6.6 Hormones, homeostasis and reproduction
Essential idea: Hormones are used when
signals need to be widely distributed.
Thyroxin is a hormone produced by the thyroid gland. It's
key role is in controlling the metabolism of cells. If affects
almost every physiological process in the body including
growth and development. Most hormones affect more
than one target tissue in more than one way.
By Chris Paine
https://bioknowledgy.weebly.com/
https://commons.wikimedia.org/wiki/File:Thyroid_system.svg
https://commons.wikimedia.org/wiki/File:%28S%29-Triiodthyronine_Structural_Formulae_V2.svg
Understandings
6.6.U1
Statement
Insulin and glucagon are secreted by β and α cells of
the pancreas respectively to control blood glucose
concentration.
6.6.U2
Thyroxin is secreted by the thyroid gland to regulate the
metabolic rate and help control body temperature.
6.6.U3
Leptin is secreted by cells in adipose tissue and acts on
the hypothalamus of the brain to inhibit appetite.
6.6.U4
Melatonin is secreted by the pineal gland to control
circadian rhythms.
6.6.U5
A gene on the Y chromosome causes embryonic
gonads to develop as testes and secrete testosterone.
6.6.U6
Testosterone causes pre-natal development of male
genitalia and both sperm production and development
of male secondary sexual characteristics during
puberty.
6.6.U7
Estrogen and progesterone cause pre-natal
development of female reproductive organs and female
secondary sexual characteristics during puberty.
6.6.U8
The menstrual cycle is controlled by negative and
positive feedback mechanisms involving ovarian and
pituitary hormones.
Guidance
The roles of FSH, LH, estrogen and
progesterone in the menstrual cycle
are expected.
Applications and Skills
Statement
6.6.A1 Causes and treatment of Type I and Type II
diabetes.
6.6.A2
Testing of leptin on patients with clinical obesity
and reasons for the failure to control the disease.
6.6.A3
Causes of jet lag and use of melatonin to
alleviate it.
6.6.A4
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.
6.6.A5
William Harvey’s investigation of sexual
reproduction in deer.
6.6.S1
Annotate diagrams of the male and female
reproductive system to show names of structures
and their functions.
Guidance
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.
The Endocrine System
A stimulus is received and processed.
Hormones are secreted directly into the blood.
They are carried to the target tissues (the place of intended action).
The action of the hormone changes the condition of the tissue.
This change in monitored through feedback.
Most hormonal change results in negative feedback.
Key endocrine glands:
1.
2.
3.
4.
5.
6.
7.
8.
Endocrine glands from: http://en.wikipedia.org/wiki/Endocrine_gland
The Endocrine System
A stimulus is received and processed.
Hormones are secreted directly into the blood.
They are carried to the target tissues (the place of intended action).
The action of the hormone changes the condition of the tissue.
This change in monitored through feedback.
Most hormonal change results in negative feedback.
Key endocrine glands:
1.
2.
3.
4.
5.
6.
7.
8.
Pineal gland
Pituitary gland
Thyroid gland
Thymus
Adrenal gland
Pancreas
Ovary (female)
Testes (male)
Endocrine glands from: http://en.wikipedia.org/wiki/Endocrine_gland
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose
concentration.
http://medmovie.com/portfolio-item/diabetes/
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose
concentration.
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose
concentration.
6.6.A1 Causes and treatment of Type I and Type II diabetes.
6.6.U2 Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
Thyroxin
Produced by: thyroid gland
Targets: most body cells
Effects:
• increases metabolic rate / rate of
protein synthesis
• increases heat production (e.g.
increased respiration)
https://commons.wikimedia.org/wiki/File:T3-3D-vdW.png
6.6.U3 Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.
Leptin
Produced by: adipose cells (fat storage cells)
Targets: appetite control centre of the
hypothalamus (in brain)
Effects:
An increase in adipose tissue increases leptin secretions into the blood,
causing appetite inhibition and hence reduced food intake.
https://commons.wikimedia.org/wiki/File:Fatmouse.jpg
https://commons.wikimedia.org/wiki/File:Leptin.png
6.6.A2 Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.
