Chapter 6- Hormones, Homeostatis And Reproduction

Question 1

What do cells in the pancreas respond to?

Answer 1

Changes in blood glucose levels - if deviates significantly from
Norm, homeostasis mechanisms mediated by the pancreatic hormones insulin and glucagon are initiated

Question 2

Pancreas has two glands- 1 secretes to small intestine, 1 secretes to blood, these what are the second region called?

Answer 2

Islets of langerhans

Question 3

Explain the role of alpha cells in islets of langerhans

Answer 3

Synthesize and secrete glucagon if the blood level falls below the set point - hormone stimulates breakdown of glucagon into glucose in liver cells and it’s released into the blood

Question 4

Explain the role of beta cells in islets of langerhans

Answer 4

Synthesize insulin and secret it when blood glucose levels are too high- hormone stimulates uptake of glucose by various tissues- stimulates conversion of glucose to glycogen

Question 5

Causes of type 1/ type 2 diabetes

Answer 5

1) caused by inability to produce sufficient quantities of insulin
2) caused by inability to process or respond to insulin because of deficiency of insulin receptors - caused by sugary fatty diet, prolonged obesity and lack of exercise

Question 6

Treatment of type 1/2 diabetes

Answer 6

1) testing blood glucose levels conc regularly and injecting insulin when they are too high - often done before a meal
2) treated by adjusting diet- small amounts of food should be eaten regularly then big meals- sugary food should be avoided etc

Question 7

Where is thyroxin secreted from/ what does it do?

Answer 7

By the thyroid gland to regulate the metabolic rate and help control body temp

Question 8

What do cooling triggers do?

Answer 8

Increase thyroxin secretion by the thyroid gland, which stimulates heat production so body temp rises

Question 9

What are the effects of thyroxin deficiency? (Hypothyroidism)

Answer 9

1) lack of energy and feeling tired all the time
2) forgetfulness and depression
3) weigh gain despite loss of appetite as less glucose fats are being broken down
4) feeling cold all the time as no heat is being generated
5) constipation because contractions of muscles in the wall of the guy slow down
6) impaired brain development in kids

Question 10

Where is leptin secreted from and what does it do?

Answer 10

Secreted by cells in the adipose tissue and acts on the hypothalamus of the brain to inhibit appetite

Question 11

How does leptin work?

Answer 11

Leptin binds to receptors in the membrane of adipose tissues - if tissue increases, blood leptin conc rises causin. Long term appetite inhibition to reduce food intake

Question 12

How was the importance of leptin discovered?

Answer 12

Through a strain of mice in the 1950s that fed ravenously- leptin became inactive and gain body weight- breeding showed that these mice us the recessive allele ob- mice that have the two recessive allele ob cannot produce leptin- with leptin injections there appetite declined

Question 13

What is melatonin/ what does it do?

Answer 13

It is secreted by the pineal gland to control the circadian rhythm

Question 14

What are circadian rhythms?

Answer 14

Humans are adapted to live a 24 hour cycle and have rhythms on behaviour that fit this cycle

Question 15

What do circadian rhythms depend on?

Answer 15

On two groups of cells in the hypothalamus called the suprachiasmastic nuclei (SCN) - these cells set a daily rhythm even if grown in culture with no external cues about the time of day- in brain control secretion of melatonin

Question 16

When does melatonin secretion increase?

Answer 16

In the evenings and drops to a low level at dawn as the hormone is removed from the body by liver

Question 17

What is the main effect of melatonin on the body?

Answer 17

Sleep wake cycle- high melatonin levels cause feelings of drowsiness and promote sleep through the night- falling melatonin encourage waking at the end of the night

Question 18

What else does melatonin have an effect onV

Answer 18

Contributed to the nkght time drop in the core body temp

Also in kidney, suggesting that decreased urine production at night may be another effect of this hormone

Question 19

What helps melatonin keep to day-night cycle?

Answer 19

Cells called ganglion in retina detect light and pass impulses to SCN - helps it adjust

Question 20

Causes of jet lag?

Answer 20

Common experience for those who have crossed 3 or more time zones
- difficultly in remaining awake during the daylight hours and sleeping at night - fatigue, irritability, headaches and indigestion.

Question 21

How can melatonin help with jet lag?

Answer 21

Taken orally- helps promote sleep to reduce jet lag

Question 22

What does a gene on the Y chromosome cause?

Answer 22

Embryonic gonads to develop as testes and secrete testosterone

Question 23

Which gene is present to make boy which gene for girl

Answer 23

1) if gene SRY is present- gonads develop into tested - this is located on Y chromosome- codes for TDF protein- stimulates expression of other genes that cause testis development
2) girls don’t have SRY do TDF is not produced

Question 24

What does testosterone do?

Answer 24

Causes prenatal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty

Question 25

What do estrogen and progesterone cause?

Answer 25

Causes prenatal development of female reproductive organs and female secondary sexual characterises during puberty

Question 26

What is the menstrual cycle controlled by?

Answer 26

Negative and positive feedback mechanisms involving ovarian and pituitary hormones

Question 27

What is the first half of the menstrual cycle called? What happens?

Answer 27

1) The follicular phase because a group of follicles is developing in the ovary
2) in each follicle there an egg is stimulates to grow- same time lining of uterus is repaired and starts to thicken- most developed follicles break open, releasing eggs into the oviduct

Question 28

What is the second half of the menstrual cycle called?

What happens?

Answer 28

1) called luteal phase because the wall of the follicle that released an egg becomes a body called the corpus luteum
2) continued development of the uterus prepares it for implantation of an embryo- if fertilisation doesn’t occur the ovary breaks down- uterus breaks down and is shed

Question 29

What hormones help control the menstrual cycle?

Answer 29

1) FSH and LH are protein hormones produced by the pituitary gland that bind to FSH and LH receptors in the membranes of follicle cells
2) estrogen and progesterone are ovarian hormones, produced by wall of the follicle and corpus luteum- they are absorbed by many cells in the female body where they influence gene expression. And therefore development

Question 30

What are insulin and glucagon secreted by?

Answer 30

Secreted by alpha and beta cells in the pancreas to control blood glucose concentration