HORMONES, HOMEOSTASIS AND REPRODUCTION 6.6

Question 1

Explain the control of blood glucose concentration, including the roles of glucagon, insulin and the alpha and beta cells in the pancreatic islets.

Answer 1

When blood glucose levels are high
Insulin is released from beta cells of the pancreas and cause a decrease in blood glucose concentration
may involve promoting glucose uptake by the liver and adipose tissue or increase the rate of glucose breakdown.

When blood glucose levels are low
Glucagon is released from alpha cells of the pancreas and cause an increase in blood glucose concentration
May involve stimulating glycogen breakdown in the liver, promoting glucose release by the liver and adipose tissue or decreasing the rate of glucose breakdown

Question 2

Describe the structure and function of thyroxin.

Answer 2

Function - increase the basal metabolic rate. It does this by stimulating carbohydrate and lipid metabolism via the oxidation of glucose and fatty acids.

for structure see notion

Question 3

Outline thyroxin’s role in body temperature regulation.

Answer 3

Thyroxin helps to control body temperature because a consequence of increasing metabolism is the production of heat.
Thyroxin is released in response to a decrease in body temperature to stimulate heat production.

Question 4

List symptoms of thyroxin deficiency.

Answer 4

Tiredness
Sensitivity to cold
Slow movement and thoughts
Depression
Muscle cramps

Question 5

what is leptin?

Answer 5

leptin is a protein hormone produced by adipose cells. It regulates fat stores within the body by suppressing appetite.

Question 6

Outline the mechanism of action of leptin.

Answer 6

Leptin binds to receptors located within the hypothalamus to inhibit appetite, reducing food intake.
Overeating causes more adipose cells to form and more leptin is produced, which further suppresses appetite.
Periods of starvation lead to a reduction in adipose tissue and hence less leptin is released, triggering hunger.

Question 7

Define circadian rhythm.

Answer 7

The body’s physiological response to the 24 hr day-night cycle.
Circadian rhythms are driven by an internal circadian clock.

Question 8

Describe the secretion and action of melatonin.

Answer 8

Melatonin is a hormone produced by the pineal gland in response to changes in light.

Question 9

Outline the mechanism that regulates melatonin secretion in response to the day-night cycle.

Answer 9

Light exposure to the retina is relayed via the suprachiasmatic nucleus and inhibits melatonin secretion
Melatonin is therefore secreted in response to periods of darkness, resulting in higher concentrations at night.

Question 10

Describe the mechanism by which the SRY gene regulates embryonic gonad development.​​

Answer 10

Y chromosome includes the SRY gene which leads to male development.
SRY gene codes for a TDF (testes determining factor) a protein that binds to DNA and stimulates the expression of genes that causes embryonic gonads to form into testes.
In the absence or mutation of the SRY gene instead the embryonic gonads develop into ovaries.

Question 11

Outline role of testosterone in prenatal development of male genitalia.

Answer 11

TDF protein causes production of testorone during embyonicn developemtn which causes the prenatal development of male genitalia.

produced in small amounts by adrenal glands in both female and male

Question 12

State testosterone’s role in stimulating the primary sexual characteristic of males.

Answer 12

large amounts of testosterone are produced by the testes during puberty which causes spern proudction and developepment of male secondary sex charisticsts

Question 13

List secondary sexual characteristics triggered by testosterone at puberty.

Answer 13

Body hair
Muscle mass
Deepening of voice
Libido
External gentilia development

Question 14

State the sources of estrogen and progesterone used in embryonic development.

Answer 14

They are secreted by mother’s ovaries and placenta

Question 15

Describe prenatal development of female reproductive organs.

Answer 15

estrogen and progestrone proudced by the mother’s ovaries and the placenta induce the development of female reporductive organs in the embryo

Question 16

List secondary sexual characteristics triggered by estrogen and progesterone at puberty.

Answer 16

Breast development
Body hair development
Widening of the hips/fat deposition

Question 17

Outline events occurring during the follicular, ovulation and luteal phases of the menstrual cycle.

Answer 17

Follicular:
Follicle stimulating hormone (FSH) is secreted from the anterior pituitary and stimulates growth of ovarian follicles
The dominant follicle produces estrogen, which inhibits FSH secretion (negative feedback) to prevent other follicles growing
Estrogen acts on the uterus to stimulate the thickening of the endometrial layer

Ovulation
Midway through the cycle (~ day 12), estrogen stimulates the anterior pituitary to secrete hormones (positive feedback)
This positive feedback results in a large surge of luteinizing hormone (LH) and a lesser surge of FSH
LH causes the dominant follicle to rupture and release an egg (secondary oocyte) – this is called ovulation

Luteal Phase

The ruptured follicle develops into a slowly degenerating corpus luteum
The corpus luteum secretes high levels of progesterone, as well as lower levels of oestrogen
Estrogen and progesterone act on the uterus to thicken the endometrial lining (in preparation for pregnancy)
Estrogen and progesterone also inhibit secretion of FSH and LH, preventing any follicles from developing

Question 18

State the source and location of action of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinising hormone), estrogen and progesterone.

Answer 18

FSH and LH
source: Anterior Pituitary Gland

Estrogen and Progesterone
source: ovaries

Question 19

Outline the role of hormones in the menstrual cycle, in the case of fertilization and no fertilization

Answer 19

FSH: stimulate follicular growth in ovaries ->follicles also increases estrogen secretion

(increase in estrogen leads to an increase in LH)

LH: causes ovulation and results in the formation of a corpus luteum (when egg is matured and pops out of ovary, it leaves behind a corpus luteum).

corpus luteum continues prodcution of estrogen and progestorone.

if then fertilization of the egg happens, estrogen and progesterone will stay high and thicken the endometrium linning further.

therefore Estrogen and Progesterone will inhibts FSH and LH so no more new eggs will mature and be released.

if no fertilization happens then the corpus leuteum will begin to break down causing less progestrone and estrogen to be produced, a period will occur -> ednometrium linning will be shed.

everything restarts again.