Leptin treatment for obesity
1949 Scientists discovered the ob/ob or
obese mouse. It is a mutant mouse that eats
excessively and becomes profoundly obese.
It was found that obese mice possess two
recessive alleles and consequently do not
produce any leptin.
Obese mice treated with
leptin saw large losses
of weight
Clinical trials were carried out to see if the effect was similar, but trials failed:
• Most people have naturally high levels of leptin
• If linked to leptin, obesity in people is due to resistance, of the appetite control
centre, to leptin
• Very few patients in the clinical trial experienced significant weight loss
• Many patients experienced side-effects such as skin irritations
https://commons.wikimedia.org/wiki/File:Fatmouse.jpg
6.6.U4 Melatonin is secreted by the pineal gland to control circadian rhythms. AND 6.6.A3 Causes of jet lag and
use of melatonin to alleviate it.
Melatonin
Produced by: pineal gland in darkness
Targets: pituitary and other glands
Effects:
synchronization of the circadian rhythms including
sleep timing and blood pressure regulation
Jet lag is a condition caused by travelling rapidly between time zones. Symptoms
often experienced are sleep disturbance, headaches, fatigue, irritability. Symptoms
usually fade after a few days.
Jet lag is caused by the pineal gland
continuing to set a circadian rhythm for
the point of origin rather than the current
time zone.
Taking melatonin close to the sleep time of
the destination can alleviate symptoms.
https://commons.wikimedia.org/wiki/File:Melatonin_molecule_ball.png
http://www.nhs.uk/Livewell/travelhealth/PublishingImages/sb10065516i-001_jet-lag_377x171.jpg
6.6.U5 A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone.
Sex determination
Humans have 23 pairs of chromosomes in
diploid somatic cells (n=2).
22 pairs of these are autosomes, which are
homologous pairs.
One pair is the sex chromosomes.
XX gives the female gender, XY gives male.
SRY
The X chromosome is much larger than the Y.
X carries many genes in the non-homologous
region which are not present on Y.
The presence and expression of the SRY
gene on Y leads to male development.
Chromosome images from Wikipedia: http://en.wikipedia.org/wiki/Y_chromosome
6.6.U5 A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone.
Sex determination
In embryos the first appearance of the
gonads is essentially the same in the
two sexes. Gonads could become either
ovaries or testes.
If present the SRY gene encodes for a
protein known as testis determining
factor (TDF). TDF is a DNA binding
protein which acts as a transcription
factor promoting the expression of
other genes.
In the presence of TDF the gonads
become testis. In the absence of TDF
the gonads become ovaries and the
developing fetus becomes female.
SRY
6.6.U6 Testosterone causes pre-natal development of male genitalia and both sperm production and development
of male secondary sexual characteristics during puberty.
Testosterone
The testes develop from the
embryonic gonads when the the
embryo is becoming a fetus.
The testes secrete
testosterone which
causes the male
genitalia to develop.
At puberty the secretion of testosterone
increases causing:
• The primary sexual characteristic of sperm
production in the testes
• Development of secondary sexual
characteristics such as enlargement of the
penis, growth of pubic hair and deepening of
the voice
http://schoolbag.info/biology/concepts/188.html
6.6.U7 Estrogen and progesterone cause pre-natal development of female reproductive organs and female
secondary sexual characteristics during puberty.
Estrogen and progesterone
Estrogen and progesterone
are present. At first they are
secreted by the first by the
mother’s ovaries and later by
her placenta.
In the absence of fetal testosterone
and the presence of maternal
estrogen and progesterone, female
reproductive organs develop (ovaries
develop from the embryonic gonads)
due to:
• estrogen and progesterone
• No testosterone
At puberty the secretion of estrogen and
progesterone increases causing:
• Primary sexual characteristic of egg
release
• Development of female secondary
sexual characteristics such as
enlargement of the breasts and growth
of pubic hair
http://schoolbag.info/biology/concepts/188.html
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their
functions.
Can you label and annotate the diagram of the female reproductive system?
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their
functions.
