6.6 Homeostasis

Question 1

Where is insulin and glucagon released from?

Answer 1

Islets of langerhans (pancreatic pits)

Question 2

What occurs when blood glucose levels are high? (2)

Answer 2

• insulin is released from beta cells of pancreas and cause decrease in blood sugar levels
• involves stimulating glycogen synthesis in liver (glycogenesis), promoting glucose uptake by liver and adipose tissue
  Or
• increases rate of glucose breakdown

Question 3

What occurs when blood glucose are low? (2)

Answer 3

• glucagon is released in alpha cells of the pancreas and causes Ann increase in blood glucose concentration
• involves stimulating glycogen breakdown in liver (glycolysis), promoting glucose release by liver and adipose tissue
  Or
• decreasing the rate of glucose breakdown (reducing cell respiration rates)

Question 4

Where is thyroxin secreted?

Answer 4

Thyroid gland

Question 5

What is role of thyroxin? (3)

Answer 5

Increase basal metabolic rate
- stimulates carbohydrate and lipid metabolism via oxidation of glucose and fatty acids
- control body temperature (released to decrease body temp)

Question 6

What is thyroxin composed of? (2)

Answer 6

Composed of iodine
(Iodine deficient will cause enlarge thyroid gland)

Question 7

Where is Leptin produced?

Answer 7

Adipose cell

Question 8

What is the role of Leptin?

Answer 8

Régulâtes fat stores in body by suppress apetite
- Leptin binds to receptors in the hypothalamus to inhibit appète and reduce food intake

Question 9

What does overeating and undeating do?

Answer 9

• More adipose cells to form and more Leptin is produce, suppressing further appetite
• periods of starvation lead to reduction in adipose tissue and less pet in is release, triggers hunger

Question 10

What occurs to obese people? (3)

Answer 10

• constantly producing high levels of Leptin and body becomes desensitised to hormone
• they are more likely to feel hungry, less likely to recognise when they are full (more likely to overeat)
• Leptin resistance develops worth age (potential for weight gain later in life)

Question 11

What was the process of Leptin trials on obese mice with no Leptin?

Answer 11

• Leptin in blood of healthy mouse was transferred to obese mouse (parabiotically fused)
• obese mice responded to Leptin began to lose weight demonstrating the potential viability of Leptin treatment

Question 12

What was the process of Leptin trials on obese mice with defective Leptin receptors?

Answer 12

• defective mous and normal mouse was fused parabiotically
• Leptin transferred to healthy mouse (obese jour overproduce Leptin to compensate for low receptors sensitivity
• obses mouse remained obses as its body could not respond to Leptin
• healthy mouse because emancipated due to abnormally high levels of Leptin transférer into bloodstream

Question 13

What are human experiments to do with Leptin? (4)

Answer 13

• most cases of obesity are caused by unresponsiveness to leptin and not a leptin deficiency
• in clinical trials, very few participants experienced significant weight loss in response to leptin injections
• many patients did experience adverse side effects from leptin injections, including skin irritations
• so, leptin treatments are not considered to be an effective way of controlling obesity

Question 14

Where is melatonin produces?

Answer 14

Pineal gland

Question 15

What does melatonin respond to? (2)

Answer 15

• light exposure to retina is relayed via suprachiasmatic nucleus (hypothalamus) and inhibits melatonin secretion
• melatonin is therefore secreted in response to periods of darkness (high conc at night)

Question 16

What is circadian rhythm? (2)

Answer 16

• Circadian rhythms are the body’s physiological responses to the 24 hour day-night cycle
• Circadian rhythms are driven by an internal (endogenous) circadian clock,but they can be modulated by external factors

Question 17

How does melatonin synchronise circadian rhythms and regulate body’s sleep schedule? (5)

Answer 17

• melatonin is suppressed by bright light (increase at night)
• over prolonged period melatonin secretion become

Question 18

debunking soil and seed theory? (4)

Answer 18

• William Harvey studied sexual organs of female deer after making to identify embryo
• he detected growing embryo until 6-7 weekes
• artistotle’e theory was incorrect and mentrual blood did not contribute to development of foetus

Question 19

what leads to male development? (3)

Answer 19

• Y chromosome includes SRY gene
• SRY gene codes for testis determining factor that causes embryonic gonads to form into testes
• absence of TDF ptortin the embryonic gonad will develop into ovaries

Question 20

what is testosterone responsible for? (4)

Answer 20

• prenatal development of genetalia
• sperm production
• secondary sex characteristics (body hair, muscle mass, deepening of voice)
• sex drive (libido)

Question 21

what are progesterone and estrogen responsible for?

Answer 21

• promote natal developemtn of femal reproducitve organs
• development of secondary sex charactersitics (body hair, breast development)
• menstrual cycle

Question 22

what is the strucutre of male reproductive system?(6)

Answer 22

• testis - production of sperm and testosterone
• epididymis - sperm matures and develops ability to be motile
• vas deference - long tube which conducts sperm from teste to prostrate gland (during ejaculation)
• seminal vesicle - secretes fluid containing fructose (nourish sperm), mucus (protect sperm) and prostaglandin (triggers uterine contractions)
• prostate gland - secretes alkaline fluid to neutralise vaginal acids (maintain sperm viability)
• urethra - conducts sperm/ semen from prostrate gland to outside of body

Question 23

What is the process of menstruation? (15)

Answer 23

■ FSH and LH are produced by the pituitary
■ estrogen and progesterone are produced by the ovary
■ FSH stimulates the ovary to produce a follicle
■ developing follicles secrete estrogen
■ estrogen inhibits FSH / negative feedback
■ estrogen stimulates growth of endometrium / uterine lining
■ estrogen stimulates LH secretion / positive feedback
■ LH stimulates ovulation
■ follicle becomes corpus luteum
■ corpus luteum secretes estrogen and progesterone
■ estrogen and progesterone maintain the lining of the uterus / endometrium
■ estrogen and progesterone inhibit LH and FSH / negative feedback
■ after two weeks corpus luteum degenerates
■ ovarian hormone levels / progesterone / estrogen fall
■ menstrual bleeding begins / lining of uterine wall / endometrium lost

Question 24

What is the process of IVF? (10)

Answer 24

■ (IVF) is fertilization outside body / “in glass”
■ (drug) stops normal menstrual cycle
■ (inject FSH) to stimulate ovaries / stimulate production of eggs
■ (HCG) matures the follicles
■ eggs are removed from follicles / ovaries / mother
■ male provides sperm / sperm donor
■ washing / capacitation of sperm
■ eggs are mixed with sperm
■ 2-3 embryos are implanted into uterus
■ pregnancy test is done to see if implantation / pregnancy has occurred