Topic 6.6: Hormones, Homeostasis and Reproduction

Question 1

Homeostasis

Answer 1

Homeostasis is the maintenance of a constant internal environment within physiological tolerance limits
1) A disease ensues if a factor deviates from its normal range

Question 2

Regulation of physiological processes

Answer 2

Physiological processes are regulated by negative feedback
• An effect is antagonistic (opposite) to the stimulus
• This means the detected change is reversed

Question 3

Endocrine System

Answer 3

1) It releases chemical messengers (hormones) into the blood to act on distant target cells.
2) The endocrine system works in tandem with the nervous system to maintain physiological balance (homeostasis)

Question 4

Control of blood glucose concentration

Answer 4

Blood sugar levels are regulated by insulin and glucagon

• These hormones are secreted by cells in the pancreas

Question 5

Insulin

Answer 5

1) Secreted by β-cells to lower blood sugar levels
2) Stimulates glucose uptake by the liver and adipose cells
3) Increases the rate of glucose metabolism

Question 6

Glucagon

Answer 6

1) Secreted by α-cells to raise blood sugar levels
2) Stimulates glycogen breakdown within the liver
3) Decreases the rate of glucose metabolism

Question 7

Diabetes mellitus

Answer 7

Metabolic disorder that results from a high blood glucose concentration over a prolonged period

Question 8

Diabetes mellitus Type I

Answer 8

1) Usually occurs during childhood
2) Body does not produce sufficient insulin
3) Caused by the destruction of B-cells
4) Requires insulin injections to regulate blood glucose

Question 9

Diabetes mellitus Type II

Answer 9

1) Usually occurs during adulthood
2) Body does not respond to insulin production
3) Caused by the down-regulation of insulin receptors
4) Controlled by managing diet and lifestyle

Question 10

Control of body temperature

Answer 10

Body temperature is regulated by the hormone thyroxin

Question 11

Thyroxin

Answer 11

1) Thermoreceptors (skin) send signals to the hypothalamus
2) Thyroxin is released from the thyroid gland when body temperature is low and increases metabolism
3) Thyroxin production requires iodine and a deficiency will result in goitre

Question 12

Control of appetite

Answer 12

Appetite suppression is regulated by the hormone leptin

Question 13

Leptin

Answer 13

1) Adipose cells secrete leptin to suppress appetite (

2) Leptin binds to receptors located in the hypothalamus

Question 14

Leptin and Obesity

Answer 14

1) Over-eating causes more fat cells to be produced
2) Over time, obese people become desensitized to leptin and are more likely to continue to over-eat
3) Hence, leptin treatments for obese people are ineffective (obesity linked to leptin unresponsiveness - not leptin deficiency)

Question 15

Control of circadian rhythms

Answer 15

1) Circadian rhythms are regulated by the hormone melatonin

2) The body’s physiological responses to the 24 hour day-night cycle

Question 16

Melatonin

Answer 16

1) Photoreceptors (eyes) send signals to the hypothalamus
2) Melatonin is secreted by the pineal gland (in the brain)
3) Melatonin release is inhibited by light (levels high at night)
4) High levels of melatonin promote sleep in diurnal animals

Question 17

Jet lag and melatonin

Answer 17

1) Changing time zones can disrupt melatonin release
2) It causes headaches, lethargy, and fatigue
3) Melatonin supplements can recalibrate sleep patterns

Question 18

Reproductive theories

Answer 18

Soil and seed theory

Modern theory

Question 19

Soil and seed theory (Aristotle)

Answer 19

Males provide all the information for life in a ‘seed’, which forms an egg when mixed with menstrual blood (the ‘soil’)

Question 20

Modern theory (William Harvey)

Answer 20

1) He dissected deer after the mating season and was unable to identify embryos until several months after mating
2) The ‘soil and seed’ theory was incorrect and that menstrual blood did not contribute to fetal growth

Question 21

Male sex development

Answer 21

1) Male sex is determined by a gene on the Y chromosome which causes gonads to develop as testes and secrete testosterone
2) Testosterone produces sperm and male sex characteristics

Question 22

Female sex development

Answer 22

1) Female reproductive organs develop in the absence of this gene
2) Estrogen and progesterone develop female sex characteristics

Question 23

Testosterone

Answer 23

1) Secreted by the testes
2) Responsible for the prenatal development of male genitalia
3) Involved in sperm production
4) Involved in the development of secondary sex characteristics
5) Maintain the male sex drive (libido)

Question 24

Estrogen | Progesterone

Answer 24

1) Promote the prenatal development of the female reproductive organs
2) Responsible for the development of secondary sex characteristics
3) Involved in monthly preparation of egg release following puberty (via the menstrual cycle)

