Chapter 6- Hormones, Homeostatis And Reproduction Flashcards Preview

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What do cells in the pancreas respond to?

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


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

Islets of langerhans


Explain the role of alpha cells in islets of langerhans

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


Explain the role of beta cells in islets of langerhans

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


Causes of type 1/ type 2 diabetes

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


Treatment of type 1/2 diabetes

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


Where is thyroxin secreted from/ what does it do?

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


What do cooling triggers do?

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


What are the effects of thyroxin deficiency? (Hypothyroidism)

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


Where is leptin secreted from and what does it do?

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


How does leptin work?

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


How was the importance of leptin discovered?

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


What is melatonin/ what does it do?

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


What are circadian rhythms?

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


What do circadian rhythms depend on?

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


When does melatonin secretion increase?

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


What is the main effect of melatonin on the body?

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


What else does melatonin have an effect onV

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


What helps melatonin keep to day-night cycle?

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


Causes of jet lag?

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.


How can melatonin help with jet lag?

Taken orally- helps promote sleep to reduce jet lag


What does a gene on the Y chromosome cause?

Embryonic gonads to develop as testes and secrete testosterone


Which gene is present to make boy which gene for girl

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


What does testosterone do?

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


What do estrogen and progesterone cause?

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


What is the menstrual cycle controlled by?

Negative and positive feedback mechanisms involving ovarian and pituitary hormones


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

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


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

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


What hormones help control the menstrual cycle?

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


What are insulin and glucagon secreted by?

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

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