https://commons.wikimedia.org/wiki/File:Thyroid_system.svghttps://commons.wikimedia.org/wiki/File:%28S%29-Triiodthyronine_Structural_Formulae_V2.svg

Essential idea: Hormones are used when signals need to be widely distributed.

6.6 Hormones, homeostasis and reproduction

By Chris Paine

https://bioknowledgy.weebly.com/

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.

UnderstandingsStatement Guidance

6.6.U1 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.

The roles of FSH, LH, estrogen and progesterone in the menstrual cycle are expected.

Applications and SkillsStatement Guidance

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.

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.

6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.

The Endocrine SystemA 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 SystemA 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. Pineal gland2. Pituitary gland3. Thyroid gland4. Thymus5. Adrenal gland6. Pancreas7. Ovary (female)8. 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 cellsEffects:• 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.

Produced by: adipose cells (fat storage cells)Targets: appetite control centre of the hypothalamus (in brain)

Leptin

https://commons.wikimedia.org/wiki/File:Leptin.pnghttps://commons.wikimedia.org/wiki/File:Fatmouse.jpg

Effects:An increase in adipose tissue increases leptin secretions into the blood, causing appetite inhibition and hence reduced food intake.

6.6.A2 Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.

https://commons.wikimedia.org/wiki/File:Fatmouse.jpg

1949 Scientists discovered the ob/ob or obese mouse. It is a mutant mouse that eats excessively and becomes profoundly obese.

Leptin treatment for obesity

It was found that obese mice possess two recessive alleles and consequently do not produce any leptin.

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

Obese mice treated with leptin saw large lossesof weight

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 darknessTargets: pituitary and other glandsEffects:synchronization of the circadian rhythms including sleep timing and blood pressure regulation

Taking melatonin close to the sleep time of the destination can alleviate symptoms.

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.

http://www.nhs.uk/Livewell/travelhealth/PublishingImages/sb10065516i-001_jet-lag_377x171.jpghttps://commons.wikimedia.org/wiki/File:Melatonin_molecule_ball.png

6.6.U5 A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone.

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.

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

Sex determination

SRY

6.6.U5 A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone.

Sex determination

SRY

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.

6.6.U6 Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty.

http://schoolbag.info/biology/concepts/188.html

The testes develop from the embryonic gonads when the the embryo is becoming a fetus.

Testosterone

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

The testes secrete testosterone which causes the male genitalia to develop.

6.6.U7 Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty.

http://schoolbag.info/biology/concepts/188.html

Estrogen and progesterone

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

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

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.

a. uterus• Provides protection, nutrients and waste removal

for the developing fetus• Muscular walls contract to aid birthing processb. fallopian tube (oviduct)• Connects the ovary to the uterus• Fertilisation of the egg occurs herec. ovary• (meosis) eggs stored, develop and mature• Produced estrogen and progesteroned. 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 canalg. kidney h. ureteri. bladder j. urethra

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 male reproductive system?

6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.

a. Vas deferens (sperm duct)• carries sperm to the penis during ejaculationb. Prostate gland• Adds alkaline fluids that neutralise the vaginal

acidsc. urethra• Delivers semen during ejaculation and urine

during excretiond. 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)

Can you label and annotate the diagram of the male reproductive system?

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.

Video and doctors’ advice from NHS UK:http://www.nhs.uk/Video/Pages/Menstrualcycleanimation.aspx

More Menstrual Cycle Animations

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

http://course.zju.edu.cn/532/study/theory/2/Genital%20system/Menstrual%20cycle.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 can you outline their roles?

Insulin

Thyroxin

Leptin

Melatonin

FSH

LH

Estrogen

Progesterone

Testosterone

Glucagon

Key Hormones in IB Biology can you outline their roles?

Insulin

Thyroxin

Leptin

Melatonin

FSH

LH

Estrogen

Progesterone

Testosterone Pre-natal development of male genitalia, sperm production, development of male secondary sexual characteristics during puberty.

Lowers blood glucose concentration – converts glucose to glycogen for storage in the liver

Raises blood glucose concentration – converts glycogen, in the liver, to glucoseGlucagon

inhibits appetite

Regulates the metabolic rate and helps to control body temperature

controls circadian rhythms

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.

Stimulates the growth and development of ovarian follicles (bodies containing eggs).

Triggers ovulation, the release of the oocyte (egg) from the ovary

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

Uterus

Tube administering dye via vagina

Fallopian tube filled with dye

Dye in the pelvic cavity

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

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

http://goo.gl/XqAOk

http://www.sumanasinc.com/webcontent/animations/content/invitrofertilization.html

Introduction to In vitro fertilisation (IVF)

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.

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

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.

Hormonal treatments involved in IVF

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.

6.6.A5 William Harvey’s investigation of sexual reproduction in deer.

https://commons.wikimedia.org/wiki/File:Fawn_and_mother.jpg

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.

‘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.

William Harvey’s investigation of sexual reproduction

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).

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)

https://commons.wikimedia.org/wiki/File:Fawn_and_mother.jpg

His biggest problem was that without microscopes (invented 17 years after his death) that sperm, eggs and embryos are too small to observe.

William Harvey’s investigation of sexual reproduction

His findings, both true and false, are based on a misinterpretation of insufficient data.

Bibliography / Acknowledgments

Bob Smullen

Jason de Nys