduction of the
hormone leptin?
Insulin
Glucagon
Leptin
Thyroxin
Melatonin
Testosterone
Estrogen
Biology Journal 11/11/2013
What does homeostasis mean?
What is a negative feedback
loop? What does it have to do
with homeostasis?
Biology Journal 3/19/2015
What are the roles of insulin and glucagon in
balancing blood sugar?
Which type of diabetes can develop as an
adult? What could be a reason that it is a
problem in this country?
Biology Journal 11/19/2013
Is blood clotting a
positive or negative
feedback cycle. How
do you know?
Biology Journal 11/14/2013
When you eat salty foods, the salt is absorbed into
your blood (through the small intestine). The kidneys
detect this extra salty blood, and react by increasing
the amount of water in the blood. This extra water
dilutes the extra salt and brings the blood’s saltiness
back to a specific amount.
Could this be positive or negative feedback? Explain why you think so.
How does a pregnant woman’s body decide when to
give birth? The process begins when the uterus
(womb) begins to release a hormone called oxytocin,
which causes contractions. The brain detects oxytocin
and the contractions, and begins to make more
oxytocin. This causes even more contractions, which
makes the brain release more oxytocin. This keeps
escalating until the baby comes out.
Could this be positive or negative feedback? Explain why you think so.
Biology Journal 3/28/2014
Which of these pictures best represents
positive feedback? Why do you think so?
Which of these pictures best represents
negative feedback? Why do you think so?
Negative feedback:
Keeps your body in balance
Positive feedback:
Takes things to the extreme
What could be 6 values that your body
monitors and regulates through negative
feedback?
Blood sugar concentration
pH
Blood Pressure
Temperature
Water concentration
CO2 concentration
Hormones and Homeostasis
Hormones are chemical signaling molecules.
They are made by glands and transported by the
blood. This is called the endocrine system.
Homeostasis is the processes in which
the body monitors and maintains a
stable internal environment.
What internal temperature is kept stable in the body?
98.6° F or 37° C
What is normal blood pressure?
120/80 (the units of blood pressure are mmHg)
What is normal blood pH?
7.4
What is normal blood sugar concentration?
80 mg/dl (that’s milligrams of glucose per decaliter of blood)
What is normal water concentration in the blood?
Around 90% of blood volume
What is normal CO2 concentration in the blood?
10 to 13 kPa (kilopascals, which is pressure)
What does your body do to regulate its
temperature?
A gland (thyroid gland) monitors temperature
Too cold?
Secrete thyroxin to speed
up metabolic rate, raising
temperature.
Too hot?
Stop thyroxin secretion to slow
down metabolic rate,
conserving energy and heat.
What if your temperature gets too high or too low?
Fevers are caused by your
own body! It is generally
believed that fevers help
the immune system to
fight off an infection.
Hypothermia is when
you body loses too much
body heat to keep
functioning normally.
Negative feedback is when the results of a
process reduce the process itself.
•This is how the body regulates
homeostasis.
Cells in the pancreas
regulate the glucose
levels.
•High blood sugar: βcells make insulin and
glucose is stored
•Low blood sugar: αcells makes liver
release glucagon,
increasing blood sugar
What are the names the disease that happens
when this system is not working? What’s the
difference between the names?
Type I diabetes:
You are born with it. It is often an autoimmune
disease, where your immune system attacks and
destroys your β-cells.
Type II diabetes:
Adult-onset diabetes. This occurs as the body
develops resistance to normal insulin functioning.
It is closely tied to obesity.
Gestational diabetes:
Diabetes occurring in a pregnant woman. She will
have high glucose levels, but returns to normal
following birth.
Positive feedback is when the results of a
process increase the process itself.
•These are rare, because they make an
imbalance
Clotting blood is a positive
feedback cycle.
•Damaged tissues release
clotting factors, causing
other cells to do the same.
It starts a reaction
culminating in a clot.
When you eat salty foods,
the salt is absorbed into your
blood (through the small
intestine). The kidneys
detect this extra salty blood,
and react by increasing the
amount of water in the
blood. This extra water
dilutes the extra salt and
brings the blood’s saltiness
back to a specific amount.
Could this be positive or negative
feedback? Explain why you think so.
How does a pregnant woman’s
body decide when to give birth?
The process begins when the
uterus (womb) begins to release
a hormone called oxytocin, which
causes contractions. The brain
detects oxytocin and the
contractions, and begins to make
more oxytocin. This causes even
more contractions, which makes
the brain release more oxytocin,
which escalates until the baby
comes out.
