6.6 Hormones, homeostasis and reproduction
Distinguish between type 1 and type 2 diabetes.
- Type 1: early onset (childhood), body produces inefficient amounts of insulin, caused by destruction of beta cells, requires insulin injections to control glucose levels - Type 2: late onset (adulthood), body does not respond to insulin, caused by down regulation of insulin receptors, can be controlled with low carbohydrate diet
Where is the hormone leptin secreted
Adipose Tissue
Define hyperglycemia.
Blood glucose levels above 180 mg/dl.
Define hypoglycemia.
Blood glucose levels below 70 mg/dl.
What does oestrogen cause in pre-natal development?
Development of female reproductive organs
Outline the role of FSH in the menstrual cycle
FSH is secreted at the start of the cycle / early in the cycle / days 1 to 5 / when progesterone / estrogen is low FSH stimulates the development of follicles FSH stimulates estrogen secretion (by the developing follicle)
How is the concentration of leptin in the blood controlled?
Food intake and amount of adipose tissue in the body.
What is the main function of leptin?
It regulates food intake and body weight. Leptin also acts on specific receptors in the hypothalamus to inhibit appetite through both counteractive and stimulatory mechanisms. Leptin counteracts the effects of a feeding stimulant released in the gut called neuropeptide Y as well as the effects of a cannabinoid neurotransmitter called adandamide which stimulates appetite. Leptin also promotes the synthesis of an appetite suppressant called α-melanocyte-stimulating hormone
Outline the role of LH in the menstrual cycle
LH is secreted in the middle of the cycle / before ovulation / days 10 to 14 LH causes ovulation LH causes the development of the corpus luteum LH causes secretion of progesterone LH stimulates less estrogen
Explain the control of blood glucose concentration, including the roles of glucagon, insulin and the alpha and beta cells in the pancreatic islets.
Pancreatic cells monitor the levels of blood glucose. Two hormones, insulin and glucagon, are responsible for controlling blood glucose concentration. When glucose levels are low, the alp of the pancreatic islets produce glucagon. Glucagon stimulates the liver to break glycogen into glucose which leads to an increase in blood glucose levels. At high glucose levels the beta cells of the pancreatic islets will produce insulin, which stimulates the uptake of glucose into cells and uptake of glucose into the liver where it is stored in the form of glycogen. This leads to a decrease in blood glucose levels. These two processes are constantly occurring in humans in order to keep blood sugar levels within a set range and to maintain homeostasis.
What is the role of progesterone in the menstrual cycle?
Prepares uterus for the implantation of an embryo
Which hormone is produced by developing testes in the foetus?
Testosterone
From where is the hormone thyroxin secreted?
The thyroid gland in the neck.
explain the term -ve feedback in terms of blood glucose regulation
appropriate hormone is released into the blood when glucose is above or below a set point is active until the levels detected are back to normal at which point the hormonal release is stopped.
Oviduct
collet eggs at ovulation, provide a site for fertilisation then move the embryo to the uterus
Outline the role of estrogen in the menstrual cycle
estrogen stimulates the repair of the uterus lining rapid increase in estrogen stimulates LH production, (positive feedback) low levels of estrogen initially inhibit FSH (and LH) secretion
What is the chemical structure of thyroxin?
four atoms of iodine
What hormone is secreted (and from where) when blood glucose levels drop (like when you go a long time without a meal or have high physical demands that use up glucose more quickly than it is supplied?)
glucagon is secreted from the endocrine alpha cells of the ilets of langerhans of the pancreas
Scrotum
holds testes at lower than core temperature
What hormone is secreted (and from where) when blood glucose rises after a meal?
insulin is secreted from endocrine beta cells of the islets of langerhans of the pancreas
What does thyroxin regulate?
metabolic rate
What organ controls blood glucose levels?
pancreas detects blood glucose levels
Penis
penetrate the vagina for ejaculation of semen near the cervix
Ovary
produce eggs, oestrogen and progesterone
Testis
produce sperm and testosterone
Outline the function of melatonin
produced in the pineal gland in limbic midbrain helps control circadian rhythms and sleep and wake cycles melatonin tablets can be taken to reduce or prevent a jet lag it is taken orally at the time when sleep should ideally be commencing
Outline the role of progesterone in the menstrual cycle
progesterone causes thickening of the uterus lining / prepares uterine lining for implantation progesterone / estrogen inhibits the secretion of LH / FSH falling progesterone levels at the end of the cycle allow FSH production / menstruation lower concentrations of estrogen and / or progesterone allow disintegration of endometrium / menstruation occurs;
Vulva
protect internal parts of the female reproductive system
Cervix
protect the fetus during pregnancy and then dilate to provide a birth canal
Uterus
provide for the needs of the embryo and then fetus during pregnancy
Seminal vesicle/prostate gland
secrete fluid containing alkali, proteins and fructose that is added to sperm to make semen
Vagina
stimulate penis to cause ejaculation and provide birth canal
Epididymis
store sperm ejaculation
what is the target organ of insulin and glucagon and how does it respond to each?
the liver has receptors for insulin which stimulates it to convert glucose to glycogen storage molecule reducing blood glucose; when glucagon is detected by receptors in the liver, it will elicit the reverse response whereby the liver converts the glucagon back to glucose thereby raising blood glucose levels.
Urethra
transfer semen during ejaculation and urine during urination
Sperm duct
transfer sperm during ejaculation