Question 20

Describe the negative feedback loops that regulates secretion of FSH.

Answer 20

The estrogen has a negative feedback on FSH, which causes it to stop being secreted.

Question 21

Describe the positive feedback loop that regulates secretion of estrogen.

Answer 21

estrogen now stimulates LH secretion, which in turn stimulates more estrogen production by the follicle.

Question 22

Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and follicular development, ovulation, changes to the corpus luteum, menstruation and the thickening of the endometrium.

Answer 22

see notion

Question 23

Distinguish between causes and treatment of type I and type II diabetes.

Answer 23

Type 1 - treated with insulin injections
Type 2 - carefully monitoring and controlling dietary intake.

Question 24

State symptoms of jet lag.

Answer 24

Headaches, lethargy, increased irritability and reduced cognitive function.

Question 25

Outline the biological cause of jet lag.

Answer 25

Jet lag results from a change to the body’s circadian rhythm.
The pineal gland continues to secrete melatonin according to the old time zone so that the sleep schedule is not synchronised in the new time zone.

Question 26

Describe use of melatonin in treatment for jet lag.

Answer 26

You can take melatonin near the sleep time of the new time zone to help recalibrate the body.

Question 27

Define in vitro fertilization.

Answer 27

In vitro fertilisation (IVF) refers to fertilisation that occurs outside of the body.

involves using drugs to suspend normal ovulation (down regulation), before using hormone treatments to collect multiple eggs (superovulation)

Question 28

Outline the process of in vitro fertilisation including down-regulation, superovulation, harvesting, fertilization and implantation.

Answer 28

Down regulation

Drugs are used to halt the regular secretion of FSH and LH – this in turn stops the secretion of estrogen and progesterone
By arresting the hormonal cycle, doctors can take control of the timing and quantity of egg production by the ovaries
The drug treatment usually takes about two weeks and is typically delivered in the form of a nasal spray

Super ovulation
using artificial doses of hormones to develop and collect multiple eggs from the woman
firstly injected with large amounts of FSH to stimulate the development of many follicles
follicles are then treated with hCG – a hormone usually produced by a developing embryo
hCG stimulates the follicles to mature and the egg is then collected (via aspiration with a needle) prior to the follicles rupturing

Fertilisation

The extracted eggs are then incubated in the presence of a sperm sample from the male donor
The eggs are then analysed under a microscope for successful fertilisation

Implantation

Approximately two weeks prior to implantation, the woman begins to take progesterone treatments to develop the endometrium
Healthy embryos are selected and transferred into the female uterus (or the uterus of a surrogate)
Multiple embryos are transferred to improve chances of successful implantation (hence multiple births are a possible outcome)
Roughly two weeks after the procedure, a pregnancy test is taken to determine if the process has been successful

Question 29

Label a diagram of the male reproductive system, including the bladder, sperm duct, penis (with foreskin and erectile tissue), urethra, testis, scrotum, epididymis, prostate gland and seminal vesicle.

Answer 29

see notion

Question 30

Outline the function of the following male reproductive structures: testis, scrotum, epididymis, sperm duct, seminal vesicle, prostate gland, urethra and penis.

Answer 30

testis: responsible for the production of sperm and testosterone (male sex hormone)

scrotum: responsible for protecting the testes. thermoregulation of the testicles which is an essential factor for sperm production.

epididymis: Site where sperm matures and develops the ability to be motile (i.e. ‘swim’) – mature sperm is stored here until ejaculation

sperm duct (vas deferens): Long tube which conducts sperm from the testes to the prostate gland (which connects to the urethra) during ejaculation

seminal vesicle: secretes fructose which allows sperms in the vas deferens to make lots of ATP for when they swim. mucus (to protect sperm) and prostaglandin (triggers uterine contractions)

protaste gland: secretes bicarbonate which amkes sperm slightly alkaline to counteract/neutralize the acidity of the vagina.

urethra: Conducts sperm / semen from the prostate gland to the outside of the body via the penis (also used to convey urine)

penis: deposit sperm in vagina

Question 31

Label a diagram of the female reproductive system, including the ovary, uterus, bladder, urethra, vulva, vagina, cervix and oviduct.

Answer 31

see notion

Question 32

Outline the function of the following female reproductive structures: ovary, oviduct, uterus, cervix, vagina, and vulva.

Answer 32

ovary: The ovary is where oocytes mature prior to release (ovulation) – it also responsible for estrogen and progesterone secretion

oviduct (fallopian tubes): transports the oocyte to the uterus – it is also typically where fertilisation occurs

uterus: the organ where a fertilised egg will implant and develop (becoming an embryo)

endometrium: The mucous membrane lining of the uterus, it thickens in preparation for implantation or is otherwise lost (via menstruation)

cervix: allows fluids, such as menstrual blood, to pass from the uterus into the vagina. It also widens during the birth of a baby.

vagina: Passage leading to the uterus by which the penis can enter (uterus protected by a muscular opening called the cervix)

vulva: o protect the internal parts from infection and allow sperm to enter your vagina.

Question 33

How does leptin effect obese people?

Answer 33

Because obese people are constantly producing more leptin, their bodys become progressively desensitised to the hormone.
This means they are more likely to feel hungry and less likely to recognise when they are full.