Could this be
positive or
negative
feedback? Explain
why you think so.
Which of these pictures best represents
positive feedback? Why do you think so?
Which of these pictures best represents
negative feedback? Why do you think so?
Negative feedback:
Keeps your body in balance
Positive feedback:
Takes things to the extreme
What are the hormones involved in
gender?
Functions of Testosterone:
1. Pre-natal development of male sex organs
SRY gene on the Y chromosome causes a surge of testosterone in the developing
baby, causing a penis and testes to develop.
If Y chromosome is
present, it’s SRY gene
causes testosterone
surge
6 week old embryo
(has no gender yet)
If Y chromosome is
absent, no testosterone
surge occurs
Functions of Testosterone:
2. Secondary sexual characteristics in puberty
Increased muscle mass, pubic and body hair, male grows taller, voice deepens,
increased aggression, sperm production begins.
Testosterone released during puberty
Testosterone released during puberty
Testosterone released during puberty
Functions of Testosterone:
3. Sex Drive and Aggression
Testosterone increases male sex drive and makes sperm production constant for
his entire life. Aggression is likely an evolutionary adaptation for hunting, defense,
and mate competition.
Andre the Giant was a person who suffered from
acromegaly, in which the pituitary gland overproduces
growth hormone (GH).
Functions of Estrogen and Progesterone:
1. Pre-natal development of female sex organs
If the SRY gene on the Y chromosome is absent, then estrogen and progesterone
manufacture begins, and the fetus becomes a female.
Low levels of estrogen
and progesterone
(due to the presence a Y
chromosome’s SRY gene)
6 week old embryo
(has no gender yet)
High levels of estrogen
and progesterone
(due to the lack of a Y
chromosome’s SRY gene)
Functions of Estrogen and Progesterone:
2. Secondary sexual characteristics in puberty
Female grows taller, development of pubic hair, voice deepens, changed
distribution of body fat, development of breasts.
Estrogen and Testosterone released during puberty
determine
Estrogen and Testosterone released during puberty
Estrogen and Testosterone released during puberty
Functions of Estrogen and Progesterone:
3. Regulation of the menstrual cycle.
Much more on that to come…
Biology Journal 3/31/2014
The menstrual cycle is regulated by 4 hormones. It
“begins” with menstrual bleeding, and repeats about
every 28 days. What could be some reasons for this
bleeding? Why does it happen?
Bleeding is when the uterus gets rid of
the endometrium lining. This lining is
what the uterus prepares to be the
placenta, providing blood-borne
nutrients to the baby, if the woman
becomes pregnant.
Biology Journal 3/23/2014
Right before ovulation, the hormones _________,
_________, and _________ reach their highest
concentration. The leftover part of the follicle that released
the egg, now called the corpus luteum, releases the
hormone _________, which causes the build up of the lining
of the _________, called the endometrium. This will be shed
during _________, if a female is not _________.
Biology Journal 3/23/2014
Right before ovulation, the hormones
estrogen, luteinizing hormone (LH), and
follicle stimulating hormone (FSH) reach
their highest concentration. The leftover
part of the follicle that released the egg, now
called the corpus luteum, releases the
hormone progesterone which causes the
build up of the lining of the uterus called the
endometrium. This will be shed during the
mensturation if a female is not pregnant.
The Analysis and Evaluation portions of
your IA are due on Wednesday, April 1st.
• This is the calculations, graphing, statistical
analysis, and conclusion.
• Print off and turn in your whole IA thus far,
so Mr. Lawton can refer to it.
• Use the checklists on your IA guide!
• Do not wait until the night before to do it,
something will go frustratingly wrong with
your graphing, and you’ll be horribly sad…
The hormones _________ and _________ stimulate a follicle to
develop. Ovulation happens when the hormones _________,
_________, and _________ reach their highest concentration.
After ovulation, the follicle turns into a structure called
_________, which will produce the hormone _________. But,
when this structure disappears, and stops making hormone,
then _________ happens. If a female becomes pregnant,
however, then the endometrium becomes the _________, and
produces the hormone _________, so that it is not shed, which
would kill the fetus.
