6.6 HORMONES, HOMEOSTASIS, AND

REPRODUCTIONPart 1

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.

Melatonin is secreted by the

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.

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

GETTING BACK TO SET POINT

http://upload.wikimedia.org/wikipedia/commons/2/22/105_Negative_Feedback_Loops.jpg

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

THYROXINSecreted by the thyroid gland

Two forms: T3 (three iodine atoms) and T4 (four iodine atoms)

Targets almost all cells

Responsible for metabolic rate

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

LEPTINSecreted by adipose tissue

Targets hypothalamus of the brainstem

Lowers appetite

http://www.bullyextreme.com/wp-content/uploads/2013/03/leptin-weight-loss.gif

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

MELATONINSecreted 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

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-orange-Time-Zone-Clocks.jpg

INSULINSecreted 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

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

TYPE I DIABETESImmune 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

TYPE II DIABETESCell receptors stop responding to insulin (insulin resistance)

Controlled by diet

Can be caused by genetics, poor diet, obesity, and/or age

EFFECTS OF DIABETESBlindness

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

6.6 HORMONES, HOMEOSTASIS, AND

REPRODUCTIONPart 2

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.

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

DEBUNKING THE ’SOIL AND SEED’ THEORYWilliam 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

HUMAN REPRODUCTIONFertilization 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

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&h=188

Eight week embryo

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/Testosterone.gif

Sperm produced here in seminiferous tubulesSperm are stored here to mature

Sperm travels from epididymis to urethra

Produces seminal fluid with nutrients for sperm

Sacs that hold testes outside of the body cavity

Male sex organ; becomes erect as a result of blood engorgement to facilitate ejaculation

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

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 the vagina

Female sex organ; canal that leads from external genitalia to cervix

Vulva External female genitalia

MORE ON ESTROGEN

Released by ovaries

Enters bloodstream

Endometrium Pituitary gland

Increases density of blood vessels in preparation of implantation

http://images.clipartpanda.com/uterus-clipart-uterus-1024x697.jpg

Releases more FSH/LH

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

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

OVULATION

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

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

HUMAN EMBRYONIC DEVELOPMENTConception: 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

Implantation of blastocyst

Blastocyst

Endo-metrium

Cavity

Inner cell mass

Trophoblast

EARLY POSTFERTILIZATION EVENTS

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

IVFWoman 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 manEggs and sperm combined in culture dishUsually multiple fertilized eggs are implanted into the woman’s uterusUnused embryos frozen