Can you label and annotate the diagram of the female reproductive system?
a. uterus
•
•
Provides protection, nutrients and waste removal
for the developing fetus
Muscular walls contract to aid birthing process
b. fallopian tube (oviduct)
•
•
Connects the ovary to the uterus
Fertilisation of the egg occurs here
c. ovary
•
•
(meosis) eggs stored, develop and mature
Produced estrogen and progesterone
d. endometrium (lining of the uterus)
•
•
develops each month in readiness for the
implanation of a fertilised egg
(site of implantation becomes the placenta)
e. cervix
f. vagina
•
•
•
Muscular opening/entrance to the uterus
Closes to protect the developing fetus and opens
to form the birth canal
•
Accepts the penis during sexual intercourse and
sperm are recevied here
With the cervix forms the birth canal
g. kidney
h. ureter
i. bladder
j. urethra
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their
functions.
Can you label and annotate the diagram of the male reproductive system?
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their
functions.
Can you label and annotate the diagram of the male reproductive system?
a. Vas deferens (sperm duct)
•
carries sperm to the penis during ejaculation
b. Prostate gland
•
Adds alkaline fluids that neutralise the vaginal
acids
c. urethra
•
Delivers semen during ejaculation and urine
during excretion
d. Penis/erectile muscle
•
•
Muscles become erect to penetrate the vagina
during sexual intercourse
Delivers sperm to the top of the vagina
e. Seminal vesicle
f. epididymis
•
•
•
•
adds nutrients including fructose sugar for
respiration
Adds mucus to protect sperm
Sperm mature here and become able to move
Sperm stored awaiting ejaculation
g. testis (pl. testes)
h. scrotum
•
•
•
Produces (millions) of sperm (every day)
Produces testosterone
Protects and holds the testes outside the body (to
maintain a lower optimum temperature for sperm
production)
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones.
Click on the animation above to go to watch
the graph form (APBI Schools.org.uk)
http://goo.gl/eCNcH
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones.
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones.
More Menstrual Cycle Animations
Video and doctors’ advice from NHS UK:
http://www.nhs.uk/Video/Pages/Menstrualcycleanimation.aspx
http://course.zju.edu.cn/532/study/theory/2/Genital%20syste
m/Menstrual%20cycle.swf
How does the contraceptive pill work?
 this site has a good comparison of the
regular menstrual cycle and the cycle with
the influence of contraceptive pills.
http://www.pbs.org/wgbh/amex/pill/sfeature/sf_cycle.swf
Edited from: http://www.slideshare.net/gurustip/reproduction-core
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones.
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones.
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones.
Explain the role of hormones in the regulation of the menstrual cycle
(8 marks)
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones.
Explain the role of hormones in the regulation of the menstrual cycle
(8 marks)
FSH and LH are produced by the pituitary gland;
estrogen and progestin are produced by the ovary;
FSH stimulates the ovary to promote development of a follicle;
The developing follicles secrete estrogen, which inhibits FSH (negative feedback);
Estrogen stimulates growth of endometrium;
Estrogen stimulates LH secretion (positive feedback);
LH stimulates follicle growth and triggers ovulation;
(the secondary oocyte leaves the ovary and) follicle becomes corpus luteum;
The corpus luteum secretes estrogen and progesterone;
Estrogen and progesterone maintain the endometrium;
Estrogen and progesterone inhibit LH and FSH (negative feedback);
After (two weeks) the corpus luteum degenerates progesterone and estrogen levels fall;
This triggers menstrual bleeding, the loss of endometrium;
The pituitary gland secreted FSH and LH, as they are no longer inhibited (and the menstrual
cycle continues);
May credit marks that are clearly drawn and correctly labelled on diagrams or flow charts
Key Hormones in IB Biology
Insulin
Glucagon
Leptin
Thyroxin
Melatonin
Testosterone
FSH
LH
Estrogen
Progesterone
can you outline their roles?
Key Hormones in IB Biology
can you outline their roles?
Insulin
Lowers blood glucose concentration – converts glucose to glycogen for storage
in the liver
Glucagon
Raises blood glucose concentration – converts glycogen, in the liver, to glucose
Leptin
inhibits appetite
Thyroxin
Regulates the metabolic rate and helps to control body temperature
Melatonin
controls circadian rhythms
Testosterone
Pre-natal development of male genitalia, sperm production, development of
male secondary sexual characteristics during puberty.