The hormones FSH and LH stimulate a follicle to
develop. Ovulation happens when the hormones
FSH, LH, and estrogen reach their highest
concentration. After ovulation, the follicle turns
into a structure called corpus luteum which will
produce the hormone progesterone. But, when
this structure disappears, and stops making
hormone, then menstruation happens. If a female
becomes pregnant, however, then the
endometrium becomes the placenta and produces
the hormone progesterone, so that it is not shed,
which would kill the fetus.
Biology Journal 4/2/2014
What is the release of an egg (ovum) from the ovary
called?
What is the structure called that develops this egg?
What hormone does it make?
What does this structure turn into after releasing an
egg?
Biology Journal 4/2/2014
What is the release of an egg (ovum) from the ovary
called?
Ovulation
This is also when a female is most fertile.
What is the structure called that develops this egg?
Follicle
Immature eggs are called oocytes.
What does this structure turn into after releasing an
egg?
Corpus luteum
This begins to make progesterone, before completely
breaking down.
Biology Journal 3/20/2015
List the structures that a
sperm cell passes through
from spermatogenesis, to
when it is released out of
the penis through
ejaculation.
1. Testicle, where spermatogenesis happens.
2. Epididymis the cells mature
3. Carried along vas deferens, where it passes through 2 glands…
4. Seminal vesicle adds fructose and mucus
5. Prostate adds fluids to neutralize acid in vagina
6. Urethra carries sperm through the…
7. Penis where it exits the body
Biology Journal 3/24/2015
What makes FSH and LH?
The pituitary gland in the brain.
What do FSH and LH make
happen?
They cause the formation of a
follicle, and then ovulation.
What makes estrogen?
The follicle
What makes progesterone?
The corpus luteum (the follicle turns into the corpus luteum after it ovulates)
What do estrogen and progesterone do?
They develop and maintain the endometrium layer in the uterus.
(When these hormones disappear, the endometrium dies and is released through menstruation)
Biology Journal 3/25/2015
What is IVF? How does
it work? What are some
arguments for and
against it?
Mr. Lawton needs your first IA
in digital format!
This will benefit you, too! Submit it
to turnitin.com and Mr. Lawton will
keep it for you forever… (and you
will want it later)
6.6 Reproduction
What are the male sex cells called?
Sperm, aka spermatozoa, aka male gamete
What are the female sex cells called?
Eggs, or oova (when mature), or oocyte (when immature), aka
female gamete
What is a haploid cell?
These have a half set of DNA (23 chromosomes in humans)
What is a diploid cell?
These have a full set of DNA (46 chromosomes in humans)
What kind of cells does mitosis make?
Mitosis
Mitosis starts with a body cell (diploid)
and makes another identical body cell
(diploid).
1 → 2 cells (identical)
What kind of cells does meiosis make?
Mitosis starts with a body cell (diploid) and
makes 4 haploid cells that are all different.
1 → 4 cells (not identical, half DNA)
Meiosis
Gametes are haploid sex cells that fuse through fertilization in
sexual reproduction to form a diploid embryo.
Whoa, that’s a lot of science vocabulary. Does it make sense to you?
A sperm cell’s journey…
1.
2.
3.
4.
5.
6.
Spermatogenesis in a testicle
Maturation in epididymis
Carried along vas deferens
Fructose and mucus picked up at seminal vesicle
Prostate adds fluids to neutralize acid in vagina
Ejaculation through penis, through the urethra
About 250 million sperm cells are released
during one male ejaculation!
Seminal Vesicle
Bladder
Adds fructose and mucus
to sperm
Stores urine (not a reproductive organ)
Prostate
Adds fluids to neutralize
acid in vagina to sperm
Urethra
Duct for urine or sperm
Vas Deferens
Sperm travels
through this tube
during ejaculation
Penis
Enters vagina to deliver
sperm
Epididymis
Testicle
Spermatogenesis happens here
Newly formed sperm
mature / stored here
What is this kind of chart called?
It’s a karyotype, a picture of all of a person’s chromosomes
What can we determine about the person from this chart?
We can determine that it is a male (XY sex chromosomes)
and that this person has down syndrome (trisomy 21)
*Female reproductive
organs do not share a
passageway with urinary
system, like it does in
males.
Uterus
Holds fetus and placenta
during pregnancy
Oviduct
(aka Fallopian Tube)
Egg (or embryo, if fertilized)
travels to uterus
Ovary
Muscle Wall
Eggs and follicles
develop here
Contracts to push out fetus
and dead endometrium
Endometrium
Cervix
Creates seal to block infections.
