1. 6.6 Hormones, Homeostasis, & Reproduction

2. Hormones

3. Blood Glucose Levels and the Pancreas
normal blood glucose = 5 mmol/L if it deviates substantially the pancreas mediates this by releasing insulin and glucagon
the pancreas has both exocrine and endocrine functions
exocrine: digestive enzymes passed through the ducts to the small intestine
endocrine: islets of Langerhans - secretes hormones directly into the bloodstream
Islet of Langerhans
alpha cells (α cells) synthesize and secrete glucagon when blood sugar is too low
beta cells (β cells) synthesize and secrete insulin when blood sugar is too high
<<Antagonistic process (opposite effects); to reach same goal: regulate blood sugar!

4. Negative Feedback Loop
This process happens 24 hours a day, everyday, because our blood does not receive constant levels of glucose
Glucose vs Glycogen: Glucose is stored as glycogen in liver and muscle cells

5. Diabetes Characterized by:
consistently elevated blood glucose levels, even during prolonged fasting (hyperglycemia); damaged tissues and proteins; impairs water reabsorption in urine increasing urine output and dehydration
Type I / Early Onset
inability to produce sufficient quantities of insulin
destruction of β cells by the body’s immune system
test blood often and inject needed insulin typically before a meal
newer method use a implanted device
Type II / Late Onset
inability to process or respond to insulin because of a deficiency of insulin receptors or glucose transporters
variety of factors relating to onset
dietary restriction, strenuous exercise and weight loss

6. Thyroxin
secreted by the thyroid gland (neck) to regulate the metabolic rate and help control body temperature
4 atoms of iodine
almost all cells in the body are targets - all cells have a metabolism!
in normal body, cooling triggers more thyroxin to increase body temp
lack of thyroxin → hypothyroidism
lack of energy
forgetfulness and depression
weight gain
feeling cold
constipation
impaired brain development

7. Leptin
secreted by cells in adipose tissue and acts on the hypothalamus to inhibit appetite
if adipose tissue increases than leptin concentrations increase, causing long term appetite inhibition and reduced food intake
discovered in mice that lacked leptin and their body grew to 100 g instead of the average size of g
leptin was injected into the mice and they dropped 30% of their body mass in a month
this was tried on humans and it did not work
**humans that are obese typically have high concentrations of leptin in their blood - perhaps it works like type II diabetes

8. Melatonin secreted by the pineal gland to control circadian rhythms
suprachiasmatic nuclei (SCN) - they set a rhythm even if grown in culture with no external cues
melatonin increases in the evening and drops at the dawn
causes decrease in body temp and thought to cause a decrease in urine production at night
Jet lag - cross 3 or more time zones caused by the SCN continuing the cycle from the departing time zone only lasts a few days

9. Reproductive Development

10. Sex Determination in GENERAL
**Initially, development of the embryo is the same in all embryos and the gonads that develop could either become ovaries or testes.
Developmental pathway of embryonic gonads depends on the presence or absence of one gene.
Sex Determination

11. Male Reproductive Development

12. Sex Determination in Males
A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone
SRY gene found on Y chromosome
If the SRY gene is present embryonic gonads develop into testes
Codes for DNA binding protein called TDF (testis determining factor)
TDF stimulates the expression of other genes that cause testis development

13. Sex Determination in Males
Testosterone causes prenatal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty.
Testes develop in 8th week of development along with specialized cells that secrete testosterone until 15th week of pregnancy causing male genitalia to develop
Onset of puberty causes testosterone development to increase
Primary Sex Characteristic: sperm production in testes
Secondary Sex Characteristics: enlargement of penis, growth of pubic hair, deepening of voice due to growth in larynx

14. Annotate diagrams of the male reproductive system to show names of structures and their functions
Testis: produce sperm and testosterone
Scrotum: hold testes at lower temp
Epididymis: store sperm until ejaculation
Sperm duct (vas deferens): transfer sperm during ejaculation
Seminal vesicle and Prostate gland: secrete fluid containing alkali, proteins, and fructose; added to sperm to make semen
Urethra: transfer semen during ejaculation and urine during urination
Penis: penetrate the vagina for ejaculation of semen near the cervix