Question 25

Male reproductive system

Answer 25

1) Testis 2) Epididymis 3) Vas deferens 4) Seminal vesicle 5) Prostate gland 6) Erectile tissue 7) Penis 8) Urethra 9) Scrotum

Question 26

Testis

Answer 26

Responsible for the production of sperm and testosterone

Question 27

Epididymis

Answer 27

1) Site where sperm matures and develops the ability to be motile 2) Mature sperm is stored here until ejaculation

Question 28

Vas Deferens

Answer 28

Long tube which conducts sperm from the testes to the prostate gland

Question 29

Seminal Vesicle

Answer 29

Secretes fluid containing: 1) Fructose (to nourish sperm) 2) Mucus (to protect sperm) 3) Prostaglandin (triggers uterine contractions)

Question 30

Prostate gland

Answer 30

Secretes an alkaline fluid to neutralise vaginal acids

Question 31

Urethra

Answer 31

Conducts sperm / semen from the prostate gland to the outside of the body via the penis

Question 32

Female reproductive system

Answer 32

1) Vagina 2) Cervix 3) Endometrium 4) Uterus 5) Oviduct 6) Fimbriae 7) Ovary

Question 33

Ovary

Answer 33

1) Site where oocytes mature prior to release | 2) Responsible for estrogen and progesterone secretion

Question 34

Fimbria

Answer 34

Fringe of tissue adjacent to an ovary that sweep an oocyte into the oviduct

Question 35

Oviduct

Answer 35

1) Transports the oocyte to the uterus | 2) Site where fertilisation occurs

Question 36

Uterus

Answer 36

Organ where a fertilised egg will implant and develop

Question 37

Endometrium

Answer 37

Mucous membrane lining of the uterus, it thickens in preparation for implantation

Question 38

Vagina

Answer 38

Site in which the penis can enter

Question 39

In vitro fertilization (She's fit)

Answer 39

1) Stop normal menstrual cycle with drugs 2) Hormone treatments to induce ovulation 3) Extract multiple eggs from female 4) Sperm sample is collected from male 5) Fertilisation occurs externally (in vitro) 6) Implantation of embryos into surrogate 7) Test for pregnancy to determine success

Question 40

Menstrual Cycle Hormones

Answer 40

1) Pituitary Hormones (FSH and LH) act on the ovaries | 2) Ovarian Hormones (estrogen and progesterone) act on the uterus to prepare for pregnancy

Question 41

Menstrual Cycle Stages

Answer 41

1) Follicular phase 2) Ovulation (12 - 14) 3) Luteal phase 4) Menstruation

Question 42

Pituitary Hormone Levels

Answer 42

1) FSH levels are initially high (to develop follicles) before being inhibited by estrogen production 2) A huge pike in LH levels (and to a lesser extent, FSH) triggers ovulation (release of an ova) 3) Rising levels of estrogen and progesterone inhibit both FSH and LH (levels therefore decrease) 4) When the corpus luteum degenerates, estrogen and progesteron levels fall and FSH levels rise

Question 43

Ovaria cycle levels

Answer 43

1) FSH causes follicle to mature and produce estrogen (inhibiting development of other follicles) 2) An LH surge causes ovulation (follicle ruptures and releases a secondary oocyte) 3) Ruptured follicle forms a corpus luteum and secretes progesterone (and some estrogen) 4) When the corpus luteum degenerates (forms a corpus albicans), a new ovarian cycle can begin

Question 44

Ovarian hormone levels

Answer 44

1) Estrogen levels rise as estrogen is produced by developing follicles (progesterone not produced) 2) Estrogen levels drop upon ovulation (follicle is ruptured, cannot produce estrogen) 3) Progesterone levels rise with the development of the corpus luteum (estrogen levels also rise) 4) When the corpus luteum degenerates, estrogen and progesterone levels fall

Question 45

Uterine cycle

Answer 45

1) Follicles release estrogen which causes the uterine wall to thicken 2) When the follicle ruptures and develops into a corpus luteum , progesterone is produced 3) Progesterone and estrogen are released from the corpus luteum and thicken the endometrium 4) The endometrium is sloughed away when the corpus luteum degenerates

Question 46

* Stimulate follicular growth within the ovaries * Stimulate estrogen secretion (from the ovarian follicles) * Stimulate progesterone secretion (from corpus luteum) * A mid-cycle surge in LH triggers ovulation (egg release)

Answer 46

Pituitary Hormones (FSH / LH)

Question 47

* Promote development / thickening of the endometrium * Promote FSH / LH secretion during the follicular phase * Inhibit FSH / LH secretion during the luteal phase

Answer 47

Ovarian Hormones (Estrogen / Progesterone)