However, sperm, menstrual
fluid, and babies pass through it
Redevelops every menstrual
cycle, turns into placenta
Vagina
during pregnancy
Passageway for penis and fetus.
Is acidic, to discourage infections
Pituitary Hormones
FSH Stimulates oocyte (immature
egg) development in ovary
LH
Also stimulates oocyte
development. Causes ovulation
(release of mature egg)
Hormones of Ovaries
Develops
Estrogen
endometrium
These hormones are released
by the pituitary gland.
Progesterone Maintains
endometrium. Stays
high during
pregnancy.
Menstruation happens
when this hormone
level decreases.
These hormones are released
by the ovaries.
Phases of Menstrual Cycle
1. Menstruation: endometrium (aka “menses”)
breaks down and is shed.
2. Follicular phase: a follicle in the ovary
develops and release a new egg.
3. Luteal phase: the follicle becomes the corpus
luteum, which secretes progesterone, then
disappears, triggering menstruation. If
pregnancy happens, the placenta produces
progesterone to prevent menstruation.
Menstruation
The Birth Control Pill
Red pill
• It’s a placebo (no hormones)
• Menstruation happens on
regular basis at this time
Blue Pill
• It’s made with estrogen and
progestin (synthetic
progesterone)
• When these hormones are
high, the pituitary gland thinks
the body is pregnant, so no
ovulation occurs (thus no
ability to become pregnant)
Cramps!
If no fertilization (and pregnancy) occurs, the endometrium
needs to be shed and replaced with a new one.
•
•
The endometrium breaks down as progesterone levels drop (because the corpus luteum,
which makes progesterone, degenerates)
The uterus muscle contracts, restricting blood flow to the endometrium, helping to kill
the endometrium cells, and then keeps contracting to force them out of the cervix.
Cramps!
Up to 50% of women experience menstrual
cramps, with around 15% suffering from
severe pain. This is known as
dysmenorrhea. Type I dysmenorrhea
begins in puberty. Type II begins much later
and could be a sign of an internal health
problem.
Seminal Vesicle
Bladder
Adds fructose and mucus
to sperm
Stores urine (not a reproductive organ)
Prostate
Adds fluids to neutralize
acid in vagina to sperm
Urethra
Duct for urine or sperm
Vas Deferens
Sperm travels
through this tube
during ejaculation
Penis
Enters vagina to deliver
sperm
Epididymis
Testicle
Spermatogenesis happens here
Newly formed sperm
mature / stored here
*Female reproductive
organs do not share a
passageway with urinary
system, like it does in
males.
Uterus
Holds fetus and placenta
during pregnancy
Oviduct
(aka Fallopian Tube)
Egg (or embryo, if fertilized)
travels to uterus
Ovary
Muscle Wall
Eggs and follicles
develop here
Contracts to push out fetus
and dead endometrium
Endometrium
Cervix
Creates seal to block infections.
However, sperm, menstrual
fluid, and babies pass through it
Redevelops every menstrual
cycle, turns into placenta
Vagina
during pregnancy
Passageway for penis and fetus.
Is acidic, to discourage infections
Male
Female
Sperm cells start here and travel from…
Contains a gland called the
function
to
Pituitary Gland
the…
Which
makes a 2
hormones
called…
Which
stands
for
Which
stands
for
function
to
Vas Deferens
to
These 2 hormones stimulate the ovary to make a structure
that will eventually release an egg; this structure is called a
the…
makes a
hormone
called
function
The egg is eventually
released; this is called
the…
Which causes the uterus to build the
function
to
the…
The leftover follicle changes
into a structure called the
function
to
It makes
a
hormone
called
the…
function
to
the…
If the egg is fertilized, then the
endometrium becomes the
which causes the uterus to maintain the
Progesterone
If the egg is not fertilized, then there is a
decrease in the level of the hormone
function
Ejaculation happens, and sperm
first enters the female’s
and then travels through the
female’s cervix, uterus, and
fallopian tube to find an egg
which will produce the hormone
and provide nutrients to the embryo for about 9 months until
the uterus contracts, pushing the fetus out through the
This causes the endometrium to die; it will
be pushed out by contractions of the
and will exit through the vagina in a process called
Male
Female
Brain
Sperm cells start here and travel from…
Testicle
to
the…
Epididymis
to
the…
Urethra
to
function
Follicle
Sperm travels through this
tube during ejacultion
function
function
Adds fructose (a sugar for
sperm food) and mucus (to
lubricate sperm)
function