15. Annotate diagrams of the male reproductive system to show names of structures and their functions

16. Annotate diagrams of the male reproductive system to show names of structures and their functions

17. Female Reproductive Development

18. Sex Determination in Females
Estrogen and progesterone cause prenatal development of female reproductive organs and female secondary sexual characteristics during puberty
No Y chromosome, no SRY gene, gonads develop as ovaries
Estrogen and progesterone secreted by mother’s ovaries and placenta
Absence of testosterone and presence of e and p lead to female reproductive organ development
Secretion of estrogen and progesterone increases at onset of puberty causing secondary sexual characteristics to emerge - enlargement of breasts and growth of pubic and underarm hair

19. Annotate diagrams of the female reproductive system to show names of structures and their functions
Ovary: produces eggs, estrogen, progesterone
Oviduct (fallopian tube): collect eggs at ovulation, provide site for fertilization then moves embryo to uterus
Uterus: Provide for the needs of embryo and then fetus during pregnancy
Cervix: Protect the fetus during pregnancy and then dilate to provide birth canal
Endometrium: Highly vascular inner lining of the uterus
Vagina: Stimulate penis to cause ejaculation and provide birth canal

20. Annotate diagrams of the female reproductive system to show names of structures and their functions

21. Annotate diagrams of the female reproductive system to show names of structures and their functions

22. Menstrual Cycle
The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones
Occurs from puberty to menopause, apart from pregnancy
Each cycle gives the chance of pregnancy
Follicular phase
Follicles containing eggs stimulated to grow
Lining of uterus (endometrium) repaired and thickens
Most develop follicle breaks open, releasing egg into oviduct
Luteal phase
wall of follicle that was released called corpus luteum
continued development of endometrium for implantation
If fertilization/implantation does not occur, lining breaks down and is shed

23. Animation of the Menstrual Cycle

24. Menstrual Cycle
The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones
Important hormones
Pituitary hormones: FSH (follicle stimulating hormone) and LH (luteinizing hormone)
protein
bind to receptors in follicle cells
Ovarian hormones: estrogen and progesterone
produced by wall of follicle and corpus luteum
absorbed by cells in body, influence gene expression and development

25. Menstrual Cycle
The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones
FSH
rises to peak towards end of menstrual cycle
stimulates development of follicles containing oocyte, secretion of estrogen by follicle wall
Estrogen
rises to peak towards end of follicular phase
stimulates repair and thickening of endometrium and increase in FSH receptors, making follicles more receptive to FSH, boosting estrogen (positive feedback)
High levels of estrogen inhibit secretion of FSH (negative feedback), stimulating LH production

26. Menstrual Cycle
The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones LH
rises to sudden and sharp peak towards end of follicular phase
stimulates completion of meiosis in oocyte and partial digestion of follicle wall allowing for it to burst during ovulation
Promotes development of follicle after ovulation into corpus luteum, which secretes estrogen (positive feedback) and progesterone
Progesterone
rise at start of luteal phase, reach a peak, and then drop back to low
promotes thickening and maintenance of endometrium
inhibits FSH and LH secretion by pituitary (negative feedback)

27. Follicular Phase Luteal Phase
Menstrual Cycle
Follicular Phase Luteal Phase

28. Menstrual Cycle

29. Today:
IVF
You will take turns presenting your reviews that you were supposed to make last class
Test Wednesday over ch 6

30. In vitro fertilization
The use of 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
Down-regulation
stops production of FSH or LH, estrogen and progesterone also stops
Superovulation
Injections of FSH and LH at much higher than normal levels given daily to stimulate follicle development, far more than usual (12-20!)
Follicles stimulated to mature (HCG), eggs washed out of follicles and added to petri dish with sperm
Successfully fertilized embryos are placed in uterus at about 48 hours old
extra progesterone given to ensure uterus lining