1. 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.

2. The Endocrine System Key endocrine glands:
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:
Endocrine glands from:

3. The Endocrine System Key endocrine glands:
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:
Pineal gland
Pituitary gland
Thyroid gland
Thymus
Adrenal gland
Pancreas
Ovary (female)
Testes (male)
Endocrine glands from:

4. 6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.

5. 6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.

6. 6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.

7. 6.6.A1 Causes and treatment of Type I and Type II diabetes.

8. Thyroxin Produced by: thyroid gland Targets: most body cells Effects:
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)

9. Leptin Produced by: adipose cells (fat storage cells)
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.

10. Leptin treatment for obesity
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

11. Melatonin Produced by: pineal gland in darkness
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.

12. 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:

13. 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

14. 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

15. Estrogen and progesterone
6.6.U7 Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty.
Estrogen and progesterone
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
Estrogen and progesterone are present. At first they are secreted by the first by the mother’s ovaries and later by her placenta.
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

16. 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?

17. 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

18. 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?

19. 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)

20. 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)

21. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.

22. More Menstrual Cycle Animations
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:
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.
Edited from:

23. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.

24. 6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.

25. Explain the role of hormones in the regulation of the menstrual cycle
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)

26. Explain the role of hormones in the regulation of the menstrual cycle
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

27. Key Hormones in IB Biology can you outline their roles?
Insulin
Glucagon
Leptin
Thyroxin
Melatonin
Testosterone
FSH LH
Estrogen
Progesterone

28. 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 LH
Estrogen
Progesterone
Stimulates the growth and development of ovarian follicles (bodies containing eggs).
Triggers ovulation, the release of the oocyte (egg) from the ovary
Pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. Causes the uterine lining to thicken.
Pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. Maintains the lining of the uterus.

29. On the right is a special x-ray called a hydrosalpingogram.
IVF is often used to overcome infertility caused by blocked Fallopian tubes.
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
Dye in the pelvic cavity
Uterus
Fallopian tube filled with dye
Tube administering dye via vagina

30. Other causes of infertility:
Female:
Ova not maturing or being released
Abnormality in uterus prevents implantation
Antibodies in cervical mucus impair sperm
Male
Unable to achieve an erection or normal ejaculation
Low sperm count or sperm are abnormal with low motility
Blocked vas deferens
Two tailed sperm, unable to swim

31. Introduction to In vitro fertilisation (IVF)
Edited from:

32. Hormonal treatments involved in IVF
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.

33. William Harvey’s investigation of sexual reproduction
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).

34. William Harvey’s investigation of sexual reproduction
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.