Adds fluids that neutralize
the acids in the vagina, to
help the sperm survive
function
The egg is eventually
released; this is called
function
makes a
hormone
called
Corpus Luteum
Which
stands
for
LH
Luteinizing
hormone
Estrogen
Endometrium
It makes
a
hormone
called
If the egg is fertilized, then the
endometrium becomes the
Enters the vagina,
delivering the sperm and
semen
Placenta
and then travels through the
female’s cervix, uterus, and
fallopian tube to find an egg
Vagina
Follicle stimulating
hormone
which causes the uterus to build the
The leftover follicle changes
into a structure called the
A duct shared between
urine and sperm
Ejaculation happens, and sperm
first enters the female’s
FSH
Ovulation
the…
Penis
Which
makes a 2
hormones
called…
These 2 hormones stimulate the ovary to make a structure that
will eventually release an egg; this structure is called a
the…
Prostate
to
Sperm matures here and is
stored until ejaculation
the…
Seminal vesicle
to
Pituitary Gland
the…
Vas Deferens
to
function
Which
stands
for
Contains a gland called the
Spermatogenesis happens
here
which will produce the hormone
Progesterone
and provide nutrients to the embryo for about 9 months until
the uterus contracts, pushing the fetus out through the
Vagina
which causes the uterus to maintain the
Progesterone
If the egg is not fertilized, then there is a
decrease in the level of the hormone
Progesterone
This causes the endometrium to die; it will
be pushed out by contractions of the
Uterus
and will exit through the vagina in a process called
Menstruation
Male
Female
Brain
Sperm cells start here and travel from…
Testicle
to
the…
Epididymis
to
the…
Urethra
to
function
Follicle
Sperm travels through this
tube during ejacultion
function
function
Adds fructose (a sugar for
sperm food) and mucus (to
lubricate sperm)
function
Adds fluids that neutralize
the acids in the vagina, to
help the sperm survive
function
The egg is eventually
released; this is called
function
makes a
hormone
called
Corpus Luteum
Which
stands
for
LH
Luteinizing
hormone
Estrogen
Endometrium
It makes
a
hormone
called
If the egg is fertilized, then the
endometrium becomes the
Enters the vagina,
delivering the sperm and
semen
Placenta
and then travels through the
female’s cervix, uterus, and
fallopian tube to find an egg
Vagina
Follicle stimulating
hormone
which causes the uterus to build the
The leftover follicle changes
into a structure called the
A duct shared between
urine and sperm
Ejaculation happens, and sperm
first enters the female’s
FSH
Ovulation
the…
Penis
Which
makes a 2
hormones
called…
These 2 hormones stimulate the ovary to make a structure that
will eventually release an egg; this structure is called a
the…
Prostate
to
Sperm matures here and is
stored until ejaculation
the…
Seminal vesicle
to
Pituitary Gland
the…
Vas Deferens
to
function
Which
stands
for
Contains a gland called the
Spermatogenesis happens
here
which will produce the hormone
Progesterone
and provide nutrients to the embryo for about 9 months until
the uterus contracts, pushing the fetus out through the
Vagina
which causes the uterus to maintain the
Progesterone
If the egg is not fertilized, then there is a
decrease in the level of the hormone
Progesterone
This causes the endometrium to die; it will
be pushed out by contractions of the
Uterus
and will exit through the vagina in a process called
Menstruation
What is going on in the uterus at these times?
Uterine walls are mostly “empty”
Menstruation
(endometrium is shed)
Endometrium is building up,
and up and up…
What is going on in the ovaries at these times?
Follicle matures
Follicle turns into
Ovulation corpus luteum
Follicle appears
What hormone does the follicle make? Estrogen
What hormone does the corpus luteum make? Progesterone
Corpus
luteum
disappears
At what time is a female most fertile? Why?
Right before and after ovulation a female is most fertile. It is at this
time that she has released a “fresh” egg, and afterwards the egg dies.
Therefore, right before and after menstruation is when she is least
fertile.
Most fertile!
Quiz, Quiz Trade
1. Put your name and hour on the front of the note card
(the side with lines).
2. Write 3 questions that you think will be on the test on
the front of the note card.
 Look at the topics guide
 Look at your old journals and notes
 Look at your review guides
3. Write the answers to these 3 questions on the back side
of the note card.
Why is Quiz, Quiz, Trade a great activity?