FSH
Stimulates the growth and development of ovarian follicles (bodies containing
eggs).
LH
Triggers ovulation, the release of the oocyte (egg) from the ovary
Estrogen
Pre-natal development of female reproductive organs and female secondary
sexual characteristics during puberty. Causes the uterine lining to thicken.
Progesterone
Pre-natal development of female reproductive organs and female secondary
sexual characteristics during puberty. Maintains the lining of the uterus.
IVF is often used to overcome
infertility caused by blocked
Fallopian tubes.
Dye in the
pelvic cavity
On the right is a special x-ray
called a hydrosalpingogram.
A dye is infused through the
cervix into the uterus and from
there it flows through the
fallopian tubes and into the
pelvic cavity.
This woman is all clear, you can
see the swirls of dye coming out
the ends of her tubes
Uterus
Fallopian
tube filled
with dye
Tube administering
dye via vagina
http://commons.wikimedia.org/wiki/File:Hysterosalpingogram.jpg
Other causes of infertility:
Female:
• Ova not maturing or being released
• Abnormality in uterus prevents
implantation
• Antibodies in cervical mucus impair
sperm
Two tailed sperm,
unable to swim
Male
• Unable to achieve an erection or
normal ejaculation
• Low sperm count or sperm are
abnormal with low motility
• Blocked vas deferens
http://goo.gl/XqAOk
Introduction to In vitro fertilisation (IVF)
http://www.sumanasinc.com/webcontent/animatio
ns/content/invitrofertilization.html
Edited from: http://www.slideshare.net/gurustip/reproduction-core
6.6.A4 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.
Hormonal treatments involved in IVF
Down-regulation is the first step in IVF is the shutting down of the menstrual cycle, by stopping secretion
of the pituitary and ovarian hormones. The process takes about two weeks and allows better control of
superovulation. Down-regulation is done with a drug, commonly in the form of a nasal spray.
Next superovulation collects multiple eggs from the woman. High doses of FSH are injected over
approximately a ten day period to stimulate the development of multiple follicles (the developing
egg and their surrounding cells). When follicles reach 15-20mm in diameter an injection of HCG is
given to start maturation process. Approximately 36 hours later, under a general anesthetic,
follicles (typically 8 – 12) are collected from the ovaries.
Prepared eggs (removed from the follicles) are combined with sperm in sterile conditions.
Successfully fertilised eggs are then incubated before implantation.
For approximately two weeks before implantation the woman takes progesterone (which maintains
the endometrium), usually in the form of a suppository, to aid implantation. This treatment is
continued until pregnancy test, and if positive, until 12 weeks of gestation.
As the natural success rate of implantation is around 40% usually two or three blastocysts (growing fertilised egg) are
implanted. As a consequence the chances of IVF treatment leading to multiple pregnancies are high.
http://hopefulmum.co.nz/wp-content/uploads/2015/05/IVF.jpg
6.6.A5 William Harvey’s investigation of sexual reproduction in deer.
William Harvey’s investigation of sexual reproduction
‘seed and soil’ theory of Aristotle states that the male produces a
seed which forms an egg when mixed with menstrual blood. The
egg then develops into a fetus inside the mother.
Harvey studied animal reproduction,
particularly in chickens and deer. He
dissected female deer after mating to
observe changes in the sexual organs
and found none.
Harvey came to understand that menstrual
blood did not contribute to the formation of a
fetus (true), putting Aristotle's idea to rest.
He also questioned the direct role of semen in
reproduction (false).
https://commons.wikimedia.org/wiki/File:Fawn_and_mother.jpg
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. (1.8)
William Harvey’s investigation of sexual reproduction
His findings, both true and false, are based
on a misinterpretation of insufficient data.
His biggest problem was that without microscopes
(invented 17 years after his death) that sperm, eggs
and embryos are too small to observe.
https://commons.wikimedia.org/wiki/File:Fawn_and_mother.jpg
Bibliography / Acknowledgments
Jason de Nys
Bob Smullen