A. In order to create 3 questions, you are forced to
carefully anticipate what you think is on the test.
B. You have to consider everything we studied, and
decide what is most important.
C. You’ll discover what other students thought was
important.
D. You have the potential to quiz yourself on at least
100 questions!
Seminal Vesicle
Bladder
Adds fructose and mucus
to sperm
Stores urine (not a reproductive organ)
Prostate
Adds fluids to neutralize
acid in vagina to sperm
Urethra
Duct for urine or sperm
Vas Deferens
Sperm travels
through this tube
during ejaculation
Penis
Enters vagina to deliver
sperm
Epididymis
Testicle
Spermatogenesis happens here
Newly formed sperm
mature / stored here
*Female reproductive
organs do not share a
passageway with urinary
system, like it does in
males.
Uterus
Holds fetus and placenta
during pregnancy
Oviduct
(aka Fallopian Tube)
Egg (or embryo, if fertilized)
travels to uterus
Ovary
Muscle Wall
Eggs and follicles
develop here
Contracts to push out fetus
and dead endometrium
Endometrium
Cervix
Creates seal to block infections.
However, sperm, menstrual
fluid, and babies pass through it
Redevelops every menstrual
cycle, turns into placenta
Vagina
during pregnancy
Passageway for penis and fetus.
Is acidic, to discourage infections
Kish’s notes:
6.6 Hormones, homeostasis and
reproduction
Hormones are used when signals
need to be widely distributed.
Insulin and glucagon are secreted by β and α
cells of the pancreas respectively to control
blood glucose concentration.
Application: Causes and treatment of
Type I and Type II diabetes.
Thyroxin is secreted by the thyroid gland to
regulate the metabolic rate and help control
body temperature.
Q: Why do we iodize our salt?
Leptin is secreted by cells in adipose tissue and acts on
the hypothalamus of the brain to inhibit appetite.
Application: Testing of leptin on patients with
clinical obesity and reasons for the failure to
control the disease.
Melatonin is secreted by the pineal
gland to control circadian rhythms.
Q: Define circadian rhythm.
Q: Explain how levels of melatonin are related
to the sleep-wake cycle.
Application: Causes of jet lag and use of
melatonin to alleviate it.
A gene on the Y chromosome causes embryonic
gonads to develop as testes and secrete testosterone.
Q: What combinations of chromosomes are
connected to males and females?
• Testosterone causes pre-natal development of
male genitalia and both sperm production and
development of male secondary sexual
characteristics during puberty.
Q: About when could you determine if a baby was
a male? Justify your answer.
Q: List three secondary sex characteristics of males.
Skill: Annotate diagrams of the male and
female reproductive system to show names of
structures and their functions.
• Testis – produce sperm and
testosterone
• Scrotum – keep testis below body
temperature
• Epididymis – store sperm until
ejaculation
• Sperm duct – transfer sperm
during ejaculation
• Seminal vesicle and prostate
gland – secrete fluids added to
sperm to make semen
• Urethra – transfer semen during
ejaculation and urine during
urination
• Penis – penetrate vagina for
ejaculation of semen near the
cervix
Estrogen and progesterone cause pre-natal development of
female reproductive organs and female secondary sexual
characteristics during puberty.
Q: List three secondary sex characteristics of
females.
Skill: Annotate diagrams of the male and
female reproductive system to show names of
structures and their functions.
•
•
•
•
•
•
Ovary – produce eggs, estrogen, and progesterone
Oviduct – collect eggs at ovulation, provide a site for fertilization then move the embryo to uterus
Uterus – provides the needs of the embryo and then fetus during pregnancy
Cervix – protect fetus during pregnancy and then dilate to provide a birth canal
Vagina – stimulate penis to cause ejaculation and provide a birth canal
Vulva – protect internal parts of female reproductive system
The menstrual cycle is controlled by negative and positive feedback
mechanisms involving ovarian and pituitary hormones. The roles of FSH, LH,
estrogen and progesterone in the menstrual cycle are expected.
• Q: Explain the functions of each of the four
hormones listed above. (Do not talk about
concentrations at this point)
Application: 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.
• Application: William Harvey’s investigation of
sexual reproduction in deer.
• Nature of science: Developments in scientific
research follow improvements in apparatus—
William Harvey was hampered in his
observational research into reproduction by
lack of equipment. The microscope was
invented 17 years after his death.
End Kish’s notes